[FFmpeg-devel] [PATCH] avformat/rtpdec: Fix prft wallclock time.

[Carl Eugen Hoyos]

Am Do., 25. März 2021 um 05:47 Uhr schrieb Alok Priyadarshi <alokpr at gmail.com>:
>
> Timestamp difference is available in media timebase (1/90K) where as
> rtcp time is in the default microseconds timebase. This patch fixes
> the calculated prft wallclock time by rescaling the timestamp delta
> to the microseconds timebase.
> ---
>  libavformat/rtpdec.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/rtpdec.c b/libavformat/rtpdec.c
> index b935dba1b8..21c1d01785 100644
> --- a/libavformat/rtpdec.c
> +++ b/libavformat/rtpdec.c
> @@ -585,14 +585,19 @@ void ff_rtp_parse_set_crypto(RTPDemuxContext *s, const char *suite,
>  }
>
>  static int rtp_set_prft(RTPDemuxContext *s, AVPacket *pkt, uint32_t timestamp) {
> +    int64_t rtcp_time, delta_timestamp, delta_time;
> +
>      AVProducerReferenceTime *prft =
>          (AVProducerReferenceTime *) av_packet_new_side_data(
>              pkt, AV_PKT_DATA_PRFT, sizeof(AVProducerReferenceTime));
>      if (!prft)
>          return AVERROR(ENOMEM);
>
> -    prft->wallclock = ff_parse_ntp_time(s->last_rtcp_ntp_time) - NTP_OFFSET_US +

> -                      timestamp - s->last_rtcp_timestamp;

Wouldn't this patch get much more readable if you only replace this line?

> +    rtcp_time = ff_parse_ntp_time(s->last_rtcp_ntp_time) - NTP_OFFSET_US;
> +    delta_timestamp = (int64_t)timestamp - (int64_t)s->last_rtcp_timestamp;
> +    delta_time = av_rescale_q(delta_timestamp, s->st->time_base, AV_TIME_BASE_Q);
> +
> +    prft->wallclock = rtcp_time + delta_time;

Carl Eugen