How to Convert M2TS (AVCHD Camcorder Footage) to MP4

An M2TS file contains H.264 (AVC) video and either AC3 (Dolby Digital) or LPCM (uncompressed) audio, packaged in an MPEG-2 Transport Stream container. The video codec is the same H.264 that MP4 files use — the difference is entirely in the container format.

This is important because it means the video data doesn't necessarily need to be re-encoded. In theory, the H.264 stream could be extracted from the M2TS container and placed into an MP4 container — a process called remuxing — with zero quality loss. In practice, some M2TS streams have characteristics (like certain NAL unit structures or SEI messages) that not all MP4 parsers handle correctly, so most converters do a light re-encode to be safe.

The audio is a different story. AC3 audio is common in AVCHD but not widely supported in MP4 containers. Most converters will transcode the audio from AC3 to AAC, which is the standard audio codec for MP4. This is a lossy-to-lossy conversion, but both formats sound fine for video audio at 128-256 kbps.

Upload your M2TS file to the iFormat Video Converter, select MP4 as the output format, and download the result. The converter handles the codec conversion and container repackaging in one step.

For quality settings:

High quality — use this for footage you want to keep looking sharp. The output file will be roughly the same size as the M2TS original (or slightly smaller since MP4 container overhead is lower than M2TS).

Medium quality — a good balance for sharing. Files are 40-60% smaller than the originals. Quality is excellent on phones and laptops.

Lower quality — for getting under upload size limits. Expect visible compression in complex scenes but still watchable.

HandBrake is the best free desktop tool for this job, especially for batch conversion of many files.

Open HandBrake, drag in your M2TS file (or open it via File > Open Source). The default "Fast 1080p30" preset works well for most AVCHD footage. Here are the key settings to check:

Video codec — H.264 (x264) is the default and the safe choice. H.265 (x265) produces smaller files but encoding is 2-3x slower.

Quality (RF/CRF) — the default 22 is good. Lower numbers = higher quality and bigger files. For archival quality, try RF 18-20. For sharing, 22-24 is fine.

Encoder preset — this controls encoding speed vs efficiency. "Medium" is the default and a good balance. "Slow" produces slightly smaller files at the same quality but takes significantly longer. "Veryfast" is quick but files are larger.

Audio — change to AAC and set bitrate to 160 kbps for a good balance of quality and size. HandBrake defaults to AAC passthru if the source is AAC, but AVCHD files typically have AC3 audio, so it'll need to transcode.

For command-line users, FFmpeg gives you the most control:

ffmpeg -i input.m2ts -c:v libx264 -crf 20 -preset medium -c:a aac -b:a 192k output.mp4

For 1080i interlaced footage, add deinterlacing:

ffmpeg -i input.m2ts -vf yadif -c:v libx264 -crf 20 -preset medium -c:a aac -b:a 192k output.mp4

To batch-convert all M2TS files in a folder:

for f in *.m2ts; do ffmpeg -i "$f" -c:v libx264 -crf 20 -c:a aac -b:a 192k "${f%.m2ts}.mp4"; done

If you want to try remuxing without re-encoding (fastest, zero quality loss, but doesn't always work perfectly with all players):

ffmpeg -i input.m2ts -c:v copy -c:a aac -b:a 192k output.mp4

The -c:v copy flag copies the video stream without re-encoding. The audio still gets transcoded from AC3 to AAC because most MP4 players expect AAC.

When you copy files from an AVCHD camcorder, you might be tempted to just grab the .m2ts files from the STREAM folder. That works for conversion, but you lose metadata — recording dates, scene markers, clip thumbnails — stored in the CLIPINF and PLAYLIST folders.

For long-term archival, copy the entire PRIVATE/AVCHD folder structure to your computer first. Then convert the individual M2TS files from the STREAM subfolder. Keep the original folder structure as your master archive and use the MP4 files for everyday playback and sharing.

If you're importing into an NLE before converting, the folder structure matters more — see our guide on fixing camcorder import issues for NLE-specific instructions.

One common mistake: don't convert from the memory card directly. Copy the files to your computer's local drive first. SD cards and USB connections are slow, and some conversion tools behave unpredictably when reading from removable media — FFmpeg can produce output errors if the read speed can't keep up with the decode rate.

AVCHD camcorders often split recordings into multiple clips. Some split automatically at the FAT32 file size limit (4 GB, roughly 25 minutes at 24 Mbps). Others create a new clip every time you hit record. Either way, you end up with a dozen M2TS files for what was essentially one continuous event.

If you want one continuous MP4 from multiple M2TS clips, FFmpeg's concat demuxer handles this cleanly. Create a text file called clips.txt with entries like:
file '00001.m2ts'
file '00002.m2ts'
file '00003.m2ts'

Then run:
ffmpeg -f concat -safe 0 -i clips.txt -c:v libx264 -crf 20 -c:a aac -b:a 192k merged.mp4

This joins all clips and re-encodes to a single MP4. If the clips were all recorded at the same settings (same bitrate, resolution, frame rate), the join is seamless. If settings changed between clips (e.g., you switched from 1080i to 720p mid-event), you'll want to convert each clip separately.

At CRF 18-20 (high quality), the converted MP4 is visually identical to the M2TS original. There's a generation loss in theory — you're decoding H.264 and re-encoding to H.264 — but modern x264 encoder at these settings preserves essentially all visible detail.

The MP4 file size will be similar to or slightly smaller than the M2TS original at equivalent quality, because the MP4 container has less overhead (no transport stream packets, no 4-byte timestamp prefix per packet that M2TS adds).

At CRF 22-24 (medium quality), you start saving meaningful file space — 30-50% smaller files. Quality is still excellent for sharing and playback. For archival purposes, stick with CRF 18-20.

One thing to watch for: if your source is 1080i and you deinterlace during conversion, the deinterlacing itself changes the image. Yadif and Decomb are both good deinterlacers, but any deinterlacing slightly softens the image compared to the interlaced source. This isn't a quality loss from the format conversion — it's a necessary trade-off to make the video look right on progressive displays.

Can I convert M2TS to MP4 without re-encoding?
In many cases, yes — FFmpeg's -c:v copy flag remuxes the video stream without re-encoding. Not all players handle the result perfectly, though. A light re-encode at high quality is the safer option and the quality difference is imperceptible.

Why are my converted files larger than the originals?
If you're using a very low CRF (high quality) setting, the x264 encoder might actually produce more data than the original camcorder encoder, which typically used hardware encoding at fixed bitrates. Try CRF 22 instead of 18 — you'll get smaller files while still maintaining excellent quality.

My M2TS files have combing / horizontal lines in motion. What's going on?
That's interlacing. Your camcorder recorded in 1080i (1080 interlaced). Apply deinterlacing during conversion — HandBrake's Decomb filter or FFmpeg's yadif filter fix this.

Can I merge multiple M2TS clips into one MP4?
Yes. FFmpeg can concatenate clips: create a text file listing all inputs, then use ffmpeg -f concat -i list.txt -c copy merged.mp4. HandBrake doesn't support joining files, so use FFmpeg or the online converter for this.

Should I keep the original M2TS files?
For irreplaceable footage (family events, client work), yes. Keep them as the unaltered source. Storage is cheap — a 4TB external drive costs under $100.

For more on camcorder formats and what they actually mean, check our M2TS vs MTS vs MP4 comparison guide.