Extract audio

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Ed. note: Sorry this is more like a blog post.

Having recorded the Molin Upper Elementary 5th Grade Christmas Concert using my video camera, I wanted to extract just the audio portion so that I could listen to the music all by itself without having to play the video. Besides, I could send the audio portion much more easily than I could send the 948 MB video file through email. The half-hour concert produced a lossless .ogg file of 21 MB and 14 MB in lossy mp3 format.

The Video Editing article gives some examples for using mencoder and ffmpeg, but in this case I found using ffmpeg on the command line was the easiest tool after some initial trial and error. I was surprised to find out that Avidemux didn't just do what I wanted. With Avidemux, I tried 'save audio' which produced a relatively large file, that didn't play in anything. I ran ffmpeg -i on it, and it reported "unknown format"

# try mplayer, but it did not work
mplayer -dumpaudio VID00001.AVI -dumpfile molin-5th-grade-xmas-concert.mp3

## Try instead to use ffmpeg
# tell me information about my source file
ffmpeg -i VID00001.AVI

# copy the audio codec; but name the output .mp3 (of course this will not work)
ffmpeg -i VID00001.AVI -acodec copy molin-5th-grade-xmas-concert.mp3

# copy the audio codec; disable video; but name the output .mp3 (of course this will not work)
ffmpeg -i VID00001.AVI -vn -acodec copy molin-5th-grade-xmas-concert.mp3

# disable video; use mp3 codec (that is not the name of a valid codec)
ffmpeg -i VID00001.AVI -vn -acodec mp3 molin-5th-grade-xmas-concert.mp3

# let ffmpeg figure out what I want (WORKED)
ffmpeg -i VID00001.AVI -vn molin-5th-grade-xmas-concert.mp3

header.png For creating the .ogg file, I went with the easier GUI approach and used SoundConverter


Download YouTube Videos[edit | edit source]

See https://github.com/rg3/youtube-dl/

sudo pip install -U youtube-dl

will give you a YouTube downloader that can do a lot of things, including extract the audio portion (relying on ffmpeg)


cd ~/Music
youtube-dl --extract-audio --prefer-ffmpeg $video
scp Dave\ Matthews\ Band\ -\ You\ \&\ Me-kD9CrZODlNA.m4a admin@qnap:$musicdir'/Dave\ Matthews\ Band/You\ And\ Me.m4a'
scp Dave\ Matthews\ Band\ -\ You\ \&\ Me-kD9CrZODlNA.mp4 admin@qnap:$videodir'/You\ And\ Me.mp4'