Video signal loss detection
A video signal and signal technology, applied in the direction of TV, image communication, electrical components, etc., can solve the problems of lack of picture content, failure to detect analog signal waveforms, etc.
Active Publication Date: 2008-05-21
BRITISH TELECOMM PLC
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[0004] However, these methods suffer from the disadvantage that they cannot detect errors in the picture content (or lack thereof) of the nature that the analog signal waveform consistently meets the relevant standard specification
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[0006] Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings.
[0007] In the detection system shown in FIG. 2 , an analog video input signal (possibly from the satellite decoder of FIG. 1 ) is passed through input 100 to analog-to-digital converter 101 . Each successive video frame is stored in frame memory 102 as it is received. Alternatively, the frames, already in digital form, may be fed directly to the frame memory 102, or a compressed digital input may be fed to the frame memory 102 through a suitable decoder.
[0008] The frame memory 102 stores the latest received frame, ie, "current frame". The second frame memory 103 stores a previous frame, usually the frame immediately preceding the frame stored in the memory 102 . Assume that when a new frame is loaded into memory 102, an existing frame in memory 102 is transferred to memory 103; this is shown for clarity, in practice it is preferable to alternat...
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Faults resulting in reception of a still, but unknown, frame are recognised by comparing each received frame of the video signal with its predecessor, incrementing a counter in the event that the difference between the frames falls below a threshold; and generating an alarm signal in the event that the count of the counter exceeds a predetermined count. Other types of fault such as loss of signal (i.e. reception of just noise) are recognised by incrementing the counter whenever the difference exceeds a threshold. Similar results may be obtained by instead the monitoring quantisation step size and / or number of transmitted bits of a digitally coded signal, and noting that it falls below, or exceeds, a threshold. A preferred option is to compute a complexity measure, being a monotonically increasing function (e.g. the product) of the quantisation step size and of the number of coded bits and compare this with the threshold value. Faults occasioned by receipt of a particular fixed image instead of the wanted picture are recognised by comparing each frame of the video signal with the fixed image, and generating an alarm signal in the event that the difference between the frames consistently falls below a threshold.
Description
technical field [0001] The present invention relates to video signal loss detection. The invention is particularly useful for video streaming, but it can be useful in other situations as well. Background technique [0002] Figure 1 shows a typical video streaming system. A video encoder 1 receives multimedia content from a content source, eg from a satellite decoder 2 . The encoder encodes the live content and sends the encoded representation to the server 3 . The server both stores the encoded content for later retrieval and streams it live to individual client terminals 5 over the IP network 4 . In error cases, the audiovisual signal received by the encoder may be lost. This may be due to a malfunctioning satellite decoder and no content in the signal received from the satellite due to a problem with the source of the content. To ensure continuity of content delivery, these error conditions need to be detected and overcome. Once an error condition is detected, the be...
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IPC IPC(8): H04N17/00
CPCH04N17/004
Inventor 迈克尔·埃尔林·尼尔森罗里·斯图尔特·特恩布尔罗伯托·阿尔瓦雷斯·阿雷瓦洛
Owner BRITISH TELECOMM PLC