Convert MPG to 3GP — Free Online Tool
Convert MPG video files — encoded with MPEG-1 or MPEG-2 codecs originally designed for broadcast and DVD — into 3GP, a mobile-optimized container that re-encodes the video using H.264 (libx264) and audio using AAC, dramatically reducing file size for compatibility with 3G-era and legacy mobile devices.
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
MPG files carry MPEG-1 or MPEG-2 video streams, which are not supported by the 3GP container. This means the conversion requires a full re-encode of both the video and audio tracks. The video is transcoded from MPEG-2 to H.264 using the libx264 encoder, which achieves far better compression at equivalent quality — critical for the low-storage, low-bandwidth constraints 3GP was designed for. The audio, typically MP2 in MPG files, is transcoded to AAC, which is the native audio format for 3GP and delivers better quality than MP2 at lower bitrates. A scale filter is also applied to ensure the output dimensions are divisible by 2, a hard requirement for H.264 encoding that prevents errors when the source MPG has odd-numbered pixel dimensions (which can occur with some broadcast or VCD sources).
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool. In the browser version of this tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm), so no files are sent to a server. |
-i input.mpg
|
Specifies the input MPG file. FFmpeg reads the MPEG-2 video and MP2 audio streams from this container to begin the conversion pipeline. |
-c:v libx264
|
Sets the video encoder to libx264, which encodes the MPEG-2 video stream into H.264. H.264 is the only widely supported video codec for 3GP and achieves far better compression than MPEG-2 at the same visual quality level. |
-c:a aac
|
Sets the audio encoder to AAC, transcoding the MP2 audio from the MPG source. AAC is the native audio codec for the 3GP container and delivers better quality than MP2 at the lower bitrates required for mobile-optimized files. |
-crf 23
|
Controls H.264 video quality using Constant Rate Factor. A CRF of 23 is the libx264 default, balancing output quality against file size — lower values produce better quality and larger files, higher values produce smaller but more compressed output. |
-b:a 64k
|
Sets the AAC audio bitrate to 64 kilobits per second, consistent with 3GP's mobile-optimized design. This is substantially lower than the typical MP2 bitrate in MPG files but sufficient for voice and moderate audio content on mobile devices. |
-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 required because libx264 cannot encode video with odd pixel dimensions, and some MPG sources from broadcast or VCD origins may have non-standard resolutions that would otherwise cause the conversion to fail. |
output.3gp
|
Specifies the output filename and container format. The .3gp extension tells FFmpeg to wrap the H.264 video and AAC audio into a 3GP container as defined by the Third Generation Partnership Project standard. |
Common Use Cases
- Sharing legacy broadcast or VHS-captured MPG recordings on older mobile phones that only support 3GP playback
- Reducing the file size of MPEG-2 DVD rips or VCD captures for storage on memory-constrained mobile devices
- Preparing MPG footage from security cameras or broadcast archives for playback on feature phones or embedded systems that support 3GP but not MPEG-2
- Converting MPG training or instructional videos for distribution via MMS messaging, where 3GP was the standard mobile video format
- Archiving old MPG home videos into a more compact format for transfer to a microSD card on a legacy handset
- Testing H.264-in-3GP compatibility for developers building or debugging media playback on older Android or Symbian devices
Frequently Asked Questions
Yes, in most cases the size reduction is substantial. MPEG-2 video in MPG files typically uses much higher bitrates than H.264 at equivalent visual quality, so re-encoding to H.264 inside a 3GP container can reduce file size by 50–80% depending on the source. The lower default audio bitrate (64k AAC vs. the typical 192k MP2 in MPG) also contributes meaningfully to the smaller output. However, you should expect some quality loss since both the video and audio are being transcoded, not copied.
The 3GP container format does not support MPEG-1 or MPEG-2 video streams — it is defined to carry H.264 (or MPEG-4 Part 2) video. Because the codec in the source MPG is incompatible with 3GP, FFmpeg must fully decode and re-encode the video into H.264. There is no way to avoid this transcoding step for this format pair, unlike some container-to-container conversions (such as MKV to MP4) where the video stream can sometimes be copied directly.
The flag '-vf scale=trunc(iw/2)*2:trunc(ih/2)*2' ensures the output video dimensions are divisible by 2. H.264 encoding with libx264 requires even-numbered width and height, and many MPG files — particularly those ripped from VCDs or captured from broadcast — can have non-standard resolutions with odd pixel counts. Without this filter, FFmpeg would throw an error and the conversion would fail. The filter preserves the original dimensions as closely as possible while making the adjustment.
The '-crf 23' flag controls H.264 video quality using Constant Rate Factor. CRF values range from 18 (higher quality, larger file) to 51 (lower quality, smaller file), with 23 as a balanced default. For a smaller 3GP file suitable for very constrained mobile storage, try '-crf 30' or '-crf 35'. For better quality when file size is less critical, use '-crf 18'. You can also lower the audio bitrate from '-b:a 64k' to '-b:a 32k' or '-b:a 48k' for additional size savings on the audio track.
The MP2 audio content is preserved in terms of the sound itself, but it is transcoded — decoded from MP2 and re-encoded as AAC at 64k. MP2 is not a supported audio codec in the 3GP container, so transcoding to AAC is mandatory. AAC at 64k is generally considered acceptable quality for voice and moderate audio, though it will be noticeably lower fidelity than the original MP2 track if the source was encoded at a high bitrate. If you need better audio quality, increase '-b:a' to '96k' or '128k' in the command.
Yes. On Linux or macOS, you can run a shell loop: 'for f in *.mpg; 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%.mpg}.3gp"; done'. On Windows Command Prompt, use: 'for %f in (*.mpg) 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 applies the same encoding settings to every MPG file in the current directory, outputting a matching 3GP file for each.
Technical Notes
MPG is a relatively rigid container tied to the MPEG-1 and MPEG-2 codec family, originally engineered for broadcast television and physical media like VCD and DVD. Converting to 3GP requires a complete codec replacement on both streams: MPEG-2 video becomes H.264 and MP2 audio becomes AAC. Because this is a lossy-to-lossy transcode, each generation of re-encoding introduces some quality degradation — starting from a higher-quality MPG source (lower -q:v value, higher bitrate) will yield a better-looking 3GP output. The 3GP format intentionally caps resolution and bitrate for mobile compatibility; very high-resolution MPG files (such as 1080i broadcast captures) will be technically converted but may look soft or show compression artifacts at 3GP's typical bitrates. Metadata support is minimal in both formats — chapter markers, subtitle tracks, and multiple audio tracks present in some MPG files are not preserved in the 3GP output, as 3GP does not support these features. The output 3GP file is playable on devices supporting the 3GPP Release 4 standard or later, and is also widely supported by modern media players including VLC and Android's native media framework.