lektor-ai/docs/usage.md

Usage

ComfyUI must be running before any command that generates speech (~/comfy-tts-app/start_comfyui.sh). --rebuild is the exception — it only touches ffmpeg and works with the backend stopped.

Invocation

python3 lektor_ai_comfy.py [SRT] VIDEO [options]

Both positionals are optional in the argparse sense, because several modes do not need an SRT file. The rule:

# External subtitle file — pass both, SRT first
python3 lektor_ai_comfy.py input/film.pl.srt input/film.mkv

# Subtitles inside the video — pass the video alone
python3 lektor_ai_comfy.py input/film.mkv --embedded-subs

# --rebuild and --regen also need only the video
python3 lektor_ai_comfy.py input/film.mkv --rebuild

When a single positional is given in a mode that needs no SRT, the script moves it into the video slot automatically. Always quote paths containing spaces or parentheses:

python3 lektor_ai_comfy.py "input/Star City (2026)/S01_E01 The Eyes.mkv" --embedded-subs

Working modes

Full generation (default)

Parses subtitles, generates one TTS clip per block, assembles, muxes.

python3 lektor_ai_comfy.py input/film.mkv --embedded-subs

Roughly real-time-ish on a 4070 Ti SUPER: a 60-minute episode of ~700 subtitle blocks takes on the order of an hour. Each clip is saved as it completes, so a crash never loses more than the clip in flight.

--embedded-subs

Lists the video's subtitle tracks and prompts for one:

  Available subtitle tracks in S01_E01 The Eyes.mkv:
    [1] Stream #2: subrip [eng] — Forced
    [2] Stream #3: subrip [eng]
    [3] Stream #4: subrip [eng] — SDH
   ...
    [30] Stream #31: subrip [pol]
  Select track number: 30

The chosen track is extracted to embedded_sub.srt in the job folder and processed exactly like an external file. Image-based tracks are listed but marked unusable — they hold bitmaps, not text.

--rebuild

Reassembles audio from existing clips and rebuilds the video, with no TTS at all. This is the fast iteration loop — seconds to minutes rather than an hour.

python3 lektor_ai_comfy.py input/film.mkv --rebuild
python3 lektor_ai_comfy.py input/film.mkv --rebuild --orig-volume 0.5 --tts-volume 2.0

Use it after --regen, or to adjust the mix. It reads that video's job folder (output/clips/<video name>/) and needs its tts_input.srt plus a complete set of clip_NNNN.flac, reporting which are missing if any are.

If the original run used --end, pass it again so the same video fragment is used.

--regen

Regenerates specific clips by block number, leaving everything else alone.

python3 lektor_ai_comfy.py input/film.mkv --regen 12 22 41
python3 lektor_ai_comfy.py input/film.mkv --rebuild        # then apply

Block numbers match that job's tts_input.srt and its clip_NNNN.flac files. Only the selected FLAC files are replaced — --rebuild afterwards is what actually updates the video.

This is the intended fix for a bad clip. There is no automatic retry; when the model hallucinates, mumbles, or truncates, note the number and regenerate it. A different seed usually resolves it, and --seed 0 (the default) randomises every run.

--resume-from

Continues a crashed run, loading clips 1..N-1 from disk and generating from N onward.

python3 lektor_ai_comfy.py input/film.mkv --resume-from 47

The console prints [47/693] style progress, so the number to resume from is the last one that completed.

--skip-tts

Uses a pre-assembled audio file and goes straight to the mux.

python3 lektor_ai_comfy.py input/film.mkv --skip-tts "output/clips/film/tts_assembled.flac"

Settings file

Defaults live in settings.ini next to the script, so the values you always want no longer need to be typed on every run. Precedence:

command-line flag   >   settings.ini   >   built-in default

[tts]
voice = gudowski_short
speed = 1.2
temperature = 0.9
max_tokens = 4096
strip_leading_ms = 0
trailing_fade_ms = 80

[mix]
orig_volume = 0.60
tts_volume = 1.8

[paths]
output_dir = output

[comfy]
comfy_url = http://127.0.0.1:8189

Every one of these has a matching flag that overrides it for a single run:

# settings.ini says tts_volume = 1.8; this run uses 2.5
python3 lektor_ai_comfy.py film.mkv --embedded-subs --tts-volume 2.5

Each run prints which file it used, so there is never any doubt:

  Settings: /home/lukas/Programy/lektor_ai/settings.ini

Alternative profiles — keep per-show settings side by side and select one:

python3 lektor_ai_comfy.py film.mkv --embedded-subs --settings profiles/docu.ini

Behaviour when things are missing or wrong, none of which is fatal:

Situation	Result
No settings.ini	Built-in defaults; the run says so
Key absent from the file	That key falls back to its built-in default
Value unparseable (speed = fast)	Warning, that key falls back, run continues
File is not valid INI	Warning, all built-in defaults, run continues

Comments use # or ;, inline comments included. Deleting a line is a valid way to return it to its built-in default.

Not in the file, by design: --start, --end, --seed, --regen, --rebuild, --resume-from, --embedded-subs, --skip-tts. These describe a particular run rather than your setup, so pinning them in config would be a trap.

Options

Every option below can also be set in settings.ini, except those noted as run-specific.

Range

Flag	Default	Meaning
--start MM:SS	00:00	Start of the range to process
--end MM:SS	(end)	End of the range

With --end, a matching fragment is extracted to video_fragment.mkv in the job folder and all TTS timestamps become relative to --start. Pass the same values to any later --rebuild, or the audio will not line up.

--end 01:00 is the quickest way to sanity-check a new voice or speed setting.

Voice and model

Flag	Default	Meaning
--voice NAME|PATH	gudowski_short	Name in voices/, or a path to a WAV
--seed N	0	Base seed; 0 randomises each run
--temperature T	0.9	Sampling temperature
--max-tokens N	4096	Token ceiling per clip

--temperature is worth understanding. At 1.0 the model sometimes recites the reference transcript instead of the subtitle. 0.9 largely prevents that; lower is more deterministic but flatter. A per-clip seed of base_seed + index means a fixed --seed reproduces a run exactly.

Raise --max-tokens only if long clips are cut off mid-word.

Timing and cleanup

Flag	Default	Meaning
--speed FACTOR	1.2	Per-clip speed-up via atempo
--strip-leading-ms MS	0	Trim the start of each clip
--trailing-fade-ms MS	80	Fade the end of each clip

--speed compresses speech so a clip is more likely to fit its subtitle window. It is applied per clip, before assembly — never to the assembled track, which would shift every timestamp by speeding up the silences too.

--strip-leading-ms removes an inhale artifact at clip starts; try 80–150 if you hear one. --trailing-fade-ms suppresses tail pops; 0 disables it.

Mixing

Flag	Default	Meaning
--orig-volume 0-1	0.60	Original audio level inside the lektor mix
--tts-volume 0-2	1.8	Voiceover level inside the lektor mix

These affect Track 1 only. Track 0 is always the untouched original, so nothing is lost by mixing aggressively. Changing them needs only --rebuild.

Typical starting point for dialogue-heavy material: --orig-volume 0.5 --tts-volume 2.0. For quiet sources, --orig-volume 1.0 --tts-volume 1.4.

Paths

Flag	Default	Meaning
--output-dir DIR	output	Where everything is written
--comfy-url URL	http://127.0.0.1:8189	Backend address

Output

Everything belonging to one video is kept together in a job folder named after the video file. Only the finished video is written to the top level.

output/
  clips/
    S01_E01 The Eyes/          job folder, named after the video file
      clip_NNNN.flac           one lossless clip per block, kept for --regen
      tts_input.srt            processed text actually sent to TTS
      tts_assembled.flac       all clips at their final positions, lossless
      embedded_sub.srt         extracted subtitle (--embedded-subs only)
      video_fragment.mkv       extracted segment (--end only)
    F1 The Movie 2025/
      ...
  S01_E01 The Eyes_lektor.mkv  the finished video
  F1 The Movie 2025_lektor.mkv

Each run prints the folder it is using:

  Job folder: output/clips/S01_E01 The Eyes

This is what makes --rebuild and --regen safe across films. tts_input.srt and the clips are a matched pair — block N in the SRT is clip_NNNN.flac — so both live in the job folder. They previously sat at the top level and every new job overwrote the last one's, which meant rebuilding an older film paired its clips with the newest film's text. Any past job can now be rebuilt at any time.

The folder is derived from the video filename, so --rebuild and --regen locate it automatically; just pass the same video path.

The finished file contains:

Track	Content
Video	Stream-copied, untouched
Audio 0	Original — stream-copied, full 5.1 if the source had it
Audio 1	Polish — lektor mix, AAC 192k stereo, language=pol
Subtitles	Every track from the source, stream-copied

The lektor track is stereo deliberately; see troubleshooting.md.

FLAC is used for every intermediate so repeated processing stays lossless. Only the final voiceover track is ever encoded.

Recipes

Check a voice before committing to a full run

python3 lektor_ai_comfy.py input/film.mkv --embedded-subs --end 02:00 --voice gudowski

Tune the mix without regenerating speech

python3 lektor_ai_comfy.py input/film.mkv --rebuild --orig-volume 0.45 --tts-volume 2.1

Fix a handful of bad clips

# read output/clips/<video name>/tts_input.srt, note the offending block numbers
python3 lektor_ai_comfy.py input/film.mkv --regen 88 91 104
python3 lektor_ai_comfy.py input/film.mkv --rebuild

Reproduce a run exactly

python3 lektor_ai_comfy.py input/film.mkv --embedded-subs --seed 123456

Speech running long and overlapping the next line

python3 lektor_ai_comfy.py input/film.mkv --embedded-subs --speed 1.35

Reading the console

[1/4] Parsing subtitles 00:00–end…
      693 entries after dialogue splitting.
[2/4] Generating TTS (693 clips, speed 1.2×)…
  [12/693] 00:01:34,120  'Nie wiem, o czym mówisz.'
    Waiting for a3f8b201… done.
    → placed at 00:01:34,120, duration 1.84s

→ placed at reveals timing drift. A clip that overruns its window pushes the next one forward, shown as [+1.20s behind SRT]. Small values are normal and self-correct at the next natural gap in the subtitles; values that keep growing mean --speed is too low for the material.

Assembly then shows a progress bar per batch (clips are assembled 500 at a time to stay under the open-file limit), followed by the two-pass mux.