[FFmpeg-devel] [PATCH] avformat/mpegts: use a buffer pool for PES payloads

[James Almer]

On 4/2/2020 3:27 PM, Marton Balint wrote:
> 
> 
> On Thu, 2 Apr 2020, Marton Balint wrote:
> 
>>
>>
>> On Thu, 2 Apr 2020, James Almer wrote:
>>
>>> On 3/29/2020 6:07 PM, James Almer wrote:
>>>> This produces a small speed up in demuxing
>>>>
>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>>> ---
>>>>  libavformat/mpegts.c | 20 ++++++++++++++++----
>>>>  1 file changed, 16 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
>>>> index 7f56bacb2c..7746a524c4 100644
>>>> --- a/libavformat/mpegts.c
>>>> +++ b/libavformat/mpegts.c
>>>> @@ -157,6 +157,8 @@ struct MpegTSContext {
>>>>      int resync_size;
>>>>      int merge_pmt_versions;
>>>>
>>>> +    AVBufferPool *pool;
>>>> +
>>>>      /******************************************/
>>>>      /* private mpegts data */
>>>>      /* scan context */
>>>> @@ -1177,8 +1179,7 @@ static int mpegts_push_data(MpegTSFilter *filter,
>>>>                          pes->total_size = MAX_PES_PAYLOAD;
>>>>
>>>>                      /* allocate pes buffer */
>>>> -                    pes->buffer = av_buffer_alloc(pes->total_size +
>>>> - 
>> AV_INPUT_BUFFER_PADDING_SIZE);
>>>> +                    pes->buffer = av_buffer_pool_get(ts->pool);
>>>>                      if (!pes->buffer)
>>>>                          return AVERROR(ENOMEM);
>>>>
>>>> @@ -1351,8 +1352,7 @@ skip:
>>>>                      if (ret < 0)
>>>>                          return ret;
>>>>                      pes->total_size = MAX_PES_PAYLOAD;
>>>> -                    pes->buffer = av_buffer_alloc(pes->total_size +
>>>> - 
>> AV_INPUT_BUFFER_PADDING_SIZE);
>>>> +                    pes->buffer = av_buffer_pool_get(ts->pool);
>>>>                      if (!pes->buffer)
>>>>                          return AVERROR(ENOMEM);
>>>>                      ts->stop_parse = 1;
>>>> @@ -3032,6 +3032,10 @@ static int mpegts_read_header(AVFormatContext
>>>> *s)
>>>>      ts->stream     = s;
>>>>      ts->auto_guess = 0;
>>>>
>>>> +    ts->pool = av_buffer_pool_init(MAX_PES_PAYLOAD + 
>> AV_INPUT_BUFFER_PADDING_SIZE, NULL);
>>>> +    if (!ts->pool)
>>>> +        return AVERROR(ENOMEM);
>>>> +
>>>>      if (s->iformat == &ff_mpegts_demuxer) {
>>>>          /* normal demux */
>>>>
>>>> @@ -3200,6 +3204,8 @@ static void mpegts_free(MpegTSContext *ts)
>>>>
>>>>      clear_programs(ts);
>>>>
>>>> +    av_buffer_pool_uninit(&ts->pool);
>>>> +
>>>>      for (i = 0; i < NB_PID_MAX; i++)
>>>>          if (ts->pids[i])
>>>>              mpegts_close_filter(ts, ts->pids[i]);
>>>> @@ -3295,6 +3301,12 @@ MpegTSContext 
>> *avpriv_mpegts_parse_open(AVFormatContext *s)
>>>>      ts->stream = s;
>>>>      ts->auto_guess = 1;
>>>>
>>>> +    ts->pool = av_buffer_pool_init(MAX_PES_PAYLOAD + 
>> AV_INPUT_BUFFER_PADDING_SIZE, NULL);
>>>> +    if (!ts->pool) {
>>>> +        av_free(ts);
>>>> +        return NULL;
>>>> +    }
>>>> +
>>>>      mpegts_open_section_filter(ts, SDT_PID, sdt_cb, ts, 1);
>>>>      mpegts_open_section_filter(ts, PAT_PID, pat_cb, ts, 1);
>>>>      mpegts_open_section_filter(ts, EIT_PID, eit_cb, ts, 1);
>>>
>>> Will apply soon if no one objects.
>>
>> LGTM.
> 
> On second thought aint this going to waste too much memory on small
> packets? If packets are queued somewhere it can make a huge difference
> if every buffer is 200kb...
> 
> Does the speedup goes away if only unbound packets make use of the
> buffer pool?
> 
> Thanks,
> Marton

I tried these two LG 4k HDR sample videos, and the pool was never bigger
than 3 to 5 buffers for the entire demuxing process.

I'll bench again with your suggestion, but i don't think it will be a
problem even as is.