Transcoded stream responses only carried Last-Modified (the source file's
mtime, which is identical across every bitrate/format/offset), so a client
had no cheap way to confirm it already holds a specific transcoded
representation and re-downloaded the full audio on every repeat request
within a single playback.
Advertise a weak, representation-specific ETag derived from the transcode
cache key (id, mtime, bitrate, format, sampleRate, bitDepth, channels,
offset). On the fully-cached seekable path http.ServeContent now answers a
matching If-None-Match with 304 Not Modified instead of re-sending the
audio, cutting redundant transfer for repeated in-playback requests. The
tag is weak because ffmpeg output is not guaranteed byte-identical across
runs; it stays valid for If-None-Match revalidation while http.ServeContent
correctly declines to use it for If-Range sub-range assembly.
Fixes#5720
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: TowyTowy <towy@airreps.link>
8d77a06ea0