[FFmpeg-devel] Would like to work on lavf-based concatenation tool for GSoC qualification

Geza Kovacs gkovacs
Wed Apr 1 22:30:59 CEST 2009

Hello all,

I have attached my initial implementation of the lavf-based catenation
tool for GSoC qualification (this does not of course address the full
scope of the project description, it merely performs concatenation of
identical-format files). For now it is implemented as a standalone
application for simplicity (though I could also add it as an option in
ffmpeg's parse_options() if needed, I would simply need details on the
desired invocation syntax for the option).

The application currently supports both avi and mp4 input/output
containers, and appears to work with a variety of codecs (though I have
primarily tested with mpeg4 and huffyuv). According to ffplay there seem
to be issues with some files related to writing the header files,
presumably because I haven't fully populated the oformat struct, but the
files appear to play nevertheless; I will hopefully be able to track
this down before Friday.

I have attempted to follow the described coding and comments standards
as closely as possible, but if there's an issue please let me know.

Thanks for the feedback,

On Tue, 2009-03-31 at 10:55 -0700, Baptiste Coudurier wrote:
> Hi guys,
> On 3/31/2009 7:26 AM, Robert Swain wrote:
> > On 31/3/09 15:00, Geza Kovacs wrote:
> >> I'd like to know, by "concatenation" I assume this means "without
> >> re-encoding"; therefore I assume I'm not supposed to handle situations
> >> when multiple files are encoded with different framerate settings or
> >> different codecs (or do I instead transcode them into an intermediate
> >> format in these situations?).
> > 
> > Concatenate means to link to together. I'm not sure what the plans are
> > for handling differences in frame rates or resolutions. Differing source
> > formats shouldn't matter for transcoding purposes as long as on entry to
> > the video encoder the resolution, frame rate and pixel format as all
> > appropriate and similarly the number of channels, sample rate and sample
> > format for the audio encoder, there shouldn't be any major problem.
> > 
> > I expect Baptiste will elaborate on this. I think he had plans to allow
> > specification of command line options per input so that one could affect
> > the different inputs to make them concatenate-able.
> Here is the project description:
> Playlist/Concatenation Support
> - primary goal: implement a playlist/concatenation interface to
>     transcode(FFmpeg) and play(FFplay) media
> - interface will use commandline switches.
> - interface must support every input format FFmpeg support
> - interface must work with different input stream parameters (different
>     formats, codecs, video resolution, audio sample rate, audio
>     channels, etc..)
> - interface must support track selection
> - interface must support existing playlist format files .m3u, .pls,
>     xpsf.
> So according to this, different resolution must be handled. About
> different frame rates, this could be added later I think.
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