Data within the JFIF contains segments separated by a 2 byte marker This marker

Data within the jfif contains segments separated by a

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Data within the JFIF contains segments separated by a 2-byte marker. This marker has a binary value of 1111 1111 (FF h ) followed by a defined marked field. If a 1111 1111 (FF h ) bit field occurs anywhere within the file (and it isn’t a marker), the stuffed 0000 0000 (00 h ) byte is inserted after it so that it cannot be read as a false markers. Multimedia System 030728.ppt 76 File Format - Multimedia MPEG ISO established the Moving Picture Expert Group with the mission to develop standards for the coded representation of moving picture and associated audio information on digital storage media. MPEG standardization are best known for their video compression, they also support high-quality audio compression. There are currently Five MPEG Standards in various stages of completion. Each consists of numerous parts addressing aspects of video compression, storage, and delivery.
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Multimedia System 030728.ppt 77 File Format - Multimedia MPEG-1: ISO 11172, “Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5Mbits/s. (such as CD- ROM) A file contain a video, an audio stream, or a system stream stream which interleaves some combination of audio and video stream. The MPEG-1 bit-stream syntax allows for picture sizes of up to 4095 x 4095 pixels. Many of the applications using MPEG-1 compressed video have been optimized the SIF (source intermediate format) video format. As in MPEG-1, input pictures are coded in the YC b C r colour space. This is referred to as the 4:2:0 subsampling format. Multimedia System 030728.ppt 78 Medium Specific Decoder System Decoder Clock Control Audio Decoder Video Decoder Digital Storage Medium Decoded Audio Decoded Video ISO/IEC 11172 Audio ISO/IEC 11172 Video ISO 11172 Stream MPEG1 (ISO/IEC 11172) Decoder Multimedia System 030728.ppt 79 Temporal Picture Structure (MPEG-1) Sequence group of pictures picture macroblock slice block Multimedia System 030728.ppt 80 mapping quantizer and coding Frame packing Encoded bitstream Psychoacoustic model PCM audio samples 32 44.1 48kHz ISO/IEC 11172-3 encoder Ancillary data MPEG1 (ISO/IEC 11172) Audio Encoder
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Multimedia System 030728.ppt 81 Illustration of I-picture (I) and P-picture (P) in a video sequence Y1 Y2 Y3 Y4 U V MB 1 2 3 4 Coding Order a: Frame Prediction b: Macroblock I P P P MPEG-1 Coding Algorithm Multimedia System 030728.ppt 82 File Format - Multimedia MPEG-2: ISO 13818, “Generic Coding of Moving Pictures and Associated Audio” The maximum coded bit rate to 10Mbits/s. It could successfully support higher bit rates, e.g 80-100Mbits/s for HDTV applications. MPEG-2 supports the 4:2:2 colour subsampling format. Multimedia System 030728.ppt 83 Basic Objects in MPEG-2 Video sequence Group of pictures Block Group of pictures consisting of a sequence of pictures, grouped into “Group of Pictures” Macroblock Slice Picture holding the pixel values holding up to 4 blocks for each Y, Cr or Cb consists of macroblocks, which are grouped into slices Multimedia System 030728.ppt 84 Matrixes for 4:4:4 and 4:2:2 Sampled Frame Cb Chrominance Values Cr Y Chrominance Values Luminance Values 4:4:4 Frame Cb Chrominance Values Cr Y Chrominance Values Luminance Values 4:2:2 Frame
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Multimedia System 030728.ppt
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