[FFmpeg-user] Random repetitions in output

[Carl Eugen Hoyos]

2017-11-06 12:23 GMT+01:00 Moritz Barsnick <barsnick at gmx.net>:
> On Sun, Nov 05, 2017 at 21:14:26 +0100, Mikael Persson wrote:
>> Regarding: -vsync vfr
>> From the doc: Frames are passed through with their timestamp or dropped so
>> as to prevent 2 frames from having the same timestamp.
>>
>> This would ensure no repetitions, but does not guarantee that no frames are
>> lost. I want both to be ensured.
>
> Did you read the "-vsync" docs? Value "passthrough" is described like
> "vfr", without the dropping:
>
>     ‘0, passthrough’
>         Each frame is passed with its timestamp from the demuxer to the muxer.

Thank you, that was what I meant!
(I don't think it makes a difference for the described use-case though.)

>> Further does -vsync have any effect at all if no output framerate is
>> specified?
>
> Yes, as there often needs to be an output framerate.

This does not sound completely correct to me, but may
just be a wording issue.

> How ffmpeg derives it, I would have to dig through the sources to
> understand.

> It seems the image2 muxer uses the framerate reported by the
> demuxer (but as cfr).

This is wrong, the image2 muxer does not know anything about
the input frame rate.

Carl Eugen