H.264句法和语法总结（十四）CAVLC 残差句法

来源：互联网发布：长春java培训编辑：程序博客网时间：2024/05/16 14:21

转载地址：

http://blog.csdn.net/tanningzhong/article/details/52415865

residual_block_cavlc( coeffLevel, maxNumCoeff ) { C      Descriptor
    for( i = 0; i < maxNumCoeff; i++ )
        coeffLevel[ i ] = 0
    // coeff_token      指明了非零系数的个数，拖尾系数的个数。
    coeff_token
    if( TotalCoeff( coeff_token ) > 0 ) {
        if( TotalCoeff( coeff_token ) > 10    &&    TrailingOnes( coeff_token ) <
3 )
            suffixLength = 1
        else
            suffixLength = 0
        for( i = 0; i < TotalCoeff( coeff_token ); i++ )
            if( i < TrailingOnes( coeff_token ) ) {
                // trailing_ones_sign_flag 拖尾系数的符号
                    -     如果trailing_ones_sign_flag = 0, 相应的拖尾系数是+1。
                    -     否则，trailing_ones_sign_flag =1，相应的拖尾系数是-1。
                trailing_ones_sign_flag
                level[ i ] = 1 – 2 * trailing_ones_sign_flag
            } else {
                // level_prefix and level_suffix 非零系数值的前缀和后缀。
                level_prefix
                levelCode = ( level_prefix << suffixLength )
                if( suffixLength > 0    | |    level_prefix >= 14 ) {
                    level_suffix
                    levelCode += level_suffix
                }
                if( level_prefix    = =    15    &&    suffixLength    = =    0 )
                    levelCode += 15
                if( i    = =    TrailingOnes( coeff_token )    &&
                      TrailingOnes( coeff_token ) < 3 )
                    levelCode += 2
                if( levelCode % 2    = =    0 )
                    level[ i ] = ( levelCode + 2 ) >> 1
                else
                    level[ i ] = ( –levelCode – 1 ) >> 1
                if( suffixLength    = =    0 )
                    suffixLength = 1
                if( Abs( level[ i ] )    >    ( 3 << ( suffixLength – 1 ) )    &&
                      suffixLength < 6 )
                    suffixLength++
            }
        if( TotalCoeff( coeff_token ) < maxNumCoeff ) {
            // total_zeros    系数中 0 的总个数。
            total_zeros
            zerosLeft = total_zeros
        } else
            zerosLeft = 0
        for( i = 0; i < TotalCoeff( coeff_token ) – 1; i++ ) {
            if( zerosLeft > 0 ) {

                run_before
                run[ i ] = run_before
            } else
                run[ i ] = 0
            zerosLeft = zerosLeft – run[ i ]
        }
        run[ TotalCoeff( coeff_token ) – 1 ] = zerosLeft
        coeffNum = -1
        for( i = TotalCoeff( coeff_token ) – 1; i >= 0; i-- ) {
            coeffNum += run[ i ] + 1
            coeffLevel[ coeffNum ] = level[ i ]
        }
    }
}

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