[Libav-user] Encoding with variable frame rate

Robert Krüger krueger at lesspain.de
Mon May 20 15:01:57 CEST 2013

On Mon, May 20, 2013 at 2:06 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> Robert Krüger <krueger at ...> writes:
>> On Mon, May 20, 2013 at 12:11 PM, Carl Eugen Hoyos wrote:
>> > Pradeep Karosiya <praks411 <at> ...> writes:
>> > > Also I came to know not all codec support
>> > > variable frame rate.
>> >
>> > (?, that sounds unlikely.)
>> >
>> > FFmpeg's mov muxer does not support vfr.
>> Do you know what exactly is missing?
> No, but it was discussed recently on irc.

OK, I am asking because in the code there is neither a comment
regarding that nor is it obvious that a frame rate is used anywhere
with the exception of timecode tracks where it is needed for obvious
reasons and in mov_write_uuidprof_tag, which is only used in PSP mode
and the Quicktime spec AFAIK offers no means of specifying a constant
frame rate explicitly. It will just result in a time-to-sample table
that looks differently if it is constant. But, of course, there may be
not so obvious places in the code, where constant frame rate is
assumed and for people considering working on the mov muxer, this
would be valuable information. That's why I am asking. Is IRC traffic
archived publicly somewhere?

>> What happens when one feeds the muxer with packets
>> that have timestamps with differing offsets?
> I am not sure but I would expect you get an
> invalid mov file.
> Please try to set your mailer to text-only,

Sorry, I was not aware that it wasn't already set to that.


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