[libdv-dev] Re: simpledv interface to libdv

[Charles 'B. K. <kr...@ac...>]

Vladimir Vukicevic <vla...@In...> writes:

> Ah, beautiful.. I never noticed those before. I'll use the non-SDL
> patches. Is there anything else you'd like to see in the simpledv
> interface? 

Probably, but I don't have specifics at the moment.

So the best way, as you are doing, is to start simple and proceed from
there.

> I'm still going to maintain getting a RGB frame out, but
> YUV will be an option dvf_open. Note that I plan to keep using
> GdkPixbuf because then the interface can be transparent whether it's
> YUV or RGB, if gdk_pixbuf_render is used to draw. The only concern I
> have is if someone wants to use simpledv without Gtk/GdkPixbuf --
> I'll probably make this a compiletime #define at least.

Sounds good.  

> Also, I thought that the native NTSC DV format was 4:1:1, but there seems
> to be cases where it's 4:2:0? I don't have the spec so I can't check...

> 	- Vlad

You should get the spec from smpte.  It is only $34 USD.  There's a pointer
on libdv.sourceforget.net.

For NTSC, DV uses 4:2:0 for the rightmost two columns of macroblocks
in each frame.  This is because 720 is not a exact multiple of 32
(each 4:1:1 macroblock is 4 blocks wide).  Plus "superblocks" which
are groups of macroblocks are not square.  What a hack, eh?

PAL DV is different.  The original PAL DV, as defined by the IEC
61834, uses 4:2:0 throughout the entire frame.  The newer version
defined by smpte 314M uses 4:1:1 throughout.  I'm not sure why they
switched, but I think it has to do with interoperability with newer
high bitrate modes.  50Mbit DV looks a great deal like 25, except it
uses 4:2:2.  

There are a newer family of IEC specs for DV, number 61883?, that I
have not seen yet.  I don't know if they match smpte version of PAL
yet.

So far, I think we've only tested IEC style PAL bitstreams.

-- Buck