Method and apparatus for decoding an enhanced video stream
View Patent ↗A method of decoding an enhanced video stream composed of base layer video access units and enhancement layer video access units, each access unit comprising a plurality of syntax structures, includes passing the syntax structures of the base layer access units to a base layer buffer, passing syntax structures of the enhancement layer access units to an enhancement layer buffer, outputting the syntax structures passed to the base layer buffer in a predetermined sequence, outputting the syntax structures passed to the enhancement layer buffer in a predetermined sequence, and recombining the sequences of syntax structures output by the base layer buffer and the enhancement layer buffer respectively to form a complete enhanced access unit, composed of base layer syntax structures and enhancement layer syntax structures in a predetermined sequence.
1. A method of decoding an enhanced multiplexed transport stream comprising a succession of enhanced access units, each comprising a base layer access unit and at least one enhancement layer access unit, each access unit comprising a plurality of syntax structures, said method comprising:
passing the syntax structures of the base layer access units to a base layer buffer,
passing syntax structures of the enhancement layer access units to an enhancement layer buffer, wherein the syntax structures of the enhancement layer access units comprise video layer syntax structures and non-video layer syntax structures,
separating the syntax structures of the base layer access units from the succession of enhanced access units, including separating non-video layer syntax structures of the enhancement layer access units from the succession;
outputting the syntax structures passed to the base layer buffer in a predetermined sequence,
outputting the syntax structures passed to the enhancement layer buffer in a predetermined sequence, and
recombining the sequences of syntax structures output by the base layer buffer and the enhancement layer buffer respectively to form a complete enhanced access unit, comprising base layer syntax structures and enhancement layer syntax structures in a predetermined sequence;
wherein:
the syntax structures passed to the base layer buffer include enhancement layer non-video syntax structures;
all the video layer syntax structures of the enhancement layer access units pass to the enhancement layer buffer; and
none of the enhancement layer non-video syntax structures of the enhancement layer access units pass to the enhancement layer buffer.
2. A method according to claim 1 , wherein the syntax structures of an enhancement layer access unit in the succession of enhanced access units comprise video layer syntax structures, non-video layer syntax structures, and a delimiting syntax structure marking a boundary of the video layer syntax structures of the enhancement layer access unit, and the step of separating the syntax structures of the base layer access units from the unitary succession of access units includes passing syntax structures prior to the delimiting syntax structure to the base layer buffer and passing syntax structures after the delimiting syntax structure to the enhancement layer buffer.
3. A method according to claim 1 , comprising receiving a multiplexed transport stream conveying, with different respective program identifiers, the syntax structures of the base layer access units and said remaining syntax structures, demultiplexinge the transport stream to create at least two program streams based on the different respective program identifiers, and passing the two program streams to the base layer buffer and the enhancement layer buffer respectively.
4. A method according to claim 1 , wherein the base layer buffer includes an elementary stream buffer segment and the enhancement layer buffer includes an elementary stream buffer segment, and the method comprises dynamically adjusting the combined sizes of the elementary stream buffer segments to optimize decoding of the enhanced multiplexed transport stream while restricting the maximum size of the elementary stream buffer segment of the base layer buffer.
5. A method according to claim 1 , comprising passing the complete enhanced access unit to a video decoder.
6. A method according to claim 1 , wherein the enhancement layer access units contain syntax structures of at least first and second enhancement layers, and the step of passing remaining syntax structures to an enhancement layer buffer includes passing syntax structures of the first and second enhancement layers to first and second enhancement layer buffers respectively.
7. A method according to claim 6 , wherein the enhanced multiplexed transport stream comprises a succession of enhanced access units each comprising a base layer access unit and at least first and second enhancement layer access units, and the method comprises separating the syntax structures of the base layer access units from the succession of enhanced access units.
8. A method according to claim 7 , wherein the syntax structures of each enhancement layer access unit comprise video layer syntax structures and non-video layer syntax structures, and the step of separating the syntax structures of the base layer access units from the succession of enhanced access units includes separating non-video layer syntax structures of the first and second enhancement layer access units from the succession, whereby the syntax structures passed to the base layer buffer include enhancement layer non-video syntax structures, and wherein all the video layer syntax structures of the first and second enhancement layer access units pass to the first and second enhancement layer buffers respectively.
9. A method according to claim 7 , wherein the syntax structures of an enhancement layer access unit in the succession of enhanced access units comprise video layer syntax structures, non-video layer syntax structures, and a delimiting syntax structure marking a boundary of the video layer syntax structures of the enhancement layer access unit, and the step of separating the syntax structures of the base layer access units from the unitary succession of access units includes passing syntax structures prior to the delimiting syntax structure to the base layer buffer and passing syntax structures after the delimiting syntax structure to the enhancement layer buffer.
10. A method according to claim 6 , comprising receiving a multiplexed transport stream conveying the syntax structures of the base layer access units with a first program identifier, syntax structures of the first enhancement layer with a second program identifier, and syntax structures of the second enhancement layer with a third program identifier, demultiplexing the transport stream to create at least first, second and third program streams based on the first, second and third program identifiers respectively, and passing the first, second and third program streams to the base layer buffer and the first and second enhancement layer buffer respectively.
11. A method according to claim 6 , wherein the base layer buffer includes an elementary stream buffer segment and the first and second enhancement layer buffers includes a first and second elementary stream buffer segments respectively, and the method comprises dynamically adjusting the combined sizes of the elementary stream buffer segments to optimize decoding of the enhanced multiplexed transport stream while restricting the maximum size of the elementary stream buffer segment of the base layer buffer.
12. A method according to claim 6 , comprising passing the complete enhanced access unit to a video decoder.
13. A decoding apparatus for decoding a base layer program stream conveying a succession of base layer access units of an enhanced multiplexed transport stream and at least one enhancement layer program stream conveying a succession of enhancement layer access units of said enhanced multiplexed transport stream, each access unit comprising a plurality of syntax structures, each enhancement layer comprising video layer syntax structures and non-video layer syntax structures, the decoding apparatus comprising:
a base layer buffer connected to receive the base layer program stream and the non-video layer syntax structures and configured to output syntax structures of each base layer access unit and the non-video layer syntax structures in a predetermined sequence,
an enhancement layer buffer connected to receive the enhancement layer video layer syntax structures and to output the video layer syntax structures of each enhancement layer access unit in a predetermined sequence,
a reassembly functional element connected to receive the syntax structures output by the base layer buffer and the enhancement layer buffer respectively and to form a complete enhanced access unit, comprising base layer syntax structures and enhancement layer syntax structures in a predetermined sequence;
wherein no non-video layer syntax structures are received by the enhancement layer buffer.
14. A decoding apparatus according to claim 13 , further comprising a video decoder connected to receive the complete enhanced access unit, the video decoder being operative to decode the enhanced access unit to form a video presentation unit.
15. A decoding apparatus according to claim 13 , wherein the base layer program stream and the enhancement layer program stream are encapsulated in a transport stream, and the decoding apparatus comprises a transport stream demultiplexer for receiving the transport stream and outputting separately the base layer program stream and the enhancement layer program stream.
16. A decoding apparatus according to claim 15 , wherein syntax structures included in each enhancement layer access unit comprise video coding layer enhancement layer access units, each enhancement layer access unit of the enhancement layer program stream encapsulated in the transport stream conveys a delimiting syntax structure marking a boundary of the video coding layer access units included in the enhancement layer access unit, and the transport stream demultiplexer extracts the enhancement layer access units from the transport stream based on the delimiting syntax structure.
17. A non-transitory computer readable medium containing software that, when executed by a computer having an input for receiving an enhanced multiplexed transport stream that conveys a succession of enhanced access units each comprising a base layer access unit and at least one enhancement layer access unit, each access unit comprising a plurality of syntax structures, processes the enhanced multiplexed transport stream by a method comprising:
passing the syntax structures of the base layer access units to a base layer buffer,
passing syntax structures of the enhancement layer access units to an enhancement layer buffer, wherein the syntax structures of the enhancement layer access units comprise video layer syntax structures and non-video layer syntax structures,
separating the syntax structures of the base layer access units from the succession of enhanced access units, including separating non-video layer syntax structures of the enhancement layer access units from the succession;
outputting the syntax structures passed to the base layer buffer in a predetermined sequence,
outputting the syntax structures passed to the enhancement layer buffer in a predetermined sequence, and
recombining the sequences of syntax structures output by the base layer buffer and the enhancement layer buffer respectively to form a complete enhanced access unit, comprising base layer syntax structures and enhancement layer syntax structures in a predetermined sequence;
wherein:
the syntax structures passed to the base layer buffer include enhancement layer non-video syntax structures;
all the video layer syntax structures of the enhancement layer access units pass to the enhancement layer buffer; and
none of the enhancement layer non-video syntax structures of the enhancement layer access units pass to the enhancement layer buffer.