Feature request: add audio track to video

[christiaanwesterbeek]

Add a new tool to overlay or replace an audio track in a video file. This complements existing features like video trim/rotate/merge, audio trim/merge, and audio extraction from video, enabling users to customize video audio without external software. All processing remains client-side for privacy.

Rationale

Users often need to dub videos with new audio (e.g., music, voiceover) or fix audio issues. Given OmniTools' focus on lightweight, browser-based media editing, this fits seamlessly and enhances the video/audio suite.

Implementation Suggestion

Create a new tool under src/tools/video (similar to VideoTrimmer or VideoReverser), using the existing FFmpeg.wasm integration (assuming it's used for trim/merge/extract, as common in client-side media processing with @ffmpeg/ffmpeg).

• UI: Inputs for video file and audio file; options for "replace existing audio" (default) or "mix/add as secondary track"; output format selector.
• Logic: Load files via File API; use FFmpeg commands:
  • Replace: ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 output.mp4
  • Mix/Add: ffmpeg -i video.mp4 -i audio.mp3 -filter_complex "[0:a][1:a]amix=inputs=2:duration=shortest" -c:v copy output.mp4 (for mixing) or -map 0 -map 1:a -c copy (add track).
• Reuse shared utils for file handling/progress (e.g., from merge tools).
• Test: Ensure compatibility with common formats; handle duration mismatches by trimming longer audio.

This should be lightweight (~similar complexity to audio merge), leveraging existing libs without new dependencies.