Convert M2TS to 3GP — Free Online Tool
Convert M2TS Blu-ray and AVCHD files to 3GP format for playback on 3G mobile devices and low-bandwidth environments. This tool re-encodes the high-definition H.264 or HEVC video stream from the BDAV transport stream container into a mobile-optimized 3GP file with AAC audio, dramatically reducing file size for mobile compatibility.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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Settings
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
M2TS files use the BDAV MPEG-2 Transport Stream container, which packages high-definition video (typically H.264 or HEVC) alongside multi-channel audio tracks like Dolby TrueHD or DTS-HD MA. Converting to 3GP requires a full re-encode — not a simple remux — because 3GP is designed for constrained mobile environments. The video is re-encoded using H.264 (libx264) with CRF 23 compression, and the audio is transcoded to AAC at 64k bitrate. A critical scaling filter (scale=trunc(iw/2)*2:trunc(ih/2)*2) is applied to ensure pixel dimensions are divisible by 2, preventing encoding errors common when downscaling HD source resolutions like 1080p or 4K. The resulting file will be a fraction of the original size but suitable for 3G mobile playback. Only a single audio track is retained, and subtitles embedded in the M2TS are dropped since the 3GP container does not support them.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary to begin processing. In this browser-based tool, FFmpeg runs via WebAssembly (ffmpeg.wasm) entirely client-side — no server is involved. |
-i input.m2ts
|
Specifies the input file as an M2TS BDAV transport stream. FFmpeg automatically detects the 192-byte packet structure with the TP extra header and demuxes all video, audio, and subtitle streams from the container. |
-c:v libx264
|
Re-encodes the video stream using the H.264 codec via libx264. This is necessary because the M2TS source may contain HEVC, VC-1, or anamorphic H.264 that is not directly compatible with the 3GP mobile container profile. |
-c:a aac
|
Transcodes the audio stream to AAC using FFmpeg's native AAC encoder. This replaces any high-fidelity audio from the M2TS source — such as Dolby TrueHD or DTS-HD MA — with a compressed AAC stream compatible with 3GP mobile playback. |
-crf 23
|
Sets the Constant Rate Factor for H.264 encoding to 23, the default quality level. For Blu-ray source material being downscaled to mobile output, this balances visual quality and file size well; increase the value toward 35-40 if a smaller 3GP file is the priority. |
-b:a 64k
|
Sets the AAC audio bitrate to 64 kilobits per second, which is the appropriate target for 3GP mobile audio. This is a significant reduction from the multi-megabit lossless audio tracks typically found in M2TS Blu-ray files. |
-vf scale=trunc(iw/2)*2:trunc(ih/2)*2
|
Applies a video filter that rounds the output width and height down to the nearest even number. This is essential when converting high-definition M2TS sources, as H.264 encoding in the 3GP container requires dimensions divisible by 2, and HD resolutions or anamorphic content can produce odd pixel counts after scaling. |
output.3gp
|
Defines the output file with the .3gp extension, signaling FFmpeg to wrap the encoded H.264 video and AAC audio into a 3GP container formatted for 3G mobile device compatibility. |
Common Use Cases
- Archiving footage from an AVCHD camcorder as a lightweight 3GP preview clip to share over MMS or older messaging platforms with strict file size limits
- Creating mobile-compatible versions of Blu-ray rip clips for playback on older 3G feature phones or embedded devices that only support the 3GP container
- Reducing large M2TS broadcast recordings to compact 3GP files for transmission over low-bandwidth cellular networks in field reporting or remote monitoring scenarios
- Converting AVCHD travel or event footage captured by Sony or Panasonic camcorders into 3GP format for quick sharing on platforms that require small file sizes
- Producing low-bitrate video clips from high-definition M2TS source material for use in early-generation mobile apps or kiosk systems with limited storage and processing power
- Sampling a specific scene from a Blu-ray M2TS file as a small 3GP clip for quick review on a mobile device before committing to a full-quality export
Frequently Asked Questions
Yes, significant quality reduction is expected and inherent to this conversion. M2TS files are designed for high-definition Blu-ray playback with bitrates commonly ranging from 15 to 40 Mbps, while 3GP targets mobile devices with far lower bitrate budgets. The re-encode to H.264 at CRF 23 with 64k AAC audio is lossy, and the original multi-channel audio (e.g., Dolby TrueHD, DTS-HD) will be downmixed and compressed significantly. The 3GP output is best treated as a mobile preview or distribution copy, not an archival replacement.
The scale=trunc(iw/2)*2:trunc(ih/2)*2 filter ensures that the output video dimensions are always divisible by 2, which is a hard requirement for H.264 encoding. M2TS sources can have resolutions like 1920x1080 or 1440x1080, and while those are already even, downscaling or anamorphic sources can produce odd pixel counts that will cause FFmpeg to throw an encoding error. It is strongly recommended to keep this filter in place. If you want to also resize to a specific mobile resolution, you can modify it to something like scale=320:240 while still keeping the divisibility guarantee.
Those lossless, multi-channel audio formats are not supported by the 3GP container and will not be passed through. FFmpeg will transcode the primary audio track to AAC at 64k bitrate, which is mono or stereo output suitable for mobile playback. The high-fidelity surround sound from the source is permanently downgraded in this conversion. If your M2TS has multiple audio tracks, only the first (default) track is included in the 3GP output.
No. The 3GP container does not support subtitle streams, so any PGS, DVB, or text-based subtitles embedded in the M2TS file will be dropped during conversion. If subtitles are essential, you would need to burn them into the video stream using a filter like subtitles= or ass= before conversion, though this requires additional processing steps beyond the default command.
To reduce file size, increase the CRF value — for example, changing -crf 23 to -crf 35 or -crf 40 will produce smaller files at the cost of lower visual quality. For audio, lowering -b:a from 64k to 48k or 32k will also reduce size. Conversely, lowering the CRF value (e.g., to 18) improves quality but increases file size. You can also add -s 320x240 to explicitly scale to a common mobile resolution, which significantly reduces bitrate requirements compared to passing a 1080p source through.
Yes. On Linux or macOS, you can use a shell loop: for f in *.m2ts; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 64k -vf scale=trunc(iw/2)*2:trunc(ih/2)*2 "${f%.m2ts}.3gp"; done. On Windows Command Prompt, use: for %f in (*.m2ts) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 64k -vf scale=trunc(iw/2)*2:trunc(ih/2)*2 "%~nf.3gp". This is particularly useful when pulling multiple clips off an AVCHD camcorder card.
Technical Notes
M2TS uses the BDAV transport stream wrapper (.m2ts), which includes PAT/PMT tables and a 4-byte TP extra header on each 192-byte packet — a superset of the standard MPEG-TS format. FFmpeg handles this demuxing automatically. The source video codec is most commonly H.264 (AVC) on AVCHD material, but Blu-ray discs may carry H.265 (HEVC) or even VC-1, all of which require a full re-encode to produce a 3GP-compatible H.264 stream. The 3GP container itself is based on the ISO Base Media File Format (ISOBMFF), like MP4, but with stricter constraints for mobile profiles. Only a single video and single audio track are supported, so M2TS files with multiple audio languages or angle streams will lose all but the primary track. Chapters and metadata such as disc titles are not preserved. The default AAC audio codec in this conversion is the FFmpeg native AAC encoder, which is adequate for 64k mobile output. For files over 1GB — common with raw Blu-ray M2TS rips — running the FFmpeg command locally on desktop hardware is strongly recommended over browser-based processing.