AMV video format
Encyclopedia
AMV is a proprietary
video file format, produced for MP4 players, as well as S1 MP3 player
s with video playback. There are now two different MTV formats: the older one for the Actions chip, and a newer one for ALi
’s M5661 chip. This format for ALi one was ALIAVI.
. 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, 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 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.
the format to produce a Perl-based decoder and Pavlinušić, Tom Van Braeckel and Vladimir Voroshilov produced a version of FFmpeg
that works on AMV files. The AMV code has been sent upstream to the main FFmpeg project and the mainline version of FFmpeg now decodes AMV.
Proprietary software
Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
video file format, produced for MP4 players, as well as S1 MP3 player
S1 MP3 Player
S1 MP3 players are a type of digital audio players based on many different kinds of chipsets. The popular ones include Actions and ALI chipsets...
s with video playback. There are now two different MTV formats: the older one for the Actions chip, and a newer one for ALi
Acer Laboratories Incorporated
Acer Laboratories Incorporated is a major designer and manufacturer of integrated circuits for the personal computer and embedded systems markets. It is a subsidiary of the Acer group....
’s M5661 chip. This format for ALi one was ALIAVI.
Format
The container is a modified version of AVIAudio Video Interleave
Audio Video Interleave , known by its acronym AVI, is a multimedia container format introduced by Microsoft in November 1992 as part of its Video for Windows technology. AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback...
. The video format is a variant of Motion JPEG, with fixed rather than variable quantisation
Quantization (image processing)
Quantization, involved in image processing, is a lossy compression technique achieved by compressing a range of values to a single quantum value. When the number of discrete symbols in a given stream is reduced, the stream becomes more compressible. For example, reducing the number of colors...
tables. The audio format is a variant of IMA
Interactive Multimedia Association
The Interactive Multimedia Association was an industry association which developed a set of audio algorithms. The most important is the ADPCM algorithm which is in use by Apple and Microsoft....
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
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
variant). Video compression ratio is low — around 4 pixels/byte, compared with over 10 pixels/byte for MPEG-2
MPEG-2
MPEG-2 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 which permit storage and transmission of movies using currently available storage media and transmission...
— though as the files are of low resolution (96×96 up to 208×176) and frame rate (10, 12, or 16 frame/s
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
), 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 engineeredReverse engineering
Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation...
the format to produce a Perl-based decoder and Pavlinušić, Tom Van Braeckel and Vladimir Voroshilov produced a version of FFmpeg
FFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...
that works on AMV files. The AMV code has been sent upstream to the main FFmpeg project and the mainline version of FFmpeg now decodes AMV.
External links
- All about AMV file format (MultimediaWiki)