Philips 14AA3322/40B Guia de Instalação descarregar pdf (Página 22)

Generation of a transport stream for DVB and realisation of a HF-modulated DVB-signal

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 Systems (storage and synchronization of video, audio, and other data together)

 Video (compressed video content)

 Audio (compressed audio content)

 Conformance testing (testing the correctness of implementations of the standard)

 Reference software (example software showing how to encode and decode according to

the standard)

Systems: MPEG-1 Systems specifies the logical layout and methods used to store the encoded

audio, video, and other data into a standard bitstream, and to maintain synchronization

between the different contents. This file format is specifically designed for storage on media,

and transmission over data channels that are considered relatively reliable. Only limited error

protection is defined by the standard, and small errors in the bitstream may cause noticeable

defects. This structure was later named an MPEG program stream, because the MPEG-1

Systems design is essentially identical to the MPEG-2 Program Stream structure.

Video: MPEG-1 Video uses such compression methods to significantly reduce the data rate

required by a video stream. It reduces or completely discards information in certain frequencies

and areas of the picture that the human eye has limited ability to fully perceive. It also exploits

temporal (over time) and spatial (across a picture) redundancy common in video to achieve

better data compression than would not be possible otherwise.

Audio: MPEG-1 Audio uses psychoacoustics to significantly reduce the data rate required by an

audio stream. It reduces or completely discards certain parts of the audio that the human ear

cannot hear, either because they are in frequencies where the ear has limited sensitivity, or are

masked by other louder sounds. It also uses four types of channel encoding. Mono, joint stereo,

stereo and dual (two uncorrelated mono channels). The sampling rates for the audio are 32000,

44100 and 48000 Hz. The audio part of the MPEG-1 format consists of three layers.

 The Layer I uses 384-sample frame size for very low delay, and finer resolution. This is

advantageous for applications like teleconferencing and studio editing. It also has lower

complexity than Layer II to facilitate real-time encoding

 The Layer II is a lossy audio format designed to provide high quality at about 192 kbit/s

for stereo sound. Typically is an update from the Layer I.

 The Layer III is a lossy audio format designed to provide acceptable quality at about 64

kbit/s for monaural audio over single-channel links, and 128 kbit/s for stereo sound.

Conformance testing: It is a procedure to test the conformance. Provides two sets of guidelines

and reference bitstreams for testing the conformance of MPEG-1 audio and video decoders, as

well as the bitstreams produced by an encoder.

Reference software: It includes some examples of software that can be used to encode and

decode audio and video. Also, software for multiplexing and demultiplexing.

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Philips 14AA3322/40B Guia de Instalação Página 22