Free online MTS to M4A converter

Source format: MTS

MTS is a video container format commonly used by AVCHD camcorders and some other digital cameras. It usually contains H.264/AVC video with AC-3 or PCM audio, and it is mainly used for recording high-definition footage directly from a camera. MTS files are often found on memory cards or copied from camera storage after filming.

Target format: M4A

M4A is an audio-only container based on the MPEG-4 standard. It is widely used for music, voice recordings, podcasts, and other audio playback on phones, computers, and media players. Its main advantages are good compression efficiency, broad compatibility, and support for high-quality audio such as AAC or ALAC.

How to perform the conversion

Converting MTS to M4A means extracting the audio track from the video file and saving it as an audio file. The best tool depends on whether you want a simple one-step conversion or more control over audio quality.

Option 1: FFmpeg is the most reliable choice for this conversion because it can directly extract and encode audio.

1. Install FFmpeg on your computer.
2. Open a terminal or command prompt in the folder containing the MTS file.
3. Run a command such as ffmpeg -i input.mts -vn -c:a aac -b:a 192k output.m4a.
4. The -vn option disables video, and -c:a aac creates an M4A-compatible AAC audio file.

If you want to copy the original audio without re-encoding and the source audio is already compatible with M4A, you can try ffmpeg -i input.mts -vn -c:a copy output.m4a. This is faster and avoids quality loss, but it only works when the audio codec is supported in the M4A container.

Option 2: VLC media player can also extract audio for basic conversions.

1. Open VLC and go to Media → Convert / Save.
2. Add the .mts file and choose Convert / Save.
3. Select an audio profile that outputs M4A/AAC if available.
4. Choose the destination filename ending in .m4a and start the conversion.

Option 3: 101convert.com can convert the file online for free without installing any software. Upload the .mts file, choose M4A as the output format, and download the converted audio when it is ready.

Notes on quality, compatibility, or limitations

MTS is a video format, so converting it to M4A removes the video and keeps only the audio track. If the MTS file contains multiple audio tracks, you may need to choose the correct one before conversion. Also, if the original audio is AC-3, many M4A workflows will re-encode it to AAC, which can slightly reduce quality, though the result is usually very good.

For best quality, use a high AAC bitrate such as 192 kbps or 256 kbps. If you need exact preservation of the original audio, check whether your source codec can be copied into M4A; otherwise, re-encoding is required. Compatibility is generally excellent for AAC-based M4A files across modern devices and apps.