Method and Apparatus for Fast Channel Change

Abstract

Providing a fast channel change function in a digital television system by processing compressed video streams to provide high priority (HP) and low priority (LP) encoded streams, which streams may also be hierarchically modulated to provide, respectively, long interleave and short interleave modulated signals for transmission, wherein a receiver may rapidly demodulate and use information within the low priority signal of a new channel to more rapidly change to the new channel.

What is claimed is: 
     
         1 . An apparatus, comprising:
 a stream processor configured to process an encoded audiovisual stream to provide thereby a high priority (HP) encoded stream and a corresponding low priority (LP) encoded stream;   wherein a number of frames per unit time of the LP encoded stream is less than a number of frames per unit time of the HP encoded stream;   wherein the frames of the LP encoded stream correspond to respective ones of the frames of the HP encoded stream.   
     
     
         2 . The apparatus of  claim 1 , wherein one of the frames of the LP encoded stream corresponding to a respective one of the frames of the HP encoded stream is temporally aligned with the respective one of the frames of the HP encoded stream. 
     
     
         3 . The apparatus of  claim 1 , wherein a quality of video content of the LP encoded stream is less than a quality of video content of the HP encoded stream, and wherein the LP encoded stream is adapted to enable a receiving device to rapidly transition to the HP encoded stream. 
     
     
         4 . The apparatus of  claim 1 , further comprising:
 at least one modulator configured to modulate the HP encoded stream to provide thereby a modulated HP encoded stream and to modulate the LP encoded stream to provide thereby a modulated LP encoded stream;   wherein the modulated LP encoded stream is adapted to enable a receiving device to rapidly transition to the modulated HP encoded stream.   
     
     
         5 . The apparatus of  claim 4 , wherein the modulation comprises hierarchical modulation to provide thereby a hierarchically modulated signal comprising an HP layer including the HP encoded stream and an LP layer including the LP encoded stream. 
     
     
         6 . The apparatus of  claim 4 , wherein the modulation comprises hierarchical modulation to provide thereby a hierarchically modulated signal comprising an HP layer including higher quality video content and an LP layer including corresponding lower quality video content. 
     
     
         7 . The apparatus of  claim 6 , wherein the LP layer includes additional information adapted to provide error resilience. 
     
     
         8 . The apparatus of  claim 4 , wherein the at least one modulator is configured to use a relatively long interleaver length for modulating the HP encoded stream and to use a relatively short interleaver length for modulating the LP encoded stream. 
     
     
         9 . The apparatus of  claim 4 , wherein the at least one modulator comprises an HP modulator configured to modulate the HP encoded stream to provide thereby the modulated HP encoded stream and an LP modulator configured to modulate the LP encoded stream to provide thereby the modulated LP encoded stream. 
     
     
         10 . The apparatus of  claim 4 , wherein the modulated HP encoded stream and the modulated LP encoded stream comprise a television channel content stream. 
     
     
         11 . The apparatus of  claim 4 , wherein the at least one modulator is configured to provide the modulated HP encoded stream and the modulated LP encoded stream, for transmission toward a receiver via at least one of a wireless transmission medium, a wireline transmission medium, or an optical transmission medium. 
     
     
         12 . The apparatus of  claim 4 , wherein the at least one modulator is configured to use Quadrature Amplitude Modulation (QAM). 
     
     
         13 . The apparatus of  claim 1 , wherein the LP encoded stream includes audio data. 
     
     
         14 . The apparatus of  claim 13 , wherein the audio data of the LP encoded stream and audio data of the HP encoded stream are substantially the same. 
     
     
         15 . The apparatus of  claim 1 , wherein the HP encoded stream comprises a repeating structure of an intra-coded frame associated with a plurality of predictively coded frames, wherein the LP encoded stream comprises a sequence of SI frames temporally corresponding to some of the predictively coded frames of the HP encoded stream. 
     
     
         16 . The apparatus of  claim 15 , wherein the LP encoded stream further comprises SI frames temporally corresponding to the intra-coded frames of the HP encoded stream. 
     
     
         17 . The apparatus of  claim 1 , further comprising:
 an encoder configured to encode audiovisual information to provide thereby the encoded audiovisual stream.   
     
     
         18 . A method, comprising:
 processing an encoded audiovisual stream to provide thereby a high priority (HP) encoded stream and a corresponding low priority (LP) encoded stream;   wherein a number of frames per unit time of the LP encoded stream is less than a number of frames per unit time of the HP encoded stream;   wherein the frames of the LP encoded stream correspond to respective ones of the frames of the HP encoded stream.   
     
     
         19 . The method of  claim 18 , further comprising:
 modulating the HP encoded stream and the LP encoded stream to provide thereby, respectively, a modulated HP encoded stream and a modulated LP encoded stream;   wherein the modulated LP encoded stream is adapted to enable a receiving device to rapidly transition to the modulated HP encoded stream.   
     
     
         20 . A receiving device, comprising:
 a demodulator configured to selectively demodulate a content channel comprising a modulated high priority (HP) encoded stream and a corresponding modulated low priority (LP) encoded stream to provide thereby an HP encoded stream and a corresponding LP encoded stream, wherein a number of frames per unit time of the LP encoded stream is less than a number of frames per unit time of the HP encoded stream, wherein the frames of the LP encoded stream correspond to respective ones of the frames of the HP encoded stream;   a decoder configured to decode the HP encoded stream and the LP encoded stream to provide thereby a decoded HP audiovisual stream and a decoded LP audiovisual stream; and   a switch configured to select between the decoded HP audiovisual stream and the decoded LP audiovisual stream.   
     
     
         21 . The receiving device of  claim 20 , wherein information within the modulated LP encoded stream is used to improve error resilience associated with the modulated HP encoded stream. 
     
     
         22 . The receiving device of  claim 20 , wherein the content channel comprises a hierarchically modulated signal having an HP layer including higher quality video content and an LP layer including corresponding lower quality video content.