H.263/H.263+/H.264 video frequency code technology introduction
H.263 video frequency code standard
- H.263 is uses in the low code rate video frequency code most early the ITU-T standard, afterwards appears second edition (H.263+ and H.263++ increased many options, enable it to have a more widespread serviceability.H.263 is ITU-T is lower than the video frequency code standard which 64kb/s the narrow band communications channel formulates.It is develops in the H.261 foundation, its standard input image form may be S-QCIF, QCIF, CIF, 4CIF or the 16CIF colored 4∶2∶0 Asian sample image.H.263 and H.261 compared have used half picture element motion compensation, and increased 4 kind of effective compression code pattern.
H.263+ video frequency compression standard
- ITU-T revised after the H.263 issue had issued the H.263 standard edition 2, the unofficial naming was the H.263+ standard.It in guaranteed in the original H.263 standard core syntax and the semantic invariable foundation, increased certain options to enhance the efficiency of compression or to improve some aspect the function.The original H.263 standard has limited its application image input form, only permits 5 kind of video frequency source form.H.263+ standard permission wide range image input form, from definition image size, thus has opened up the standard use scope, enables it to be possible to process based on the Windows computer image, the higher frame frequency image sequence and the wide screen image.In order to enhance the efficiency of compression, H.263+ uses in the advanced frame to code the pattern; The enhancement PB- frame pattern improved the H.263 insufficiency, strengthened the effect which the frame forecast; Not only went to the blocking effect filter to enhance the efficiency of compression, moreover provided the reconstruction image the subjective quality.In order to adapt the network transmission, H.263+ increased the time graduation, the signal-to-noise ratio and the spatial graduation, to transmits the video signal in the noise channel and in the existence massive package loss network to have the significance very much; Moreover, the piece structure pattern, the reference frame choice pattern strengthened the video frequency transmission anti-error code ability.
H.264 video frequency compression standard
- H.264 is the union video frequency group (JVT formulation new generation of video frequency compression code standard which is composed by ISO/IEC and ITU-T.Is strong to the channel latency compatibility, also may work the low latency pattern satisfies the real-time service, like videoconference and so on; Also may work in the non-latency limit situation, like video frequency memory and so on.
- enhances the network compatibility, the use “the network is friendly” the structure and the grammar, strengthens to the error code and drop processing, enhances the decoder the mistake to restore ability.
- in arranges/in the decoder to use the order of complexity to be possible to grade the design, may grade between the picture quality and code processing, adapts the different order of complexity application.
- was opposite in the ahead of time video frequency compression standard, H.264 has introduced very many advanced technologies, including 4×4 in the integer transformation, in the air zone frame forecast, 1/4 picture element precision movement estimate, the multi-reference frame and many kinds of big scrap frame the forecasting technology and so on.The new technology has brought the high compression ratio, simultaneously enhanced the algorithm order of complexity greatly.
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