how can I batch extract audio from mp4 files with ffmpeg without decompression (automatic audio codec detection)?
Solution 1
You say you want to "extract audio from them (mp3 or ogg)". But what if the audio in the mp4 file is not one of those? you'd have to transcode anyway. So why not leave the audio format detection up to ffmpeg?
To convert one file:
ffmpeg -i videofile.mp4 -vn -acodec libvorbis audiofile.ogg
To convert many files:
for vid in *.mp4; do ffmpeg -i "$vid" -vn -acodec libvorbis "${vid%.mp4}.ogg"; done
You can of course select any ffmpeg parameters for audio encoding that you like, to set things like bitrate and so on.
Use -acodec libmp3lame
and change the extension from .ogg
to .mp3
for mp3 encoding.
If what you want is to really extract the audio, you can simply "copy" the audio track to a file using -acodec copy
. Of course, the main difference is that transcoding is slow and cpu-intensive, while copying is really quick as you're just moving bytes from one file to another. Here's how to copy just the audio track (assuming it's in mp3 format):
ffmpeg -i videofile.mp4 -vn -acodec copy audiofile.mp3
Note that in this case, the audiofile format has to be consistent with what the container has (i.e. if the audio is AAC format, you have to say audiofile.aac
). You can use the ffprobe
command to see which codec you have, this may provide some information:
ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -print_format csv=p=0 "videofile.mp4"
A possible way to automatically parse the audio codec and name the audio file accordingly would be:
mkdir -p output
# current directory has to contain at least one .mp4 file
for vid in *.mp4; do
codec="$(ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -print_format csv=p=0 "$vid")"
case "$codec" in
mp3 ) filetype=mp3 ;;
vorbis ) filetype=ogg ;;
* ) filetype= ;;
esac
if [ "$filetype" ]; then
ffmpeg -i "$vid" -vn -acodec copy output/"${vid%.*}"."$filetype"
else
ffmpeg -i "$vid" -vn -acodec libvorbis output/"${vid%.*}".ogg
done
Notes: the output files are created in sub-directory output
it creates in the beginning (if necessary). For other codecs than mp3 and vorbis it converts audio to ogg. Ubuntu 14.04 does not have ffmpeg in standard repositories, but you could add ppa:mc3man/trusty-media repository and install ffmpeg package to get the needed software. See here for details.
Solution 2
As Nicolas Raoul stated, this needs updating. Here's the same line that roadmr gave but using avconv instead:
for vid in *.mp4; do avconv -i "$vid" "${vid%.mp4}.mp3"; done
Comments
-
wryrych almost 2 years
I have 228 mp4 files (2.6GB) and would like to extract audio from them (mp3 or ogg). I want to batch extract them - preferably with bash. I'm not sure if all files use the same audio codec as they were recorded in different years, ranging from 2006-2012.
I want to loop through all of them, pick the file name, detect audio codec and use ffmpeg to extract the audio.
Is it possible?
-
Mahesh over 11 yearsThis is a scripting question and as such has nothing to do with Ubuntu. It's not off topic here, but SO or unix.SE might be a better place to ask.
-
wryrych over 11 yearsThanks. Next time I'll try to ask such a question in more appropriate place.
-
-
wryrych over 11 yearsI put it wrong. I wanted to have mp3 or ogg but as you noticed the audio codec was different - aac in this example. So I have to transcode them anyway. Thank you very much for your help!
-
Andrew Beals about 11 yearsYour automagic example breaks with filenames that have spaces in them because you didn't quote $file in the ffprobe sub-statement. Changing it to: for file in *mp4 *avi; do ffmpeg -i "$file" -vn -acodec copy "$file".
ffprobe "$file" 2>&1 |sed -rn 's/.*Audio: (...), .*/\1/p'
; done Fixes that. -
Nicolas Raoul about 10 years+1 but looks like this answer could use an update:
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
-
jarno over 8 years
ffmpeg
orffprobe
are not available for Ubuntu 14.04 or later. -
jarno over 8 years
avconv
andavprobe
are available for same use. -
llogan over 8 years@jarno The real
ffmpeg
returned to Ubuntu in 15.04, and it looks like the Libav chaffavconv
andavprobe
has been removed in 15.10. -
llogan over 8 yearsThis is now outdated. FFmpeg is back and Libav is gone.
-
jarno over 8 years@LordNeckbeard Good point. In 15.10
avconv
andavprobe
are just symbolic links toffmpeg
andffprobe
, respectively. IIRCavconv
andffmpeg
had minor differences in syntax, so I wonder, if that may be a problem. -
jarno over 8 yearsIn Ubuntu 14.04 you could add ppa:mc3man/trusty-media repository from launchpad.net/~mc3man/+archive/ubuntu/trusty-media and install ffmpeg package to get the needed software.
-
Scooby-2 over 8 yearsAbsolutely correct. If anyone thought ffmpeg was going to die, read this: en.wikipedia.org/wiki/Libav#Confusion