|WikiProject Computing / Software|
Technical Details. Entropy Coding seems wrong.
The article says, that in Class50 only CABAC can be used. This seems to be wrong. The SMPTE Recommended Practice 2027-2007 only recommends to use CABAC for Class50 and CAVLC for Class100, see Annex B for details. RP actually does allow any of entropy coding for both classes, for example: "In addition, specific applications where higher complexity, such as high performance processing, justifies using CABAC to achieve higher picture quality, CABAC might be selected for the Class 100 specification.".
You are right about SMPTE-RP. AVC-Intra could use CABAC for 100 class, but Panasonic chose not to do so. This info used to be in Panasonic's whitepaper, but they appear to have simplified the document. If you check out page 7 of the previous version, still available here: http://www.serv.com.ua/img/zstored/File/AVC_Intra_White_Paper_Ver_1_3.pdf you will find the following;
"The AVC-I CODEC utilizes CABAC for increased efficiency at the 50 Mb/s bit rate. At lower bit rates, hence higher compression, CABAC provides significantly better compression efficiency than would CAVLC. Indeed as a result of data from numerous test sequences, CABAC has been shown to reduce the bit rate 20～30% more than CAVLC for the 50Mbps of AVC-I compression. For less compressed, higher bit rate images, CABAC’s efficiency benefit lessens, hence at the AVC-I 100Mb/s level we chose to use CAVLC."