How to Convert MTS to MP4 for Easy Sharing

Why MTS Files Need Converting

MTS is the file extension used by AVCHD (Advanced Video Coding High Definition) camcorders from manufacturers like Sony, Panasonic, and Canon. When you connect your camcorder or insert its SD card, you will find .mts files inside a PRIVATE/AVCHD/BDMV/STREAM folder. These files contain H.264 video at 1080i or 1080p resolution with AC3 (Dolby Digital) audio.

The format itself is technically sound — it uses efficient H.264 compression and delivers broadcast-quality video. The problem is the ecosystem around it. Editing software often struggles with the AVCHD folder structure, social media platforms reject MTS uploads, and many media players cannot handle the interlaced content properly. Converting to MP4 strips away the AVCHD packaging and gives you a clean, universally playable file.

The good news is that since MTS files already use H.264 video, you can often remux them to MP4 without any re-encoding. The video stream is simply copied from the MTS container into an MP4 container — a process that takes seconds and loses nothing.

MTS vs. MP4: Technical Breakdown

Step-by-Step: Remux MTS to MP4

Basic Lossless Remux

Since MTS already contains H.264 video, a simple copy operation works:

ffmpeg -i input.mts -c:v copy -c:a aac -b:a 192k \
  -movflags +faststart output.mp4

We copy the video stream (-c:v copy) but re-encode the audio to AAC (-c:a aac) because some players handle AC3 poorly in MP4 containers. If you prefer to keep the original AC3 audio:

ffmpeg -i input.mts -c copy -movflags +faststart output.mp4

Deinterlacing 1080i Footage

Most consumer AVCHD camcorders shoot in 1080i (interlaced), where each frame contains only half the vertical resolution. For playback on modern progressive displays, deinterlacing produces a cleaner result:

ffmpeg -i input.mts -vf "yadif=mode=0:parity=auto" \
  -c:v libx264 -crf 18 -preset slow \
  -c:a aac -b:a 192k -movflags +faststart output.mp4

The yadif filter is FFmpeg's standard deinterlacer. mode=0 sends one frame per field (maintaining the original frame rate), while parity=auto lets FFmpeg detect the field order automatically.

Batch Convert All MTS Files

Camcorder recordings often span multiple files (the AVCHD spec limits individual files to around 2 GB on FAT32 SD cards). Convert them all at once:

mkdir -p converted
for file in *.mts; do
  [ -f "$file" ] || continue
  ffmpeg -i "$file" -c:v copy -c:a aac -b:a 192k \
    -movflags +faststart "converted/${file%.mts}.mp4"
done

For advanced batch processing workflows, see our batch processing guide.

Joining Split AVCHD Recordings

AVCHD camcorders split long recordings across multiple MTS files due to FAT32 file size limits. To rejoin them into a single MP4:

# Create a file list
echo "file 'input1.mts'" > filelist.txt
echo "file 'input2.mts'" >> filelist.txt
echo "file 'input3.mts'" >> filelist.txt

# Concatenate and remux
ffmpeg -f concat -safe 0 -i filelist.txt \
  -c:v copy -c:a aac -b:a 192k \
  -movflags +faststart output.mp4

This concatenation is lossless for the video stream since all segments share identical encoding parameters (same camcorder, same recording session).

Online Conversion

For a quick conversion without command-line tools, use the MTS to MP4 converter online. Upload your MTS file, and the converter handles codec detection and optimal conversion settings automatically. The full Video Converter offers additional output format options.

Quality and Settings Recommendations

When remuxing (no re-encode), quality is identical to the original. There is nothing to configure — you are copying bits.

When re-encoding (for deinterlacing or compression), use these guidelines:

Audio: AVCHD uses AC3 at 256 kbps (5.1) or 192 kbps (stereo). When converting to AAC, match or exceed the original bitrate: 256 kbps for 5.1 content, 192 kbps for stereo. For more on audio settings, read our audio bitrate guide.

Frame rate: Do not change the frame rate unless you have a specific reason. AVCHD footage is recorded at a precise frame rate (23.976, 29.97, or 59.94 fps in NTSC regions; 25 or 50 fps in PAL regions). Altering it causes judder. Let FFmpeg preserve the original rate with -r omitted.

Common Issues and Troubleshooting

"Discarding non-monotone timestamps" on Panasonic footage

Some Panasonic AVCHD camcorders write slightly irregular timestamps. This warning is usually harmless, but if you see sync issues in the output:

ffmpeg -fflags +genpts+igndts -i input.mts -c copy output.mp4

Video plays at wrong speed

This happens when the player misreads the frame rate. Adding -r 29.97 (or your source frame rate) to the FFmpeg command explicitly sets the output rate:

ffmpeg -i input.mts -c:v copy -c:a aac -b:a 192k \
  -r 29.97 -movflags +faststart output.mp4

Choppy playback from interlaced content

If the output looks like it has horizontal lines or combing artifacts, the source is interlaced and you skipped deinterlacing. Re-encode with the yadif filter as shown above.

Missing audio in output

Some MTS files have LPCM (uncompressed) audio, which MP4 does not support. Convert the audio:

ffmpeg -i input.mts -c:v copy -c:a aac -b:a 256k output.mp4

For further reading on video codecs and container formats, check out our container vs codec explained guide.

Conclusion

MTS files from AVCHD camcorders contain perfectly good H.264 video that just needs repackaging for modern devices. A simple remux copies the video untouched into an MP4 container in seconds. If your footage is interlaced (most consumer AVCHD is 1080i), deinterlacing with the yadif filter during re-encoding produces clean progressive output suitable for editing, uploading, and sharing.

Ready to convert? Try our free MTS to MP4 converter — no registration required.