- AMV video format
AMV is a proprietary video file format, produced for
MP4 player s, as well asS1 MP3 player s with video playback.Infobox file format
name = AMV
icon =
logo =
extension = .amv
mime =
type code =
uniform type =
magic =
owner =
genre =
container for = Audio, video
contained by =
extended from =AVI andMotion JPEG
extended to =
standard = proprietaryFormat
The container is a modified version of AVI.cite web|url=http://code.google.com/p/amv-codec-tools/wiki/AmvDocumentation|title=AmvDocumentation|publisher=Google Code|author=voroshil|date=2007-10-15|accessdate=2008-04-06] The video format is a variant of
motion JPEG , with fixed rather than variable quantisation tables. [ [http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-October/037356.html forcing mjpegenc to use fixed quantisation tables] (Tom Van Braeckel, FFmpeg-devel mailing list, 28 October 2007)] The audio format is a variant of IMA ADPCM, 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 — though as the files are of low resolution (96×96 up to 208×176) and frame rate (10, 12, or 16 fps), file sizes are small in bytes per second. With a resolution of 128×96 pixels and a framerate of 12 fps, 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 format to produce a Perl-based decoder [ [http://blog.rot13.org/2007/08/amv_free_decoder_works.html AMV free decoder] (Dobrica Pavlinušić, personal blog, 19 August 2007)] and Pavlinušić, Tom Van Braeckel and Vladimir Voroshilov produced a version of
FFmpeg that works on AMV files. [ [http://code.google.com/p/amv-codec-tools/ amv-codec-tools] (Google Code )] The AMV code has been sent upstream to the main FFmpeg project. [ [http://groups.google.com/group/amv-codec-tools/browse_thread/thread/3afc2809797c1109 What needs to be done - this is an asynchronous meeting by mailing list.] (Tom Van Braeckel, AMV codec tools group mailing list, 26 October 2007)]References
Wikimedia Foundation. 2010.
