Convert MTS to MP3 — Free Online Tool
Extract audio from AVCHD camcorder footage (.mts files) and convert it to MP3, decoding the AC-3 or AAC audio track embedded in the MPEG-2 Transport Stream and re-encoding it with the LAME encoder. Ideal for pulling clean audio from Sony or Panasonic camcorder recordings without needing to process the H.264 video.
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FFmpeg Command
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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 are AVCHD containers — a variant of the MPEG-2 Transport Stream format used by Sony and Panasonic camcorders — which typically carry H.264 video alongside AC-3 (Dolby Digital) or AAC audio. Converting to MP3 is a purely audio extraction operation: the video stream is discarded entirely, and the audio stream is decoded from its original codec (AC-3 or AAC) and then re-encoded using the LAME MP3 encoder at the specified bitrate (default 128k). Because both the source audio codec and MP3 are lossy formats, this is a lossy-to-lossy transcode, meaning there is a small but measurable generation loss compared to encoding from a lossless source. The result is a standalone MP3 file containing only the audio from your camcorder recording.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool, which handles demuxing the MPEG-2 Transport Stream container of the MTS file, decoding the audio stream, and encoding the MP3 output. |
-i input.mts
|
Specifies the input AVCHD file. FFmpeg automatically detects the MPEG-2 Transport Stream container and identifies the embedded video (H.264) and audio (AC-3 or AAC) streams within it. |
-c:a libmp3lame
|
Instructs FFmpeg to encode the audio stream using the LAME MP3 encoder. Since MP3 cannot carry AC-3 or AAC streams natively, the source audio is fully decoded to PCM internally and then re-encoded as MPEG Layer III audio. |
-b:a 128k
|
Sets the MP3 output bitrate to 128 kilobits per second, a standard quality level suitable for voice and general-purpose audio. Increase to 192k or 320k for music or higher-fidelity recordings from the camcorder. |
output.mp3
|
Defines the output filename and triggers FFmpeg to use the MP3 container format. The video stream from the MTS file is automatically discarded because the MP3 format cannot carry video — no explicit '-vn' flag is required. |
Common Use Cases
- Extract interview or dialogue audio from camcorder footage to use as a podcast episode or audio-only publication
- Pull the audio track from a wedding or event recording captured on a Sony or Panasonic camcorder to share with a DJ or audio editor
- Create an MP3 from a live music performance recorded in AVCHD format for distribution on music platforms that don't accept video
- Extract lecture or conference presentation audio from MTS footage for archiving or transcription services
- Strip the audio from a camcorder recording to sync with a separately recorded high-quality audio track in post-production
- Convert MTS audio to MP3 for playback on devices or media players that don't support AVCHD or AC-3 audio
Frequently Asked Questions
Yes. MTS files typically contain AC-3 (Dolby Digital) or AAC audio, both of which are already lossy compressed formats. Re-encoding to MP3 introduces a second round of lossy compression, which causes a small but real reduction in audio quality known as generation loss. To minimize this, use the highest bitrate option available (320k). If audio fidelity is critical, consider converting to a lossless format like WAV or FLAC instead of MP3.
It must be re-encoded. MP3 is an entirely different codec (MPEG Layer III, encoded by LAME) and cannot carry AC-3 (Dolby Digital) streams directly — the two formats are incompatible at the container and bitstream level. FFmpeg fully decodes the AC-3 audio to uncompressed PCM internally, then re-encodes it as MP3 using the LAME encoder. There is no stream-copy path possible for this conversion.
By default, FFmpeg selects the first audio track in the MTS file. If your camcorder recording has multiple audio tracks (for example, a stereo mix and a surround sound track), only the default track will be included in the output MP3. To select a specific track, you can add '-map 0:a:1' to the command to select the second audio track, or '-map 0:a:0' for the first. Note that MP3 does not support multiple audio tracks in a single file.
Change the value after '-b:a' to any supported MP3 bitrate. For example, use '-b:a 320k' for the highest quality (closest to the source audio), or '-b:a 64k' for the smallest file size at reduced quality. The default of 128k is a common balance for voice recordings, but for music captured on a camcorder, 192k or 256k is recommended. You can also use the VBR quality flag instead: replace '-b:a 128k' with '-q:a 2' for high-quality variable bitrate MP3 encoding.
Yes. On Linux or macOS, you can use a shell loop: 'for f in *.mts; do ffmpeg -i "$f" -c:a libmp3lame -b:a 128k "${f%.mts}.mp3"; done'. On Windows Command Prompt, use: 'for %f in (*.mts) do ffmpeg -i "%f" -c:a libmp3lame -b:a 128k "%~nf.mp3"'. This processes every MTS file in the current directory and outputs a corresponding MP3 with the same base filename.
Generally no. MTS files embed metadata in the MPEG-2 Transport Stream structure and AVCHD-specific metadata blocks that are not directly transferable to MP3's ID3 tag system. FFmpeg may carry over basic tags if present, but camcorder-specific metadata such as recording date, GPS coordinates, or camera model is typically lost. If you need to preserve recording date, manually add it as an ID3 tag using '-metadata date=YYYY-MM-DD' in the command, or use a dedicated tagging tool after conversion.
Technical Notes
MTS is the file extension used for AVCHD recordings produced by Sony and Panasonic camcorders. The container is based on the MPEG-2 Transport Stream (M2TS) format, which is designed for broadcast and streaming reliability rather than editing. Audio in these files is almost always either AC-3 (Dolby Digital, typically 5.1 or stereo) or AAC, depending on the camera model and settings. When extracting to MP3, only stereo or mono audio is preserved — if the source is 5.1 surround AC-3, FFmpeg will downmix it to stereo by default, which may cause some spatial audio information to be blended into the stereo field rather than discarded. MP3 supports a maximum of 2 channels (stereo). The libmp3lame encoder used here is the reference implementation of the LAME encoder, which produces high-quality MP3 output and is widely compatible with virtually all media players, streaming platforms, and devices. MP3 does not support chapters, multiple audio tracks, or subtitles, so all of these elements from the MTS source are dropped during conversion. If your camcorder records in AVCHD Progressive (60p or 50p modes), this has no effect on the audio extraction — audio is sampled independently of video frame rate.