Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Patent
1998-02-25
2000-08-29
Tung, Bryan
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
3488451, H04N 736
Patent
active
061119172
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a video transmission system and method for transmitting video data via a transmission path such as a wireless transmission path or a LAN, in which considerable numbers of transmission errors may occur.
BACKGROUND ART
In common video-coding methods such as MPEG or the like, differences between two successive pictures are generally determined in order to compress the amount of video data information. In such an inter-picture prediction method (called the "inter-picture coding method" hereinbelow), a present picture is predicted according to a previous picture, and a predicted difference is transmitted.
However, when an error is incorporated into a picture passing through a transmission path, thus is rendering the relevant data erroneous, the corresponding picture at the receiving side is also erroneous because the picture is constructed using erroneous data. As a further problem, the next picture is predicted based on the error-containing picture, and the error is propagated to subsequent pictures.
Such a situation in which an error is incorporated into video data occurs when a reading error from a storage medium such as a CD-ROM exists, or a transmission error via a transmission path exists. In particular, significant transmission errors occur if a radio transmission path is used.
As the first conventional example of the video transmission method using such an error-prone transmission path, an intra-picture coding method will be explained, in which if an error is detected at the receiving side, the receiving side informs the video sending side of the situation, and the sending side which received the information encodes video data without using the inter-picture coding method.
FIG. 18 shows an example of a combination system arrangement of the above first conventional example and a general video coding method in which motion compensation and discrete cosine transformation (DCT) are combined.
First, a difference between an input picture and a reference picture is calculated by subtracter 101, and the DCT is performed at DCT section 102. The DCT coefficient as a result of the DCT is quantized by quantizer ("Q") 103 and is temporarily stored in buffer ("buff.") 109. The stored data are read out through control by error controller ("error cont.") 110 and are transmitted through transmission path 120. The signal quantized by quantizer 103 is inverse-quantized by inverse quantizer "Q.sup.-1 " 104 and is then subjected to inverse DCT in inverse DCT section ("IDCT") 105. To the output from section 105, the same reference picture signal as the signal used at the subtracter 101 is added and the added result is stored into picture memory ("PM") 107. Picture-differential controller 108 reads out a reconstructed picture of one picture before and sends it as an reference picture signal to subtracter 101. When the error controller 110 is informed of error detection from the receiving side, the controller 110 interrupts the inputting of a reference picture signal via picture-differential controller 108 into subtracter 101 and switches the coding method to the intra-picture coding.
Whether or not a receiving error exists in the information transmitted through transmission path 120 is determined by error detector 111 at the video receiving side. If no error is detected, the information is inverse-quantized by inverse quantizer ("Q.sup.-1 ") 112 and then inverse DCT is performed by inverse DCT section ("IDCT") 113. To the output from section 113, a received picture of one picture before, stored in picture memory ("PM") 115, is added as an reference picture signal by adder 114. The added result is output to a monitor or the like, and is simultaneously stored in PM 115. If a receiving error was detected by the error detector 111, this fact is communicated to the video sending side.
As the second conventional example of the video transmission method using an error-prone transmission path, another method will be explained in which error propagation is prevented by changing a re
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Akimoto Takaaki
Ichikawa Tadashi
Kimata Hideaki
Kimura Tsukasa
Suzuki Ryota
Nippon Telegraph and Telephone Corporation
Tung Bryan
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