MPEG-2
MPEG-2 is a generic MPEG standard for video coding with video compression and audio coding with audio compression , both lossy. In this context, generic means that a data format and a decoding method are specified without specifying parameters such as the resolution that determine the quality.
introduction
MPEG-2 was introduced in 1994 and is a complement to and successor to MPEG-1 . The patents are administered by the MPEG Licensing Administration . At the end of 2018, 7 patents were still active and 1,075 had already expired. Since these patents are only active in Malaysia and the Philippines, MPEG-2 is de facto patent-free with the end of the patents in the USA and Europe.
The standard has gained widespread use thanks to the DVD : These are encoded in MPEG-2 (video). The audio part of the DVD can also be coded as MPEG-2 Audio Layer-2 (ISO / IEC 13818-3), but this is rarely used in practice; The audio signal on DVDs is almost always stored in Dolby Digital (AC-3) and sometimes also in DTS . MPEG-2 is also used on SVCDs , but with - compared to DVD - lower resolution and lower data rate.
The various variants ( DVB-S , DVB-C , DVB-T ) of digital television also prefer to use the MPEG-2 format.
Overview
The MPEG-2 standard consists of several parts, which are defined in ISO / IEC 13818:
Part 1
Systems - describes the synchronization and multiplexing of audio and video. Contains the descriptions of the program stream and transport stream .
Part 2
Video codec. Also known as H.262.
Part 3
Audio codec. A multi-channel extension of MPEG-1 audio. Contains the descriptions of MP1 , MP2, and MP3 .
Part 4
Part 4 describes the test procedures for conformity.
Part 5
Part 5 describes the software simulation.
Part 6
Extensions for DSM-CC (Digital Storage Media Command and Control.)
Part 7
Advanced Audio Coding (AAC)
Part 8
Part 8 “10-bit extension of the video” was discarded.
Part 9
Extensions for real-time applications.
Part 10
Conformity extensions for DSM-CC.
Part 11
IPMP ( Intellectual Property Management and Protection) on MPEG-2 systems.
MPEG-2 video
The main features of MPEG-1 have been retained in MPEG-2: separation of color information from the black-and-white image and coarsening of the same, since the human eye also perceives color differences more coarsely than differences in brightness; Division of the image into 8 × 8 pixel blocks, the data requirements of which are greatly reduced by means of discrete cosine transformation and subsequent quantization ; Combination of four blocks each to form 16 × 16 pixel macroblocks, whose similarity to macroblocks in previous and / or following images is also used to reduce data; and use of binary codes with variable length in order to be able to represent more frequent bit sequences in a shorter manner than less frequent ones.
On the video side, the MPEG-2 standard aims for higher quality and associated data rates than its predecessor MPEG-1 - up to 15 Mbit / s or with a higher chrominance (color) resolution up to 50 Mbit / s - and in contrast to MPEG-1 also uses interlacing . MPEG-2 was originally designed for digital television broadcasting and studio applications. MPEG-1 was not completely superseded, and it is still a better choice than MPEG-2 for low data rates.
| Abbr. | Surname | Frames | YUV | Streams | comment |
|---|---|---|---|---|---|
| SP | Simple profile | P , I | 4: 2: 0 | 1 | no interlacing |
| MP | Main Profile | P, I, B | 4: 2: 0 | 1 | |
| 422P | 4: 2: 2 profiles | P, I, B | 4: 2: 2 | 1 | |
| SNR | SNR profiles | P, I, B | 4: 2: 0 | 1-2 | SNR: Signal-to-Noise-Ratio |
| Spatial | Spatial profiles | P, I, B | 4: 2: 0 | 1-3 | Low, medium and high quality decoding |
| HP | High profile | P, I, B | 4: 2: 2 | 1-3 |
| Abbr. | Surname | Pixel / line | Lines | Frame rate (Hz) | Bit rate (Mbit / s) |
|---|---|---|---|---|---|
| LL | Low level | 352 | 288 | 30th | 4th |
| ML | Main level | 720 | 576 | 30th | 15th |
| H-14 | High 1440 | 1440 | 1152 | 30th | 60 |
| HL | High level | 1920 | 1080 | 30th | 80 |
| Profile @ Level | Resolution (px) | Max. Frame rate (Hz) | Sampling | Bit rate (Mbit / s) | Example application |
|---|---|---|---|---|---|
| SP @ LL | 176 × 144 | 15th | 4: 2: 0 | 0.096 | mobile applications |
| SP @ ML | 352 × 288 | 15th | 4: 2: 0 | 0.384 | PDAs |
| 320 × 240 | 24 | ||||
| MP @ LL | 352 × 288 | 30th | 4: 2: 0 | 4th | Set-top boxes (STB) |
| MP @ ML | 720 × 480 | 30th | 4: 2: 0 | 15 (DVD: 9.8) | DVD, SD-DVB |
| 720 × 576 | 25th | ||||
| MP @ H-14 | 1440 × 1080 | 30th | 4: 2: 0 | 60 (HDV: 25) | HDV |
| 1280 × 720 | 30th | ||||
| MP @ HL | 1920 × 1080 | 30th | 4: 2: 0 | 80 | ATSC 1080i, 720p60, HD-DVB (HDTV) |
| 1280 × 720 | 60 | ||||
| 422P @ LL | 4: 2: 2 | ||||
| 422P @ ML | 720 × 480 | 30th | 4: 2: 2 | 50 | Sony IMX (I-Frame only), Broadcast Video (I- and P-Frames only) |
| 720 × 576 | 25th | ||||
| 422P @ H-14 | 1440 × 1080 | 30th | 4: 2: 2 | 80 | possibly for future MPEG-2 based HD products from Sony and Panasonic |
| 1280 × 720 | 60 | ||||
| 422P @ HL | 1920 × 1080 | 30th | 4: 2: 2 | 300 | Record profile of some professional Canon products such as the XF100 camcorder. |
| 1280 × 720 | 60 |
MPEG-2 audio
On the audio side, all three layers are expanded to include lower data rates and more channels ( 5.1 or 7.1 ). There are two variants of the multi-channel coding: those who can make good use of the bit stream generated during the MPEG-1 decoder forward compatible, and not backward compatible version ( English non backward compatible , NBC ). The NBC variant is in Part 7 of the MPEG-2 standard under the name AAC ( Advanced Audio Coding ).
MPEG-2 file formats
MPEG-2 defines the video streaming formats program stream (PS) and transport stream (TS) for the interlacing of video and audio . Over time, however, MPEG-2 has been used in a variety of file formats. Below is an overview of where MPEG-2 files can typically be found:
- .mpg (can also be MPEG-1 or MPEG-4 )
- .mpeg (can also be MPEG-1 or MPEG-4)
- .m2v (MPEG-2 Elementary Video Stream)
- .m2a (MPEG-2 Elementary Audio Stream)
- .m2s (MPEG-2 Elementary Data Stream)
- .ts (MPEG-2 Transport Stream)
- .ps (MPEG-2 Program Stream)
- .vob (DVD Video Object)
- .vro (Video Recording Object)
- .mod (MPEG-2 with AC3 audio e.g. for JVC or Panasonic video cameras)
- .m2t (MPEG-2 transport e.g. on Sony HD cameras)
See also
literature
- Tilo Strutz: Image data compression. Basics, coding, wavelets, JPEG, MPEG, H.264. 4th revised and supplemented edition, Vieweg + Teubner, Wiesbaden 2009, ISBN 978-3-8348-0472-3 .
Individual evidence
- ↑ MPEG LA : MPEG-2 Attachment 1 . January 1, 2017, accessed on February 21, 2017 (pdf, English) - Continuously updated list of all patents with patent number and status relating to the patent portfolio of the MPEG-2 license.
- ↑ MPEG-2. MPEG LA , 2019, accessed on July 22, 2019 (English, MPEG-2 de facto patent-free).
- ↑ ISO International Classification for Standards 35.040: Character sets and information coding (English) - overview page at ISO
- ↑ Atul Puri (Ed.), Puri (Author), Tsuhan Chen (Author): Multimedia Systems, Standards, and Networks. Edition 2000, Marcel Dekker Inc, p. 94.
- ↑ Canon XF100 product page