[Mp4-tech] H264 Please help me about the CAVLC of H.264

[tetsuo kosuge]

Hallo  Bill.
Level[i] derives as follows(detail shows H.264 standard 7.3.5.3.1).
Level (1) : 
 level_prefix = 0 (prefix-code  1);
 levelCode = (Min(15,level_prefix)<<suffixLength) = 0;
 ....
 if(levelCode%2 == 0)
    Level(1) = (levelCode+2)>>1 = 1;
 ...
Level (0) : 
 level_prefix = 2(prefix-code  001);
 levelCode = (Min(15,level_prefix)<<suffixLength) = 4;
 level_suffix = 0 (level_suffix-code 0);
 levelCode += level_suffix -> 4;
 ....
 if(levelCode%2 == 0)
    Level(0) = (levelCode+2)>>1 = 3;
 ...
Thanks 
Regards.
>Dear All,
>
>Please help me on CAVLC of H.264.
>
>I am reading the book, H.264 and MPEG-4 Video Compression Video Coding for Next-generation Multimedia,
>by Iain E. G. Richardson, about the CAVLC parts of H.264 at page 204, the book shows the following example:
>
>Reordered block:
>0,3,0,1,-1,-1,0,1,0. . .
>
>TotalCoeffs = 5 (indexed from highest frequency, 4, to lowest frequency, 0)
>total zeros = 3
>TrailingOnes = 3 (in fact there are four trailing ones but only three can be encoded as a 壮pecial
>case・
>
>
>
>Encoding:
>
>Element                     Value                                             Code
>-----------------------------------------------------------------------------------------
>coeff token         TotalCoeffs = 5,                             0000100
>                            TrailingOnes= 3 (use Table 1)
>TrailingOne sign (4)      +                                             0
>TrailingOne sign (3)      -                                              1
>TrailingOne sign (2)      -                                              1
>Level (1)             +1 (use suffixLength = 0)                 1 (prefix)
>Level (0)             +3 (use suffixLength = 1)                 001 (prefix) 0 (suffix)
>total zeros             3                                   111
>run before(4)         ZerosLeft = 3; run before =1          10
>run before(3)         ZerosLeft = 2; run before =0         1
>run before(2)         ZerosLeft = 2; run before =0         1
>run before(1)         ZerosLeft = 2; run before =1         01
>run before(0)         ZerosLeft = 1; run before = 1     No code required;
>last coefficient.
>The transmitted bitstream for this block is 000010001110010111101101.
>
>
>But I cannot understand the level(1) and level(0), how to get the prefix code value and suffix value? I look up the 
table of level_prefix, if value is 3, I can get the code of 0001, why does the example show me the 001 as code? 
>Why the suffix value is 0? why not 1? does that means 0 for +3, and 1 for -3?
>
>Thanks
>
>Regards.
>
>Bill.
>______________________________________________________________________
>
>_______________________________________________
>NOTE: Please use clear subject lines for your posts. Include [audio, [video], [systems], [general] or another 
apppropriate identifier to indicate the type of question you have.
>
>Note: Conduct on the mailing list is subject to the Antitrust guidelines found at 
http://www.mpegif.org/public/documents/vault/mp-out-30042-Antitrust.php
-------------------------------------------
小菅	哲夫（こすげ　てつお)
三洋電機（株）　半導体カンパニー　
システムソリューション統括BU デジタルソリューション第一BU
デジタル映像開発部
TEL	048-529-7216(4734)
FAX	048-529-7229