Asking for 2160p quality on a 720p source kept the daemon's qcap.VideoBitrate
at 25 Mbps even after outputHeight was clamped to the source. The level
H264LevelForHeight picks for the 720p output is 3.1 / 4.0, which rejects any
VBV >20 Mbps — libx264 then exited with "VBV bitrate (25000) > level limit"
on every restart, ffmpeg auto-restarted 3 times, master.m3u8 never appeared,
and the player got stuck at "Preparando sesión".
Re-derive the (height, bitrate) cap from the EFFECTIVE outputHeight via the
new capForHeight helper. Result: 720p source asked for 2160p → outputs 720p
with the 3500 kbps bitrate the level actually accepts. ffmpeg runs cleanly,
master.m3u8 appears, playback starts.
The web also clamps effectiveQuality to source resolution before the session
row is written, so the daemon mostly receives sane labels. This change keeps
the daemon defensive against (a) older web clients that still ask for
upscaled qualities, and (b) future quality="original" requests where qcap
is empty and Transcode.VideoBitrate could overshoot the level too.
Three related fixes around 4K-source transcoding that left the web
player stuck on "preparing session" with no useful diagnostics:
1. Dynamic -level:v derived from output height (hls.go, transcoder.go).
The previous fixed "4.0" silently rejected anything taller than 1080p
inside libx264 — "frame MB size > level limit", "DPB size > level
limit" — and emitted unplayable segments. Helper H264LevelForHeight()
now picks 4.0 / 5.0 / 5.1 / 6.0 from the actual encode height.
2. New `unarr probe-hwaccel` diagnostic command. Lists the HW encoders
compiled into ffmpeg, the device files / drivers present, and the
backend the daemon would actually pick today. Surfaces the canonical
gotcha: a host with an RTX 3090 + nvidia-smi but a Homebrew ffmpeg
built without --enable-nvenc still falls back to libx264 software.
3. Register payload now includes hwAccel + maxTranscodeHeight so the web
side can suggest a smaller alternate quality before the user even
tries to play a 4K source on a software-only host. Software-only =
1080p cap, any HW backend = 2160p cap.
1. -profile:v main + -level:v 4.0 to avoid Chrome's HW decoder path that
failed with "VaapiWrapper: failed initializing for h264 high" on Linux.
2. setparams to rewrite HDR HEVC color metadata to SDR Rec.709 so browsers
don't reject wide-gamut output.
3. serveRange caps `want` by estimated final size (not current). ReadAt
blocks until ffmpeg catches up — that's the right behaviour. Returning
RangeEnd inmediato was making the browser abort with "Format error".
4. Debug log on every range_req.
Adds WebRTCSession.Quality to the sync payload so the daemon can pick a
MaxHeight + bitrate per session instead of using the global config cap.
resolveQualityCap() maps the label to a (height, b:v) pair and
buildStreamSource() promotes a passthrough decision to ActionTranscodeVideo
when the source resolution exceeds the cap (4K source on a phone client
with quality="720p" must transcode, not pass-through).
Also lands the transcode-on-by-default fix for legacy configs without a
[downloads.transcode] section so existing installs pick up h264+aac
fallback for HEVC/AC3 content without re-running setup.
Source files in HEVC, AV1, AC3, DTS, EAC3, etc. now transcode through ffmpeg
to fragmented MP4 (h264 + aac) on-the-fly when the browser would otherwise
play silent black. Decision matrix lives in engine.DecideAction:
passthrough → remux → audio-transcode → full video-transcode.
Architecture — temp file + growing-size source:
- engine.streamSource interface abstracts byte source. Two impls:
* diskFileSource: passthrough when codecs are already browser-friendly.
* transcodeSource: spawns ffmpeg writing to a /tmp/tc-stream-*.mp4 file.
A ticker polls file size and wakes blocked ReadAt callers as ffmpeg
produces output. Estimate of final size (bitrate × duration) is
announced over the wire so the browser's scrubber has something to
anchor on.
- dataChannelPump now reads from streamSource instead of *os.File. HELLO
carries Transcoding=true + an estimated total size; Seekable=true (we
read random-access from the temp file even while writing).
- Transcoder runtime resolved per session by buildTranscodeRuntime in
cmd/daemon: ffmpeg/ffprobe path lookup + HWAccel auto-detection
(NVENC/QSV/VAAPI/VideoToolbox).
- New [downloads.transcode] TOML section: enabled (default true), hw_accel
(auto), preset (veryfast), video_bitrate (5M), audio_bitrate (192k),
max_height (optional downscale), max_concurrent (safety cap).
Falls back to passthrough if ffprobe is missing, fails, or codecs are
already browser-friendly. tmp file is cleaned up on session shutdown.
