alass ☆

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Description:
Automatic Language-Agnostic Subtitle Synchronization

Type: Formula | Latest Version: 2.0.0@0 | Tracked Since: Dec 17, 2025

Links: Homepage | formulae.brew.sh

Category: Multimedia

Tags: subtitles multimedia synchronization cli video

Install: brew install alass

About:
Alass is a command-line tool that automatically synchronizes subtitle files with their corresponding video content. It analyzes audio waveforms to detect and correct timing drifts, cuts, and shifts without requiring manual timestamps. This ensures perfect lip-sync and eliminates the need for tedious manual adjustment of subtitle delays.

Key Features:

Audio waveform analysis for precise synchronization
Handles variable frame rates and different frame rates between video and subtitles
Supports multiple subtitle formats including SRT and ASS
Can split and merge subtitle files based on video chapters or cuts

Use Cases:

Fixing out-of-sync subtitles downloaded from the internet
Adjusting subtitles for video files that have been re-encoded or edited
Synchronizing subtitles for anime episodes with different release versions

Alternatives:

Subtitle Edit – GUI-based tool with extensive manual editing features, but lacks Alass's automated waveform-based synchronization
ffsubsync – Similar automated sync functionality but implemented as a Python package with different algorithmic approach

License: GPL-3.0-or-later

Bottles available for: arm64_tahoe, arm64_sequoia, arm64_sonoma, arm64_ventura, arm64_monterey, arm64_big_sur, sonoma, ventura, monterey, big_sur, arm64_linux, x86_64_linux

Version History

Detected	Version	Rev	Change	Commit
Sep 13, 2025 10:31am		0	VERSION_BUMP	b6ce6714