[FFmpeg-devel] [PATCH] g722 decoder, no licensing fame

[Kenan Gillet]

On Apr 4, 2009, at 12:06 PM, Kenan Gillet wrote:

> Hi
> On Apr 4, 2009, at 11:46 AM, Kenan Gillet wrote:
>>
>> On Apr 3, 2009, at 9:42 PM, Michael Niedermayer wrote:
>>
>>> On Tue, Mar 31, 2009 at 11:34:34PM -0700, Kenan Gillet wrote:
>
> [...]
>>>> +/**
>>>> + * adaptive predictor
>>>> + *
>>>> + * @note On x86 using the MULL macro in a loop is slower than  
>>>> not using the macro.
>>>> + */
>>>> +static void do_adaptive_prediction(struct G722Band *band, const  
>>>> int cur_diff)
>>>> +{
>>>> +    int sg[2], limit, i, cur_part_reconst;
>>>> +
>>>> +    band->qtzd_reconst_mem[1] = band->qtzd_reconst_mem[0];
>>>> +    band->qtzd_reconst_mem[0] = av_clip_int16((band->s_predictor  
>>>> + cur_diff) << 1);
>>>> +
>>>> +    cur_part_reconst = band->s_zero + cur_diff < 0;
>>>> +
>>>> +    sg[0] = sign_lookup[cur_part_reconst != band- 
>>>> >part_reconst_mem[0]];
>>>> +    sg[1] = sign_lookup[cur_part_reconst == band- 
>>>> >part_reconst_mem[1]];
>>>
>>> i dont see why a LUT should be used here, its not really more  
>>> readable
>>> and i doubt its faster.
>>
>> it is faster
>>
>> on Core 2 Duo 2Ghz , gcc 4.2.1
>> LUT based:
>> testing for 64kb 16KHz: [OK][ 1574 dezicycles in  
>> do_adaptive_prediction, 262130 runs, 14 skips ]
>> testing for 56kb 16KHz: [OK][ 1668 dezicycles in  
>> do_adaptive_prediction, 262110 runs, 34 skips ]
>> testing for 48kb 16KHz: [OK][ 1607 dezicycles in  
>> do_adaptive_prediction, 262112 runs, 32 skips ]
>> testing for 64Kb  8KHz: [OK][ 1584 dezicycles in  
>> do_adaptive_prediction, 131066 runs, 6 skips ]
>> testing encoding for 64Kb  16KHz: [OK][ 1558 dezicycles in  
>> do_adaptive_prediction, 262108 runs, 36 skips ]
>>
>>
>> non-LUT:
>> testing for 64kb 16KHz: [OK][ 1686 dezicycles in  
>> do_adaptive_prediction, 262126 runs, 18 skips ]
>> testing for 56kb 16KHz: [OK][ 1719 dezicycles in  
>> do_adaptive_prediction, 262107 runs, 37 skips ]
>> testing for 48kb 16KHz: [OK][ 1689 dezicycles in  
>> do_adaptive_prediction, 262126 runs, 18 skips ]
>> testing for 64Kb  8KHz: [OK][ 1676 dezicycles in  
>> do_adaptive_prediction, 131065 runs, 7 skips ]
>> testing encoding for 64Kb  16KHz: [OK][ 1673 dezicycles in  
>> do_adaptive_prediction, 262116 runs, 28 skips ]
>>
>> i can revert to non-LUT if you prefer
>
> sorry for the noise, it though the comment was about using the sg  
> array not just the lookup table.
> remove the use of the lookup table locally

I knew I should not have answered before benchmarking,
conter intuitive but the LUT is still faster
with LUT:
testing for 64kb 16KHz: [OK][ 1575 dezicycles in  
do_adaptive_prediction, 262113 runs, 31 skips ]
testing for 56kb 16KHz: [OK][ 1663 dezicycles in  
do_adaptive_prediction, 262131 runs, 13 skips ]
testing for 48kb 16KHz: [OK][ 1608 dezicycles in  
do_adaptive_prediction, 262117 runs, 27 skips ]
testing for 64Kb  8KHz: [OK][ 1583 dezicycles in  
do_adaptive_prediction, 131066 runs, 6 skips ]
testing encoding for 64Kb  16KHz: [OK][ 1558 dezicycles in  
do_adaptive_prediction, 262117 runs, 27 skips ]


without LUT:
testing for 64kb 16KHz: [OK][ 1672 dezicycles in  
do_adaptive_prediction, 262138 runs, 6 skips ]
testing for 56kb 16KHz: [OK][ 1713 dezicycles in  
do_adaptive_prediction, 262087 runs, 57 skips ]
testing for 48kb 16KHz: [OK][ 1685 dezicycles in  
do_adaptive_prediction, 262125 runs, 19 skips ]
testing for 64Kb  8KHz: [OK][ 1683 dezicycles in  
do_adaptive_prediction, 131065 runs, 7 skips ]
testing encoding for 64Kb  16KHz: [OK][ 1652 dezicycles in  
do_adaptive_prediction, 262138 runs, 6 skips ]


Kenan