Configuration

All settings are controlled via environment variables.

Variable	Default	Description
SOURCE_FOLDER	/app/source	Path to the directory containing original videos
DEST_FOLDER	/app/destination	Path to the directory for encoded output
ENABLE_HW_ACCEL	true	Enable hardware-accelerated encoding
HW_ENCODING_TYPE	nvidia	Hardware encoder: nvidia or intel
HW_DECODE	true	Decode and scale on the GPU as well as encode; false decodes and scales in software (see Decoding on the GPU)
ENCODING_CODEC	hevc	Output codec: hevc, h264, or av1
OUTPUT_CONTAINER	auto	Container: auto (MP4 for H.264, MKV otherwise), mkv, or mp4
ENCODING_QUALITY	LOW	Quality preset: LOW, MEDIUM, or HIGH
AUDIO_CODEC	auto	Audio codec: auto (AAC for MP4, AC3 for MKV), aac, or ac3
AUDIO_BITRATE	auto	Bitrate per audio track: auto (192k stereo, 384k multichannel) or a value such as 256k
AUDIO_CHANNELS	auto	Channels per audio track: auto (AAC keeps up to 5.1, AC3 downmixes to stereo) or a count such as 2
SYMLINK_TARGET_PREFIX	(empty)	Absolute path prefix for Jellyfin version symlinks (same-host mode)
SYMLINK_MANIFEST_TARGET	(empty)	Path prefix for cross-host manifest-based symlinks (see Cross-Host Setup)
SYMLINK_VERSION_SUFFIX	- 720p	Suffix appended to symlink filenames
CLEANUP_INTERVAL_HOURS	6	Hours between automatic orphan cleanup runs
POLL_INTERVAL	60	Seconds the folder watcher waits between scans of the source tree (see Polling interval)
DEST_MIN_FREE_GB	0	Free-space floor for the destination, in GB: encodes wait while the destination filesystem has less than this free (see Free-space floor)
FFMPEG_LOGLEVEL	warning	What FFmpeg writes to the container log during an encode (see FFmpeg log level)
PRIORITY_FILE	$SOURCE_FOLDER/.encoder-priority.json	JSON list of source paths to encode before the rest (see Priority list)
PRIORITY_MAX_AGE_HOURS	0	Hours a priority list counts after its generated time; older lists are ignored. 0 turns the check off (see Priority list)
MAX_HW_WORKERS	1	Encodes run at once on the GPU; ignored when ENABLE_HW_ACCEL is false (software runs one worker per CPU core)
SKIP_IF_LOW_QUALITY_EXISTS	true	Skip a source when a sibling file already at 720p or lower sits beside it
IMAGE_MOVED_TO	(empty)	Set only on drumsergio/jellyfin-encoder images; makes the startup log say where the image moved

Quality Presets

Each preset defines constant-quality (CQ) values for hardware encoding and constant rate factor (CRF) values for software fallback.

Preset	HEVC CQ / CRF	H.264 CQ / CRF	AV1 CQ / CRF	Intended Use
LOW	32 / 30	28 / 26	45 / 40	Mobile devices, minimal storage footprint
MEDIUM	26 / 26	24 / 23	35 / 35	Balanced quality and file size
HIGH	22 / 22	21 / 20	28 / 28	Higher fidelity, larger files

H.264, AAC and MP4 Output

Set ENCODING_CODEC: "h264" and new encodes come out as H.264 video with AAC audio in an MP4 container. Nothing else about the setup changes.

Aspect	What you get
Video encoder	h264_qsv (Intel), h264_nvenc (NVIDIA), libx264 (software fallback)
Container	.mp4, with the index written at the front so players can start before reading the whole file
Audio	AAC, source channel layout up to 5.1, at 192 kbps stereo or 384 kbps multichannel
Pixel format	Forced to 8-bit yuv420p, so 10-bit sources encode instead of failing on hardware H.264

hevc and av1 still produce .mkv with the stereo AC3 audio they always have. To pair a codec with a different container, set OUTPUT_CONTAINER explicitly.

Switching codec never re-encodes what you already have

Changing ENCODING_CODEC on a library that is already encoded produces zero re-encodes.

An output on disk counts as done whatever container it is in. If your destination is full of Movie - 720p.mkv files and you switch to ENCODING_CODEC: "h264", the encoder leaves those files alone. It picks up only the titles that have no encode at all, and those come out as .mp4. Switching back to hevc works the same way in reverse, respecting the .mp4 outputs you already have.

The skip check, orphan cleanup, the symlink manifest, and source-deletion handling all match on the filename stem rather than the extension. A destination folder holding a mix of .mkv and .mp4 works fine, so the two formats can coexist for as long as you like.

Subtitles in MP4

MP4 carries text subtitles only. The encoder converts text tracks (SRT, ASS/SSA, WebVTT) to mov_text and drops bitmap tracks (PGS, DVB), which have no MP4 equivalent. Keep external .srt sidecars next to the encode if you need those. If FFmpeg fails with subtitles mapped, the encoder retries once without them. A subtitle track FFmpeg cannot handle costs you the subtitles, never the encode.

Free-space floor

DEST_MIN_FREE_GB=1000 makes the encoder hold each new encode while the destination filesystem has less than 1 TB free, re-check every five minutes, and carry on by itself when space returns. Encodes already running finish, and the floor is checked again after the wait for a still-growing source, right before ffmpeg starts. If the free space cannot be read at all, the encode proceeds and ffmpeg reports whatever is really wrong, so the floor is a courtesy to the disk's other tenants, not a guarantee against ENOSPC. Use it when the destination shares a disk with something that must never see ENOSPC, such as an object store node or a database. The default 0 keeps the old behaviour: encode until the disk is full.

Priority list

At every start the encoder queues every source in the order the folder walk finds them, so on a large library the next episode of a show people are watching can sit thousands of files down the queue. PRIORITY_FILE lets something outside the encoder put those first; the Quality Gate plugin writes it from what capped viewers are about to watch, and anything else may write the same format. The encoder only reads it, so it can live on a read-only source mount.

{
  "generated": "2026-01-01T00:00:00Z",
  "paths": [
    "Show A (2001)/Season 02/",
    "Film B (2002)/Film B (2002).mkv",
    "Show C (2003)/"
  ]
}

• The file is UTF-8 JSON. A leading byte order mark, as some Windows tools write, is fine.
• Each entry is a path relative to SOURCE_FOLDER: a folder (ends with /) or one file. The list is in priority order, highest first.
• A queued file belongs to the first entry that is its own path or a folder holding it. Matching is on whole path components, so Show A/ covers Show A/S01/E01.mkv and not Show AB/S01/E01.mkv.
• Both sides are compared in Unicode NFC, so an accented name matches whether the list or the filesystem spells é as one character or as e plus a combining accent. Nothing else is folded: show a/ does not match Show A/.
• Files of an earlier entry encode before files of a later one. Within one entry they go in path order, so S01E01 comes before S01E02. Files no entry covers go last, in the order they were queued.
• Before each pick the encoder checks the file's modification time and size, and re-reads it when either changed. A new list re-orders what is still waiting; encodes already running finish. A file the watcher finds later goes straight to its place in the order.
• A missing, unreadable, empty or invalid file changes nothing. The queue runs in the order files were found, as it did before this setting existed, and the encoder logs each change of state once, not on every pick.
• PRIORITY_MAX_AGE_HOURS guards against a producer that stopped running. When it is above 0, a list whose generated time is older than that many hours counts as absent, and so does a list whose generated is missing or is not an ISO 8601 extended time, with a T between date and time and a Z or UTC offset (2026-01-01T00:00:00Z, 2026-01-01T01:00:00+01:00). The age is checked at every pick, so a list expires without being touched, and it counts again once it is rewritten with a recent time. The log says why the list was set aside, once per change. A producer should rewrite the file at least once a day, and the setting should leave room for a missed run: with a daily producer, 48 survives one failure and ignores the list after the second. The default 0 never reads generated.

At startup, and on every reload, the log says how many waiting files the list matched and which one runs first:

Priority list /app/source/.encoder-priority.json: 3 entries, 42 of 51876 pending files match; first: Show A (2001)/Season 02/S02E05.mkv

FFmpeg log level

At warning, the default, FFmpeg prints nothing for a healthy encode and everything it complains about for a failing one. The encoder's own lines stay either way: the full command it ran, Encoding succeeded: with the finished path, and FFmpeg encoding failed (exit N) with the code FFmpeg died on.

The encoder used to run FFmpeg at verbose, which redraws a progress line twice a second. Python reads FFmpeg's output in text mode, where the carriage return that redraws the line counts as a newline, so every redraw became a log record of its own. A Docker json-file log at the default few megabytes then held a few hours, and anything older was gone before anyone went looking for it.

Set FFMPEG_LOGLEVEL=verbose on one container when a single file needs the full FFmpeg dump. The nine level names work: quiet, panic, fatal, error, warning, info, verbose, debug, trace. FFmpeg's numeric levels and its flag syntax, repeat+level+verbose, are not passed through. Anything outside the nine falls back to warning and logs a line naming what it takes, because a level FFmpeg does not know makes it exit before it opens the input, which would fail every encode.