Why does my recording only play in one ear?

Usually a mono microphone was plugged into one input of a stereo interface, leaving the other side empty. Choose “Stereo to mono” with the side that has sound, or “Mono to stereo” as dual mono, and both ears will hear it.

After converting to mono the audio got quieter or disappeared — why?

The left and right channels were out of phase, so they cancel when added. Use “Invert one channel” first, then convert to mono. A slight drop in level is normal: the mix takes half of each side so the sum cannot clip.

Which coefficients does the 5.1 downmix use?

The ITU-R BS.775 standard: front left/right pass through, center and surround channels are mixed in at −3 dB, the LFE is left out unless you tick the option, and the gains are normalized so the downmix cannot clip.

Are my files uploaded? Which formats work?

No — everything runs in your browser with FFmpeg (WebAssembly). MP3, WAV, M4A, FLAC, OGG, OPUS and more are supported, and you can drop in a video to process its audio track. The tool is free with no sign-up.

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🔈Audio Channel Tools - Stereo to Mono, Swap & Split Channels

Recording only plays in one ear? Two interview mics landed on the left and right channels? Left and right are reversed, the sound feels hollow, or you need a 5.1 movie track as headphone-friendly stereo? This tool gathers the everyday channel fixes in one place. Stereo to mono can mix both sides or keep only the left or right channel (handy when one side is noise). Mono to stereo copies the signal to both sides, or widens it into pseudo-stereo with complementary comb filters that still sum back to the original in mono. You can also swap left and right; split every channel into its own mono file (stereo gives L/R, 5.1 gives six files: FL, FR, FC, LFE and the surrounds); mute one side; adjust the balance; invert one channel by 180° to fix out-of-phase recordings that sound hollow and nearly vanish in mono; and downmix 5.1 to stereo with the ITU-R BS.775 coefficients, optionally including the LFE, normalized so nothing clips. Each file shows its channel layout (mono, stereo, 5.1…) after upload, whole batches can be processed at once, and the output keeps the original format or converts to MP3, M4A, WAV, FLAC, OGG or OPUS.

Free · No sign-up · Runs in your browserLast updated: 2026-10-26

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How to use Audio Channel Tools

1Upload one or more audio files (videos work too) and check the channel layout shown
2Pick a channel operation and set the source channel, balance or output format
3Click Process and download the results (several files can be zipped)

FAQ

Why does my recording only play in one ear?: Usually a mono microphone was plugged into one input of a stereo interface, leaving the other side empty. Choose “Stereo to mono” with the side that has sound, or “Mono to stereo” as dual mono, and both ears will hear it.
After converting to mono the audio got quieter or disappeared — why?: The left and right channels were out of phase, so they cancel when added. Use “Invert one channel” first, then convert to mono. A slight drop in level is normal: the mix takes half of each side so the sum cannot clip.
Which coefficients does the 5.1 downmix use?: The ITU-R BS.775 standard: front left/right pass through, center and surround channels are mixed in at −3 dB, the LFE is left out unless you tick the option, and the gains are normalized so the downmix cannot clip.
Are my files uploaded? Which formats work?: No — everything runs in your browser with FFmpeg (WebAssembly). MP3, WAV, M4A, FLAC, OGG, OPUS and more are supported, and you can drop in a video to process its audio track. The tool is free with no sign-up.