Re: [gentoo-user] ot - video encoding

Re: [gentoo-user] ot - video encoding

[Boyd Stephen Smith Jr.]

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On Saturday 24 February 2007, Kellystewart00@yahoo.com.au wrote 
about '[gentoo-user] ot - video encoding':
> Hi List im looking for a program to encode from avi to divx does anyone
> know of a program to do this?

Short answer: mencoder

Longer answer:
(1) Avi is not a format -- or at least it's not a video format.  It's 
a "wrapper" format that can hold various video formats with various audio 
formats interleaved.  AVI = Audio/Video Interleave

(2) Mplayer and Xine are the big a/v decoders, with ffmpeg being used by 
both projects (IIRC); vlc is a very useful third place, and gstreamer does 
have some "native" codecs although it can (and IIRC, still generally does) 
call out to the xine, mplayer, or ffmpeg libraries for some formats.

(3) Encoders are much more fragmented, although ffmpeg provides many 
encoders, and mplayer can use the ffmpeg encoders as well as any native 
ones it might have, plus it understands the libraries (or interfaces via 
system() calls) with some others.  Xine, vlc, and gstreamer are, AFAIK not 
oriented towards encoding.

(4) Divx is just an video format and if you intend to combine it with 
audio, you'll have to choose a format for that.  I prefer vorbis; with 
speex for those cases where is audio is literally just a voice-over.  
However, vorbis and speex decoders generally aren't shipped with 
proprietary OSes such as OS X or Windows and are playable on relatively 
few portable devices.  MP3 is fine for mono or stereo audio, but AFAIK it 
doesn't support more channels.  AC3 is IME larger for the same quality, 
but does support 5.1 and other formats with more channels.

(5) Again, divx is just a video format, so you'll need a container format 
if you want to combine it with other media, like subtitles or audio.  I 
prefer Matroska or ogg.  Neither is shipped with proprietary OSes and both 
have poor support on portables, although ogg has marginally better support 
than Matroska.  I don't believe divx is can be shipped in the standard mp4 
container, but I could be wrong.  It's normally shipped in, oddly enough 
in your case, AVI format.

So, you have a couple more high-level decisions to make before you 
transcode.  Once you decide on them, you'll still need to determine 
encoder-specific parameters, bitrates, and whotnot, although sane defaults 
are generally provided by most tools when possible.  However, the shear 
number of options may be a little bit overwhelming.  Tip: doesn't change 
any settings you don't have to the first time, you can play with all 
the "knobs" once you get base functionality.

Mencoder is probably is most featureful transcoding tool, but you may be 
able to find a GUI that the features you need and is user-friendly.  I 
don't do enough transcoding to have any recommendations other than 
mencoder, because I got familiar enough with it to do what I needed and 
stopped looking for anything else.

-- 
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