[NUT-devel] [PATCH] libnut muxer: write at least one timebase

[Clemens Ladisch]

> On Fri, Feb 02, 2007 at 11:38:32AM +0100, Michael Niedermayer wrote:
> > On Fri, Feb 02, 2007 at 11:10:32AM +0200, Oded Shimon wrote:
> > > On Mon, Jan 22, 2007 at 02:24:07PM +0100, Clemens Ladisch wrote:
> > > > This patch adds code to make sure that there is at least one timebase.
> > > > Otherwise, creating a file without any stream would result in an
> > > > invalid file, or the muxer would crash when trying to write max_pts
> > > > in the index.
> > > 
> > > Is a file without any streams valid?..
> > 
> > hmm, i think we havent thought about that ...
> > at least such a file cannot contain any frames, stream headers or syncpoints
> > and without timebases it cannot contain an (useless) index and info packets
> > 
> > now the timebase less case really is useless because the only thing which
> > you could store in the file would be the main header and possibly future
> > new headers ...

The spec explicitly forbids having no timebases.

> > in the streamless but not timebase less case you could store an index which
> > would contain nothing and info packets iam not sure if theres any use for
> > that? seperating info packets from actual streams like providing just a
> > info packet file for some other file, like providing detailed info for
> > a dvd, so someone could take th dvd remux it to nut and add the info somehow
> > ?

In a video editor application, it would make sense to be able to save a
file with some global metadata even when the user hasn't yet created any
streams.  If streamless files were not allowed, the program would have
to create a dummy stream, or say "I'm sorry Dave, I'm afraid I cannot do
that".

Oded Shimon wrote:
> I have no strong feeling on this. I would not be against a 'stream_count 
> MUST be >0' ...

This change to the spec would not be backwards compatible ...  ;-)

In practice, it wouldn't make much of a difference if the error message
of a media player would be either "I cannot play a file without any
data" or "A file without data is not a valid nut file".


Regards,
Clemens