[FFmpeg-user] Why are these different?

[Vincent Deconinck]

Hi,

I will probably get flamed because I'm for jumping into this conversation
while being a complete newbie :-), but I think nobody replied with an
answer to Mark's question "why".

All I know is the ffmpeg page on seeking -
https://trac.ffmpeg.org/wiki/Seeking - ends with a paragraph saying:
"Using -ss as input/output option *together with -c:v copy might not be
accurate* since ffmpeg is forced to only use/split on i-frames" (emphasis
mine)
The page also states that:
"As of FFmpeg 2.1, when transcoding with ffmpeg (*i.e. not stream copying*),
-ss is now also "frame-accurate" even when used as an input option"
My understanding is thus that with input seeking, the requested start time
will not be satisfied without transcoding; while with output seeking, the
requested start time will always be guaranteed correct, even with -c copy.

But I might be wrong ;-)

Peace.

Vincent

On Sun, Feb 11, 2024 at 8:29 PM Paul B Mahol <onemda at gmail.com> wrote:

> On Sun, Feb 11, 2024 at 7:12 PM Mark Filipak <markfilipak.imdb at gmail.com>
> wrote:
>
> > On 11/02/2024 13.09, Bouke / Videotoolshed wrote:
> > > So do you, so why ask the question?
> > > Now go away!
> >
> > I do not know the answer.
> >
>
> In most cases you will get in most times different results for those 2
> variants.
>
> Only for perfect containers and perfect implementations it will give same
> result in every case.
> For last one I do not have any example ffmpeg command to show you. (And I'm
> not sure if it even exist)
>
>
> >
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