[XviD-devel] Seeking help for Video encoding

Dark Sylinc dark_sylinc at yahoo.com.ar
Tue Mar 18 20:06:42 CET 2008


Hi,

> Hi Team
>        I am a new developer in this field.

Welcome!

> To understand the whole 
> source code what should i do?What are the contents
> which i have to go 
> through before understanding the whole source code
> and make developments 
> in the source code.

As with anything, the 1st thing to do is to USE it.
There are three examples on how to use it packed with
XviD.
Is that isn't enough for you, try looking at some
media players or open source encoder interfaces that
directly use XviD (such as MPlayer.)
You can later enable/disable options & plugins that
will let you know what they do.

As for the source code, it contains generic C code
that (theoretically) works on all (or most) decent
plattforms.
But the key in XviD is using assembly optimization, so
you may have:
void (*my_func) ();
void C_my_func ();
void MMX_my_func ();
void SSE_my_func ();

where my_func() points to either C_ MMX_ or SSE_
depending on the system capabilities. So if you modify
the C version (which is the easiest to understand) to
see what has changed, be sure it is being actually
used (disable all optimizations using a flag).
This is usually set on xvid.c, encoder.c & decoder.c

> I want to create a source code
> for video encoding,
Be carefull, as XviD is GPL. If you use XviD code in
your project, be sure to release your code under
GPL-compatible license

> I want to create a source code
> for video encoding,
> for that i am looking forward for ur help.What are
> the things which i have 
> to keep in mind while creating a source code for
> video encoding.I don't 
> know how to begin.

Are you trying to benefit XviD or benefit yourself?
We can guide you in the initial steps then:
What to look for:
1) Quality. The decompressed video has to have the
highest quality. That also depends if you're looking
for lossy or lossless compression.
2) Bandwidth: The lowest size of course. Define what
is acceptable. Nowadays we have the advantage of
Broadband conections, which affects the balance
quality-bandwidth.

I can't help you much with the encoding method, as I
am not the most appropiate person for it.
I suggest you to look at the XviD devel lists history,
as these questions are asked frequently.
If you're interested in deeply knowing how MPEG-4
works, you should look at Doom9.org resources, or
buy a copy of the ISO whitepapers
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39259
(although, I haven't read them, so I can't say if
they're easy to follow, but I wouldn't expect that
from a technical specification paper)

But be aware, MPEG-4 has a lot of legal issues if you
don't plan to use it for personal reasons:
http://ffmpeg.mplayerhq.hu/legal.html
ffmpeg is a different project from XviD, however I
believe the legal stuff still applies. (see specially
question: "Q: Since FFmpeg is licensed under the LGPL,
is it perfectly alright to incorporate the whole
FFmpeg core into my own commercial product?" )

I hope this helps
Dark Sylinc

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