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James Ussher

James Ussher (or Usher; 4 January 1581 – 21 March 1656) was the Church of Ireland Archbishop of Armagh and Primate of All Ireland between 1625 and 1656. He was a prolific Irish scholar and church leader, who today is most famous for his identification of the genuine letters of the church father, Ignatius of Antioch, and for his chronology that sought to establish the time and date of the creation as "the entrance of the night preceding the 23rd day of October... the year before Christ 4004"; that is, around 6 pm on 22 October 4004 BC, per the proleptic Julian calendar.

Education
Ussher was born in Dublin to a well-to-do family. His maternal grandfather, James Stanihurst, had been speaker of the Irish parliament. Ussher's father, Arland Ussher, was a clerk in chancery who married Stanihurst's daughter, Margaret (by his first wife Anne Fitzsimon), who was reportedly a Roman Catholic.

Ussher's younger and only surviving brother, Ambrose, became a distinguished scholar of Arabic and Hebrew. According to his chaplain and biographer, Nicholas Bernard, the elder brother was taught to read by two blind, spinster aunts. A gifted polyglot, he entered Dublin Free School and then the newly founded (1591) Trinity College Dublin on 9 January 1594, at the age of thirteen (not an unusual age at the time). He had received his Bachelor of Arts degree by 1598 and was a fellow and MA by 1600 (though Bernard claims he did not gain his MA till 1601). In May 1602, he was ordained in the Trinity College Chapel as a deacon in the Protestant, established, Church of Ireland (and possibly priest on the same day, while Martin Gorst says that he became a priest on 20 December 1601 ) by his uncle Henry Ussher, the Archbishop of Armagh and Primate of All Ireland.

Ussher went on to become Chancellor of St Patrick's Cathedral, Dublin in 1605 and Prebend of Finglas. He became Professor of Theological Controversies at Trinity College and a Bachelor of Divinity in 1607, Doctor of Divinity in 1612, and then Vice-Chancellor in 1615 and vice-provost in 1616. In 1613, he married Phoebe, daughter of a previous Vice-Provost, Luke Challoner, and published his first work. In 1615, he was closely involved with the drawing up of the first confession of faith of the Church of Ireland, the Irish Articles of Religion.

Early life and career
In 1619 Ussher travelled to England, where he remained for two years. His only child was Elizabeth (1619–93), who married Sir Timothy Tyrrell, of Oakley, Buckinghamshire. She was the mother of James Tyrrell. He became prominent after meeting James I. In 1621 James I nominated Ussher Bishop of Meath. He became a national figure in Ireland, becoming Privy Councillor in 1623 and an increasingly substantial scholar. A noted collector of Irish manuscripts, he made them available for research to fellow scholars such as his friend, Sir James Ware. From 1623 until 1626 he was again in England and was excused from his episcopal duties to study church history. He was nominated Primate of All Ireland and Archbishop of Armagh in 1625 and succeeded Christopher Hampton, who had succeeded Ussher's uncle Henry twelve years earlier.

Primate of All Ireland
After his consecration in 1626, Ussher found himself in turbulent political times. Tension was rising between England and Spain, and to secure Ireland Charles I offered Irish Catholics a series of concessions, including religious toleration, known as The Graces, in exchange for money for the upkeep of the army. Ussher was a convinced Calvinist and viewed with dismay the possibility that people he regarded as papists might achieve any sort of power. He called a secret meeting of the Irish bishops in his house in November 1626, the result being the "Judgement of the Arch-Bishops and Bishops of Ireland". This begins:

"The religion of the papists is superstitious and idolatrous; their faith and doctrine erroneous and heretical; their church in respect of both, apostatical; to give them, therefore, a toleration, or to consent that they may freely exercise their religion, and profess their faith and doctrine, is a grievous sin."

The Judgement was not published until it was read out at the end of a series of sermons against the Graces given at Dublin in April 1627. Following Thomas Wentworth's attainder in April 1641, King Charles and the Privy Council of England instructed the Irish Lords Justices on 3 May 1641 to publish the required Bills to enact the Graces. However, the law reforms were not properly implemented before the rebellion in late 1641.

During a four-year interregnum between Lord Deputies from 1629 on, there was an increase in efforts to impose religious conformity on Ireland. In 1633, Ussher wrote to the new Archbishop of Canterbury, William Laud, in an effort to gain support for the imposition of recusancy fines on Irish Catholics. Thomas Wentworth, who arrived as the new Lord Deputy in Ireland in 1633, deflected the pressure for conformity by stating that firstly, the Church of Ireland itself would have to be properly resourced, and he set about its re-endowment. He settled the long-running primacy dispute between the sees of Armagh and Dublin in Armagh's favour. The two clashed on the subject of the theatre: Ussher had the usual Puritan antipathy to the stage, whereas Wentworth was a keen theatre-goer, and against Ussher's opposition, oversaw the foundation of Ireland's first theatre, the Werburgh Street Theatre.

Ussher soon found himself at odds with the rise of Arminianism and Wentworth and Laud's desire for conformity between the Church of England and the more Calvinistic Church of Ireland. Ussher resisted this pressure at a convocation in 1634, ensuring that the English Articles of Religion were adopted as well as the Irish articles, not instead of them, and that the Irish canons had to be redrafted based on the English ones rather than replaced by them. Theologically, he was a Calvinist although on the matter of the atonement he was (somewhat privately) a hypothetical universalist. His most significant influence in this regard was John Davenant, later an English delegate to the Synod of Dort, who managed to significantly soften that Synod's teaching regarding limited atonement.

In 1633, Ussher had supported the appointment of Archbishop Laud as Chancellor of the University of Dublin. He had hoped that Laud would help to impose order on what was, Ussher accepted, a somewhat mismanaged institution. Laud did that, rewriting the charter and statutes to limit the authority of the fellows, and ensure that the appointment of the provost was under royal control. In 1634, he imposed on the college an Arminian provost, William Chappell, whose theological views, and peremptory style of government, were antithetical to everything for which Ussher stood. By 1635, it was apparent that Ussher had lost de facto control of the church to John Bramhall, Bishop of Derry, in everyday matters and to Laud in matters of policy.

William M. Abbott, Associate Professor of History at Fairfield University, argues that he was an effective and politically important bishop and archbishop. The Oxford Dictionary of National Biography notes that he was reactive and sought conciliation rather than confrontation. The story that he successfully opposed attempts to reintroduce the Irish language for use in church services by William Bedell, the Bishop of Kilmore, has been refuted.

Ussher certainly preferred to be a scholar when he could be. He engaged in extensive disputations with Roman Catholic theologians, and even as a student he challenged a Jesuit relative, Henry Fitzsimon (Ussher's mother was Catholic), to dispute publicly the identification of the Pope with the Antichrist. Ussher had an obsession with "Jesuits disguised as" Covenanters in Scotland, highwaymen when he was robbed, non-conformists in England, it was a remarkable list. However, Ussher also wrote extensively on theology, patristics and ecclesiastical history, and these subjects gradually displaced his anti-Catholic work. After Convocation in 1634, Ussher left Dublin for his episcopal residence at Drogheda, where he concentrated on his archdiocese and his research. In 1631, he produced a new edition of a work first published in 1622, his "Discourse on the Religion Anciently Professed by the Irish", a ground-breaking study of the early Irish church, which sought to demonstrate how it differed from Rome and was, instead, much closer to the later Protestant church. This was to prove highly influential, establishing the idea that the Church of Ireland was the true successor of the early Celtic church.

In 1639, he published the most substantial history of Christianity in Britain to that date, Britannicarum ecclesiarum antiquitates – the antiquities of the British churches. It was an astonishing achievement in one respect – in gathering together so many previously unpublished manuscript sources. Ussher was very reluctant to arrive at firm judgements as to the sources' authenticity – hence his devotion of a whole chapter to the imaginative but invented stories of King Lucius and the creation of a Christian episcopate in Britain.

Wars of the Three Kingdoms

In 1640, Ussher left Ireland for England for what turned out to be the last time. In the years before the Wars of the Three Kingdoms, his reputation as a scholar and his moderate Calvinism meant that his opinion was sought by both King and Parliament. After Ussher lost his home and income through the Irish uprising of 1641, Parliament voted him a pension of £400 while the King awarded him the income and property of the vacant See of Carlisle.

Despite their occasional differences, he remained a loyal friend to Thomas Wentworth, 1st Earl of Strafford, and when the latter was sentenced to death by Parliament, pleaded with the King not to allow the execution of the verdict: unlike some of his episcopal colleagues, he insisted that the King was absolutely bound in conscience by his promise to Strafford that whatever happened his life would be spared. The King did not take his advice, but clearly afterwards regretted not doing so, as is shown by his reference on the scaffold to Strafford's death as "that unjust sentence which I suffered to take effect".

In early 1641 Ussher developed a mediatory position on church government, which sought to bridge the gap between the Laudians, who believed in an episcopalian church hierarchy (bishops), and the Presbyterians, who wanted to abolish episcopacy entirely. His proposals, not published until 1656, after his death, as The Reduction of Episcopacy, proposed a compromise where bishops operated in a Presbyterian synodal system, were initially designed to support a rapprochement between Charles and the parliamentarian leadership in 1641, but were rejected by the King. They did, however, have an afterlife, being published in England and Scotland well into the eighteenth century. In all, he wrote or edited five books relating to episcopacy.

As the middle ground between King and Parliament vanished in 1641–1642, Ussher was forced, reluctantly, to choose between his Calvinist allies in parliament and his instinctive loyalty to the monarchy. Eventually, in January 1642 (having asked parliament's permission), he moved to Oxford, a royalist stronghold. Though Charles severely tested Ussher's loyalty by negotiating with the Catholic Irish, the Primate remained committed to the royal cause, though as the king's fortunes waned Ussher had to move on to Bristol, Cardiff, and then to St Donat's.

In June 1646, he returned to London under the protection of his friend, Elizabeth, Dowager Countess of Peterborough, in whose houses he stayed from then on. He was deprived of the See of Carlisle by Parliament on 9 October 1646, as the English episcopacy was abolished for the duration of the Commonwealth and the Protectorate. He became a preacher at Lincoln's Inn early in 1647, and despite his royalist loyalties was protected by his friends in Parliament. He watched the execution of Charles I from the roof of the Countess of Peterborough's home in London but fainted before the axe fell.

Scholarship on Ignatius
Ussher wrote two treatises on the epistles of Ignatius of Antioch while doing his work on church hierarchy. They were scholarly achievements that modern experts largely concur with. In Ussher's time, the only collection of Ignatius's writing easily available was the Long Recension, a set of 16 epistles. Ussher closely examined it and found problems that had gone uncommented on for centuries: differences in tone, theology, and apparent anachronistic references to theological disputes and structures that did not exist during Ignatius's time. Additionally, medieval authors commenting on Ignatius did not appear to be reading the same letters of the Long Recension. Ussher researched and found a shorter set, usually called the Middle Recension, and argued that only the letters contained in it were authentically Ignatius's. The unknown compiler of the Long Recension edited Ignatius's work and included some of his own, and seems to have had Arian tendencies. He published this Latin edition of the genuine Ignatian works in 1644. The only major difference between Ussher's stance and modern scholars is that Ussher thought that the Epistle of Ignatius to Polycarp was also inauthentic; most modern scholars believe it to be a genuine production of Ignatius, however.

Chronology

Ussher now concentrated on his research and writing and returned to the study of chronology and the church fathers. After a 1647 work on the origin of the Creeds, Ussher published a treatise on the calendar in 1648. This was a warm-up for his most famous work, the Annales veteris testamenti, a prima mundi origine deducti ("Annals of the Old Testament, deduced from the first origins of the world"), which appeared in 1650, and its continuation, Annalium pars posterior, published in 1654. In this work, he calculated the date of the Creation to have been nightfall on 22 October 4004 BC. (Other scholars, such as Cambridge academic, John Lightfoot, calculated their own dates for the Creation.) The time of the Ussher chronology is frequently misquoted as being 9 a.m., noon or 9 p.m. on 23 October. See the related article on the chronology for a discussion of its claims and methodology.

Ussher's work is now used to support Young Earth Creationism, which holds that the universe was created thousands of years ago (rather than billions). But while calculating the date of the Creation is today considered a fringe activity, in Ussher's time such a calculation was still regarded as an important task, one also attempted by many Post-Reformation scholars, such as Joseph Justus Scaliger and physicist Isaac Newton.

Ussher's chronology represented a considerable feat of scholarship: it demanded great depth of learning in what was then known of ancient history, including the rise of the Persians, Greeks and Romans, as well as expertise in the Bible, biblical languages, astronomy, ancient calendars and chronology. Ussher's account of historical events for which he had multiple sources other than the Bible is usually in close agreement with modern accounts – for example, he placed the death of Alexander in 323 BC and that of Julius Caesar in 44 BC. Ussher's last biblical co-ordinate was the Babylonian king Nebuchadnezzar II, and beyond this point, he had to rely on other considerations. Faced with inconsistent texts of the Torah, each with a different number of years between the Genesis flood narrative and Creation, Ussher chose the Masoretic version, which claims an unbroken history of careful transcription stretching back centuries – but his choice was confirmed for him, because it placed Creation exactly four thousand years before 4 BC, the generally accepted date for the Nativity of Jesus; moreover, he calculated, Solomon's Temple was completed in the year 3000 from creation, so that there were exactly 1,000 years from the temple to Jesus, who was thought to be the 'fulfilment' of the Temple.

Death
In 1655, Ussher published his last book, De Graeca Septuaginta Interpretum Versione, the first serious examination of the Septuagint, discussing its accuracy as compared with the Hebrew text of the Old Testament. In 1656, he went to stay in the Countess of Peterborough's house in Reigate, Surrey. On 19 March, he felt a sharp pain in his side after supper and took to his bed. His symptoms seem to have been those of a severe internal haemorrhage. Two days later he died, aged 75. His last words were reported as: "O Lord, forgive me, especially my sins of omission". His body was embalmed and was to have been buried in Reigate, but at Oliver Cromwell's insistence he was given a state funeral on 17 April and was buried in the chapel of St Erasmus in Westminster Abbey.

Works

 * – The Life of James Ussher, D.D.
 * – incl. De Christianorum Ecclesiarum Successione et Statu historica Explicatio (1613)
 * – An Answer to a Challenge made by a Jesuit in Ireland
 * – incl. Gotteschalci et Praedestinatione Controversiae abeomotae Historia (1631); Veterum Epistolarum Hibernicarum Sylloge (1632)
 * – Brittanicarum Ecclesiarum Antiquitates; caput I–XIII (1639)
 * – Brittanicarum Ecclesiarum Antiquitates; caput XIV–XVII (1639)
 * – A Geographical and Historical Disquisition, touching the Asia properly so called; The Original of Bishops and Metropolitans briefly laid down; The Judgment of Doctor Rainoldes, touching the Original of Episcopacy, more largely confirmed out of Antiquity; Dissertatio non-de Ignati solum et Polycarpi scriptis, sed etiam de Apostolicis Constitutionibus et Canonibus Clementi Romano attributis (1644); Praefationes in Ignatium (1644); De Romanae Ecclesiae Symbolo vetere aliisque Fidei Formulis tum ab Occidentalibus tum ab Orientalibus in prima Catechesi et Baptismo proponi solitis (1647); De Macedonum et Asianorum Anno Solari Dissertatio (1648); De Graeca Septuaginta Interpretum Versione Syntagma, cum Libri Estherae editione Origenica et vetere Graeca altera; Epistola ad Ludovicum Capellum de variantibus Textus Hebraei Lectionibus; Epistola Gulielmi Eyre ad Usserium
 * – Annales veteris Testamenti, a Prima Mundi Origine deducti, una cum Rerum Asiaticarum Aegypticarum Chronico, a temporis historici principio usque ad Maccabaicorum initia producto (1650)
 * – Annales veteris Testamenti (contd.)
 * – Annales veteris Testamenti (contd.)
 * – Annales veteris Testamenti concludes; Annalium Pars Posterior, in qua, praeter Maccabaicam et novi testamenti historiam, Imperii Romanorum Caesarum sub Caio Julio et Octaviano Ortus, rerumque in Asia et Aegypto Gestarum continetur Chronicon ... (1654)
 * – Chronologia sacra (1660); Historia Dogmatica Controversiae inter Orthodoxos et Pontificios de Scripturis et Sacris Vernaculis; Dissertatio de Pseudo-Dionysii scriptis; Dissertatio de epistola ad Laodicenses
 * – sermons (in English)
 * – Tractatus de Controversiis Pontificiis; Praelectiones Theologicae
 * – letters (in English) (incl. first to Richard Stanihurst, his uncle)
 * – letters (in English and Latin)
 * – indexes

title: James Ussher


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Motion compensation

Motion compensation in computing is an algorithmic technique used to predict a frame in a video given the previous and/or future frames by accounting for motion of the camera and/or objects in the video. It is employed in the encoding of video data for video compression, for example in the generation of MPEG-2 files. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture may be previous in time or even from the future. When images can be accurately synthesized from previously transmitted/stored images, the compression efficiency can be improved.

Motion compensation is one of the two key video compression techniques used in video coding standards, along with the discrete cosine transform (DCT). Most video coding standards, such as the H.26x and MPEG formats, typically use motion-compensated DCT hybrid coding, known as block motion compensation (BMC) or motion-compensated DCT (MC DCT).

Functionality
Motion compensation exploits the fact that, often, for many frames of a movie, the only difference between one frame and another is the result of either the camera moving or an object in the frame moving. In reference to a video file, this means much of the information that represents one frame will be the same as the information used in the next frame.

Using motion compensation, a video stream will contain some full (reference) frames; then the only information stored for the frames in between would be the information needed to transform the previous frame into the next frame.

Illustrated example
The following is a simplistic illustrated explanation of how motion compensation works. Two successive frames were captured from the movie Elephants Dream. As can be seen from the images, the bottom (motion compensated) difference between two frames contains significantly less detail than the prior images, and thus compresses much better than the rest. Thus the information that is required to encode compensated frame will be much smaller than with the difference frame. This also means that it is also possible to encode the information using difference image at a cost of less compression efficiency but by saving coding complexity without motion compensated coding; as a matter of fact that motion compensated coding (together with motion estimation, motion compensation) occupies more than 90% of encoding complexity.

MPEG
In MPEG, images are predicted from previous frames (P frames) or bidirectionally from previous and future frames (B frames). B frames are more complex because the image sequence must be transmitted and stored out of order so that the future frame is available to generate the B frames.

After predicting frames using motion compensation, the coder finds the residual, which is then compressed and transmitted.

Global motion compensation
In global motion compensation, the motion model basically reflects camera motions such as:
 * Dolly — moving the camera forward or backward
 * Track — moving the camera left or right
 * Boom — moving the camera up or down
 * Pan — rotating the camera around its Y axis, moving the view left or right
 * Tilt — rotating the camera around its X axis, moving the view up or down
 * Roll — rotating the camera around the view axis

It works best for still scenes without moving objects.

There are several advantages of global motion compensation:
 * It models the dominant motion usually found in video sequences with just a few parameters. The share in bit-rate of these parameters is negligible.
 * It does not partition the frames. This avoids artifacts at partition borders.
 * A straight line (in the time direction) of pixels with equal spatial positions in the frame corresponds to a continuously moving point in the real scene. Other MC schemes introduce discontinuities in the time direction.

MPEG-4 ASP supports global motion compensation with three reference points, although some implementations can only make use of one. A single reference point only allows for translational motion which for its relatively large performance cost provides little advantage over block based motion compensation.

Moving objects within a frame are not sufficiently represented by global motion compensation. Thus, local motion estimation is also needed.

Block motion compensation
Block motion compensation (BMC), also known as motion-compensated discrete cosine transform (MC DCT), is the most widely used motion compensation technique. In BMC, the frames are partitioned in blocks of pixels (e.g. macro-blocks of 16×16 pixels in MPEG). Each block is predicted from a block of equal size in the reference frame. The blocks are not transformed in any way apart from being shifted to the position of the predicted block. This shift is represented by a motion vector.

To exploit the redundancy between neighboring block vectors, (e.g. for a single moving object covered by multiple blocks) it is common to encode only the difference between the current and previous motion vector in the bit-stream. The result of this differentiating process is mathematically equivalent to a global motion compensation capable of panning. Further down the encoding pipeline, an entropy coder will take advantage of the resulting statistical distribution of the motion vectors around the zero vector to reduce the output size.

It is possible to shift a block by a non-integer number of pixels, which is called sub-pixel precision. The in-between pixels are generated by interpolating neighboring pixels. Commonly, half-pixel or quarter pixel precision (Qpel, used by H.264 and MPEG-4/ASP) is used. The computational expense of sub-pixel precision is much higher due to the extra processing required for interpolation and on the encoder side, a much greater number of potential source blocks to be evaluated.

The main disadvantage of block motion compensation is that it introduces discontinuities at the block borders (blocking artifacts). These artifacts appear in the form of sharp horizontal and vertical edges which are easily spotted by the human eye and produce false edges and ringing effects (large coefficients in high frequency sub-bands) due to quantization of coefficients of the Fourier-related transform used for transform coding of the residual frames

Block motion compensation divides up the current frame into non-overlapping blocks, and the motion compensation vector tells where those blocks come from (a common misconception is that the previous frame is divided up into non-overlapping blocks, and the motion compensation vectors tell where those blocks move to). The source blocks typically overlap in the source frame. Some video compression algorithms assemble the current frame out of pieces of several different previously transmitted frames.

Frames can also be predicted from future frames. The future frames then need to be encoded before the predicted frames and thus, the encoding order does not necessarily match the real frame order. Such frames are usually predicted from two directions, i.e. from the I- or P-frames that immediately precede or follow the predicted frame. These bidirectionally predicted frames are called B-frames. A coding scheme could, for instance, be IBBPBBPBBPBB.

Further, the use of triangular tiles has also been proposed for motion compensation. Under this scheme, the frame is tiled with triangles, and the next frame is generated by performing an affine transformation on these triangles. Only the affine transformations are recorded/transmitted. This is capable of dealing with zooming, rotation, translation etc.

Variable block-size motion compensation
Variable block-size motion compensation (VBSMC) is the use of BMC with the ability for the encoder to dynamically select the size of the blocks. When coding video, the use of larger blocks can reduce the number of bits needed to represent the motion vectors, while the use of smaller blocks can result in a smaller amount of prediction residual information to encode. Other areas of work have examined the use of variable-shape feature metrics, beyond block boundaries, from which interframe vectors can be calculated. Older designs such as H.261 and MPEG-1 video typically use a fixed block size, while newer ones such as H.263, MPEG-4 Part 2, H.264/MPEG-4 AVC, and VC-1 give the encoder the ability to dynamically choose what block size will be used to represent the motion.

Overlapped block motion compensation
Overlapped block motion compensation (OBMC) is a good solution to these problems because it not only increases prediction accuracy but also avoids blocking artifacts. When using OBMC, blocks are typically twice as big in each dimension and overlap quadrant-wise with all 8 neighbouring blocks. Thus, each pixel belongs to 4 blocks. In such a scheme, there are 4 predictions for each pixel which are summed up to a weighted mean. For this purpose, blocks are associated with a window function that has the property that the sum of 4 overlapped windows is equal to 1 everywhere.

Studies of methods for reducing the complexity of OBMC have shown that the contribution to the window function is smallest for the diagonally-adjacent block. Reducing the weight for this contribution to zero and increasing the other weights by an equal amount leads to a substantial reduction in complexity without a large penalty in quality. In such a scheme, each pixel then belongs to 3 blocks rather than 4, and rather than using 8 neighboring blocks, only 4 are used for each block to be compensated. Such a scheme is found in the H.263 Annex F Advanced Prediction mode

Quarter Pixel (QPel) and Half Pixel motion compensation
In motion compensation, quarter or half samples are actually interpolated sub-samples caused by fractional motion vectors. Based on the vectors and full-samples, the sub-samples can be calculated by using bicubic or bilinear 2-D filtering. See subclause 8.4.2.2 "Fractional sample interpolation process" of the H.264 standard.

3D image coding techniques
Motion compensation is utilized in stereoscopic video coding.

In video, time is often considered as the third dimension. Still, image coding techniques can be expanded to an extra dimension.

JPEG 2000 uses wavelets, and these can also be used to encode motion without gaps between blocks in an adaptive way. Fractional pixel affine transformations lead to bleeding between adjacent pixels. If no higher internal resolution is used the delta images mostly fight against the image smearing out. The delta image can also be encoded as wavelets, so that the borders of the adaptive blocks match.

2D+Delta Encoding techniques utilize H.264 and MPEG-2 compatible coding and can use motion compensation to compress between stereoscopic images.

History
A precursor to the concept of motion compensation dates back to 1929, when R.D. Kell in Britain proposed the concept of transmitting only the portions of an analog video scene that changed from frame-to-frame. In 1959, the concept of inter-frame motion compensation was proposed by NHK researchers Y. Taki, M. Hatori and S. Tanaka, who proposed predictive inter-frame video coding in the temporal dimension.

Motion-compensated DCT
Practical motion-compensated video compression emerged with the development of motion-compensated DCT (MC DCT) coding, also called block motion compensation (BMC) or DCT motion compensation. This is a hybrid coding algorithm, which combines two key data compression techniques: discrete cosine transform (DCT) coding in the spatial dimension, and predictive motion compensation in the temporal dimension. DCT coding is a lossy block compression transform coding technique that was first proposed by Nasir Ahmed, who initially intended it for image compression, in 1972.

In 1974, Ali Habibi at the University of Southern California introduced hybrid coding, which combines predictive coding with transform coding. However, his algorithm was initially limited to intra-frame coding in the spatial dimension. In 1975, John A. Roese and Guner S. Robinson extended Habibi's hybrid coding algorithm to the temporal dimension, using transform coding in the spatial dimension and predictive coding in the temporal dimension, developing inter-frame motion-compensated hybrid coding. For the spatial transform coding, they experimented with the DCT and the fast Fourier transform (FFT), developing inter-frame hybrid coders for both, and found that the DCT is the most efficient due to its reduced complexity, capable of compressing image data down to 0.25-bit per pixel for a videotelephone scene with image quality comparable to an intra-frame coder requiring 2-bit per pixel.

In 1977, Wen-Hsiung Chen developed a fast DCT algorithm with C.H. Smith and S.C. Fralick. In 1979, Anil K. Jain and Jaswant R. Jain further developed motion-compensated DCT video compression, also called block motion compensation. This led to Chen developing a practical video compression algorithm, called motion-compensated DCT or adaptive scene coding, in 1981. Motion-compensated DCT later became the standard coding technique for video compression from the late 1980s onwards.

The first digital video coding standard was H.120, developed by the CCITT (now ITU-T) in 1984. H.120 used motion-compensated DPCM coding, which was inefficient for video coding, and H.120 was thus impractical due to low performance. The H.261 standard was developed in 1988 based on motion-compensated DCT compression, and it was the first practical video coding standard. Since then, motion-compensated DCT compression has been adopted by all the major video coding standards (including the H.26x and MPEG formats) that followed.

Applications

 * video compression
 * change of framerate for playback of 24 frames per second movies on 60 Hz LCDs or 100 Hz interlaced cathode ray tubes

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Motion compensation


text:
Istria

Istria (Croatian and Slovene: Istra; Italian and Venetian: Istria) is a region of Croatia, and is the largest peninsula to border the Adriatic Sea. The peninsula is located at the head of the Adriatic between the Gulf of Trieste and the Kvarner Gulf, and is shared by three countries: Croatia, Slovenia, and Italy, 87% of its area being part of Croatia. Croatia encapsulates most of the Istrian peninsula within Istria County.

Geography
The geographical features of Istria include the Učka/Monte Maggiore mountain range, which is the highest portion of the Ćićarija/Cicceria mountain range; the rivers Dragonja/Dragogna, Mirna/Quieto, Pazinčica, and Raša; and the Lim/Canale di Leme bay and valley. Istria lies in three countries: Croatia, Slovenia and Italy. By far the largest portion (89%) lies in Croatia. "Croatian Istria" is divided into two counties, the larger being Istria County in western Croatia. Important towns in Istria County include Pula/Pola, Poreč/Parenzo, Rovinj/Rovigno, Pazin/Pisino, Labin/Albona, Umag/Umago, Motovun/Montona, Buzet/Pinguente, and Buje/Buie. Smaller towns in Istria County include Višnjan/Visignano, Roč/Rozzo, and Hum/Colmo.

The northwestern part of Istria lies in Slovenia: it is known as Slovenian Istria, and includes the coastal municipalities of Piran/Pirano, Izola/Isola, and Koper/Capodistria. It also includes the Karstic municipality of Hrpelje-Kozina/Erpelle-Cosina.

Northwards of Slovenian Istria, there is a tiny portion of the peninsula that lies in Italy. This smallest portion of Istria consists of the comunes of Muggia/Milje and San Dorligo della Valle/Dolina with Santa Croce (Trieste) lying farthest to the north.

The ancient region of Histria extended over a much wider area, including the whole Karst Plateau with the southern edges of the Vipava Valley/Vipacco Valley, the southwestern portions of modern Inner Carniola with Postojna/Postumia and Ilirska Bistrica/Bisterza, and the Italian Province of Trieste, but not the Liburnian coast which was already part of Illyricum.

Name
The name Istria (Ἰστρία) is derived from the river Ister (Ἴστρος) (modern Danube), because the Greeks erroneously believed, at the very early period, that one branch or arm of the Danube flowed into the Adriatic sea in that area. In addition, the Greeks called the inhabitants of the area Histri (Ἴστροι) and if this was their native name, it may have initially led the Greeks to assume their connection with the river Ister.

Early history
The name is derived from the Histri (Ἱστρών έθνος) tribes, which Strabo refers to as living in the region and who are credited as being the builders of the hillfort settlements (castellieri). The Histri are classified in some sources as a "Venetic" Illyrian tribe with certain linguistic differences from other Illyrians. The Romans described the Histri as a fierce tribe of pirates, protected by the difficult navigation of their rocky coasts. It took two military campaigns for the Romans to finally subdue them in 177 BC. The region was then called together with the Venetian part the X. Roman Region of "Venetia et Histria", the ancient definition of the northeastern border of Italy. Dante Alighieri refers to it as well, the eastern border of Italy per ancient definition is the river Arsia. The eastern side of this river was settled by people whose culture was different from Histrians. Earlier influence of the Iapodes was attested there, while at some time between the 4th and 1st century BC the Liburnians extended their territory and it became a part of Liburnia. On the northern side, Histria extended much further north and included the Italian city of Trieste.

Some scholars speculate that the names Histri and Istria are related to the Latin name Hister, or Danube (especially its lower course). Ancient folktales reported —inaccurately— that the Danube split in two or "bifurcated" and came to the sea near Trieste as well as at the Black Sea. The story of the "bifurcation of the Danube" is part of the Argonaut legend. There is also a suspected link (but no historical documentation in support of it) to the commune of Istria in Constanța, Romania which is named after the ancient city Histria, named after River Hister.

In the Early Middle Ages, Istria was conquered and occupied by the Goths. Ostrogoth coins were found in Istria, as well as the remains of some buildings. South of Poreč there are the remains of the church of Sv. Petar, erected in the 5th century (with a baptistery added later), which reportedly served the Arian eastern Goths ruling Istria. Most notably, the Goths used Istrian stone to build their best known monument, the Mausoleum of Theodoric in Ravenna. In the following centuries, the peninsula was attacked and conquered by the Lombards, often in conjunction with the Slavs, such as in 601. However, the extent to which the Lombards occupied Istria is a matter of debate. After the Goths, Istria became part of the Exarchate of Ravenna. Gulfaris, who served the Byzantines but was of Lombard descent, is reported as its dux in 599.

Pope Gregory I in 600 wrote to bishop of Salona Maximus in which he expresses concern about arrival of the Slavs, "Et quidem de Sclavorum gente, quae vobis valde imminet, et affligor vehementer et conturbor. Affligor in his quae jam in vobis patior; conturbor, quia per Istriae aditum jam ad Italiam intrare coeperunt" (And as for the people of the Slavs who are really approaching you, I am very depressed and confused. I am depressed because I sympathize with you, confused because they over the Istria began to enter the Italy). Some ancient reporters, including Pope Gregory, who were unaware of the importance of the Avars in the Balkans, used the terms "Slavs" to refer to the Avars or the Avaro-Slavs.

After the fall of the Western Roman Empire, the region was pillaged by the Goths, the Eastern Roman Empire, and the Avars.

The first Avaro-Slavic invasion of Istria was recorded in 599. Another major incursion occurred around 600-602, in which all of Istria was devastated with fire and rapine. This was followed by the 611 invasion, the most devastating for the peninsula. It remains unclear when and how the first Slavic settlement occurred. Traces of early Slavic incursions and settlement are scarce. A few Avar findings have been discovered on the Istrian territory, chiefly around Nesactium. By 642 the Slavs were settled in the peninsula, as indicated by the mission of an abbot Martin, sent by Pope John IV to rescue captives held by the pagans in Istria and Dalmatia.

After the barbaric invasions, the western part of Istria was annexed to the Lombard Kingdom in 751, and then annexed to the Frankish kingdom by Pepin of Italy in 789. In 804, the Placitum of Riziano was held in the Parish of Rižan (Risanum), which was a meeting between the representatives of Istrian towns and castles and the deputies of Charlemagne and his son Pepin. The report about this judicial diet illustrates the changes accompanying the transfer of power from the Eastern Roman Empire to the Carolingian Empire and the discontent of the local residents.

Afterwards it was successively controlled by the dukes of Carantania, Merania, Bavaria and by the patriarch of Aquileia, before it became the territory of the Republic of Venice in 1267. The medieval Croatian kingdom held only the far eastern part of Istria (the border was near the river Raša), but they lost it to the Holy Roman Empire in the late 11th century.

Venetian Republic

The coastal areas and cities of Istria came under Venetian Influence in the 9th century. On 15 February 1267, Parenzo was formally incorporated with the Venetian state. Other coastal towns followed shortly thereafter. Bajamonte Tiepolo was sent away from Venice in 1310, to start a new life in Istria after his downfall. A description of the 16th-century Istria with a precise map was prepared by the Italian geographer Pietro Coppo. A copy of the map inscribed in stone can now be seen in the Pietro Coppo Park in the center of the town of Izola in southwestern Slovenia.

Habsburg Monarchy (1797–1805)
The Inner part of Istria around Mitterburg (Pazin) had been part of the Holy Roman Empire for centuries, and more specifically part of the domains of the Austrian Habsburgs since the 14th century. In 1797, with the Treaty of Campo Formio, the Venetian parts of the peninsula also passed to the Habsburg monarchy which became the Austrian Empire in 1804.

Napoleonic Era (1805–1814)
The French victory of 1809 compelled Austria to cede a portion of its South Slav lands to France. Napoleon combined Istira, Carniola, western Carinthia, Gorica (Gorizia), Trieste. and parts of Croatia, Dalmatia, and Dubrovnik to form the Illyrian Provinces. The Code Napoléon was introduced, and roads and schools were constructed. Local citizens were given administrative posts, and native languages were used to conduct official business. This sparked the Illyrian Movement for the cultural and linguistic unification of South Slavic lands. From the Middle Ages to the 19th century, Italian and Slavic communities in Istria had lived peacefully side by side because they did not know the national identification, given that they generically defined themselves as "Istrians" of "Romance" or "Slavic" culture.

Austrian Empire (1814–1918)

After this seven-year period, the Austrian Empire regained Istria, which became part of the constituent Kingdom of Illyria. This kingdom was broken up in 1849, after which Istria formed part of Austrian Littoral, also known as the "Küstenland", which also included the city of Trieste and the Princely County of Gorizia and Gradisca until 1918. At that time the borders of Istria included part of what is now Italian Venezia-Giulia and parts of modern-day Slovenia and Croatia, but not the city of Trieste.

Many Istrian Italians looked with sympathy towards the Risorgimento movement that fought for the unification of Italy. However, after the Third Italian War of Independence (1866), when the Veneto and Friuli regions were ceded by the Austrians to the newly formed Kingdom Italy, Istria remained part of the Austro-Hungarian Empire, together with other Italian-speaking areas on the eastern Adriatic. This triggered the gradual rise of Italian irredentism among many Italians in Istria, who demanded the unification of Istria with Italy. The Italians in Istria supported the Italian Risorgimento: as a consequence, the Austrians saw the Italians as enemies and favored the Slav communities of Istria, fostering the nascent nationalism of Slovenes and Croats.

During the meeting of the Council of Ministers of 12 November 1866, Emperor Franz Joseph I of Austria outlined a wide-ranging project aimed at the Germanization or Slavization of the areas of the empire with an Italian presence:

"His Majesty expressed the precise order that action be taken decisively against the influence of the Italian elements still present in some regions of the Crown and, appropriately occupying the posts of public, judicial, masters employees as well as with the influence of the press, work in South Tyrol, Dalmatia and Littoral for the Germanization and Slavization of these territories according to the circumstances, with energy and without any regard. His Majesty calls the central offices to the strong duty to proceed in this way to what has been established."

There are some claims, Istrian Italians were more than 50% of the total population of Istria for centuries, while making up about a third of the population in 1900. With its strategic position at the southern tip of the peninsula and good harbor Pula was the primary base of the Austrian Navy.

A limited tension with the Austrian state did not in fact stop the rise of the use of the Italian language, in the second part of the 19th century, when the population of predominantly Italian-speaking towns in Istria had a significant rise: in the part of Istria that eventually became part of Croatia, the first Austrian census from 1846 found 34 thousand Italian speakers, alongside 120 thousand Croatian speakers (in the Austrian censuses, the ethnic composition of the population was not surveyed, only the main "language of use" of a person). By 1910, the proportion changed significantly: there were 108 thousand Italian speakers and 134 thousand Croatian speakers. Vanni D'Alessio notes (2008), the Austrian surveys of the language of use "overestimated the diffusion of the socially dominant languages of the empire... The capacity of assimilation of the Italian language suggests that amongst those who declared themselves Italian speakers in Istria, there were people whose mother tongue was different." D'Alessio notes even members of the Austrian state bureaucracy and the members of their families with the German mother tongue tended to use Italian, after living in Istrian small towns long enough. The Poles, Czechs and Slovenes and Croats tended to join the "Slav" social group.

Italy (1919–1947)
Although a member of the Central Powers, Italy remained neutral at the start of WWI, and soon launched secret negotiations with the Triple Entente, bargaining to participate in the war on its side, in exchange for significant territorial gains. To get Italy to join the war, the secret 1915 Treaty of London the Entente promised Italy Istria and parts of Dalmatia, South Tyrol, the Greek Dodecanese Islands, parts of Albania and Turkey, plus more territory for Italy's North Africa colonies.

After the war, Italy annexed Istria. Istria's political and economic importance declined under Italian rule, and after the fascist takeover of Italy in 1922 the Italian government began a campaign of forced Italianization. In 1926, the use of Slavic languages in schools and government was banned, even Slavic family names were Italianized to suit the fascist authorities. Slavic newspapers and libraries were closed, all Slavic cultural, sporting, business and political associations were banned. As a result, 100,000 Slavic-speakers left Italian-annexed areas in an exodus, moving mostly to Yugoslavia.

The organization TIGR, founded in 1927 by young Slovene liberal nationalists from Gorizia region and Trieste and regarded as the first armed antifascist resistance group in Europe soon penetrated into Slovene and Croatian-speaking parts of Istria.

In World War II, Istria became a battleground of competing ethnic and political groups. Istrian nationalist groups which were pro-fascist and pro-Allied and Yugoslav-supported pro-communist groups fought with each other and the Italian army. After the German withdrawal in 1945, Yugoslav partisans gained the upper hand and began a violent purge of real or suspected opponents in an "orgy of revenge".

SFR Yugoslavia (1947–1991)
After the end of World War II, Istria was ceded to Yugoslavia, except for a small part in the northwest corner that formed Zone B of the provisionally independent Free Territory of Trieste; Zone B was under Yugoslav administration and after the de facto dissolution of the Free Territory in 1954 it was also incorporated into Yugoslavia. Only the small town of Muggia, near Trieste, being part of Zone A remained with Italy. The events of the period are visible in Pula. The city, located on the southernmost tip of the Istrian peninsula, had an Istrian Italian majority. Between December 1946 and September 1947, a large proportion of the city's inhabitants were forced to emigrate to Italy. Most of them left in the immediate aftermath of the signing of the Paris Peace Treaty on February 10, 1947 which granted Pula and the greater part of Istria to Yugoslavia.

After the breakup of Yugoslavia (after 1991)
The division of Istria between Croatia and Slovenia runs on the former republic borders, which were not precisely defined in the former Yugoslavia. Various points of contention remain unresolved between the two countries regarding the precise line of the border.

It became an international boundary with the independence of both countries from Yugoslavia in 1991. Since Croatia's first multi-party elections in 1990, the regionalist party Istrian Democratic Assembly (IDS-DDI, Istarski demokratski sabor or Dieta democratica istriana) has consistently received a majority of the vote and maintained through the 1990s a position often contrary to the government in Zagreb, led by the then nationalistic party Croatian Democratic Union (HDZ, Hrvatska demokratska zajednica), with regards to decentralization in Croatia and certain facets of regional autonomy. The Istrian regionalist movement is known as Istrianism.

However, that changed in 2000 when the IDS formed with five other parties a left-centre coalition government, led by the Social Democratic Party of Croatia (SDP, Socijaldemokratska Partija Hrvatske). After the reformed HDZ won the Croatian parliamentary elections in late 2003 and formed a minority government, the IDS has cooperated with the state government on many projects, both local (in Istria County) and national. Since Slovenia's accession to the European Union and the Schengen Area, customs and immigration checks have been abolished at the Italian-Slovenian border.

Demographic history
The region has traditionally been ethnically mixed. Under Austrian rule in the 19th century it included a large population of Italians, Croats, and Slovenes as well as some Istro-Romanians, Serbs, and Montenegrins; however, official statistics in those times did not show those nationalities as they do today.

In 1910, the ethnic and linguistic composition was completely mixed. According to the Austrian census results, out of 404,309 inhabitants in Istria, 168,116 (41.6%) spoke Serbo-Croatian, 147,416 (36.5%) spoke Italian, 55,365 (13.7%) spoke Slovene, 13,279 (3.3%) spoke German, 882 (0.2%) spoke Istro-Romanian, 2,116 (0.5%) spoke other languages, and 17,135 (4.2%) were non-citizens, which had not been asked for their language of communication. During the last decades of the Habsburg dynasty the coast of Istria profited from tourism within the Empire. Generally speaking, Italians lived on the western coast and in the inland cities of northern Istria, while Croats lived on the eastern coast and in the eastern and southeastern inland parts of the countryside.

In the second half of the 19th century a clash of new ideological movements, Italian irredentism (which claimed Trieste and Istria), Slovene nationalism, and Croatian nationalism (developing individual identities in some quarters while seeking to unite in a Southern Slav identity in others) resulted in growing ethnic conflict between Italians on one side and Slovenes and Croats on the other side. This was intertwined with class conflict, as inhabitants of Istrian towns were mostly Italian, while Croats and Slovenes largely lived out in the eastern countryside.

The Croatian word for the Istrians is Istrani, or Istrijani, the latter being in the local Chakavian dialect. The term Istrani is also used in Slovenia. The Italian word for the Istrians is Istriani and today the Italian minority is organized in many towns. The Istrian county in Croatia is bilingual, as are large parts of Slovenian Istria. Every citizen has the right to speak either Italian or Croatian (Slovene in Slovenian Istria and Italian in the town of Koper/Capodistria, Piran/Pirano, Portorož/Portorose, and Izola/Isola d'Istria) in public administration or in court. Furthermore, Istria is a supranational European Region that includes Italian, Slovenian and Croatian Istria.

Ethnicity
Discussions about Istrian ethnicity often use the words "Italian", "Croatian", and "Slovene" to describe the character of the Istrian people. However these terms are best understood as "national affiliations" that may exist in combination with or independently of linguistic, cultural and historical attributes. In the Istrian context, for example, the word "Italian" can just as easily refer to autochthonous speakers of the Venetian language whose antecedents in the region extend before the inception of the Venetian Republic or to the Istriot language the oldest spoken language in Istria, dated back to the Romans, today spoken in the southwest of Istria. It can also refer to Istrian Croats who adopted the veneer of Italian culture as they moved from rural to urban areas, or from the farms into the bourgeoisie.

Similarly, national powers claim Istrian Croats according to local language, so that speakers of Čakavian and Štokavian dialects of Croatian are considered to be Croatians while speakers of other dialects may be considered to be Slovene. Croatian dialect speakers are descendants of the refugees of the Turkish invasion and Ottoman Empire of Bosnia and Dalmatia in the 16th century.

The government of the Republic of Venice had settled them in Inner Istria, which had been devastated by wars and plague. As with other regions, the local dialects of the Croatian communities vary greatly across close distances. The Istrian Croatian and Italian vernaculars had both developed for many generations before being divided as they are today. This meant that Croats/Slovenes on the one side and Venetians/other Italians on the other side yielded to each other culturally while simultaneously distancing themselves from members of their ethnic groups living farther away.

Another important Istrian community are the Istro-Romanians in the south and north of the Učka mountain range of Istria. A small Albanian community, which until the late 19th century spoke the Istrian Albanian dialect is also present in the peninsula.

Austro-Hungarian census
According to Austro-Hungarian censuses, which recorded language instead of ethnicity, the composition of Istria (i.e. the Habsburg Magraviate of Istria) was as follows (in thousands):

Recent census
The 2001 population census in Croatia counted 23 languages spoken by the people of Istria. In 2021 Census show that 76.40% are Croats, Italians were 5.01%, 2.96% were Serbs, 2.48% Bosniaks, 1.05% were Albanians, while regionally declared were 5.13%.

The data for Slovenian Istria is not as neatly organized, but the 2002 Slovenian census indicates that the four Istrian municipalities (Izola/Isola d'Istria, Piran/Pirano, Koper/Capodistria, Ankaran/Ancarano) had a total of 56,482 Slovenes, 6,426 Croats, and 2,800 Italians.

The small town of Peroj has had a unique history which exemplifies the multi-ethnic complexity of the history of the region, as do some villages on both sides of the Učka that are still identified with the Istro-Romanian people which the UNESCO Redbook of Endangered Languages calls "the smallest ethnic group in Europe".

Major towns and municipalities of Istria
This list includes towns and municipalities of Istria with populations estimated to be higher than 8,000 people.

 * Koper/Capodistria
 * Pula/Pola
 * Poreč/Parenzo
 * Rovinj/Rovigno
 * Izola/Isola
 * Umag/Umago
 * Muggia/Milje
 * Labin/Albona
 * Pazin/Pisino

title: Istria


text:
Cylinder (disambiguation)

A cylinder is a basic curvilinear geometric shape.

Cylinder may also refer to:

 * Cylinder (algebra), the Cartesian product of a set with its superset
 * Cylinder (disk drive), a division of data in a disk drive
 * Cylinder (engine), the space in which a piston travels in an engine
 * Cylinder (firearms), the rotating part of a revolver containing multiple chambers
 * Cylinder (gastropod), a subgenus of sea snails
 * Cylinder (locomotive), the components that convert steam power into motion
 * Cylinder (optometry)
 * Cylinder, Iowa, a city in Palo Alto County, Iowa, United States
 * Cylinder set, a natural basic set in product spaces
 * Cylinder set measure, a way to generate a measure over product spaces
 * Gas cylinder, a high-strength container for storing gases at high pressure
 * Phonograph cylinder, the earliest commercial medium for recording and reproducing sound

title: Cylinder (disambiguation)