[Ffmpeg-devel] Re: [PATCH] DVCPRO50 support

Roman Shaposhnick rvs
Fri Mar 3 22:24:22 CET 2006

On Fri, Mar 03, 2006 at 01:47:36PM +0100, Michael Niedermayer wrote:
> Hi
> On Thu, Mar 02, 2006 at 07:57:23PM -0500, Dan Maas wrote:
> [...]
> > With regards to Baptiste's question of "why not a different codec?"-
> > DV25 and DV50 share so much code (probably 95%) that I don't see a
> > reason to split them up. In the future I may add DV100 (DVCPRO HD) to
> > the mix as well. You can determine the flavor of DV unambiguously just
> > by looking at the resolution and pixel format.
> for encoding, the supported pixel formats are a field of AVCodec, now if
> dv would support 2 pixel formats and independant of that one or more
> resolutions then a single codec_id would be fine but dv has a very strict
> small set of supported resolution-pix_fmt-framerate, other mixes arent
> allowed and in case of resolution-pix_fmt would need some new tables to
> be invented
> so while a single codec_id for encoding would work fine, the end user
> would be much more happy i think if you would add several so an application
> like ffmpeg.c could automatically select a supported pix_fmt and framerate
> from the codec_id, note, the only change for this is to duplicate your
> AVCodec structure and fill in the pix_fmt/framerate/name and register that
> AVCodec no need to touch or split any of th actual code, and for decoding
> you will probably use a single codec_id for for all ...

  I guess it depends on what the user model is: basically do we want to 
  burden the users with the knowledge of all different DV flavors out
  there (which is not a huge number, so I'm just asking) but free from
  a burden of knowing pix_fmt, frame resolution and such (ffmpeg will
  do the right thing) or is it the other way around -- we only want
  users to know what their desired constraints are and let ffmpeg 
  figure out the best CODEC for them.

  Personally -- I don't really have a preference, but then again I feel
  that mapping:

   (CODEC family, pix_fmt, resolution, bitstream constraints) -> CODEC parameters

  should be a generic thing. Its not just about DV.


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