I wanted to convert an Flash Video (flv) file from YouTube to MP3. The first tip I found essentially streamed the original file into a different file:
ffmpeg -i filename.flv -acodec mp3 -ac 2 -ab 128 -vn -y filename.mp3
This is a bit awkward, because not all flv files have the same quality (some are mono, for example). I don’t want to have to look up the number of channels (-ac 2
in the example) for each file that I need to convert.
Luckily, most flv files include an MP3 audio stream and ffmpeg can simply copy that stream to a new file:
ffmpeg -i filename.flv -acodec copy filename.mp3
This works perfectly and is much faster than the other method.
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Today I was ripping the sound from a video that would only work with the following command:
Actually, since Februari 2009, all YouTube videos use the AAC encoding for their audio. So in the above (-acodec copy) example I should have given the file with the extracted audio an extension such as .aac or .mp4.