Conditional signalling of reference picture list modification information

One or more computer-readable memory or storage devices having stored therein encoded data produced by operations comprising:

• receiving video frames;
• and
• encoding the video frames to produce the encoded data in a bit stream, wherein the encoding the video frames includes:
• as part of processing for a slice header of a slice, evaluating a condition, wherein the condition depends on whether value of a variable is greater than 1, the variable indicating a number of total reference pictures;
• and
• depending on whether the condition is satisfied, conditionally signaling in the bit stream a flag that indicates whether a reference picture list (“RPL”) is modified according to syntax elements explicitly signaled in the bit stream.

One or more computer-readable memory or storage devices having stored therein encoded data, the encoded data being organized for decoding according to operations comprising:

• receiving the encoded data in a bit stream;
• and
• decoding the encoded data to produce reconstructed video frames, wherein the decoding of the encoded data includes:
• as part of processing for a slice header of a slice, evaluating a condition, wherein the condition depends on whether value of a variable is greater than 1, the variable indicating a number of total reference pictures;
• and
• depending on whether the condition is satisfied, conditionally parsing from the bit stream a flag that indicates whether a reference picture list (“RPL”) is modified according to syntax elements explicitly signaled in the bit stream.

A computer system comprising one or more processing units and memory, wherein the computer system implements a video encoder system comprising:

• a buffer configured to receive video frames;
• and
• a video encoder configured to encode the video frames to produce the encoded data in a bit stream, wherein the video encoder is configured to perform operations comprising:
• as part of processing for a slice header of a slice, evaluating a condition, wherein the condition depends on whether value of a variable is greater than 1, the variable indicating a number of total reference pictures;
• and
• depending on whether the condition is satisfied, conditionally signaling in the bit stream a flag that indicates whether a reference picture list (“RPL”) is modified according to syntax elements explicitly signaled in the bit stream.