[Ffmpeg-devel] [PATCH] DV Tune Up

[Roman Shaposhnik]

Hi

On Wed, 2006-11-22 at 02:12 +0100, Michael Niedermayer wrote:
> > I have a patch by a coworker of mine that tunes up some issues with DV
> > encoding and outputting.  These issues came up when trying to send DV
> > data to a DV camera.  The major issue is regarding audio not being able
> > to play while the DV data was being sent.  Other issues are for writing
> > "correct" info in certain packs according to standards.  Thanks!
> 
> ping roman ...

  pong ;-) Sorry I don't see the original post anywhere in my queue, but
in order to save time I'll try to answer some questions here and if 
there are more -- please send an email to me directly.

> > dvenc.c:
> > line 129-
> > buf[3]- the speed for NTSC should be "0xa0" signalling that it is an IEC
> > stream. But this is specific to us, because cameras like incoming
> > streams to be this way.

  Where did 0xa0 came from ? Also note -- that strictly speaking ffmpeg
currently tries to always generate SMPTE streams; more on that later.

> > All the following changes are suggested to match SMPTE 314m.
> > 
> > line 204-
> > The Timecode packs should be written only for SSYB IDs- 3,4,5 and 9,10,11.

  What's your problem with extra packs? My impression has always been
that they just get ignored. Do you have contradicting evidence ?
 

> > dvdata.h:
> > line 2707-
> > For SSYB number 11 ID0 has APT2,1,0=001 (314m)

  Fair enough. Should be fixed.

> > dv.c:
> > line 1099-
> > apt should be 0 for NTSC and PAL DV

  We've been through this one before on a couple of occasions. I put
the comment near that line to end the confusion. SMPTE requires them
to be 1 if the source comes from a digital device; and yes I know
that it might mess up IEC streams -- more on that later.

Now, as promised here's the saga of SMPTE vs. IEC. Basically the only
formal document I have an access to is an SMPTE spec, hence ffmpeg's DV
encoder tries to generate SMPTE streams whenever it can. I've also put
some considerations into making sure that whatever it generates works
with my camera (Sony VX2000, NTSC). And that's it. I would gladly
accept donations of either full IEC spec, or some extra equipment to
test DV codec with (PAL being the highest priority). However, before
that happens my only choice for putting weird hacks into DV encoder (and
yes -- everything that you put in place just to satisfy a particular
camcorder is a weird hack)  would be to actually create a separate 
profile for IEC.

Thanks,
Roman.