Convert 3GP to CAVS — Free Online Tool
Convert 3GP mobile video files to CAVS (Chinese Audio Video Standard) format using H.264 video and AAC audio encoding. This tool re-encodes your 3GP content — originally compressed for 3G mobile bandwidth constraints — into a broadcast-oriented CAVS container suitable for Chinese digital media workflows.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your 3GP file here
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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
3GP files typically carry H.264 or MPEG-4 video alongside AAC or AMR audio, heavily compressed to meet the storage and bandwidth limits of early 3G mobile networks. During this conversion, the video stream is re-encoded using the libx264 encoder targeting a CRF of 23, which generally improves visual quality over the aggressive compression typical of 3GP source files. The audio is transcoded from whatever codec the 3GP file used (often low-bitrate AAC or AMR) to a clean AAC stream at 128k — a significant quality step up from the 64k default common in 3GP files. The output is wrapped in the CAVS container, a Chinese national standard format used in broadcast and digital distribution contexts. Because 3GP video was often encoded at low resolutions (240p or 320p), the output quality is ultimately bounded by the source — re-encoding cannot recover detail that was lost during original mobile compression.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg multimedia processing engine. This is the core tool running inside your browser via WebAssembly (FFmpeg.wasm), or on your local machine if you run the command directly in a terminal. |
-i input.3gp
|
Specifies the input file — your source 3GP video, a mobile container format originally designed for 3G network transmission. FFmpeg will detect the video and audio codecs inside the 3GP container automatically, whether that is H.264, MPEG-4, AAC, or AMR. |
-c:v libx264
|
Re-encodes the video stream using the libx264 encoder, producing H.264/AVC video inside the CAVS container. This replaces whatever video codec the 3GP source used and produces a widely decodable, efficiently compressed video track appropriate for broadcast contexts. |
-c:a aac
|
Transcodes the audio stream to AAC using FFmpeg's built-in AAC encoder. This is critical for 3GP files that use AMR audio (common in mobile recordings), as AMR is not supported in CAVS and must be decoded and re-encoded as AAC. |
-crf 23
|
Sets the Constant Rate Factor for the libx264 video encoder to 23, the standard default. For 3GP source material — which was typically encoded at high compression for mobile delivery — CRF 23 targets a quality level significantly higher than the source, though actual perceived quality remains bounded by the original mobile encoding. |
-b:a 128k
|
Sets the AAC audio output bitrate to 128 kilobits per second. This is double the 64k default common in 3GP audio tracks and matches the minimum quality expectation for CAVS broadcast deliverables, resulting in noticeably cleaner audio especially for speech-heavy mobile recordings. |
output.cavs
|
Specifies the output filename with the .cavs extension, which tells FFmpeg to wrap the encoded H.264 video and AAC audio streams into the Chinese Audio Video Standard container format. |
Common Use Cases
- Preparing archival 3GP footage captured on older 3G handsets for submission to Chinese broadcast platforms that require CAVS-compliant media.
- Converting mobile video recordings from feature phones into a format compatible with Chinese digital media distribution systems.
- Upgrading the audio bitrate of 3GP content — which often used 32k or 64k AAC — to the 128k AAC expected in broadcast-quality CAVS deliverables.
- Processing a library of legacy 3GP clips recorded in the mid-2000s to 2010s into a standardized format for long-term archiving in Chinese media institutions.
- Re-encoding low-bandwidth mobile video into CAVS for integration into Chinese television post-production pipelines that do not accept 3GP input.
- Generating an FFmpeg reference command for batch-converting large collections of 3GP files to CAVS on a local desktop machine, especially when file sizes exceed browser processing limits.
Frequently Asked Questions
No — both 3GP and CAVS are lossy formats, and re-encoding cannot recover detail that was discarded during the original 3GP compression. 3GP files were intentionally compressed hard for mobile networks, often at low resolutions like 176x144 or 320x240. The output CAVS file will be encoded at a reasonable CRF 23 quality setting, but the ceiling is set by the source material. If the 3GP footage looks blocky or soft, the CAVS output will look the same or very slightly worse due to the generation loss from re-encoding.
Yes — CAVS was developed as a Chinese national alternative to H.264/AVC and defines its own AVS video codec (sometimes called AVS1). However, CAVS containers can also carry H.264 video, which is what this tool produces using the libx264 encoder. Pure AVS-codec encoding requires the avs encoder in FFmpeg, which has limited support. Using H.264 inside a CAVS container is the most practical and broadly compatible approach for most conversion workflows.
AMR (Adaptive Multi-Rate) is a common audio codec in 3GP files, particularly those recorded on older mobile phones, and it is speech-optimized with very low bitrates (typically 4.75–12.2 kbps). During this conversion, the AMR audio is fully decoded and re-encoded as AAC at 128k, which is a substantial improvement in fidelity. Speech content will sound cleaner and less tinny, though music or ambient audio that was encoded in AMR may have already lost significant quality that cannot be restored.
3GP was designed for constrained mobile environments, so its default audio bitrate is 64k — enough for intelligible speech and basic audio over a 3G connection. CAVS targets broadcast and digital distribution contexts where 128k AAC is the minimum expected standard. This tool uses 128k as the output audio bitrate, which means the CAVS file's audio stream will be encoded at twice the bitrate of the 3GP default, resulting in a noticeably cleaner audio track for content that had sufficient source quality.
To adjust video quality, change the -crf value: lower numbers like 18 produce higher quality and larger files, while higher numbers like 28 or 35 produce smaller files with more compression artifacts. To change audio bitrate, replace 128k in -b:a 128k with your preferred value such as 96k for smaller files or 192k for higher fidelity. For example: ffmpeg -i input.3gp -c:v libx264 -c:a aac -crf 18 -b:a 192k output.cavs would give you higher quality output at the cost of a larger file size.
Yes — on Linux or macOS you can use a shell loop: for f in *.3gp; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.3gp}.cavs"; done. On Windows Command Prompt, use: for %f in (*.3gp) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "%~nf.cavs". This is especially useful for processing archives of legacy mobile footage where individual browser-based conversion would be impractical.
Technical Notes
3GP files do not support subtitles, chapters, or multiple audio tracks, so none of those elements carry over to the CAVS output — but since CAVS also lacks support for these features, there is no functional loss. The 3GP container sometimes stores metadata such as title, author, and creation date in proprietary atoms; this metadata is generally not preserved during re-encoding into a CAVS container. A notable technical consideration is the special scale filter used in 3GP processing — scale=trunc(iw/2)*2:trunc(ih/2)*2 — which ensures video dimensions are divisible by 2, a requirement for H.264 encoding. This is particularly relevant for 3GP files, which sometimes carry odd-resolution video from non-standard mobile encoders. The CAVS output does not require this filter since libx264 handles it implicitly, but any non-standard resolution in the source will be rounded down. File sizes after conversion will typically be larger than the source 3GP, since the original was aggressively compressed for mobile storage and the output targets a higher quality CRF and audio bitrate.