Error resilient management of picture order count in predictive coding systems
Coding techniques for input video may include assigning picture identifiers to input frames in either long-form or short-form formats. If a network error has occurred that results in loss of previously-coded video data, a new input frame may be assigned a picture identifier that is coded in a long-form coding format. If no network error has occurred, the input frame may be assigned a picture identifier that is coded in a short-form coding format. Long-form coding may mitigate against loss of synchronization between an encoder and a decoder by picture identifiers.
1. A video coding method, comprising:
coding an input frame according to predictive coding,
if a network error has occurred, coding a picture identifier in a long-form coding format,
if no network error has occurred, coding the picture identifier in a short-form coding format,
transmitting coded video data and the coded picture identifier to a channel.
2. The method of claim 1 , wherein the long-form format includes a first field representing least significant bits of the picture identifier and a second field representing most significant bits of the picture identifier.
3. The method of claim 1 , wherein the short-form format includes a first field representing least significant bits of the picture identifier.
4. The method of claim 1 , further comprising transmitting a flag indicating whether a long-form format is used.
5. The method of claim 1 , further comprising, when the network error has occurred, invalidating non-acknowledged reference frames in a local picture cache.
6. The method of claim 1 , wherein, when the network error has occurred, the coding includes performing a motion estimation search on acknowledged reference frames in a local picture cache.
7. The method of claim 1 , wherein, when no network error has occurred, the coding includes performing a motion estimation search on acknowledged reference frames and non-acknowledged reference frames in a local picture cache.
8. The method of claim 1 , wherein the long-form format is provided in a header field of a first coded slice of the input frame.
9. The method of claim 1 , wherein the long-form format is coded using a syntax as follows:
a pic_order_cnt_lsb field, representing least significant bits of the picture identifier,
a pic_order_cnt_msb_present_flag field, representing whether a pic_order_cnt_msb field is present, and
a pic_order_cnt_msb field, representing most significant bits of the picture identifier.
10. A method of decoding picture identifiers in a coded video session, comprising:
decoding the picture identifiers as a data stream according to:
pic_order_cnt_lsb
If( pic_order_cnt_msb_signaling_enabled_flag) {
pic_order_cnt_msb_present_flag
if( pic_order_cnt_msb_present_flag )
pic_order_cnt_msb
wherein pic_order_cnt_lsb, pic_order_cnt_msb_present_flag and pic_order_cnt_msb represent fields in the data stream, in which
the pic_order_cnt_lsb field represents least significant bits of the picture identifier,
the pic_order_cnt_msb_present_flag field represents whether a pic_order_cnt_msb field is present, and
a pic_order_cnt_msb field, representing most significant bits of the picture identifier; and
wherein pic_order_cnt_msb_signaling_enabled_flag represents a state variable developed in the session indicating whether the pic_order_cnt_msb_present_flag field has been enabled for the coded picture identifier.
11. A method of decoding picture identifiers in a coded video session, comprising:
decoding the picture identifiers as a data stream according to:
pic_order_cnt_lsb
if( num_explicit_pic_order_cnt_msb_cycle_bits> 0 ) {
explicit_pic_order_cnt_msb_cycle_present_flag
if( explicit_pic_order_cnt_msb_cycle_present_flag )
explicit_pic_order_cnt_msb_cycle
}
wherein pic_order_cnt_lsb, explicit_pic_order_cnt_msb_cycle_present_flag and
explicit_pic_order_cnt_msb_cycle represent fields in the data stream, in which
the pic_order_cnt_lsb field represents least significant bits of the picture identifier,
the explicit_pic_order_cnt_msb_cycle_present_flag field represents whether a pic_order_cnt_msb field is present, and
a explicit_pic_order_cnt_msb_cycle field, representing most significant bits of the picture identifier; and
wherein num_explicit_pic_order_cnt_msb_cycle_bits represents a state variable transmitted earlier in the session indicating a number of bits to be used for the explicit_pic_order_cnt_msb_cycle field.
12. A video coding method, comprising:
coding an input frame according to predictive coding,
if a network error has occurred, estimating a number of frames lost by the network error,
if the number of lost frames exceeds a predetermined threshold, coding a picture identifier in a long-form coding format,
if the number of lost frames does not exceed the threshold, coding the picture identifier in a short-form coding format,
transmitting coded video data and the coded picture identifier to a channel.
13. The method of claim 12 , wherein the long-form format includes a first field representing least significant bits of the picture identifier and a second field representing most significant bits of the picture identifier.
14. The method of claim 12 , wherein the short-form format includes a first field representing least significant bits of the picture identifier.
15. The method of claim 12 , further comprising transmitting a flag indicating whether a long-form format is used.
16. The method of claim 12 , further comprising, when the network error has occurred, invalidating non-acknowledged reference frames in a local picture cache.
17. The method of claim 12 , wherein, when the network error has occurred, the coding includes performing a motion estimation search on acknowledged reference frames in a local picture cache.
18. The method of claim 12 , wherein, when no network error has occurred, the coding includes performing a motion estimation search on acknowledged reference frames and non-acknowledged reference frames in a local picture cache.
19. The method of claim 12 , wherein the long-form format is provided in a header field of a first coded slice of the input frame.
20. The method of claim 12 , wherein the long-form format is coded using a syntax as follows:
a pic_order_cnt_lsb field, representing least significant bits of the picture identifier,
a pic_order_cnt_msb_present_flag field, representing whether a pic_order_cnt_msb field is present, and
a pic_order_cnt_msb field, representing most significant bits of the picture identifier.
21. A video coder, comprising:
a coding engine to code video data by motion-compensated predictive coding,
a reference picture cache to store reconstructed video of coded reference frames,
a transmitter to transmit coded video data to a channel
a controller, responsive to network errors, to:
code a picture identifier in a long-form coding format when a network error has occurred,
code the picture identifier in a short-form coding format when no network error has occurred.
22. The video coder of claim 21 , wherein the long-form format includes a first field representing least significant bits of the picture identifier and a second field representing most significant bits of the picture identifier.
23. The video coder of claim 21 , wherein the short-form format includes a first field representing least significant bits of the picture identifier.
24. The video coder of claim 21 , wherein the controller includes a flag in the coded video data indicating whether a long-form format is used.
25. The video coder of claim 21 , wherein, when the network error has occurred, the controller invalidates non-acknowledged reference frames in the reference picture cache.
26. The video coder of claim 21 , wherein, when the network error has occurred, the coding engine performs a motion estimation search on acknowledged reference frames in the reference picture cache.
27. The video coder of claim 21 , wherein, when no network error has occurred, the coding engine performs a motion estimation search on acknowledged reference frames and non-acknowledged reference frames in the reference picture cache.
28. The video coder of claim 21 , wherein, when a network error has occurred, the controller
estimates a number of coded video frames lost due to the network error, and
if the number of lost frames exceeds a predetermined threshold, codes the picture identifier in the long-form coding format, and
if the number of lost frames does not exceed the threshold, codes the picture identifier in the short-form coding format.
29. The video coder of claim 21 , wherein the long-form format is provided in a header field of a first coded slice of a coded input frame.
30. The video coder of claim 21 , wherein the long-form format is coded using a syntax as follows:
a pic_order_cnt_lsb field, representing least significant bits of the picture identifier,
a pic_order_cnt_msb_present_flag field, representing whether a pic_order_cnt_msb field is present, and
a pic_order_cnt_msb field, representing most significant bits of the picture identifier.
31. A non-transitory computer readable medium having instructions stored thereon that, when executed by processing device, causes the devices to:
estimate whether a communication error has occurred involving previously-coded video data,
code an input frame according to predictive coding,
if a communication error has occurred, code a picture identifier for the input frame in a long-form coding format, and
if no communication error has occurred, code the picture identifier for the input frame in a short-form coding format.
32. A decoding method, comprising:
decoding coded video data, the frames having picture identifiers provided within the coded video data, some picture identifiers provided in a long form representation and other picture identifiers provided in a short form representation,
when a long form picture identifier is received, locally estimating a long form picture identifier from a previously-received long form picture identifier and short term picture identifier(s) received subsequent to the previously-received long form picture identifier;
comparing the estimated long form picture identifier to the received long form picture identifier, and
when the comparison indicates a mismatch, identifying an error in the coded video data.