[FFmpeg-devel] [PATCH] avformat/mpegts: use buffer pools for allocating packets

[James Almer]

On 4/4/2020 11:47 AM, Marton Balint wrote:
> This brings a performance improvement when demuxing files, most of the
> improvement comes from buffer pooling unbound packets.

Yes, as i mentioned in my last reply this was my experience as well.

> 
> time ffprobe -i samples/ffmpeg-bugs/trac/ticket6132/Samsung_HDR_-_Chasing_the_Light.ts -show_packets >/dev/null 2>&1
> 
> Before:
>     real    0m1.967s
>     user    0m1.471s
>     sys     0m0.493s
> 
> After:
>     real    0m1.497s
>     user    0m1.364s
>     sys     0m0.129s
> 
> Based on a patch of James Almer.
> 
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  libavformat/mpegts.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index 7f56bacb2c..fbafc1d257 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -170,6 +170,7 @@ struct MpegTSContext {
>      int current_pid;
>  
>      AVStream *epg_stream;
> +    AVBufferPool* pools[32];

Isn't 32 way more than required?

>  };
>  
>  #define MPEGTS_OPTIONS \
> @@ -1103,6 +1104,18 @@ static int read_sl_header(PESContext *pes, SLConfigDescr *sl,
>      return (get_bits_count(&gb) + 7) >> 3;
>  }
>  
> +static AVBufferRef *buffer_pool_get(MpegTSContext *ts, int size)
> +{
> +    int index = av_log2(size + AV_INPUT_BUFFER_PADDING_SIZE);
> +    if (!ts->pools[index]) {
> +        int pool_size = FFMIN(MAX_PES_PAYLOAD + AV_INPUT_BUFFER_PADDING_SIZE, 2 << index);
> +        ts->pools[index] = av_buffer_pool_init(pool_size, NULL);
> +        if (!ts->pools[index])
> +            return NULL;
> +    }
> +    return av_buffer_pool_get(ts->pools[index]);
> +}
> +
>  /* return non zero if a packet could be constructed */
>  static int mpegts_push_data(MpegTSFilter *filter,
>                              const uint8_t *buf, int buf_size, int is_start,
> @@ -1177,8 +1190,8 @@ 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 = buffer_pool_get(ts, pes->total_size);
> +
>                      if (!pes->buffer)
>                          return AVERROR(ENOMEM);
>  
> @@ -1351,8 +1364,7 @@ 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 = buffer_pool_get(ts, pes->total_size);
>                      if (!pes->buffer)
>                          return AVERROR(ENOMEM);
>                      ts->stop_parse = 1;
> @@ -3200,6 +3212,9 @@ static void mpegts_free(MpegTSContext *ts)
>  
>      clear_programs(ts);
>  
> +    for (i = 0; i < FF_ARRAY_ELEMS(ts->pools); i++)
> +        av_buffer_pool_uninit(&ts->pools[i]);
> +
>      for (i = 0; i < NB_PID_MAX; i++)
>          if (ts->pids[i])
>              mpegts_close_filter(ts, ts->pids[i]);

LGTM. I assume the pools for the smaller sizes will not end up being
slower than just allocating new buffers each time.