MJPEG to AMR Converter

MJPEG to AMR: Read This Before You Upload

AMR is a speech codec — 3GPP's Adaptive Multi-Rate, the thing that carried voice calls on GSM networks and that Nokia and early Android phones used for voice memos. Converting to it means keeping the words and discarding everything else.

Which raises the question this page has to answer first: does your MJPEG file actually contain audio? For a large share of visitors the answer is no, and it is better to find that out here than after a failed conversion.

The Two Kinds of File Called "MJPEG"

Motion JPEG is a way of coding video — every frame is an independent JPEG — and it turns up in two very different shapes.

We measured both. A genuine raw stream reports one video stream and nothing else, and asking for audio from it stops with "Output file does not contain any stream" — no .amr is written, because there was no soundtrack to encode. The same test with a container that had merely been named .mjpeg worked exactly as expected: the file was demuxed by its actual contents, both streams were found, and the audio came out fine.

So: if your recording came from an IP camera, a machine-vision rig, a microscope or a scientific capture card, it is almost certainly the first kind and silent by construction. If it came from an older camcorder or digital camera, it is probably the second kind wearing the wrong extension — and the cleanest route for that is AVI to AMR, which is the same conversion under the file's real name.

How to Convert MJPEG to AMR

1. Upload Your MJPEG File: Drag the file onto the page or click "+ Add Files". If the job reports that there is no stream to write, the source is a raw Motion JPEG stream with no audio track — see the section above.
2. Choose AMR Narrow Band or Wide Band: AMR Narrow Band is the original GSM voice codec at 8 kHz; AMR Wide Band is ITU-T G.722.2, approved in July 2003, which doubles the sample rate to 16 kHz and sounds markedly better on speech.
3. Set the Bitrate: File Compression offers Quality Preset and Constant Bitrate. Audio Channel offers Mono only and Audio Sample Rate offers 8000 and 16000 Hz only, because AMR permits nothing else — whichever you pick, the codec's own fixed rate is what gets used.
4. Trim and Convert: Trim takes a start time and duration in seconds or HH:MM:SS.sss, which is worth using on a long recording since AMR is slow to skim through. Click "Convert" and save the .amr. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark.

Narrow Band and Wide Band Are Not Interchangeable

Both write files ending in .amr, and that is where the similarity stops. We checked the first bytes of each: narrow band begins #!AMR followed by a newline, wide band begins #!AMR-WB. A player that only knows narrow band will reject a wide band file even though the extension matches.

Because both are fixed-rate codecs, the Quality Preset does not become a quality scale the way it does for MP3 or Vorbis — it selects a target bitrate inside the codec's own range. Narrow band spans 5 to 12 kbit/s across the seven presets; wide band spans 6 to 24. The encoder then settles on the nearest coding mode its specification actually defines. We verified that behaviour by requesting a series of in-between rates — 5,000, 6,400, 7,450, 8,500, 9,900, 10,950 and 12,000 bit/s — and every one produced a valid file rather than an error, each landing on a legal mode near the request.

Frequently Asked Questions

The conversion said there was no stream to write. What went wrong?

Nothing went wrong with the conversion — the source had no audio. A raw Motion JPEG file is a sequence of JPEG images and the format has no audio track at all, so there is nothing to extract. The tool stops rather than writing you a silent file, which is the more useful behaviour: a zero-content .amr would look like success and waste your time later.

My camcorder footage is MJPEG and it definitely has sound. Why is this page failing?

Then your file is very likely an AVI or MOV that has been renamed, and the safest thing is to give it back its real extension and use the matching page. AVI to AMR handles the common case. The conversion is identical underneath; the only difference is which page's uploader accepts your file.

Can I get stereo out of AMR?

No. Both AMR variants are mono-only codecs, which is why the Audio Channel dropdown offers Mono and nothing else. A stereo source is downmixed on the way in. This is not a limitation of the tool — AMR was designed for a phone call, and a phone call has one channel.

Why can I only choose 8000 or 16000 Hz?

Because those are the only two rates AMR defines: 8 kHz for narrow band, 16 kHz for wide band. Choosing the "wrong" one alongside a codec does not break anything, because the codec's fixed rate is applied before encoding. That matters more than it sounds — the wide band encoder rejects an 8 kHz input outright with "Only 16000Hz sample rate supported", so pinning the rate in advance is what keeps the job from failing.

Will an AMR file be small?

Very. At 12.2 kbit/s — the top narrow band mode — one minute of speech is roughly 90 kilobytes, and wide band at its top mode is still under 180 kB a minute. That is the point of the format. The corresponding cost is that AMR is a speech codec: it models a human vocal tract, so music, applause and background noise come out sounding artificial.

Should I use AMR at all, or is there something better?

If the destination is an old handset, a voicemail system or a specification that names AMR, use it. For anything else, Opus at 16 to 24 kbit/s beats AMR wide band on quality and is playable in every browser, while MP3 at 32 to 64 kbps plays literally everywhere. AMR's advantage today is compatibility with old equipment, not efficiency.

What happens to the video?

It is discarded. This is an audio extraction, so the JPEG frames are decoded only far enough to find the file's structure and are never written to the output. If you want to keep the picture too, MJPEG to MP4 re-encodes both streams into one modern file — and re-encodes them dramatically smaller, since Motion JPEG stores every frame in full.

Can I convert several recordings in one go?

Yes — queue them and they are processed with the same codec and bitrate. Be aware that if some of them are raw Motion JPEG streams and some are misnamed containers, the raw ones will report having no stream to write while the containers convert normally. That mix is a symptom, not a bug: the two kinds of file genuinely differ.

Does the bitrate I type get used exactly?

Not exactly, and that is by design. AMR has a fixed ladder of coding modes rather than a continuous rate, so the encoder settles on the mode nearest the number you asked for. We requested seven different in-between values and every one produced a working file, at effective rates around 5.6, 7.2, 8.0, 8.0, 10.4, 10.4 and 12.4 kbit/s respectively. Nothing errors; the request is simply rounded to something the codec can actually do.