 | This articleis missing information about the history of the AMV video format. Please expand the article to include this information. Further details may exist on thetalk page.(November 2023) |
| AMV | |
|---|---|
| Filename extension | .amv, .mtv |
| Internet media type | video/x-amv |
| Container for | Audio, video |
| Extended from | AVI andMotion JPEG |
| Standard | proprietary |
AMV (Actions Media Video) is aproprietaryvideo file format designed forportable media players (often marketed as "MP4 players"), as well asS1 MP3 players with video playback. There are two different versions of this format: an older one forActions chips, and a newer one forALi's M5661 chip, sometimes called ALIAVI.
The container is a modified version ofAVI.[1] The video format is a variant ofMotion JPEG, with fixed rather than variablequantisation tables.[2] The audio format is a variant ofIMAADPCM, where the first 8 bytes of each frame are origin (16 bits), index (16 bits) and number of encoded 16-bit samples (32 bits); all known AMV files run sound at 22050 samples/second.[1]
Low decoder overhead is paramount as the S1 MP3 players have very low-end processors (aZ80 variant). Video compression ratio is low – around 4 pixels/byte, compared with over 10 pixels/byte forMPEG-2[1] – though as the files are of low resolution (96×96 up to 208×176) and frame rate (10, 12, or 16 frame/s), file sizes are small in bytes per second. With a resolution of 128×96 pixels and a framerate of 12 frame/s, a 30-minute video will be compressed into 80 MB.
Documentation for this format is not publicly available, but Dobrica Pavlinušićreverse engineered the format to produce a Perl-based decoder.[1][3] Pavlinušić, along with Tom Van Braeckel and Vladimir Voroshilov, produced a version ofFFmpeg that works on AMV files.[4]
Fake or clonediPod Nano (4th generation) devices are reported to only support AMV video formats for video playback. These cloned devices are sold with an AMV video converter software in a CD. These AMV video converter software are also available as freeware such as the MPxConverter by Bytessence.[5]
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