AMV (Actions Media Video) is a
proprietary video file format
A video file format is a type of file format for storing digital video data on a computer system. Video is almost always stored using lossy compression to reduce the file size.
A video file normally consists of a container (e.g. in the Matr ...
, produced for
MP4 players, as well as
S1 MP3 players with video playback. There are two different versions of this format: an older one for
Actions chips, and a newer one for
ALi’s M5661 chip, sometimes called ALIAVI.
Format
The container is a modified version of
AVI
Avi is a given name, usually masculine, often a diminutive of Avram, Avraham, etc. It is sometimes feminine and a diminutive of the Hebrew spelling of Abigail.
People with the given name include:
* Avi (born 1937), Newbery award-winning Americ ...
.
The video format is a variant of
Motion JPEG, with fixed rather than variable
quantisation tables. The audio format is a variant of
IMA ADPCM
Adaptive differential pulse-code modulation (ADPCM) is a variant of differential pulse-code modulation (DPCM) that varies the size of the quantization step, to allow further reduction of the required data bandwidth for a given signal-to-noise rati ...
, 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.
Low decoder overhead is paramount as the S1 MP3 players have very low-end processors (a
Z80 variant). Video compression ratio is low – around 4 pixels/byte, compared with over 10 pixels/byte for
MPEG-2
MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU) is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods, w ...
[ – 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
Documentation for this format is not publicly available, but Dobrica Pavlinušić reverse engineered the formatFFmpeg
FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of ...
that works on AMV files.
Uses
Fake or cloned iPod Nano (4th generation) devices are reported to only support AMV video formats for video playback. These cloned devices are sold with a AMV video converter software in a CD. These AMV video converter softwares are also available for free online (freeware) such as the MPxConverter by Bytessence.
References
External links
All about AMV file format
(MultimediaWiki)
Video codecs
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