[FFmpeg-devel] [PATCH] avformat/rtsp: Add -first_rtcp_ntp_time_path option to write the first NTP time to a file.

Jonathan Viney jonathan.viney at gmail.com
Thu May 23 11:10:13 EEST 2019


On Thu, May 23, 2019 at 7:14 PM Moritz Barsnick <barsnick at gmx.net> wrote:

> On Thu, May 23, 2019 at 16:51:16 +1200, Jonathan Viney wrote:
> > > The NTP time from the first RTCP packet is currently extracted in
> > > libavformat/rtsp.c and stored in AVFormatContext.start_time_realtime.
> > > However, there is no way to access this value when using ffmpeg from
> the
> > > commandline.
> > >
> > > This patch adds an option when using an RTSP input to write the value
> to a
> > > file when it is received.
>
> Is this useful for anything? Would it be more useful in a metadata key?
> (Just wondering, not critisizing.)
>

I agree having it transferred to a metadata key in the output would be
useful. That was my first thought, but seems like it would be a larger
patch and I wasn't sure if it would be able to write to the metadata for
streaming formats like fragmented MP4 (which is what I'm using) because the
RTCP packet arrives some time after the output metadata would have be
written (from what I understand). Please correct me if I'm wrong about that.


>
> > +                            av_strlcatf(buf, sizeof(buf), "%lld",
> s->start_time_realtime);
>
> start_time_realtime is int64_t, so the format identifier should be
> '"%" PRIi64'.
>

Thanks - will update the patch.

Regards,
-Jonathan.


>
> Moritz
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