Steps
- Choose one audio file and confirm that it contains a readable audio stream.
- Select Mono for a downmix or Stereo for two-channel output.
- Choose the MP3 bitrate required by the destination.
- Process locally, listen to the result and download it.
Audio & video / Local FFmpeg tool
Mono / Stereo Audio Converter
Downmix audio to mono or produce a two-channel stereo output.
Files stay in your browser
The first run loads an approximately 31 MB FFmpeg WebAssembly core from this site. It does not use a CDN or upload your files.
Files are limited to 200 MB total and 20 minutes; mobile devices use an 80 MB limit. Reverse, GIF and boomerang tools have lower duration caps.
At most 60 download files are generated.
Choose files, set the controls, then start.
Processed result
The first run loads an approximately 31 MB FFmpeg WebAssembly core from this site. It does not use a CDN or upload your files.Validated downloads will appear here after processing.
Practical guide
Choose mono or stereo output for the next workflow
The mono option downmixes all source channels. The stereo option keeps two-channel sources or duplicates a mono source into left and right channels, then exports the result as MP3.
Settings and output
- Mono output
- Useful for centred voice, compatibility checks or workflows that require one channel.
- Stereo output
- Keeps separate left and right channels when they exist in the source.
- Mono source to stereo
- Duplicates the same signal to both channels; it does not create new spatial information.
How to useHow to use Mono / Stereo Audio Converter ⌄
What the tool actually does
Downmix audio to mono or produce a two-channel stereo output.
Reproducible example
Example inputAudio file: sample-1.wav
Output channels = Stereo
Audio bitrate = 192 kbps — balancedCreates a probed and validated .mp3 (audio/mpeg). Actual method: Mono averages channels; stereo output duplicates mono sources when no second channel exists. Output boundary: This does not create spatial separation that was absent from a mono source.
- 1
Choose Audio file sample-1.wav and first confirm that each required audio stream exists.
- 2
Use Output channels = Stereo; Audio bitrate = 192 kbps — balanced. The actual FFmpeg rule is: Mono averages channels; stereo output duplicates mono sources when no second channel exists.
- 3
A download appears only after duration, stream type and .mp3 container validation. Also check this boundary: This does not create spatial separation that was absent from a mono source.
Local AI / Speech to text
Transcribe the current audio or video
Open-source Whisper Tiny runs in your browser. The file, audio and result are never uploaded.
Choose an audio or video file in the workbench above first.
◎ The model loads only from 321Kit; MiniMax is not called and no transcript history is stored.
Transcript
How it works
Mono / Stereo Audio Converter
Mono averages channels; stereo output duplicates mono sources when no second channel exists.
How does this tool process my file?
Mono averages channels; stereo output duplicates mono sources when no second channel exists. Processing uses single-thread FFmpeg.wasm. The page does not upload, store or inspect file content outside this device. Cancel, error and page close terminate the worker and revoke temporary object URLs.
What limits apply to the output?
This does not create spatial separation that was absent from a mono source. Files are limited to 200 MB total and 20 minutes; mobile devices use an 80 MB limit. Reverse, GIF and boomerang tools have lower duration caps.
Anonymous feedback
Did this tool solve the job?
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