Convert MTS to AC3 — Free Online Tool
Extract and convert the AC-3 or AAC audio track from your AVCHD MTS camcorder footage into a standalone Dolby Digital AC3 file. This tool decodes the audio stream from the MPEG-2 Transport Stream container and re-encodes it to AC3 at up to 640 kbps — ideal for Blu-ray authoring, broadcast workflows, and home theater systems.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
MTS files use the MPEG-2 Transport Stream container, which typically carries H.264 video alongside AC-3 or AAC audio recorded by Sony or Panasonic camcorders. This conversion discards the H.264 video stream entirely and focuses on the audio: the existing audio (whether AC-3 or AAC) is decoded and then re-encoded into a standalone Dolby Digital AC3 file using FFmpeg's built-in ac3 encoder. Because the output is audio-only, no video codec processing occurs. If the source MTS already contains AC-3 audio, the signal still passes through a decode-and-reencode cycle to produce the self-contained .ac3 file rather than being stream-copied, ensuring compatibility with the output container.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles all demuxing, decoding, encoding, and muxing. In this conversion it will demux the MPEG-2 Transport Stream, decode the camcorder audio, and encode it to Dolby Digital AC3. |
-i input.mts
|
Specifies the input AVCHD MTS file from your Sony or Panasonic camcorder. FFmpeg will parse the MPEG-2 Transport Stream container to locate the video and audio streams inside it. |
-c:a ac3
|
Tells FFmpeg to encode the audio stream using the Dolby Digital AC3 codec. The H.264 video stream from the MTS is automatically dropped since the output format (.ac3) is audio-only. |
-b:a 192k
|
Sets the Dolby Digital output bitrate to 192 kilobits per second, which is the standard minimum for stereo AC3 and the default for this tool. For 5.1 surround audio from a camcorder, increasing this to 384k or 448k is advisable to preserve full channel quality. |
output.ac3
|
Defines the output file as a standalone Dolby Digital AC3 audio file. The .ac3 extension signals FFmpeg to write raw Dolby Digital bitstream data, which is directly compatible with Blu-ray authoring tools, AV receivers, and broadcast playout systems. |
Common Use Cases
- Extracting the Dolby Digital audio track from AVCHD camcorder footage to use as a standalone surround sound file for Blu-ray disc authoring
- Preparing the audio portion of wedding or event videography MTS recordings for delivery to a post-production audio mixing engineer
- Converting camcorder-recorded concert or live performance audio to AC3 for use in a DVD or Blu-ray menu soundtrack
- Stripping the audio from MTS footage recorded on a Sony or Panasonic camcorder to create a 5.1-channel Dolby Digital track for a home theater system
- Archiving the audio content of AVCHD news or broadcast recordings in a format compatible with professional broadcast playout systems
- Generating an AC3 audio file from MTS footage to test lip-sync or audio-only playback before committing to a full video encode
Frequently Asked Questions
Yes, some quality loss is unavoidable because this is a lossy-to-lossy conversion. If your MTS file already contains AC-3 audio, decoding it and re-encoding to AC3 introduces a second generation of lossy compression. If the source has AAC audio, the decode-to-AC3 encode path also involves quality loss. At the default 192 kbps bitrate the result is generally transparent for most listeners, but selecting 320 kbps or higher (up to 640 kbps) will preserve more of the original audio fidelity.
Yes, if your AVCHD camcorder recorded 5.1 surround audio, the AC3 encoder will preserve the channel layout in the output file. Dolby Digital AC3 natively supports up to 5.1 channels, which is one of the primary reasons AC3 is a strong output choice for this type of camcorder footage. Make sure to select a bitrate of 192 kbps or higher to properly accommodate multi-channel audio.
The H.264 video stream is completely discarded. FFmpeg processes only the audio stream from the MPEG-2 Transport Stream container, producing a standalone .ac3 file with no video data. This is why the output file will be dramatically smaller than the original MTS — only the audio track is retained.
Yes — replace the '-b:a 192k' value in the command with any supported AC3 bitrate. Valid options are 96k, 128k, 192k, 256k, 320k, 384k, 448k, or 640k. For stereo audio, 192k is a solid default. For 5.1 surround audio extracted from a high-quality camcorder recording, 384k or 448k is recommended to maintain dynamic range and channel separation. The command would look like: ffmpeg -i input.mts -c:a ac3 -b:a 384k output.ac3
Yes. On Linux or macOS, use a shell loop: 'for f in *.mts; do ffmpeg -i "$f" -c:a ac3 -b:a 192k "${f%.mts}.ac3"; done'. On Windows Command Prompt, use: 'for %f in (*.mts) do ffmpeg -i "%f" -c:a ac3 -b:a 192k "%~nf.ac3"'. This is especially useful when processing large batches of MTS clips from a camcorder memory card.
Dolby Digital AC3 files are supported by most Blu-ray and DVD players, AV receivers, VLC media player, Windows Media Player (with appropriate codec pack), and professional video editing tools like DaVinci Resolve and Adobe Premiere Pro. The format is also widely accepted by Blu-ray authoring software such as Adobe Encore and DVDFab. Note that standard smartphone music players may not play .ac3 files natively — for those use cases, converting to AAC or MP3 would be more appropriate.
Technical Notes
The MTS (AVCHD) format wraps its streams in an MPEG-2 Transport Stream container, which can carry multiple audio tracks — commonly AC-3 at 192–640 kbps or AAC at 128–256 kbps, depending on the camcorder model and recording settings. When FFmpeg reads an MTS file, it selects the default audio stream (usually stream 0:1) automatically; if your MTS contains multiple audio tracks, you can target a specific one with '-map 0:a:1' (for the second audio track). The ac3 encoder in FFmpeg is a native implementation of Dolby Digital and produces files that conform to the ATSC A/52 standard. One known limitation is that AC3 does not support more than 5.1 channels (no 7.1 surround), so any audio beyond six channels would need to be downmixed. Metadata from the MTS container — including timecode, GPS, and camera-specific tags — is not carried into the .ac3 output, as the AC3 format does not support embedded metadata of this kind. File size will be proportional to duration and bitrate: at 192 kbps, one hour of audio produces approximately 86 MB.