AMV (also known as MTV) is a proprietary video file format, produced for use in Chinese MP3/MP4/MTV Players, particularly the S1 MP3 Players. Note that despite the word "MP4" in the marketing description of several such players, this is not an MP4 or Moving Picture Experts Group file format.
| AMV | |
|---|---|
| File extension: | .amv |
| Container for: | Audio, video |
| Extended from: | AVI and Motion JPEG |
| Standard(s): | proprietary |
Contents |
Format
The container is a modified version of AVI.[1] The video format is a variant of motion JPEG, with fixed rather than variable quantisation tables.[2] 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.[1] 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[1] — though as the files are of low resolution (96×96 up to 208×176) and frame rate (10fps, 12fps or 16fps), 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 of the format
Documentation of the format is not publicly available, but Dobrica Pavlinušić reverse engineered the format[1] to produce a Perl-based decoder[3] and Pavlinušić, Tom Van Braeckel and Vladimir Voroshilov produced a version of FFmpeg that works on AMV files.[4] The AMV code has been sent upstream to the main FFmpeg project.[5]
References
- ^ a b c d AmvDocumentation (Google Code)
- ^ forcing mjpegenc to use fixed quantisation tables (Tom Van Braeckel, FFmpeg-devel mailing list, 28 October 2007)
- ^ AMV free decoder (Dobrica Pavlinušić, personal blog, 19 August 2007)
- ^ amv-codec-tools (Google Code)
- ^ 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)
External links
- MTV (Multimedia Wiki)
- Perl decoder (Dobrica Pavlinušić)
- Bytessence AMV Converter (GUI version of amv-codec-tools code)
- MTV sample files (mplayerhq.hu)
