[FFmpeg-devel] [PATCH 7/7] lavf/mxfdec: add -field_rate option

[Tomas Härdin]

On Thu, 2013-03-28 at 17:33 +0100, Michael Niedermayer wrote:
> On Thu, Mar 28, 2013 at 05:15:28PM +0100, Matthieu Bouron wrote:
> > On Thu, Mar 28, 2013 at 04:37:10PM +0100, Michael Niedermayer wrote:
> > > On Thu, Mar 28, 2013 at 03:41:51PM +0100, Matthieu Bouron wrote:
> > > > Interpret sample rate as field rate for j2k codec with separate fields
> > > > or segmented frame layout.
> > > > 
> > > > This option is required to obtain a correct frame rate since S422M
> > > > specifies that the track sample rate could either be the frame rate
> > > > or the field rate for separate field layout.
> > > > 
> > > 
> > > > For segmented frame layout, the track sample rate is supposed to be the
> > > > frame rate however some sample seems to use it as the field rate.
> > > 
> > > are you sure theres no way to distingish them automatically ?
> > > file duration fields?
> > > encoder name?
> > > muxer name?
> > > ...
> > > 
> > 
> > AFAIK there is no mandatory information that can be used to interpret correctly
> > the sample rate.
> > 
> > Based on the few samples i have:
> >   - the one provided on ffmpeg trac (ntsc2.mxf): sample rate is frame
> >     rate,
> >   - the files issued by SAMMA systems: sample rate is field rate,
> >   - the files issued by Canopus Co. systems: sample rate is field rate.
> > 
> > Maybe i could use the application_supplier_name from the mxf
> > identification item to set a default behaviour ?
> 
> yes, its maybe a bit trial and error but IMHO its worth a try to set
> it automatically

I agree. We're already handling a few bad files in ways similar to this,
and it's generally how the industry handles MXF interoperability as
well. Yes, it's a complete mess.

/Tomas
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