Video format : converting MOV to MPEG ??

[Larry Grover]

Vincent Trouilliez wrote:
> Hi,
> 
> I just took about 10 little video clips with my digital camera, they are
> very crap quality of course, (blurry picture, and only 320x240, and only
> 15fps IIRC, and can last only 35 seconds each, maximum), yet they take
> lots of space, about 8MB each, way too big (75MB in all) to share them
> with my friends via e-mail or even upload them, as although I have
> broadband downstream, upstream is only 128kbps... and I am not very
> patient.
> 
> I reckon these clips, if properly compressed in MPEG, could drop the
> size down to well under 10MB for sure, which is a lot more manageable,
> without deterioring the quality the slightest bit (seeing as it's quite
> low to start with).
> 
> I search in the Application Installer for a general purpose video
> editing program, thinking I could just import the videos and save them
> as MPEG, but I can't see anything suitable.
> 
> IIRC, there are command line tools to handle audio/video
> encoding/decoding, but unless someone who knows his onions with these
> tools can take my hand, I have zero chance of succeeding I think...
> 
> Can't we just have "Adobe Premiere" for Linux, or something ?! ;-)
> 
> 
> Regards,
> 
> 
> --
> Vince


I'm not an expert, so beware, my explanations (below) may well be 
technically inaccurate.

"MOV" does not describe a single video format.  MOV is a container 
format, which can hold audio and video information, and sometimes 
other data as well.  The audio and video information inside a 
container (like MOV, AVI) can be compressed in a number of different 
ways -- using a number of different codecs (compression/decompression 
algorithms).  So the the video in the MOV files you get from your 
camera might already be stored using one of the mpeg codecs!

For example, my wife's digital camera can capture video.  The video 
files from her camera are MOV's, but the video is encoded using the 
H263+ codec, at least, that's what mplayer says when I play the videos:

Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
INFO: libavcodec init OK!
Selected video codec: [ffh263] vfm:ffmpeg (FFmpeg H263+ decoder)

Now, you may be able to transcode your videos so that they are 
smaller, depending on the audio and video codecs in the original file.

I transcoded one of my wife's videos using mencoder (the transcoder 
from mplayer):

mencoder -oac mp3lame -ovc lavc -lavcopts vcodec=mpeg4 \
-of avi 100_5314.mov -o 100_5314.mpeg4.avi

Explanation of command line options:

-oac mp3lame
encode to MPEG-1 layer 3 audio (aka, mp3) using lame

-ovc lavc
encode using libavcodec

-lavcopts vcodec=mpeg4
encode using MPEG-4 (DivX 4/5)

-of avi
use AVI container format

-o 100_5314.mpeg4.avi
output file name

and here's a comparision of the resulting file size with original file 
size:

grover at sleek:~/tmp$ ls -l 100_5314.*
-rw-r--r--  1 grover grover 7248407 Oct 31  2003 100_5314.mov
-rw-r--r--  1 grover grover 3300420 Nov 24 12:14 100_5314.mpeg4.avi

The transcoded file is less than 50% of the original file size.

Transcoding video is not simple.  There are several container formats, 
  many choices for audio and video compression (codecs), and many 
options for each codec.  If you're going to do this in linux, you 
really need to do some reading.  Pick the program you are going to use 
(I recommend mencoder or transcode) and become familiar with its 
manpage.  For general information in audio and video formats and 
codecs, it's hard to beat wikipedia.  Here are a few links which 
should get you started:

http://en.wikipedia.org/wiki/Video_file_format
http://en.wikipedia.org/wiki/Codecs
http://en.wikipedia.org/wiki/Comparison_of_container_formats
http://en.wikipedia.org/wiki/List_of_codecs
http://en.wikipedia.org/wiki/Open_source_codecs_and_containers

Regards,
Larry