Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-07-08
2001-05-08
Kelley, Chris (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06229853
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to digital video encoders and digital video encoding, and more particularly to error correcting. The method and apparatus of the invention detect errors in the synchronization signals of the incoming data stream and stop encoding until the next line, field, or frame, thereby preventing these errors from degrading the video output of the encoder and propagating through the network.
BACKGROUND OF THE INVENTION
For a digital video encoder subsystem, such as an MPEG-2 or HDTV compliant digital video encoder subsystem, the occurrence of an error, such as switching the uncompressed video source from one device or channel to another while encoding, can pose many problems. The input video stream could be disturbed in such a manner as to present the encoder with one or more of the following problem scenarios:
1. Too few pixels per line for the current input line.
2. Too many pixels per line for the current input line.
3. Not enough lines for the current field/frame before the next field/frame arrives.
4. Too many lines for the current field/frame before the next field/frame arrives.
5. Odd-to-Even or Even-to-Odd field parity switch in the middle of a field.
6. Failure to switch field parity between fields.
Typical prior art encoding subsystems may respond to such disturbances by stopping the encoding process, that is, hanging, or by producing continually shifted luminance and/or chrominance output components, or by inverting the even and odd fields, or some other undesirable output. These responses all serve to carry the disturbance through subsequent pictures.
A more desirable response to such an input video disturbance would be to correct the error and resume normal encoding as soon as possible following the input video transition.
Thus, there exists a clear need for a method and apparatus to detect and correct errors in the synchronization signals of the input bitstream to the encoder, that is, the pixel bus, before the errors propagate through the system and become perceptible to the viewer.
SUMMARY OF THE INVENTION
This invention provides a mechanism by which a digital video encoding system or subsystem, for example, an MPEG-2 compliant encoding subsystem or an HDTV compliant encoding subsystem, can respond to an input video error and the ensuing partial picture scenarios, such as an incomplete field transmission where the field parity changes before the end of the field, or identification of a field end where subsequent lines are of the same parity as the previous field, or where an erroneous line end is encountered and the rest of the line is identified as being of the wrong parity, or the like. The method and apparatus of the invention detect such errors and anomalies, and take appropriate action, such as stopping encoding of the particular picture until the next line, parity field, or picture is encountered, and thereafter resuming encoding.
According to our invention, there is provided a Partial Picture Repair Unit (“PPRU”) connected to the uncompressed video input port of the encoding subsystem. With the assistance of an “end of picture” detection mechanism, the partial picture repair unit detects each of the partial picture conditions as they are presented at the uncompressed video interface, stops encoding, and either repairs the input video stream or waits for a correct input video stream in such a manner as to make the disturbance transparent to all downstream units in the remainder of the encoding system pipeline. After the occurrence of the partial picture condition, all downstream units will continue to operate properly, although there may be, at most, two frames of transitional video where image degradation may occur.
THE FIGURES
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Gebler Charlene Ann
Ngai Agnes Yee
Vachon Michael Patrick
Woodard Robert Leslie
International Business Machines - Corporation
Kelley Chris
McGuireWoods LLP
Philippe Gims
Steinberg William H.
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