[FFmpeg-user] VFR video re-encoding

ValdikSS iam at valdikss.org.ru
Tue Feb 9 18:01:27 CET 2016

On 02/09/2016 04:29 PM, Moritz Barsnick wrote:
> On Tue, Feb 09, 2016 at 14:56:47 +0300, ValdikSS wrote:
> That's what I have been wondering all along in this thread. Who is
> doing it wrong?
> What I could observe (I think) from using the file:
> Its DTS/PTS seem to be correct. They are about 41..42 ms apart in the
> first section (corresponds to 23.98 fps), about 33..34 ms apart in the
> second section (corresponds to 29.97 fps). The pkt_duration, as
> mentioned by Valdik originally, also seems to be correct for each
> section.
> Matroska supports VFR, so this shouldn't be a general problem (should
> it?). Does it support a CFR header, and did mkvmerge insert this? Just
> wondering.
> $ ffmpeg -i rkszxnz.mkv -threads 3 -speed 5 rkszxnz.webm
> Now, what ffmpeg seems to be doing is to be converting to CFR 23.98
> (when converting to webm with libvpx-vp9). Obvious from the warnings
> and the dropped frames starting from the "cut" point around 55 s, and
> from the pkt_duration in the resulting file.
> Is this intended? What's the point of *not* retaining the DTS/PTS and
> the frame rate when converting without explicit "-r" or the likes?
> Anyway, I do not see this effect mentioned by Valdik:

That's weird. I'll try make a screen capture or find another video or moment where it's more visible a bit later.

> Not even after 55 seconds. (Using my conversion.) OTOH, I can't seek in
> the resulting video, which is wildly annoying.

Use something like -g 120

> Valdik, I must apologize at this point, none of us has yet pointed out
> that you should supply the complete, uncut console log of your ffmpeg
> calls (along with the proper command line of course). Because:
> You seem to be using a version from around July 20 2015. Have you tried
> latest git master yet?

I will try it a bit later, thanks.

> Moritz
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