MyMediaTools

Convert MTS to 3GP — Free Online Tool

Convert MTS camcorder footage (AVCHD H.264/AC-3) to 3GP, the mobile-optimized container format designed for 3G devices with constrained bandwidth and storage. This conversion re-encodes your high-bitrate AVCHD clips into a compact, mobile-friendly package suitable for older phones and low-bandwidth streaming.

FFmpeg Command

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Estimated output:

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How It Works

MTS files from Sony and Panasonic camcorders use the AVCHD standard: H.264 video wrapped in an MPEG-2 Transport Stream container, typically with AC-3 or AAC audio at high bitrates optimized for recording quality. Converting to 3GP requires full re-encoding of both streams. The H.264 video is re-encoded at a lower CRF target with a scale filter applied to ensure frame dimensions are divisible by 2 (a hard requirement of the 3GP container). The audio — whether originally AC-3 or AAC — is transcoded to AAC at 64k bitrate, a significant reduction suited to the 3GP format's mobile-first design. The output 3GP file will be substantially smaller than the source MTS, but at the cost of reduced visual and audio fidelity.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg program. When run via this browser tool, it executes FFmpeg.wasm (a WebAssembly build of FFmpeg) entirely within your browser — no file data leaves your device.
-i input.mts Specifies the input MTS file — an AVCHD MPEG-2 Transport Stream container, typically from a Sony or Panasonic camcorder, containing H.264 video and AC-3 or AAC audio.
-c:v libx264 Re-encodes the video stream using the libx264 H.264 encoder, producing output compatible with the 3GP container's supported video codec. The original AVCHD H.264 stream cannot be directly copied because bitrate, profile, and level constraints must be adjusted for mobile 3GP delivery.
-c:a aac Transcodes the audio to AAC, the required audio codec for 3GP. This is necessary whether your MTS source has AC-3 (Dolby Digital) or high-bitrate AAC audio, since 3GP requires low-bitrate AAC for mobile compatibility.
-crf 23 Sets the Constant Rate Factor for the H.264 video encode to 23, the default quality level balancing file size and visual quality for mobile screens. Lower values (e.g., 18) increase quality and file size; higher values (e.g., 35) reduce both — especially useful when targeting 3G data transfer limits.
-b:a 64k Sets the AAC audio bitrate to 64 kilobits per second, the 3GP-appropriate default that keeps file sizes small for mobile storage and streaming. This is a significant reduction from typical AVCHD audio bitrates (128–384k), so dialogue-heavy content will be fine but musical audio may sound compressed.
-vf scale=trunc(iw/2)*2:trunc(ih/2)*2 Applies a video filter that rounds the frame width and height down to the nearest even number. This is required by the 3GP muxer, which rejects video streams with odd pixel dimensions — a real risk when processing non-standard or interlaced AVCHD sources.
output.3gp Specifies the output filename with the .3gp extension, instructing FFmpeg to mux the re-encoded H.264 video and AAC audio into the 3GP container format defined by 3GPP for mobile multimedia delivery.

Common Use Cases

  • Share short camcorder clips directly to older 3G-era mobile phones that cannot play AVCHD or standard MP4 files
  • Reduce large MTS recordings to a fraction of their size for upload to legacy media platforms or MMS sharing with file size limits
  • Archive camcorder footage in a highly compressed format for low-storage environments such as embedded systems or archival microSD cards
  • Prepare video previews or proxy clips from AVCHD camcorder footage for use on mobile field monitoring apps that require 3GP input
  • Send short event clips (weddings, sports, performances) recorded on AVCHD camcorders to recipients on devices with limited data plans
  • Convert news or documentary footage captured on AVCHD camcorders to 3GP for mobile broadcast streaming over constrained 3G networks

Frequently Asked Questions

Yes. MTS files are recorded at high bitrates — often 17–28 Mbps for AVCHD — while 3GP at CRF 23 targets a much lower bitrate suitable for mobile screens. Full 1080i or 1080p AVCHD footage will show visible quality loss, particularly in motion-heavy scenes. If quality is a priority, consider increasing the CRF value downward (e.g., CRF 18) in the command, though this will produce a larger file.
The 3GP container does not support AC-3 (Dolby Digital) audio. When your MTS file contains AC-3 audio tracks — common on Panasonic camcorders — FFmpeg must transcode it to AAC, which is the standard audio codec for 3GP. The default 64k bitrate is quite compressed; if your source audio has music or complex ambience, you may want to raise it to 96k or 128k using the -b:a flag.
The flag -vf scale=trunc(iw/2)*2:trunc(ih/2)*2 ensures the output video dimensions are divisible by 2. AVCHD footage shot at resolutions like 1920x1080 is usually fine, but interlaced or non-standard MTS sources can have odd pixel dimensions that cause the 3GP muxer to fail. This filter rounds width and height down to the nearest even number without cropping, making it a safe safeguard for all MTS inputs.
Yes. On Linux or macOS you can loop over files with: for f in *.mts; 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%.mts}.3gp"; done. On Windows Command Prompt use: for %f in (*.mts) 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 especially useful for bulk-converting AVCHD clips from a camcorder's memory card.
No. The 3GP container supports only a single audio track and does not support subtitle streams. If your MTS file contains multiple language tracks or embedded subtitle data, only the default audio track will be included in the 3GP output and all subtitle streams will be dropped. If preserving multiple audio tracks is important, a format like MP4 or MKV would be more appropriate.
Video quality is controlled by the -crf flag, where lower values mean higher quality and larger files. The default CRF 23 is a reasonable middle ground; try CRF 28–35 for smaller files acceptable on small mobile screens, or CRF 18–20 if you want to preserve more of the original AVCHD detail. Audio size is controlled by -b:a; valid options for 3GP are 32k, 48k, 64k, 96k, and 128k. Note that because 3GP targets mobile delivery, very high quality settings may produce files larger than practical for the format's intended use case.

Technical Notes

MTS (AVCHD) is a broadcast-grade recording format not designed for direct mobile playback — it uses interlaced scanning (1080i is common), high bitrate H.264 profiles, and AC-3 audio that many mobile devices and the 3GP container itself cannot handle natively. The 3GP format was standardized by 3GPP for H.263 and MPEG-4 Part 2 video originally, but modern implementations accept H.264 Baseline profile, which is what FFmpeg's libx264 will produce. The scale filter is mandatory rather than optional here because the 3GP muxer in FFmpeg enforces even-dimension constraints strictly. Metadata such as recording timestamps, GPS coordinates embedded by some camcorders, and chapter markers present in AVCHD structures will not be carried over to 3GP, as the format does not support them. Multiple audio tracks common in dual-channel AVCHD recordings (e.g., main mic + external mic) will be reduced to the first/default track. If your MTS source is interlaced, you may also want to add a deinterlace filter before the scale filter (e.g., -vf yadif,scale=trunc(iw/2)*2:trunc(ih/2)*2) to avoid combing artifacts in the 3GP output.

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