Output of prior pictures for pictures starting a new coded video sequence in video coding

1. A method of decoding implemented by a video decoder, comprising:

receiving, by the video decoder, a coded video bitstream, wherein the coded video bitstream contains a gradual decoding refresh (GDR) picture and a first flag having a first value;

setting, by the video decoder, a second value of a second flag equal to the first value of the first flag;

emptying, by the video decoder, any previously-decoded pictures from a decoded picture buffer (DPB) based on the second flag having the second value after the GDR picture has been decoded; and

decoding, by the video decoder, a current picture after the DPB has been emptied.

2. The method of claim 1 , wherein the GDR picture is not a first picture of the coded video bitstream, and wherein the first value of the flag is one.

3. The method of claim 1 , wherein the GDR picture is disposed in a video coding layer (VCL) network abstraction layer (NAL) unit having a gradual decoding refresh (GDR) network abstraction layer (NAL) unit type (GDR_NUT).

4. The method of claim 1 , further comprising setting a DPB fullness parameter to zero when the first flag is set to the first value.

5. The method of claim 1 , wherein the first flag is designated as no_output_of_prior_pics_flag and the second flag is designated as NoOutputOfPriorPicsFlag.

6. The method of claim 1 , wherein the DPB is emptied after the GDR picture has been decoded.

7. The method of claim 1 , further comprising displaying an image generated based on the current picture.

8. A method of encoding implemented by a video encoder, the method comprising:

determining, by the video encoder, a random access point for a video sequence;

encoding, by the video encoder, a gradual decoding refresh (GDR) picture into the video sequence at the random access point;

setting, by the video encoder, a flag to a first value to instruct a video decoder to empty any previously-decoded pictures from a decoded picture buffer (DPB);

generating, by the video encoder, a video bitstream containing the video sequence having the GDR picture at the random access point and the flag; and

storing, by the video encoder, the video bitstream for transmission toward the video decoder.

9. The method of claim 8 , wherein the GDR picture is not a first picture of the video bitstream, and wherein the video decoder is instructed to empty the DPB after the GDR picture has been decoded.

10. The method of claim 8 , wherein the GDR picture is disposed in a video coding layer (VCL) network abstraction layer (NAL) unit having a gradual decoding refresh (GDR) network abstraction layer (NAL) unit type (GDR_NUT).

11. The method of claim 8 , further comprising instructing the video decoder to set a DPB fullness parameter to zero when the flag is set to the first value.

12. The method of claim 8 , wherein the flag is designated as no_output_of_prior_pics_flag.

13. The method of claim 8 , wherein the first value of the flag is one.

14. A decoding device, comprising:

a receiver configured to receive a coded video bitstream;

a memory coupled to the receiver, the memory storing instructions; and

a processor coupled to the memory, the processor configured to execute the instructions to cause the decoding device to:

receive the coded video bitstream, wherein the coded video bitstream contains a gradual decoding refresh (GDR) picture and a first flag having a first value;

set a second value of a second flag equal to the first value of the first flag;

empty any previously-decoded pictures from a decoded picture buffer (DPB) based on the second flag having the second value; and

decode a current picture after the DPB has been emptied.

15. The decoding device of claim 14 , wherein the GDR picture is not a first picture of the coded video bitstream.

16. The decoding device of claim 14 , wherein the first flag is designated as no_output_of_prior_pics_flag, and wherein the second flag is designated as NoOutputOfPriorPicsFlag.

17. The decoding device of claim 14 , further comprising a display configured to display an image as generated based on the current picture.

18. An encoding device, comprising:

a memory containing instructions;

a processor coupled to the memory, the processor configured to implement the instructions to cause the encoding device to:

determine a random access point for a video sequence;

encode a gradual decoding refresh (GDR) picture into the video sequence at the random access point;

set a flag to a first value to instruct a video decoder to empty any previously-decoded pictures from a decoded picture buffer (DPB); and

generate a video bitstream containing the video sequence having the GDR picture at the random access point and the flag; and

a transmitter coupled to the processor, the transmitter configured to transmit the video bitstream toward the video decoder.

19. The encoding device of claim 18 , wherein the GDR picture is not a first picture of the video bitstream.

20. The encoding device of claim 18 , wherein the flag is designated as no_output_of_prior_pics_flag.

21. The encoding device of claim 18 , wherein the memory stores the video bitstream prior to the transmitter transmitting the video bitstream toward the video decoder.