MPEG-1

MPEG-1 (ISO / IEC 11172 ) is a standard of the Moving Picture Experts Group (MPEG ) for lossy video and audio data compression.

MPEG -1 was in the 1980s with the aim of developing (1991 pictured), movies on the limited data rate to compress (up to 1.5 Mbit / s) of playing at normal speed audio CD. The result, with correspondingly more modest quality is called Video CD. The video compression of MPEG -1 in 1994 was significantly refined and improved by MPEG-2.

A video coding method

The image format of MPEG -1 is similar to the JPEG format. The parameters are, however, well defined:

  • Maximum image size 768 × 576 pixels
  • Ratio of height to width of the pixel (14 aspect ratios defined )
  • Frame rate in Hertz
  • Pictures are in the YCbCr format than 3 × 8-bit values ​​per pixel before: Y: luminance / brightness component ( 16 black, 223: white)
  • Cr: red-green color-difference component ( -112: green, red 112 )
  • Cb: blue-yellow color difference component ( -112: yellow, blue 112 )

In image processing, the images are compressed to different extents and used for different purposes. The I-pictures are compressed independently of other images - they need the most disk space, but can be independent of previous frames to decode. Therefore, they are necessary to ( almost ) to be able to jump anywhere in the video. Other pictures are coded depending on the other pictures in the video stream and need thus less space. These types of images are then dependent on the encoder, its settings and sometimes with different frequencies also used by the imagery and typically occur cyclically as so-called group of pictures (English Group of Pictures, GoP ) on. A group ranges from an I- frame to the next. The groups often have a length of half a second.

Audio coding method

Part of the standard are also three audio coding schemes. Increasing in complexity and quality of the layer 1, 2 and 3 are

The audio Layer 1 - also known as MP1 - was introduced by Philips as Low-Complexity version of the Audio Layer 2 in the standard. The digital compact cassette by Philips, which came at the same time with Sony's MiniDisc on the market and now is no longer manufactured, used this method with a data rate of 384 kbps.

The Audio Layer 2 - also known as MP2 or musicam - was the established standard in the radio sector. Almost all professional digital playback equipment used MPEG -1 Audio Layer 2 in the compression of 256 kbit / s ( 128 kbit per second per channel ), since it is then easily transferred over the left good spread in Europe ISDN infrastructure. Audio Layer 2 ( admitted rarely and only for Europe) on Video CDs and Super Video CDs, and used on DVDs and digital television.

The Audio Layer 3 - better known as MP3 - was developed by the Fraunhofer-Gesellschaft and others and is, as well as Layer 1 and Layer 2, not royalty free. That is, producers who want to develop and sell an encoder for MP3 must, for royalty payments. Not sold commercially encoder ( such as LAME ) are royalty- free.

The relatively good ratio of size on the one hand and quality on the other hand has led in the 1990s to a triumph of the MP3 format. It was based on the flourishing of online file sharing ( such as Napster ) and mobile music players ( MP3 players ) based on flash memory or hard drives.

System Definition

Finally, MPEG -1 defines another method for block entanglement ( " multiplexing " ) audio and video system streams. In these among other data to and playback times for error detection are integrated. They can be saved to file or streamed over a network. MPEG -1 system streams is designed for interference-resistant media ( VCD) and is identical to the program stream defined in MPEG-2.

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