47 lines
2.8 KiB
Markdown
47 lines
2.8 KiB
Markdown
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# YouTube channels as podcasts
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A YouTube channel (or playlist) can be subscribed to like a podcast. Only its
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sound is played, and **the server never downloads or streams a video or its
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sound**: each app finds the audio stream itself.
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## Server (diora-web, `podcasts/youtube.py`)
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- `POST /podcasts/feeds/add/` takes a YouTube address as `rss_url`: a channel
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(`/@name`, `/channel/UC…`, `/c/…`, `/user/…`), a playlist (`?list=…`), a video
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(subscribes its channel) or the feed itself. The server reads the channel page
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once (feed address, name, picture) and stores the feed
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`https://www.youtube.com/feeds/videos.xml?channel_id=UC…` (or `?playlist_id=…`).
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`GET /podcasts/search/?q=<YouTube address>` answers with that one channel.
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- From then on the feed is refreshed like any other. It carries the latest 15
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videos. **Shorts are left out.** There is no duration (`duration_seconds` 0)
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until a player knows it: `POST /podcasts/progress/save/` takes an optional
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`duration_seconds` (number, 1 s … 7 days), stored only while the episode has none.
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- An episode from such a feed has
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- `audio_url` = `https://www.youtube.com/watch?v=<11-character id>`. This is
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**the** marker: a client recognises a YouTube episode by this prefix;
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- `guid` = `yt:video:<id>`, `artwork_url` = the video's thumbnail,
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`description` = the video description as HTML (links, line breaks; timestamps
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like `00:00 Intro` work as usual).
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- Nothing on the server touches the sound of such an episode: no ID3 chapters,
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no transcripts, and `/podcasts/episodes/<id>/silences/` answers
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`{"ready": true, "spans": [], "error": "youtube"}` (skip silence is up to the
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app, as on Android anyway).
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## Apps
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A client that sees a `watch?v=` address resolves it **itself, on the device,
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to an audio-only stream** (no video track), and plays or downloads that.
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| Client | How |
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|---------|-----|
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| Android | NewPipeExtractor: the original audio track, progressive, opus before m4a, ≤ 160 kbit/s; resolved when the stream is opened and once more on a 403; downloads in 10 MB ranges (in one go YouTube throttles to ~50 KB/s) |
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| Desktop | yt-dlp in the main process (`-f bestaudio`), Electron itself as its JavaScript runtime; yt-dlp is fetched from its GitHub release on first use and kept up to date (`src/main/youtube.js`) |
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| Browser | can't (YouTube doesn't let a web page read its pages, and a stream address only works for the device that asked for it): the episode is listed but says it plays in the app |
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Stream addresses are bound to the device's IP address and run out after a few
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hours: resolve shortly before playing, and again when the player reports an
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error (podcasts-web.js reloads after a media error anyway).
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Progress, queue, played state etc. work as for any episode: they belong to the
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episode on the server, not to the stream address.
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