Jed’s fridge door notes (a.k.a. “so i won’t forget”)

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Converting video formats in unix

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I give no explanations. You can consult your man page for that. My aim is to write quick and dirty hacks, not an entire book on the topic.

We will be using 3 tools: transcode, mplayer’s mencoder and ffmpeg — all commandline tools. Anybody who has been keeping track of this journal should by now be aware that if I can, I avoid GUI point-n-click apps like the plague. Lastly, this mini howto is by no means exhaustive.

Basics
mencoder
-ovc codec for video output
-oac codec for audio output
-o outfile.avi

mencoder infile.avi -ovc lavc -oac lavc -o outfile.avi

transcode
-i input_filename.mpg
-y codec for audio/video output
-o output_filename.avi

transcode -i infile.mpg -o outfile.avi -y divx

ffmpeg

ffmpeg -i myfile.avi -target vcd /tmp/vcd.mpg

Video CD
ffmpeg -i infile.avi -target ntsc-vcd outfile.mpg

Flash Videos
ffmpeg -i infile.mpg -ab 256 outfile.flv

*note:

  • Use the “-ab” switch to control the sound quality. 64 is okay for home vidoes. For music you want something higher like 256.

    • XviD
    First, something about video bitrates.

    1. Crummy youtube-like video is around 80-150.
    2. VCD quality is around 400-500.
    3. DVD quality is approx 800.
    4. Default bitrate for mencoder is 687kbps.

    mencoder infile.avi -ovc xvid -oac mp3lame -xvidencopts bitrate=687 -o outfile.avi

    *notes:

  • If you want the outfile to have an estimated size (like 700mb), set a negative bitrate and replace the bitrate value with the expected size of the outfile like:

    • -bitrate=-700000 – will give you a ~700mb avi file.

  • Two-pass encodings will give a nicer video but will take longer to convert:

    • mencoder infile.wmv -ofps 23.976 -oac mp3lame -lameopts abr:br=92 -ovc xvid -xvidencopts pass=2:bitrate=150 -o audiofix-150bit-xvid.avi

  • Audio quality can be set via the -lameopts switch if you’re using mp3lame (-oac mp3lame) for the audio format:

    • mencoder infile.avi -ovc xvid -oac mp3lame -lameopts abr:br=256 -xvidencopts bitrate=800 -o outfile.avi

    Microsoft media files (*.wmv, *.asf, *.wmx)
    Just follow the howto for Xvid and replace the infile.avi with any M$.wmv file you have. There’s an issue regarding some players (Xine) not being able to play wmv->xvid files converted using mencoder. Just use the -ofps 23.976 switch for that.

    DivX
    transcode -i infile.mpg -o outfile.avi -y divx

    DVD
    ffmpeg -i infile.avi -target ntsc-dvd dvd.mpg

    You can now use any of the hoardes of dvd authoring tools that your favorite distro has in its repository to make a dvd out of the output mpegs you create here.

    That’s all for now. If I missed anything or something doesn’t work I’m just here.

    Written by jedrm

    May 28, 2007 at 11:53 am

    Posted in Unix One-Liners

    Tagged with , , , , , , ,

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