High quality seamless playback for video decoder clients

A transcoding method, comprising:

• buffering a first channel stream comprising:
• a first coded video sequence, consisting of frames coded according to I-coding techniques and P-coding techniques,
• a coded audio sequence, and
• an index identifying correspondence between elements of the coded video sequence and elements of the coded audio sequence;
• assembling a second channel stream having a lower frame rate than the first channel stream, the second channel stream comprising:
• a second coded video sequence consisting of the coded I-frames and coded reference P-frames of the first channel stream but omitting coded non-reference P-frames of the first channel stream,
• the coded audio sequence, and
• a second index identifying correspondence between elements of the second video sequence and elements of the coded audio sequence.

A coding apparatus, comprising:

• a coding engine to code frames of a video sequence according to motion estimation prediction in which each frame of the video sequence is constrained to be coded as one of an I-frame or a P-frame;
• a controller to determine for each coded P-frame, a distance from the respective P-frame and a most-recently coded reference frame, wherein when the distance matches a predetermined threshold distance, the respective P-frame is marked as a reference frame by the coding engine;
• a transmit buffer to transmit coded video data of the I-frame(s), the reference P-frames and the non-reference P-frames in a channel;
• a first decoder to decode coded video data of the I-frame(s) and the reference P-frames;
• and
• a reference picture cache to store decoded video data of the I-frame(s) and the reference P-frames for use in subsequent encoding of other frames of the video sequence.

A transcoding apparatus, comprising:

• a buffer to buffer a first channel stream comprising:
• a first coded video sequence, consisting of frames coded according to I-coding techniques and P-coding techniques,
• a coded audio sequence, and
• an index identifying correspondence between elements of the coded video sequence and elements of the coded audio sequence;
• a transcoding engine to assemble a second channel stream having a lower frame rate than the first channel stream, the second channel stream comprising:
• a second coded video sequence consisting of the coded I-frames and coded reference P-frames of the first channel stream but omitting coded non-reference P-frames of the first channel stream,
• the coded audio sequence, and
• a second index identifying correspondence between elements of the second video sequence and elements of the coded audio sequence.

A physical computer readable medium storing program instructions that, when executed by a processor, cause the processor to:

• code frames of a video sequence according to motion estimation prediction in which each frame of the video sequence is constrained to be coded as one of an I-frame or a P-frame;
• for each coded P-frame, determine a distance from the respective P-frame and a most-recently coded reference frame;
• when the distance matches a predetermined threshold distance, mark the respective P-frame as a reference frame;
• transmit coded video data of the I-frame(s), the reference P-frames and the non-reference P-frames in a channel;
• decode coded video data of the I-frame(s) and the reference P-frames;
• and
• store decoded video data of the I-frame(s) and the reference P-frames in a reference picture cache for use in subsequent encoding of other frames of the video sequence.

A physical computer readable medium storing program instructions that, when executed by a processor, cause the processor to:

• buffer a first channel stream comprising:
• a first coded video sequence, consisting of frames coded according to I-coding techniques and P-coding techniques,
• a coded audio sequence, and
• an index identifying correspondence between elements of the coded video sequence and elements of the coded audio sequence;
• assemble a second channel stream having a lower frame rate than the first channel stream, the second channel stream comprising:
• a second coded video sequence consisting of the coded I-frames and coded reference P-frames of the first channel stream but omitting coded non-reference P-frames of the first channel stream,
• the coded audio sequence, and
• a second index identifying correspondence between elements of the second video sequence and elements of the coded audio sequence.