Add a "Supported codecs" setting (HEVC / Enhanced Broadcasting)

[einanderson]

Summary

Adds a "Supported codecs" setting so users can opt in to Twitch Enhanced Broadcasting (HEVC), which is required to receive 1440p+ variants.

Addresses #699 (Playback broken for 2k streams) and #700 (No audio on 2k stream): those 2K streams use HEVC, which Twitch only serves when the client requests supported_codecs.

What it does

• New setting General → "Supported codecs": Twitch default / H.265 (HEVC).
• The selected value is passed to usher (live / video / live_request / video_request) via the new supported_codecs parameter.
• Default = "Twitch default" → no supported_codecs sent → behaviour unchanged (no regression).
• Opt-in by design: HEVC requires hardware decode; users without it keep the default. h264 stays in the requested list as a fallback, so non-HEVC channels/devices still get a playable variant.
• Graceful fallback: the value is only passed when the installed script.module.python.twitch accepts the parameter (feature-detected), so the plugin still works with an older library.

Pairs with

The library-side change anxdpanic/script.module.python.twitch#141, which adds the supported_codecs parameter. With an older library the setting simply has no effect.

Testing

• Default setting: usher calls are byte-for-byte unchanged (regression-safe).
• Codec mapping + graceful fallback verified; the supported_codecs=h265,h264 mechanism is in production use on Raspberry Pi 4 / Kodi 21 (HEVC 1440p plays).
• Uses only standard APIs (stdlib inspect); platform-independent.

Notes

• AV1 is intentionally left out for now (Enhanced Broadcasting AV1 is not generally served); the library parameter is codec-agnostic, so it can be added trivially later.

[einanderson]

Ready for review (no longer draft) — no rush. This builds directly on your existing quality/usher handling; it only adds a small optional "Supported codecs" setting that requests H.265 (HEVC) / Enhanced Broadcasting, so 2K streams play (with audio) through inputstream.adaptive. Default stays "Twitch standard", so nothing changes unless enabled — an addition on top of your code, not a rewrite. Addresses #699 / #700.

How to test: check out this branch + the lib PR anxdpanic/script.module.python.twitch#141 → Settings → Supported codecs = H.265 (HEVC), Video Quality = Adaptive (needs inputstream.adaptive) → a 2K channel plays 2K HEVC with audio; back to "Twitch standard" = unchanged stock behaviour. Uses inspect feature-detection so it degrades gracefully on an older lib. Tested on LibreELEC / RPi 4 / Kodi 21.