[Epidemic Sound] Add new extractor

[realRobotix]

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What is the purpose of your pull request?

• Bug fix
• Improvement
• New extractor
• New feature

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Description of your pull request and other information

see #31462

[dirkf]

Thanks for your work!

I've made a couple of suggestions. Please consider those and check the result of the CI tests too (NB the tests may appear to succeed even if individual extractor tests fail).

[realRobotix]

The Extractor is now using traverse_obj and type checking and I also added support for downloading separate tracks.
Example: https://www.epidemicsound.com/track/mj8GTTwsZd/ has separate tracks for Melody, Instruments, Bass, Drums and a Full Mix.

[dirkf]

With the new suggestions (etc) implemented I get this

$ python -m youtube_dl -F 'https://www.epidemicsound.com/track/mj8GTTwsZd/'
[EpidemicSound] mj8GTTwsZd: Downloading JSON metadata
[info] Available formats for 148700:
format code  extension  resolution note
bass         mp3        unknown    track ID 433551 
drums        mp3        unknown    track ID 433547 
instruments  mp3        unknown    track ID 433550 
melody       mp3        unknown    track ID 433548 
full         mp3        unknown    track ID 433549  (best)
$

What do you think?

[dirkf]

Now you prompted me to look at the JSON!

Should id be the id from the JSON? If so return the video_id as display_id.

Also:

• isExplicit could be used to set age_limit
• releaseDate could be used to set release_timestamp
• genres could be used to set categories
• cover could be a fallback for imageUrl.

[realRobotix]

Not sure why a user would want the id of the json. I'd just leave it out for now.

[dirkf]

The ID is meant to be a unique value that specifies the video (1-1 mapping). We can't really tell if the slug in the URL is going to be unique, but the numeric ID in the JSON looks like an internal index that ought to be unique. Putting the slug as display_id is consistent with the way other extractors work.

Here's another thing, though. Will people normally want the full version only, or the whole set of instrumental tracks? If the latter, the extractor should return all the formats as a playlist, and then the user would have to use --no-playlist to force the current behaviour. Or with the current behaviour, you can get multiple formats with comma-separated formats, like -f "full,drums", but the user has to list the formats explicitly as there's no -f all.

[realRobotix]

this should be ready to merge now

[dirkf]

As you say, just about ready to merge, but see the 3 points I've listed.

[dirkf]

The ID is meant to be a unique value that specifies the video (1-1 mapping). We can't really tell if the slug in the URL is going to be unique, but the numeric ID in the JSON looks like an internal index that ought to be unique. Putting the slug as display_id is consistent with the way other extractors work.

Here's another thing, though. Will people normally want the full version only, or the whole set of instrumental tracks? If the latter, the extractor should return all the formats as a playlist, and then the user would have to use --no-playlist to force the current behaviour. Or with the current behaviour, you can get multiple formats with comma-separated formats, like -f "full,drums", but the user has to list the formats explicitly as there's no -f all.

[realRobotix]

I think most people are just interested in the full mix but there is an issue with downloading multiple formats at the same time because the filenames are all the same. What is the recommended way to fix this? Just append the format to the title?

[dirkf]

To get distinct filenames, the user must specify an output template containing %(format_id) (or possibly %(autonumber) - can't recall ATM whether that increments for the same video ID). The default template just depends on the ID and title, which have to be the same for all formats.

If we return a playlist, the ID and/or title could be varied per track.

[realRobotix]

Ok sure, but I still think most people just want the full version and having to specify that every time would be unnecessary. Should be ready to finally merge now.

[dirkf]

And thanks again!