[FFmpeg-devel] [PATCH v2 1/2] avformat: add AVFormatContext.first_pkt_wallclock

[Gyan Doshi]

On 2022-07-02 02:12 pm, Anton Khirnov wrote:
> Quoting Gyan Doshi (2022-07-01 13:07:13)
>>
>> On 2022-07-01 03:20 pm, Anton Khirnov wrote:
>>> Quoting Gyan Doshi (2022-06-28 08:40:58)
>>>> On 2022-06-28 10:43 am, Anton Khirnov wrote:
>>>>> Quoting Gyan Doshi (2022-06-25 10:29:50)
>>>>>> Stores wallclock time for the first packet received.
>>>>>> Used for crude sync offset among inputs.
>>>>>> ---
>>>>>>     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(-)
>>>>> Why should this be in the library? Seems to me this can be just as
>>>>> easily done by the callers who need it.
>>>> To not add some extra latency,  just like how
>>>> `use_wallclock_as_timestamps` was implemented inside lavf.
>>> Where would that extra latency come from?
>> The interval between its current assigment inside ff_read_packet() and
>> the chance for assignment in process_input() in ffmpeg.c
> And why would there be a significant delay there?

With multiple inputs, get_input_packet_mt() will populate each input 
queue in async whereas process_input() will be called on that input at 
best in a round robin fashion depending on choose_output().

Regards,
Gyan