Divicom Inc.

Other

Michael G Perkins

David Arnstein

William Lynn Helms

Thomas Lookabaugh

The present invention relates to a method for dynamically allocating bandwidth to each encoder in an ensemble of video encoders whose output bit streams share a single communications channel. In accordance with the present invention, the channel bandwidth is allocated to the individual encoders in the ensemble in such a way that differences in a quality measure among the decoders are reduced. The quality measure includes a term that behaves like a peak-signal-to-noise ratio (PSNR) and a term that measures the 'masking effect' in a video signal. The 'masking effect' results because an encoded frame with a high visual complexity masks coding artifacts from the viewer when it is decoded and displayed.

Dynamic rate optimization for an ensemble of video encoders

A method and apparatus for non-seamless splicing of audio-video transport streams configured in accordance with MPEG-2 or other suitable techniques. A first transport stream is to be spliced with a second transport stream at a splice point. The first stream is configured such that the final first stream frame to be displayed will be a black frame or will have another suitable characteristic. Null packets are then delivered in place of the first stream transport packets for a predetermined period of time after the splice point. The predetermined time is generally greater than the sum of the splice decoding delay associated with the splice point and the maximum frame duration in the first stream. The transport packets of the second stream are then delivered. Null packets may be again delivered for a period of time sufficient to allow the final frame of the second stream to be displayed. The final first stream frame can be guaranteed to be a black frame by directing a digital stream insertion device to insert a black I-frame followed by an end-of-sequence code into the first stream. Alternatively, the final first stream frame could be forced to black during an encoding operation, and an end-of-sequence code could then be inserted at the splice point.

Non-seamless splicing of audio-video transport streams

A method and apparatus for reducing program clock reference (PCR) jitter in transport packets of a transport stream compliant with MPEG-2 or another suitable audio-video encoding standard. The PCRs from a given single program transport stream (SPTS) of a multi-program transport stream are processed in a phase-locked loop (PLL) to generate dejittered PCRs for that SPTS. The PLL for a given SPTS receives as inputs the PCRs from that SPTS and a cycle count for each PCR indicative of the number of asynchronous clock cycles counted since the previous PCR. The PLL generates a given dejittered PCR as a function of the previous dejittered PCR, the cycle count for the given PCR, and a clock frequency mismatch estimate for the given program clock. The clock frequency mismatch estimate is generated by filtering a sequence of jitter estimates, each corresponding to the difference between a previous PCR and its corresponding dejittered PCR. The SPTS transport packets may then be restamped with the dejittered PCRs from the PLL to provide a dejittered multi-program transport stream.

Reduction of timing jitter in audio-video transport streams

Successive frames in a video sequence are encoded by a video encoder. The bits are apportioned among successive frames to maximize overall perceived video quality when the encoded video sequence is decoded and displayed. The ongoing allocation process is constrained by the need to avoid decoder buffer exception, i.e., buffer underflow and overflow conditions, at the decoder.

Growing community of inventors

Louisville, CO, United States of America

Michael G Perkins