[FFmpeg-devel] [RFC] image2 and filename patterns

[Stefano Sabatini]

On date Sunday 2013-01-27 01:37:38 +0100, Michael Niedermayer encoded:
> On Thu, Jan 24, 2013 at 05:38:21PM +0100, Stefano Sabatini wrote:
> > On date Thursday 2013-01-24 15:59:26 +0100, Stefano Sabatini encoded:
> > > Hi,
> > > 
> > > I'm trying to address ticket #1969 and I'm collecting a few ideas and
> > > seeing some (minor) nuisances.
> > > 
> > > My idea is to implement something like this:
> > > ffmpeg INPUT -f image2 -pattern_type sequence_ts foo-%06d.png
> > > 
> > > which would force to encode the timestamps in microseconds (or
> > > selectable) in the output files.
> > > 
> > > -pattern_type would be based on the image2 demuxer homonymous option,
> > > values could be for example:
> > > sequence
> > > sequence_ts
> > > 
> > > Currently file overwrite is implemented through the not very intuitive
> > > option named 'updatefirst', a possibly cleaner solution would be to
> > > adopt another pattern like '-pattern_type file' (which would also
> > > avoid pattern escaping on the user side).
> > > 
> > > The 'file' and 'sequence_ts' could be ported to the image2 demuxer
> > > (the first would avoid the need for a -loop option at the application
> > > level, for example in ffmpeg or in the movie filter).
> > > 
> > > In the mentioned ticket a pattern of the form '%pts' was suggested,
> > > but I'm opposed to this for various reasons (need to convert %t
> > > sequence to an av_get_frame_filename() pattern, impredictability in
> > > case of arbitrary filenames provided by the user).
> > 
> > And patches...
> 
> what about timestamp discontinuities ?
> 

> with %d and %p for picture number and timestamp they could be stored
> in files with just a single %X and a sequence type it would not
> work

this is slightly more complicate to support, since we would need to
add support to an extended format (which recognized %t/%p). Also what
should be the behavior in case t = NOPTS? How should we render for
example out-%t.png?
 
> not saying this use case matters enough just wanted to raise this
> point so it is understood/considered
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