[libdv-dev] Re: some linux-dv related issues

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

Rafa³ Szcze¶niak <rf...@aw...> writes:

> I'm interested in linux DV software. Actually, i'd like to (maybe)
> create a little, quite useful program for grabbing frames and
> operating on them. I hope it wouldn't be completely "out of my
> range".

There are at least a few other people working on similar programs.  I
think we have links to them on our libdv.sourceforge.net page.  But I
don't mean to discourage you from exploring or experimenting with your
own ideas.

> However, i need at last short description of dv encoding method. I
> don't even know what does these dct*, idct*, weight*, vlc*, quant*
> prefixes stand for (well, maybe not all of them ;) ).

(i)DCT == (inverse-)discrete cosine transform
weight == coeifficient weighting
vlc == variable length codes
quant == quantization

> I'm aware that documentation is not free, but i need some BASIC
> information. It seems to me that it wouldn't be breaking the law.

The standards also assume that the reader understands these concepts,
and doesn't do any substantial explaination beyond what you see in the
code.

It sounds to me that you need to learn a little more of the basic
concepts of multimedia compression in general.  There are surely many
websites with such information, but I'd recommend finding a good book
on the subject.  My first suggestion would be "Video Demystified".
They have a web site, www.videodemystified.com.

You should know that many of the major compression standards are very
similar to each other.  For example, DV, MPEG-[124], H.26x, all use
the DCT.  The same is true for the other components of the DV video
codec.  

> I'm asking for all these, because tracing libdv sources is not easy
> and maybe there's some way to save time and spend it on writing
> actual programs.

Well, you should not necessarily need to know much of the libdv
internels to write higher level programs, if we had a proper api and
documentation in place.

Unfortunately, after a good burst of initial activity, Erik and I have
let things slide a lot.  We both took long vacations, and since my
vacation I've been kept busy by other activities.  

Erik is just back from his.  So hopefully we'll get some progress on
cleaning things up.  We do have other obligations so it won't be as
fast paced as when we did the first version.

> regards
> Rafa³

> PS. Sorry for my (not perfect) english, in advance.

Hope this helps.  

-- Buck