Re: [FFmpeg-devel] [RFC/PATCH] bitpacked_dec: Optimization for bitpacked_dec decoder performance

[James Almer <jamrial@gmail.com>]

On 5/6/2023 9:13 AM, Devin Heitmueller wrote:
> I added some instrumentation via the attached patch.  You can see the
> benefits here:
> 
> Before=1683378057.243350 After 1683378057.264239
> Before=1683378083.335424 After 1683378083.356440
> Before=1683378089.675400 After 1683378089.696512
> Before=1683378151.792324 After 1683378151.813579
> 21 ms per run
> 
> After patch:
> Before=1683378222.167796 After 1683378222.175760
> Before=1683378233.131416 After 1683378233.139326
> Before=1683378243.591895 After 1683378243.599840
> 8 ms per run
> 
> Note: this is a different platform than I did the original development
> on, and apparently the improvement on this particular box is only 2.5x
> rather than 4x.
> 
> Devin

Can you bench with the START_TIMER and STOP_TIMER macros in timer.h?
Also, define CACHED_BITSTREAM_READER in bitpacked_dec.c before including 
git_bits.h and test the actual implementation again, to see if it makes 
any difference.

> 
> 
> On Sat, May 6, 2023 at 7:53 AM Paul B Mahol <onemda@gmail.com> wrote:
>>
>> On Sat, May 6, 2023 at 1:32 PM Lance Wang <lance.lmwang@gmail.com> wrote:
>>
>>> On Sat, May 6, 2023 at 4:58 AM Devin Heitmueller <
>>> devin.heitmueller@ltnglobal.com> wrote:
>>>
>>>> Rework the code a bit to speed up the 10-bit bitpacked decoding
>>>> routine.  This is probably about as fast as I can get it without
>>>> switching to assembly language.
>>>>
>>>> Demonstratable with:
>>>>
>>>> ./ffmpeg -f lavfi -i "smptehdbars=size=3840x2160" -c bitpacked -f image2
>>>> -frames:v 1 source.yuv
>>>> ./ffmpeg -f bitpacked -pix_fmt yuv422p10le -s 3840x2160 -c:v bitpacked -i
>>>> source.yuv -pix_fmt yuv422p10le out.yuv
>>>>
>>>> On my development system, it went from 80ms for a 2160p frame
>>>> down to 20ms (i.e. a 4X speedup).  Good enough for now, I hope...
>>>>
>>>>
>>> FYI, on my development system, I run two time for the original and modified
>>> version and no obvious difference:
>>> ./ffmpeg -f lavfi -i "smptehdbars=size=3840x2160" -c bitpacked -frames:v 25
>>> source.yuv
>>> time ./ffmpeg -f bitpacked -pix_fmt yuv422p10le -s 3840x2160 -c:v bitpacked
>>> -i source.yuv -pix_fmt yuv422p10le out.yuv
>>> frame=   25 fps=0.0 q=-0.0 Lsize=  810000kB time=00:00:00.96
>>> bitrate=6912000.0kbits/s speed=1.13x
>>>
>>> real 0m0.961s
>>> user 0m1.086s
>>> sys 0m1.360s
>>>
>>> frame=   25 fps=0.0 q=-0.0 Lsize=  810000kB time=00:00:00.96
>>> bitrate=6912000.0kbits/s speed=1.16x
>>>
>>> real 0m0.936s
>>> user 0m1.358s
>>> sys 0m1.350s
>>>
>>> after apply the patch:
>>> frame=   25 fps=0.0 q=-0.0 Lsize=  810000kB time=00:00:00.96
>>> bitrate=6912000.0kbits/s speed=1.14x
>>>
>>> real 0m0.953s
>>> user 0m0.906s
>>> sys 0m1.438s
>>>
>>> frame=   25 fps=0.0 q=-0.0 Lsize=  810000kB time=00:00:00.96
>>> bitrate=6912000.0kbits/s speed=1.17x
>>>
>>> real 0m0.922s
>>> user 0m0.926s
>>> sys 0m1.066s
>>>
>>
>> Only 25 frames?
>> This is flawed.
>>
>>
>>>
>>>
>>>
>>>> Signed-off-by: Devin Heitmueller <dheitmueller@ltnglobal.com>
>>>> ---
>>>>   libavcodec/bitpacked_dec.c | 17 +++++++----------
>>>>   1 file changed, 7 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/libavcodec/bitpacked_dec.c b/libavcodec/bitpacked_dec.c
>>>> index a1ffef1..96aba27 100644
>>>> --- a/libavcodec/bitpacked_dec.c
>>>> +++ b/libavcodec/bitpacked_dec.c
>>>> @@ -28,7 +28,6 @@
>>>>
>>>>   #include "avcodec.h"
>>>>   #include "codec_internal.h"
>>>> -#include "get_bits.h"
>>>>   #include "libavutil/imgutils.h"
>>>>   #include "thread.h"
>>>>
>>>> @@ -65,7 +64,7 @@ static int bitpacked_decode_yuv422p10(AVCodecContext
>>>> *avctx, AVFrame *frame,
>>>>   {
>>>>       uint64_t frame_size = (uint64_t)avctx->width *
>>>> (uint64_t)avctx->height * 20;
>>>>       uint64_t packet_size = (uint64_t)avpkt->size * 8;
>>>> -    GetBitContext bc;
>>>> +    uint8_t *src;
>>>>       uint16_t *y, *u, *v;
>>>>       int ret, i, j;
>>>>
>>>> @@ -79,20 +78,18 @@ static int bitpacked_decode_yuv422p10(AVCodecContext
>>>> *avctx, AVFrame *frame,
>>>>       if (avctx->width % 2)
>>>>           return AVERROR_PATCHWELCOME;
>>>>
>>>> -    ret = init_get_bits(&bc, avpkt->data, avctx->width * avctx->height *
>>>> 20);
>>>> -    if (ret)
>>>> -        return ret;
>>>> -
>>>> +    src = avpkt->data;
>>>>       for (i = 0; i < avctx->height; i++) {
>>>>           y = (uint16_t*)(frame->data[0] + i * frame->linesize[0]);
>>>>           u = (uint16_t*)(frame->data[1] + i * frame->linesize[1]);
>>>>           v = (uint16_t*)(frame->data[2] + i * frame->linesize[2]);
>>>>
>>>>           for (j = 0; j < avctx->width; j += 2) {
>>>> -            *u++ = get_bits(&bc, 10);
>>>> -            *y++ = get_bits(&bc, 10);
>>>> -            *v++ = get_bits(&bc, 10);
>>>> -            *y++ = get_bits(&bc, 10);
>>>> +            *u++ = (src[0] << 2) | (src[1] >> 6);
>>>> +            *y++ = ((src[1] << 4) | (src[2] >> 4)) & 0x3ff;
>>>> +            *v++ = ((src[2] << 6) | (src[3] >> 2)) & 0x3ff;
>>>> +            *y++ = ((src[3] << 8) | (src[4]))      & 0x3ff;
>>>> +            src += 5;
>>>>           }
>>>>       }
>>>>
>>>> --
>>>> 1.8.3.1
>>>>
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