Introduction
option U-- referred to as enhanced reference frame selection, it can provide enhanced coding efficiency and regeneration channel errors (particularly in the case of packet loss), it is necessary design of multi buffer for storing multiple reference frame image.
V-- referred option data piece, which can provide enhanced error resilience (particularly where the local data during transmission disrupted) by separating the video code stream DCT the head coefficient and the motion vector data, encoded using reversible protection mode motion vectors.
W-- option to add supplementary information H263 + code stream to ensure backward compatibility enhanced, the additional information comprising: an IDCT indication point, image information and the information type employed, arbitrary binary data , text, repeated picture header, indicating the alternating field, the reference frame identification sparse. H.264 video coding standard
Details
H.263 is a standard ITU draft of ITU-T, for the low bit rate communication is designed. But in fact this standard can be used in a wide range of code stream, and not just for low bit rate applications, in many applications it may be considered to be substituted with H.261. H.263 and H.261 coding algorithm is the same, but made some improvements and changes to improve performance and error correction capability. .263 standard can be provided at a low bit rate than the H.261 better image quality, the difference are: (1) H.263 motion compensation using a half-pixel accuracy, but with the full-pixel H.261 accuracy and loop filter; certain parts of the hierarchy (2) the data flow is optional in H.263, the codec may be configured such that a lower data rate or a better error correction capability; (3) H. 263 contains four options may negotiate to improve performance; (4) H.263 uses an unrestricted motion vectors and syntax-based arithmetic coding; (5) prior to the prediction and PB-frames in MPEG frame prediction method of the same; (6) H.263 supports five kinds of resolution, i.e., in addition to supporting H.261 CIF and QCIF are supported, but also support SQCIF, 4CIF and 16CIF, SQCIF corresponding to half the QCIF resolution, 4CIF and are 16CIF CIF 4 times and 16 times.
launched in 1998 IUT-T recommendation H.263 to H.263 + is version 2, which provides 12 new negotiable mode and other features further improving compression coding performance. Only five kinds such as H.263 video source format, allowing the use of more H.263 + source format, picture clock frequency have many options, broaden the scope of application; Another important improvement is extensibility, which allows multi-display rate , multi-rate and multi-resolution, enhanced video error-prone, easy to packet loss transmission in heterogeneous network environments. Further, in H.263 to H.263 + unrestricted motion vector mode was improved, plus 12 additional optional mode, not only improve the coding performance, but also enhances the application flexibility. H.263 has largely replaced H.261.