Layer based parameter set NAL unit constraints
A video coding mechanism is disclosed. The mechanism includes receiving a bitstream comprising a picture parameter set (PPS) in a PPS network abstraction layer (NAL) unit and a coded picture comprising a set of video coding layer (VCL) NAL units. A particular VCL NAL unit does not refer to the PPS NAL unit unless a value of a NAL unit header layer identifier (nuh_layer_id) of the PPS NAL unit is less than or equal to a value of a nuh_layer_id of the particular VCL NAL unit. The coded picture is decoded from the set of VCL NAL units based on the PPS in the PPS NAL unit to produce a decoded picture. The decoded picture is forwarded for display as part of a decoded video sequence.
1. A method implemented by a decoder, the method comprising:
receiving a bitstream comprising a picture parameter set (PPS) in a PPS network abstraction layer (NAL) unit and a coded picture comprising a set of video coding layer (VCL) NAL units, wherein a particular VCL NAL unit does not refer to the PPS NAL unit unless a value of a NAL unit header layer identifier (nuh_layer_id) of the PPS NAL unit is less than or equal to a value of a nuh_layer_id of the particular VCL NAL unit, wherein the particular VCL NAL unit comprises a slice of the coded picture and a slice header containing data elements pertaining to the slice, wherein the slice header specifies an adaptation parameter set (APS) identifier (ID) of an APS, wherein the slice is associated with a picture header that contains syntax elements that apply to the slice of the coded picture, and wherein the picture header specifies a PPS ID of the PPS in use for the coded picture; and
decoding the coded picture from the set of VCL NAL units based on the PPS in the PPS NAL unit to produce a decoded picture.
2. The method of claim 1 , wherein the bitstream further comprises the APS in an APS NAL unit, and wherein the particular VCL NAL unit does not refer to the APS NAL unit unless a value of a nuh_layer_id of the APS NAL unit is less than or equal to the value of the nuh_layer_id of the particular VCL NAL unit.
3. The method of claim 1 , wherein the bitstream is a result of a sub-bitstream extraction process that removes NAL units from the bitstream based on nuh_layer_id value.
4. The method of claim 1 , further comprising:
receiving a second bitstream comprising a second PPS in a second PPS NAL unit and a second coded picture comprising a second set of VCL NAL units, wherein a second VCL NAL unit refers to the second PPS NAL unit with a value of a nuh_layer_id of the second PPS NAL unit is not less than or equal to a value of a nuh_layer_id of the second VCL NAL unit; and
in response to the receiving, taking some other corrective measures to ensure that a conforming bitstream corresponding to the second bitstream is received prior to decoding the coded picture from the second set of VCL NAL units.
5. The method of claim 1 , wherein the set of VCL NAL units are part of a layer when the set of VCL NAL units all have a particular value of nuh_layer_id.
6. The method of claim 5 , wherein the layer includes non-VCL NAL units that are associated with the set of VCL NAL units that all have a particular value of nuh_layer_id.
7. A method implemented by an encoder, the method comprising:
encoding a coded picture comprising a set of video coding layer (VCL) network abstraction layer (NAL) units in a bitstream;
encoding into the bitstream a picture parameter set (PPS) in a PPS NAL unit based on a constraint that a particular VCL NAL unit does not refer to the PPS NAL unit unless a value of a NAL unit header layer identifier (nuh_layer_id) of the PPS NAL unit is less than or equal to a value of a nuh_layer_id of the particular VCL NAL unit, wherein the particular VCL NAL unit comprises a slice of the coded picture and a slice header containing data elements pertaining to the slice, wherein the slice header specifies an adaptation parameter set (APS) identifier (ID) of an APS, wherein the slice is associated with a picture header that contains syntax elements that apply to the slice of the coded picture, and wherein the picture header specifies a PPS ID of the PPS in use for the coded picture.
8. The method of claim 7 , further comprising encoding into the bitstream the APS in an APS NAL unit based on a constraint that a particular VCL NAL unit does not refer to the APS NAL unit unless a value of a nuh_layer_id of the PPS NAL unit is less than or equal to a value of a nuh_layer_id of the particular VCL NAL unit.
9. The method of claim 7 , further comprising performing a sub-bitstream extraction process to remove NAL units from the bitstream based on nuh_layer_id value.
10. The method of claim 7 , wherein the set of VCL NAL units are part of a layer when the set of VCL NAL units all have a particular value of nuh_layer_id.
11. The method of claim 10 , wherein the layer includes non-VCL NAL units that are associated with the set of VCL NAL units that all have a particular value of nuh_layer_id.
12. A video coding device comprising:
a receiver configured to receive a bitstream comprising a picture parameter set (PPS) in a PPS network abstraction layer (NAL) unit and a coded picture comprising a set of video coding layer (VCL) NAL units, wherein a particular VCL NAL unit does not refer to the PPS NAL unit unless a value of a NAL unit header layer identifier (nuh_layer_id) of the PPS NAL unit is less than or equal to a value of a nuh_layer_id of the particular VCL NAL unit, wherein the particular VCL NAL unit comprises a slice of the coded picture and a slice header containing data elements pertaining to the slice, wherein the slice header specifies an adaptation parameter set (APS) identifier (ID) of an APS, wherein the slice is associated with a picture header that contains syntax elements that apply to the slice of the coded picture, and wherein the picture header specifies a PPS ID of the PPS in use for the coded picture; and
a processor coupled to the receiver and configured to decode the coded picture from the set of VCL NAL units based on the PPS in the PPS NAL unit to produce a decoded picture.
13. The video coding device of claim 12 , wherein the bitstream further comprises the APS in an APS NAL unit, and wherein the particular VCL NAL unit does not refer to the APS NAL unit unless a value of a nuh_layer_id of the APS NAL unit is less than or equal to the value of the nuh_layer_id of the particular VCL NAL unit.
14. The video coding device of claim 12 , wherein the bitstream is a result of a sub-bitstream extraction process that removes NAL units from the bitstream based on nuh_layer_id value.
15. The video coding device of claim 12 , wherein the set of VCL NAL units are part of a layer when the set of VCL NAL units all have a particular value of nuh_layer_id.
16. The video coding device of claim 15 , wherein the layer includes non-VCL NAL units that are associated with the set of VCL NAL units that all have a particular value of nuh_layer_id.