Re: [FFmpeg-devel] [PATCH] doc/ffmpeg: extend -dts_delta_threshold option description

[Gyan Doshi <ffmpeg@gyani.pro>]

On 2023-02-11 09:58 pm, Stefano Sabatini wrote:
> On date Saturday 2023-02-11 03:30:00 +0100, Stefano Sabatini wrote:
>> On date Thursday 2023-02-09 00:41:18 +0100, Michael Niedermayer wrote:
>>> On Mon, Feb 06, 2023 at 02:25:23AM +0100, Stefano Sabatini wrote:
>> [...]
>>>> Subject: [PATCH 2/2] ffmpeg: review -dts_delta_threshold and -dts_delta_error
>>>>   options
>>>>
>>>> Review handling of -dts_delta_threshold and -dts_delta_error options,
>>>> specify them as floating point expressed in seconds.
>>>>
>>>> Also, review and simplify logic. Adjust values for tests, since in
>>>> some cases the new values does not trigger the correction logic.
>>>>
>>>> PR: https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=8252
>>>> ---
>>>>   doc/ffmpeg.texi             | 36 ++++++++++++++++---
>>>>   fftools/ffmpeg.c            | 72 ++++++++++++++++++++-----------------
>>>>   fftools/ffmpeg.h            |  2 ++
>>>>   fftools/ffmpeg_demux.c      |  3 ++
>>>>   tests/fate/filter-audio.mak |  2 +-
>>>>   tests/fate/mpeg4.mak        |  2 +-
>>>>   6 files changed, 77 insertions(+), 40 deletions(-)
>>> This seems to break a case with concat and vsync
>>> ./ffmpeg -y -i 'concat:///home/michael/videos/angels.mpg|/home/michael/videos/angels.mpg'  -vsync 0 -an file.avi
>>>
>>> ...
>>> cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
>>> [mpeg4 @ 0x55e051b8d4c0] Invalid pts (0) <= last (11)00.00 bitrate=N/A speed=   0x
>>> [vost#0:0/mpeg4 @ 0x55e051b9d700] Error submitting video frame to the encoder
>>> Conversion failed!
>>>
>>>
>>> Ill mail you the angels.mpg, i think its online somewhere but i cant
>>> find it
>> Fixed, now the code should be equivalent to the previous
>> implementation.
>>
>> What happened in this case (and apparently in the other fate tests
>> failing), is that some sort of limit correction is applied:
>>
>> detected dts:-0.041711 < dts_limit:0.358789
>> ts delta 0.5005 applied => ts_offset_discont:0.5005 dts:0.458789
>>
>> preventing the invalid pts error.
>>
>> The limit correction, hardcoded in the ffmpeg.c code, is completely
>> unrelated to the dts_delta_threshold value, no idea if it would make
>> sense to make this parametric (but at least now it should be a bit
>> more clear from the code/logs).
> Moving the refactoring changes to a dedicated thread.
>
> Updating the doc extensions.

LGTM.

Regards,
Gyan

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