Step 1: Transfer your 3GP files using the button above or by slide and deposit.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Retrieve your converted MKV files.
3GP to MKV Conversion FAQ
How do I re-encode 3GP to MKV without losing video quality?
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Upload your 3GP file and set Quality to High Quality in the conversion options. That re-encodes the video at the highest quality setting (CRF 18 for H.264 and VP9 output), which keeps the most detail at the cost of a larger file. The default, Balanced, uses the standard setting. The MKV output gets a codec its container supports: H.264 for MP4, MOV and MKV, VP9 for WebM. 3GP holds H.263 or MPEG-4 Part 2 video with AMR narrowband speech audio, all tuned for minimal bitrate rather than quality. MKV is codec-agnostic: H.264, HEVC, VP9 and AV1 video sit happily beside AAC, FLAC, Opus, DTS or Dolby audio in the same file.
Can I add selectable subtitles once the file is MKV?
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Yes. 3GP has no usable soft-subtitle track, so subtitles for 3GP content had to be burned into the picture or shipped as a separate sidecar file. MKV carries subtitles as their own selectable stream, so after conversion you can attach an SRT track the viewer can switch on, switch off or restyle.
Can the MKV hold more than one audio track?
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Yes, and it is a real upgrade over 3GP. MKV treats every audio stream as a first-class track, so an original-language mix, a dub and a director commentary can live in one file with the player switching between them on demand. MKV is the archival container of choice because it stores unlimited audio tracks, soft subtitles, chapter markers and cover art in one file.
Does MKV support chapter markers that 3GP did not?
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It does. MKV stores chapters as container metadata, so a long recording can be navigated by section instead of by scrubbing a progress bar. 3GP has nowhere to put that information, so the converted MKV starts with no chapters; add markers afterwards with a tool such as MKVToolNix or ffmpeg.
Will the MKV still play smoothly on a phone or a TV?
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It may not. 3GP is decoded by dedicated silicon on phones, tablets and TVs, which is why it plays without flattening the battery. MKV typically falls back to software decoding on the same hardware — higher CPU load, a warmer device, and dropped frames on 4K material. For a device target, 3GP is the safer container to stay in. MKV has almost no native hardware support — phones, browsers and TVs usually need VLC or a remux before they will play it.
Both 3GP and MKV are modern containers — which should I actually keep?
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Keep whichever matches where the file is going, because neither is better in the abstract. One of these two is built for playback compatibility and the other for holding everything a file might contain, and they trade against each other exactly along that line. The pragmatic answer for most libraries is to archive in the feature-rich container and export to the compatible one on demand. 3GP files are tiny and decode on the weakest hardware imaginable, which is why feature phones and low-end handsets still record it.
Which video codec does the MKV output use?
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It depends on the MKV container. MP4, MOV and MKV output use H.264, which plays on practically every phone, browser and TV. WebM output uses VP9. AVI, WMV and MPEG output use the older codecs those formats were designed for. MKV is Matroska, an open container designed in 2002 with no licensing restrictions and no ceiling on what it can hold.
Will my audio track survive 3GP to MKV conversion?
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Yes, the main audio track comes through, re-encoded to a codec the MKV container plays, for example AAC in MP4 and MOV or Opus in WebM. Most conversions keep only that one track (the one with the most channels), so alternate languages and commentary are dropped. MP4 to MOV, and AVI, WMV, MPEG, FLV, VOB or M4V to MKV, keep every audio track.
Can I keep the original framerate when converting 3GP to MKV?
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Yes. The frame rate is kept unless you change it: a 24 fps 3GP stays 24 fps in the MKV. The Frame Rate setting can also convert to 60, 30 or 24 fps. It changes the rate only; it does not deinterlace the video or remove 3:2 pulldown.
How much will the file size change going from 3GP to MKV?
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It depends on what happens to the video. MKV to MP4 or MOV with the default settings copies the video stream unchanged, so the size stays close to the source. Most other pairs re-encode it: a high-bitrate 3GP usually comes out smaller, while an already heavily compressed one can grow. Smaller File under Quality gives the smallest output, and H.265 in the Codec setting (MP4, MOV and MKV) is usually smaller than H.264 at similar quality but plays on fewer devices.
Will the MKV file play on iPhone, Android, and Smart TVs?
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MP4 with H.264 plays on practically every phone, browser and TV. MOV with H.264 plays on Apple devices and most TVs but not on every older Android phone. MKV needs an app such as VLC on iOS, and WebM is at home in browsers. There is no device preset on this page, so choose the target format your device supports.
How long does converting a 1-hour 3GP video to MKV take?
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There is no fixed time: it depends on the length, the resolution and the target format. Conversions run on our servers' CPUs with software encoders; there is no GPU acceleration. MKV to MP4 or MOV with the default settings copies the video stream and is the quickest. A re-encode to H.264 takes longer, and WebM (VP9) is the slowest target, several times slower than H.264 in our tests.
