download only audio from youtube video using youtube-dl in python script

Question

There's a few posts on downloading audio from YouTube using youtube-dl, but none of them are concrete or too helpful. I'm wondering what the best way to do it from a Python script is.

For example, here's the README example for downloading videos:

import youtube_dl

ydl_opts = {}
with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['http://www.youtube.com/watch?v=BaW_jenozKc'])

Obviously if you just care about the audio, you'd rather not download the whole video...

The youtube-dl source is only so helpful (ie, not very).

Any suggestions how to script this?

Answer 1

Read on in the developer instructions for an amended example:

from __future__ import unicode_literals
import youtube_dl


ydl_opts = {
    'format': 'bestaudio/best',
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'mp3',
        'preferredquality': '192',
    }],
}
with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['http://www.youtube.com/watch?v=BaW_jenozKc'])

This will download an audio file if possible/supported. If the file is not mp3 already, the downloaded file be converted to mp3 using ffmpeg or avconv. For more information, refer to the format and postprocessors documentation entries in a current version of youtube-dl.

Answer 2

Use postprocessors argument. The list of all the available postprocessors can be found here.

If you want to pass additional ffmpeg or avconv options, which are not included in youtube-dl library (like audio bitrate - -ar <BR> in ffmpeg), add postprocessor_args as a list.

You can also prefer ffmpeg over avconv setting prefer_ffmpeg to True.

And to keep both original and converted audio file set 'keepvideo' to True.

For example:

from __future__ import unicode_literals
import youtube_dl

ydl_opts = {
    'format': 'bestaudio/best',
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'wav',
        'preferredquality': '192'
    }],
    'postprocessor_args': [
        '-ar', '16000'
    ],
    'prefer_ffmpeg': True,
    'keepvideo': True
}

with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['http://www.youtube.com/watch?v=BaW_jenozKc'])

The list of all the available options is in the documentation. You can read ffmpeg posprocessor's code here.

And a less complex example is in their GitHub README.