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3GP to OGG

Your video never leaves your browser. It decodes the soundtrack with the codec it already has, and this page writes the OGG. The picture is not in the file you get — this is the sound on its own.

…or drop one anywhere on this page.

The soundtrack as Ogg Vorbis.

Smaller than an MP3 at the same quality, patent-free, and what a good deal of game and web tooling expects.

This is a second generation, and here is why

The sound inside a 3GP is already compressed — its soundtrack is AAC, usually at a low bitrate. Getting it out means decoding it and encoding it again, and that second encode starts from what the first one left behind rather than from the original recording. So a lossy source becomes a lossy result twice over, and at a low bitrate you can hear it. Choosing a higher quality above costs size and buys back some of the difference; it cannot recover what the video threw away in the first place.

A stream copy would avoid this, and it is not what this does. Lifting the compressed track straight out of the container and dropping it into a new one, untouched, is lossless — but it needs a demuxer written for each container, which this site does not have. So rather than implying you are getting the original track back, the page says what it actually did. For most purposes — a podcast, a voice recording, something to listen to — the difference is not audible. For archiving a master, it is the wrong tool.

The sample rate is chosen, not discovered

This is worth being exact about, because most converters are not. A browser will not tell you what sample rate the soundtrack was recorded at. The one function that decodes audio always resamples to whatever rate it is asked for, and then reports that rate back — so the number it gives you is its own, never the file's. Measured here: a 44,100 Hz MP4 and a 48,000 Hz MP4 come back with identical rates, and the rate is whichever one was asked for.

The usual way round this is to read the rate out of the file by hand, and the usual way that goes wrong is reading it out of a video file, where the bytes that look like an audio header generally are not one. On one test clip that is 48,000 Hz throughout, that method reported 32,000 for the MP4, 44,100 for the WebM and 11,025 Hz for the MKV — and then resampled the sound down to match. Telephone quality, right length, right pitch, and nothing to say it had happened.

So this page asks you instead, defaults to 48,000 Hz because that is what video soundtracks almost always are, and says on screen that the number is the one you chose. If you know your source was 44,100, pick it and nothing is resampled at all.

The picture is gone, not hidden

OGG has nowhere to put a video track, so there is nothing in the downloaded file but sound. If it was the pictures you wanted, the same file will give you an animated GIF, or PNG or JPEG stills, and nothing is uploaded there either.

How this works, and what it downloads

Your browser decodes the soundtrack itself. No browser can write OGG, so this page needs an encoder — it is fetched from this site, once, only if you press the button, and then kept in your browser's cache. Nothing is installed and your video is never sent anywhere; the encoder comes to it.

What does not come across

Chapters, subtitles, cover art and any second audio track — a commentary, another language — are not carried. Where a file has several audio tracks your browser hands over the one it would play, which is usually the first, and there is no way from here to ask for a different one.

AVI, MOV, WMV, FLV and MTS are refused, and that is not a shortcoming of this page: no browser will decode them. If you hand one over it says so plainly rather than producing a silent file.

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