Free online MTS to MKV converter

AVCHD camcorder clips may need conversion when a media player, editor, or archive workflow handles MKV more reliably than MTS. Converting only the container can preserve the original streams without quality loss; re-encoding is needed for smaller files or codec compatibility.

What the MTS format is

MTS is the filename extension commonly used for AVCHD recordings from Sony, Panasonic, Canon, and other HD camcorders. It is an MPEG transport stream that usually contains H.264/AVC video with AC-3 or LPCM audio. MTS clips may be copied from a camera’s BDMV/STREAM folder, exported by camera software, or stored individually on an SD card.

What the MKV format is

MKV, or Matroska Video, is a flexible container that can hold video, multiple audio tracks, subtitles, chapters, attachments, and metadata. Software such as VLC, Kodi, and many desktop media players supports it. MKV is useful for archiving because it can retain existing streams while adding subtitles, alternate audio, and chapter information.

MKV does not inherently compress video more than MTS. The file becomes smaller only when the video or audio is re-encoded with different settings.

Remux without quality loss using FFmpeg

Remuxing changes the container while copying the encoded streams. It avoids decoding and re-encoding, so it is normally fast and preserves the source quality and nearly the same file size.

1. Install FFmpeg from its official distribution and open a terminal in the folder containing the MTS file.
2. Run ffmpeg -i input.mts -map 0 -c copy output.mkv.
3. Replace input.mts with the source filename and output.mkv with the desired destination filename. Quote filenames containing spaces.

-map 0 requests all detected streams, and -c copy enables stream copying. If the source contains damaged or unsupported data, FFmpeg may need an explicit stream selection or may fail to create a valid MKV.

Re-encode for smaller files or broader compatibility

Use re-encoding when the target player rejects the original AC-3 or LPCM audio, has problems with interlaced AVCHD, or requires a smaller file. This example creates H.264 video with AAC audio:

ffmpeg -i input.mts -c:v libx264 -crf 20 -preset medium -c:a aac -b:a 192k output.mkv

For H.264, a CRF value around 18–23 is a practical range: lower values generally preserve more detail and produce larger files. The preset changes encoding speed and compression efficiency, not the intended quality level. Re-encoding takes longer and cannot restore detail already lost in the source.

Use a graphical converter

1. Open a desktop converter that supports MTS input and MKV output, then add the source file.
2. Choose MKV as the output container.
3. Select copy, remux, or passthrough for video and audio if the application provides those options.
4. If stream copying is unavailable or incompatible, select H.264 video and AAC or AC-3 audio, then adjust the quality and bitrate settings.
5. Choose the output folder and start the conversion.

HandBrake is available for Windows, macOS, and Linux and can create MKV files, but it is primarily a transcoder; it normally re-encodes video rather than performing a pure container-only remux. For a lossless MTS-to-MKV change, FFmpeg or a graphical application with an explicit remux mode is more appropriate. You can also convert the file for free on 101convert.com without installing software.

Quality and compatibility limitations

• Changing MTS to MKV does not increase resolution, bitrate, frame rate, or image quality.
• Remuxing is lossless for the encoded streams, but some players and devices may not support AC-3, LPCM, interlaced AVCHD, or camera-specific metadata inside MKV.
• A device that rejects MKV may also require particular video and audio codecs; changing the filename extension cannot solve that limitation.
• An individual MTS clip may not contain the camera’s complete recording structure. Preserve the entire AVCHD folder when archiving playlists, chapters, and related metadata matter.