Re: [FFmpeg-devel] [PATCH] avformat: add AVFormatContext.first_pts_wallclock

[Gyan Doshi <ffmpeg@gyani.pro>]

On 2022-06-18 10:30 am, Andreas Rheinhardt wrote:
> Gyan Doshi:
>>
>> On 2022-06-16 02:39 pm, Gyan Doshi wrote:
>>> Stores wallclock time for the first packet received with a pts.
>> Comments?
>>> ---
>>>    doc/APIchanges         |  3 +++
>>>    libavformat/avformat.h | 10 ++++++++++
>>>    libavformat/demux.c    |  3 +++
>>>    libavformat/options.c  |  1 +
>>>    libavformat/version.h  |  2 +-
>>>    5 files changed, 18 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/doc/APIchanges b/doc/APIchanges
>>> index 5857e67ae6..3d472b8963 100644
>>> --- a/doc/APIchanges
>>> +++ b/doc/APIchanges
>>> @@ -14,6 +14,9 @@ libavutil:     2021-04-27
>>>      API changes, most recent first:
>>>    +2022-06-xx - xxxxxxxxxx - lavf 59.26.100 - avformat.h
>>> +  Add and set AVFormatContext.first_pts_wallclock field.
>>> +
>>>    2022-06-12 - xxxxxxxxxx - lavf 59.25.100 - avio.h
>>>      Add avio_vprintf(), similar to avio_printf() but allow to use it
>>>      from within a function taking a variable argument list as input.
>>> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
>>> index f12fa7d904..56f9656a68 100644
>>> --- a/libavformat/avformat.h
>>> +++ b/libavformat/avformat.h
>>> @@ -1808,6 +1808,16 @@ typedef struct AVFormatContext {
>>>         */
>>>        int max_probe_packets;
>>>    +    /**
>>> +     * Wallclock start time of the stream in real world time, in
>>> microseconds
>>> +     * since the Unix epoch (00:00 1st January 1970). That is, the
>>> first packet
>>> +     * with a set pts was received at this real world time.
>>> +     * - demuxing: Set by libavformat. Users may want to use
>>> start_time_realtime
>>> +     *             if set.
>>> +     * - muxing: unused.
>>> +     */
>>> +    int64_t first_pts_wallclock;
>>> +
>>>        /**
>>>         * A callback for closing the streams opened with
>>> AVFormatContext.io_open().
>>>         *
>>> diff --git a/libavformat/demux.c b/libavformat/demux.c
>>> index 1620716716..9335a6efcd 100644
>>> --- a/libavformat/demux.c
>>> +++ b/libavformat/demux.c
>>> @@ -628,6 +628,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
>>>              force_codec_ids(s, st);
>>>    +        if (s->first_pts_wallclock == AV_NOPTS_VALUE && pkt->pts !=
>>> AV_NOPTS_VALUE)
>>> +            s->first_pts_wallclock = av_gettime();
>>> +
>>>            /* TODO: audio: time filter; video: frame reordering (pts !=
>>> dts) */
>>>            if (s->use_wallclock_as_timestamps)
>>>                pkt->dts = pkt->pts = av_rescale_q(av_gettime(),
>>> AV_TIME_BASE_Q, st->time_base);
>>> diff --git a/libavformat/options.c b/libavformat/options.c
>>> index 0079a06d9a..4cc168939f 100644
>>> --- a/libavformat/options.c
>>> +++ b/libavformat/options.c
>>> @@ -184,6 +184,7 @@ AVFormatContext *avformat_alloc_context(void)
>>>            return NULL;
>>>        }
>>>    +    s->first_pts_wallclock = AV_NOPTS_VALUE;
>>>        si->shortest_end = AV_NOPTS_VALUE;
>>>          return s;
>>> diff --git a/libavformat/version.h b/libavformat/version.h
>>> index 966ebb7ed3..0708d619c0 100644
>>> --- a/libavformat/version.h
>>> +++ b/libavformat/version.h
>>> @@ -31,7 +31,7 @@
>>>      #include "version_major.h"
>>>    -#define LIBAVFORMAT_VERSION_MINOR  25
>>> +#define LIBAVFORMAT_VERSION_MINOR  26
>>>    #define LIBAVFORMAT_VERSION_MICRO 100
>>>      #define LIBAVFORMAT_VERSION_INT
>>> AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
> Is there anyone who asked for this feature?

I'm using it for a live inputs sync patch that I'll submit after some 
more testing in a few days,

Regards,
Gyan
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