User:Ryan Cooley/MPEG1
MPEG-1 articles (MPEG-1, MP1, MP2, MP3) on wikipedia are complete crap. Disorganized, slanted, incomplete, misconstrued, etc. It's far easier to start from scratch than try to fix all the individual existing ones, and will give far better end results; I will copy some content from the existing articles.
Do not make any changes to this page for now. This is my mind-dump and accommodating others before I'm done will just make much, much more work for me. Put any suggestions on the Talk page, and I will eventually address them.
-RC
MPEG-1 was an early standard for lossy compression of video and audio. It was designed to compress raw video and CD audio by a factor of 1:6 without discernible quality loss, making Video CDs and Digital Video Broadcasting possible.
Perhaps the most well-known part of the MPEG-1 standard today is the MP3 audio format it introduced.
The MPEG-1 standard is published as ISO/IEC 11172.
History
Modeled on the collaborative approach, successes and technology of the Joint Photographics Expert Group, which created the JPEG still-image compression standard, and CCITT Expert Group on Telephony, which created the H.261 standard for realtime video transmission on ISDN lines, the MPEG working group was established in January 1988 to address the need for standard video and audio encoding formats at data rates of about 1.5Mbps, and exploit the advantages of non-realtime encoding. [1]
Development of the MPEG-1 standard began in May 1988. 14 video and 14 audio codec proposals were submitted by individual companies and institutions for evaluation. The codecs were extensively tested for computational complexity and subjective (human perception) quality, at (combined video+audio) bitrates of 1.5Mbps. The codecs that excelled in this testing were utilized as the basis for the standard and refined further, with additional features and other improvements being incorporated. [2]
After 20 meetings of the full group in various cities around the world, and 4 1/2 years of development and testing, the final standard was approved in early November 1992. (a draft standard was produced September 1990, and only minor changes were introduced) [3] Before the MPEG-1 standard had even been finalized/publihed/drafted work began on an MPEG-2 standard, intended to extend MPEG-1 technology to provide higher quality video at high bitrates (3 - 15 Mbps), and support for interlaced video. [4] Due in part to the similarity between the two codecs, all standard MPEG-2 decoders include full support for playing MPEG-1 video.
Today, MPEG-1 is by far the most widely compatible lossy audio/video format in the world. Due to its age, most patents on MPEG-1 Video and Layer II audio technology have expired (MP3 being a notable exception), and can be implemented without payment of license fees in almost all countries. Most computer software for video playback includes MPEG-1 decoding, in addition to any other supported formats. The immense popularity of MP3 audio has established a massive installed base of hardware that can playback all 3 layers of MPEG-1 audio. The widespread popularity of MPEG-2 (mostly with broadcasters) means MPEG-1 is playable by most digital cable/satellite set-top-boxes, and digital disc and tape players.
Notably, the MPEG-1 standard very strictly defines the bitstream, and decoder function, but does not define how MPEG-1 encoding is to be performed (although they did provide a reference implementation). This means that MPEG-1 coding efficiency can drastically vary depending on the encoder used, and generally means that newer encoders perform significantly better than their predecessors.
Began development in 1988 Approved November 1992 Published August 1993 Lossy most compatible format MPEG-2
Application
VCD players DVB DAB MP3 MPEG-2? audio: SVCD DVD players (not surround) ATSC/HDTV (failed)
Video
Part 2 of the MPEG-1 standard covers video.
Part 2 Dimentions 4094x4094 Datarate Constrained Parameters Bitstream
Luma Chroma
I-frames (Intraframe) Seeking P-frames (Predicted) B-frames (Bidirectional) Complexity (memory) Delay "The DC-picture type is used to make fast searches possible on sequential DSMs such as tape recorders with a fast search mechanism. The DC-picture type is never used in conjunction with the other picture types.
GOP Keyframe placement
DCT
Quantization
Quantizer Noise
Banding
Ringing? (large coefficients in high frequency sub-bands)
Coefficients
AC
DC (Spatial prediction)
1/2 or 1/3 interpolation?
zigzag
Macroblocks
16 dimentions
Blockiness
Motion Vectors/Estimation
Black borders/Noise
pel precision (half pixel IIRC)
Two MV per macroblock (forward/backward pred)
Prediction error
Huffman Table (for frequent values)
RLE (fixed length for uncommon codes)
Variable RLE?
Others?
CBR/VBR
Spacial Complexity
Temporal Complexity
Audio
Part 3 of the MPEG-1 standard covers audio.
MPEG-1 audio utilizes perceptual masking, and sub-band coding to reduce the bitrate of the audio stream.
mono, stereo, joint stereo (impulse, m/s), dual.
Layer I
file extension .mp1 Simple 32 sub-bands Realtime Delay Digital Compact Cassette Obsolete today Time-domain coding/concealment
Layer II
dominant standard audio broadcasting Musicam Audiophile impulses superior to AC-3 pro-transparent at 256kbps 32 sub-bands joint stereo (intensity) same fundamental problem today Focus on [time-domain] critical audio error resilient Exceeds MP3 somewhere between 192-256 kbps
Achieves transparency at 1:6 compression on CD audio. Quite close to Perceptual Entropy limit of just over 1:8. [5]
Layer III/MP3
9 months? ASPEC (Fraunhoffer) freq transform encoder entropy coding Hybrid MDCT pre-echo worse aliasing issues "aliasing compensation" mid/side (or impulse) joint stereo 576 frequency components selectivity "If there is a transient, 192 samples are taken instead of 576 to limit the temporal spread of quantization noise"? psychoacoustic model and frame format from MP1/2 ringing CBR/VBR Frames are not independent
Systems
Part 1 of the MPEG-1 standard covers systems which is the logical layout of the encoded audio, video, and other bitstream data.
"The MPEG-1 Systems design is essentially identical to the MPEG-2 Program Stream structure." [7]
Program Stream Interleaving PES Wrap-around DTS Timebase correction Pixel/Display Aspect Ratio
See Also
References
- ↑ http://www.cis.temple.edu/~vasilis/Courses/CIS750/Papers/mpeg_6.pdf pp.2
- ↑ http://www.chiariglione.org/mpeg/meetings/santa_clara90/santa_clara_press.htm
- ↑ http://www.chiariglione.org/mpeg/meetings.htm
- ↑ http://www.chiariglione.org/mpeg/meetings/london/london_press.htm
- ↑ J. Johnston, Estimation of Perceptual Entropy Using Noise Masking Criteria, in Proc. ICASSP-88, pp. 2524-2527, May 1988.
- ↑ 6. J. Johnston, Transform Coding of Audio Signals Using Perceptual Noise Criteria, IEEE J. Sel. Areas in Comm., pp. 314-323, Feb. 1988.
- ↑ http://www.chiariglione.org/mpeg/faq/mp1-sys/mp1-sys.htm
External Links
- http://www.chiariglione.org/mpeg/ Official Home Page of the Moving Picture Experts Group (MPEG) a working group of ISO/IEC