Feature request: Type conversion from M3u8::Playlist to M3u8::PlaylistItem

[waterjump]

Recently I had a use case where I was looking to convert a M3u8::Playlist to M3u8::PlaylistItem. I was a bit surprised it's not supported by this gem, and that PlaylistItem instances need to be built from an options hash. This doesn't seem like a rare use case, especially when working with a master playlists, parsing media playlists they contain, working with them, and building a new master playlist as a result.

Here's a short example use case I'm imagining:

my_file = File.open('spec/fixtures/media_playlist-664.m3u8')
media_playlist = M3u8::Playlist.read(my_file)
playlist_item = M3u8::PlaylistItem.new(media_playlist)

My temporary workaround for this is to dump all of a Playlist's instance variables into a hash (excluding items, etc.) and building a new PlaylistItem from that. If there's a more intuitive way to do this that I'm missing, please let me know.

A secondary solution could be to implement a Playlist#to_options method that returns an options hash that allows for easy creation of a PlaylistItem:

my_file = File.open('spec/fixtures/media_playlist-664.m3u8')
media_playlist = M3u8::Playlist.read(my_file)
playlist_item = M3u8::PlaylistItem.new(media_playlist.to_options)

If you are on board with the feature request, I'll be happy to write the specs and open a PR.

Thanks!

[sethdeckard]

HI @waterjump, I'm a little confused by your request. A PlaylistItem represents the EXT-X-STREAM / EXT-X-I-FRAME-STREAM-INF tags in a master playlist, how do you build a instance of PlaylistItem from the attributes in a Playlist? Assuming the Playlist is a media playlist which would look something like this:

#EXTM3U
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-VERSION:4
#EXT-X-MEDIA-SEQUENCE:1
#EXT-X-DISCONTINUITY-SEQUENCE:8
#EXT-X-ALLOW-CACHE:NO
#EXT-X-TARGETDURATION:12
#EXTINF:11.344644,
1080-7mbps00000.ts
#EXT-X-DISCONTINUITY
#EXTINF:11.261233,
1080-7mbps00001.ts
#EXTINF:7.507489,
1080-7mbps00002.ts

Let me know if I've overlooked something in your request, which wouldn't surprise me. :-)

[waterjump]

Hi Seth,

Thanks for your quick response. After typing out several hundred words detailing my issue, I realized that the tags found in a media playlist are not congruent to the tags about a media playlist in the context of a master playlist, so it doesn't make sense to transmute between the two types like I thought it would. Basically, I rubber-ducked it and saved you a lot of reading I hope.

Closing

[sethdeckard]

Hi @waterjump, I see what you were trying to do now. As you already realized it's outside the scope of this project since this library doesn't actually do anything with the MPEG-TS segments referenced in a media playlist and you would need to know the media information (codecs, bitrate, etc) to generate the attributes for a variant/master playlist. However, there are some other tools that can help you with just that. You might want to take a look at variantplaylistcreator, one of the CLI tools Apple makes available for working with HLS stuff.

Here's all of them: https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/UsingHTTPLiveStreaming/UsingHTTPLiveStreaming.html