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

Matthieu Bouron matthieu.bouron at gmail.com
Thu Mar 28 17:15:28 CET 2013

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
  - 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 ?

For reference, page 5 of http://www.digitizationguidelines.gov/guidelines/FADGI_MXF_ASAP_Issues_20110815.pdf


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