py-roller 0.4.0

Composable lyric-audio alignment pipeline with staged execution, batch processing, and LRC/ASS export.

py-roller

py-roller is a CLI Solution for automatic rolling lyrics generating.

To be specific, py-roller is a composable lyric-audio alignment pipeline CLI for staged execution, batch processing, and LRC/ASS export. Designed to support multiple transcriber back-ends including WhisperX and wav2vec2.

• Package name: py-roller
• CLI command: py-roller
• Python import package: pyroller

Quick overview

py-roller treats alignment as a contiguous stage chain:

s -> f -> t -> p -> a -> w
splitter -> filter -> transcriber -> parser -> aligner -> writer

Core modes:

• run: execute one contiguous stage chain for one task
• batch: execute the same contiguous stage chain across many tasks

Core artifact types:

• input audio / lyrics
• intermediate vocal and filtered audio
• timed_units
• parsed_lyrics
• alignment_result
• written outputs such as LRC or ASS

Installation

From source:

pip install .

With audio backends and heavy model dependencies:

pip install .[audio]

After installation, the CLI command is:

py-roller

Quick start

Full pipeline: audio + lyrics -> LRC

py-roller run \
  --stages s,f,t,p,a,w \
  --audio ./song.mp3 \
  --lyrics ./song.txt \
  --filter-chain noise_gate,dereverb \
  --output-written ./song.lrc
  --language zh # Choose as you like

Start from a prepared vocal track

py-roller run \
  --stages t,p,a,w \
  --audio ./vocals.wav \
  --lyrics ./song.txt \
  --writer-backend ass_karaoke \
  --output-written ./song.ass
  --language zh # Choose as you like

Batch processing by stem

py-roller batch \
  --stages t,p,a,w \
  --audio ./audio_dir \
  --lyrics ./lyrics_dir \
  --output-written ./out_dir
  --language zh # Choose as you like

Core execution model

Contiguous stage chains only

The CLI only accepts contiguous subchains of the canonical order.

Valid examples:

• s,f,t,p,a,w
• t,p,a,w
• a,w
• w

Invalid examples:

• s,t,w
• s,p,a

Legal chain starts

Explicit artifact inputs are only valid at the correct chain start:

• --audio is valid when the chain starts at s, f, or t
• --lyrics is valid when the chain includes p
• --timed-units and --parsed-lyrics are only valid when the chain starts at a
• --alignment-result is only valid when the chain starts at w

Final outputs vs intermediate artifacts

Final user-requested outputs are only the explicit --output-* paths:

• --output-vocal-audio
• --output-filtered-audio
• --output-timed-units
• --output-parsed-lyrics
• --output-alignment-result
• --output-written

Everything else created under --intermediate is treated as intermediate state.

Common workflows

Start from raw audio

Use the full chain when you want splitting, filtering, transcription, alignment, and final writing in one command.

py-roller run \
  --stages s,f,t,p,a,w \
  --audio ./song.mp3 \
  --lyrics ./song.txt \
  --output-written ./song.lrc

Start from filtered or vocal audio

Skip splitter/filter when you already have a suitable track for transcription.

py-roller run \
  --stages t,p,a,w \
  --audio ./vocals.wav \
  --lyrics ./song.txt \
  --output-written ./song.lrc

Start from aligner artifacts

py-roller run \
  --stages a,w \
  --timed-units ./song.timed_units.json \
  --parsed-lyrics ./song.parsed_lyrics.json \
  --output-written ./song.lrc

Rewrite only from an existing alignment result

py-roller run \
  --stages w \
  --alignment-result ./song.alignment.json \
  --writer-backend ass_karaoke \
  --output-written ./song.ass

Backend defaults

Default backend selection is language-aware. Please note that the default selection of language is "mul" which works poorly when tested on both Chinese and English, please use the --language flag to specify the desired language if the language is directly supported.

Transcriber defaults

• zh -> mms_phonetic
• en -> whisperx
• mul -> wav2vec2_phoneme

Parser defaults

• zh -> zh_router_pinyin
• en -> en_arpabet
• mul -> mul_ipa

Other defaults

• aligner backend -> global_dp_v1
• writer backend -> lrc_ms
• language -> mul
• reserve_spacing -> enabled
• cleanup -> on-success

Writer behavior

LRC

The default writer is lrc_ms which writes LRC lines with millisecond precision. Other supported writer backends are:

• lrc_cs: writes LRC lines with centiscond precision
• lrc_compressed: writes LRC lines with millisecond precision, but compresses consecutive lines with the same timestamp
• ass_karaoke: see below

ASS karaoke

ass_karaoke writes ASS dialogue lines with karaoke timing tags.

Current defaults:

• structural / spacing lines are skipped by default
• display end time prefers matched unit timing instead of blindly extending to the next line
• unmatched lines receive a short visible duration fallback

Example:

py-roller run \
  --stages w \
  --alignment-result ./song.alignment.json \
  --writer-backend ass_karaoke \
  --output-written ./song.ass

Progress reporting

The project exposes a reusable progress-reporting interface so CLI and future GUI frontends can share the same stage updates.

Current behavior:

• splitter: Demucs progress plus wrapper stage progress
• filter: phase progress
• transcriber: phase progress
• aligner: phase progress plus DP row progress

In single-task run, progress is shown as CLI progress bars when the terminal supports it. In batch, per-task progress is logged to avoid multiple workers fighting for one terminal.

Intermediate files and cleanup

Intermediate files live under:

--intermediate/<task-id>/splitter
--intermediate/<task-id>/filter
--intermediate/<task-id>/logs

Default intermediate root:

<system temp>/py-roller-artifacts

Cleanup policy:

• --cleanup on-success keeps successful runs tidy by removing per-task intermediate directories
• --cleanup never keeps intermediate audio and logs for inspection

Batch mode

batch uses the same stage semantics as run, but applies them to many tasks.

Directory pairing

Directory mode currently supports:

--pair-by stem

Default candidate globs:

• --audio-glob "*.mp3"
• --lyrics-glob "*.txt"

Matching is non-recursive.

Example:

py-roller batch \
  --stages t,p,a,w \
  --audio ./audio_dir \
  --lyrics ./lyrics_dir \
  --output-written ./out_dir

Batch controls

• --jobs N: maximum number of parallel workers
• --continue-on-error: keep processing remaining tasks after failures
• --skip-existing: skip tasks whose declared final outputs already exist
• --manifest jobs.yaml: load explicit per-task paths from YAML instead of pairing by stem

Parallelism guidance

--jobs controls how many tasks run at the same time. This is separate from any model-level batch size.

Recommended starting point:

• CPU-only: --jobs 1 or --jobs 2
• single GPU: usually --jobs 1

YAML manifest format

Manifest mode is useful when filenames do not match cleanly by stem.

The manifest defines per-task input and output paths only. It does not override stage selection, language, backend choice, filter settings, jobs, or other batch-level options.

Supported top-level forms:

tasks:
  - id: song01
    audio: ./audio/song01_master.mp3
    lyrics: ./lyrics/song01_final.txt
    output_written: ./out/song01.lrc

or:

- id: song01
  audio: ./audio/song01_master.mp3
  lyrics: ./lyrics/song01_final.txt
  output_written: ./out/song01.lrc

Allowed manifest input keys:

• audio
• lyrics
• timed_units
• parsed_lyrics
• alignment_result

Allowed manifest output keys:

• output_vocal_audio
• output_filtered_audio
• output_timed_units
• output_parsed_lyrics
• output_alignment_result
• output_written

Optional helper key:

• id

Validation rules:

• each task must be a mapping
• unknown keys are rejected
• inputs must match the selected chain start
• outputs must be valid final outputs for the selected chain
• task ids / stems must be unique
• final output paths must not conflict across tasks
• relative paths are resolved relative to the manifest file location

YAML config for default CLI options

Use --config to load YAML defaults.

Priority order:

built-in defaults < config YAML < explicit CLI arguments

Section model:

• shared: defaults applied to both run and batch
• run: currently no extra keys beyond shared
• batch: defaults for batch-only options such as jobs and skip_existing

Example:

shared:
  language: mul
  reserve_spacing: true
  writer_backend: lrc_ms
  intermediate: ./tmp/py-roller-artifacts
  cleanup: on-success
  transcriber_device: cpu
  splitter_demucs_model: htdemucs
  filter_chain:
    - noise_gate
    - dereverb

batch:
  jobs: 2
  audio_glob: "*.mp3"
  lyrics_glob: "*.txt"
  continue_on_error: true

filter_chain can be written either as a comma-separated string or as a YAML list.

Troubleshooting

Interruption and child process cleanup

Batch fail-fast actively stops launching further work after the first task failure when --continue-on-error is not set, and worker cleanup includes a Windows-specific process-tree branch.

For older runs or already orphaned processes, Linux/macOS cleanup examples are still useful:

pkill -TERM -f 'python .*pyroller'
pkill -TERM -f 'demucs.separate|demucs'

If anything still survives:

pkill -KILL -f 'python .*pyroller'
pkill -KILL -f 'demucs.separate|demucs'

Inspect candidates first with:

ps -ef | grep -E 'pyroller|demucs'