How to Convert AVCHD to MP4 on Windows

What AVCHD actually is

AVCHD stands for Advanced Video Codec High Definition. It is a camcorder recording specification created by Sony and Panasonic in 2006. The video is usually H.264, the audio is usually AC-3 or PCM, and the whole thing sits inside an MPEG-2 transport stream.

On a camera or SD card, AVCHD is not a single file. It is a folder structure:

PRIVATE/
  AVCHD/
    BDMV/
      STREAM/     ← the .MTS or .M2TS video clips
      PLAYLIST/
      CLIPINF/
      INDEX.BDM

The STREAM folder is where your footage lives. The other folders contain playlists and metadata. Some tools can read the whole structure; others only want the individual .MTS files.

AVCHD was common from roughly 2006 to 2015. It is not the same as MP4. A file can contain H.264 video and still be an AVCHD transport stream, which is why renaming .MTS to .MP4 does not make it play.

Before you start

• Copy the whole folder. Copy PRIVATE/AVCHD from the card or camera to your PC. Do not work directly from the card; a failed conversion is easier to recover from a copy.
• Leave room for output. A converted MP4 can be smaller than the source, but you still need temporary space. Keep at least the size of the source folder free.
• Install the converter. The trial is enough to test one clip. Do not buy until you have checked audio sync and orientation on your own footage.
• Find the clips. In BDMV/STREAM, sort by size. The largest files are usually the real recordings; tiny files may be thumbnails or metadata.

Method 1: Raize HD Video Converter (Windows, one-click)

This is the shortest path if you want a desktop app with a batch queue and no upload. The product is Windows-only and handles AVCHD, MTS and M2TS input.

1. Open the app and add the clips. Drag the .MTS or .M2TS files from BDMV/STREAM into the window, or use the Add button. Add several clips if you want a batch.
2. Choose MP4 output. Select MP4 as the output format. For archive footage, choose 1920×1080 and keep the source frame rate (often 25, 29.97 or 30 fps). For sharing, 1280×720 is smaller and still looks good on phones.
3. Set the bitrate. For 1080p archive, 10–16 Mbps is a reasonable starting range. For sharing, 6–8 Mbps is usually enough. Higher bitrate means larger files, not automatically “better” video.
4. Choose an output folder. Use a separate folder such as D:\Converted\AVCHD so you do not overwrite the originals.
5. Convert and check a sample. Run the queue. Play the first output and check audio sync, orientation and duration before converting the rest.

Method 2: HandBrake (free)

HandBrake is free, open source and available for Windows, macOS and Linux. It is more flexible than a one-click converter, but it exposes more settings. Use it if you are comfortable choosing a preset and checking the result.

1. Open the source. Drag an .MTS file into HandBrake, or use “Open Source” and select the file. HandBrake may not understand the AVCHD playlist; if it shows one title, select the largest clip in STREAM.
2. Choose MP4 and H.264. Set the container to MP4 and the video encoder to H.264. A 1080p preset is a good starting point.
3. Set quality. Use a constant quality value around RF 20–22 for a good balance. Lower RF means higher quality and larger files.
4. Set audio. Choose AAC at 192–256 kbps stereo. If the source is AC-3 5.1 and you want surround, keep the channels; otherwise stereo is simpler.
5. Add to queue and start. Use “Add to Queue” for multiple clips, then “Start Queue”. Check the first output before walking away.

If you only need to watch an AVCHD file, VLC can usually play it without conversion. VLC is not a batch conversion tool, so it is a playback fix, not an archive workflow.

Paid vs free: which should you use?

If you already use HandBrake comfortably, it is a capable free option. The paid tool is for users who want a Windows batch workflow without tuning settings.

Quality settings that actually matter

• Keep 1080p for archive. Downscaling to 720p is fine for sharing, but keep a 1080p master if the footage matters.
• Do not upscale. Converting 1080i to 4K does not add detail; it adds file size.
• Match the frame rate. Use the source rate (often 25, 29.97 or 30 fps). Changing it can introduce judder.
• Deinterlace only when needed. AVCHD is often 1080i. If the output looks combed on moving subjects, enable deinterlacing in HandBrake (Decomb/Yadif) or the equivalent setting in your converter.
• Use AAC audio at 192–256 kbps. Stereo is fine for most family footage; keep 5.1 only if you have a surround workflow.
• Handle 4 GB splits. Long AVCHD recordings may be split into multiple MTS files. Convert every part; join them in an editor if you need one continuous file.

Troubleshooting

No audio after conversion

The source may use AC-3 or PCM audio that the output profile does not carry. Choose an AAC audio track, and check the file in a second player (VLC is a good test).

Audio is out of sync

Convert the original clip rather than a trimmed range, use a constant frame rate, and check whether the source has variable frame timing. HandBrake’s “Constant Framerate” option often fixes stubborn sync issues.

Black frames or missing clips

AVCHD playlists can span multiple MTS files. Some tools read the playlist, others read one file. Convert the individual files in BDMV/STREAM and check the boundaries.

The output looks combed

The source is probably interlaced 1080i. Enable deinterlacing. If your converter has no such option, use HandBrake with Decomb or Yadif.

The file is not recognized

Do not rename MTS to MP4. Copy the folder from the camera again and check the file with MediaInfo. A file that is still being written or was partially copied can also fail.

The output is too large

Lower the bitrate or resolution. For phone playback, 720p at 4–6 Mbps is usually enough. Keep the 1080p original if you may need it later.

FAQ

Related guides

• How to convert MTS to MP4 — the camcorder-side extension explained.
• How to convert M2TS to MP4 — disc-side naming and large files.
• Raize HD Video Converter — the Windows tool used in Method 1.