[FFmpeg-devel] [PATCH v2 2/3] avformat/mpegtsenc: make first_pcr sync with the first valid dts

[Marton Balint]

On Thu, 22 Oct 2020, lance.lmwang at gmail.com wrote:

> From: Limin Wang <lance.lmwang at gmail.com>
>
> now first_pts assume dts will start from zero, if it's not true(copyts is enable),
> too many null packet will be inserted for cbr output.
>
> Please test with below command, you'll get huge test.ts without the patch:
> ./ffmpeg -y -copyts -i ../fate-suite/mpegts/loewe.ts  -c:v libx264 -x264opts \
>   nal-hrd=cbr:force-cfr=1 -b:v 3500k -minrate 3500k -maxrate 3500k -bufsize \
>   1000k  -c:a mp2 -muxrate 4500k  -vframes 1000 test.ts
>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> libavformat/mpegtsenc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
> index 5c97d63..415a64e 100644
> --- a/libavformat/mpegtsenc.c
> +++ b/libavformat/mpegtsenc.c
> @@ -81,6 +81,7 @@ typedef struct MpegTSWrite {
>     int64_t pat_period; /* PAT/PMT period in PCR time base */
>     int nb_services;
>     int64_t first_pcr;
> +    int first_dts_check;

It is minor nitpicking, but can you rename this to first_dts_checked and 
reverse the logic? So this can be 0 by default (so it does not have to be 
explicitly initialized), and you set it to 1 after it is checked.

Thanks,
Marton

>     int64_t next_pcr;
>     int mux_rate; ///< set to 1 when VBR
>     int pes_payload_size;
> @@ -1134,6 +1135,7 @@ static int mpegts_init(AVFormatContext *s)
>
>     if (ts->copyts < 1)
>         ts->first_pcr = av_rescale(s->max_delay, PCR_TIME_BASE, AV_TIME_BASE);
> +    ts->first_dts_check = 1;
>
>     select_pcr_streams(s);
> 
> @@ -1688,6 +1690,11 @@ static int mpegts_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
>         stream_id = side_data[0];
>
>     if (ts->copyts < 1) {
> +        if (ts->first_dts_check && dts != AV_NOPTS_VALUE) {
> +            ts->first_pcr += dts * 300;
> +            ts->first_dts_check = 0;
> +        }
> +
>         if (pts != AV_NOPTS_VALUE)
>             pts += delay;
>         if (dts != AV_NOPTS_VALUE)
> -- 
> 1.8.3.1
>
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