7.2Review of list of actions for text of version 1 of HEVC
The actions taken at the meeting for finalization of the text of version 1 of the HEVC video coding specification are listed in this section.
NOTE – Editorial issues for aspects where the text is essentially correct (e.g. adding explanatory notes in the text) are not listed here.
Communication to and by parent bodies (primary section 3.1)
Relevant actions are noted below.
Draft text specification of version 1 (primary section 3.3)
Updates in JCTVC-L0030.
Profile, level and constraint definition changes (primary section 3.5)
Increase maximum bit expansion ratio from 4/3 to 5/3 (regardless of profile) (reference notes for JCTVC-L0292).
Deblocking filter (primary section 6.1)
No action.
High-level syntax (primary section 6.2)
General high-level syntax cleanups (primary section 6.2.1)
Classify NAL unit types 48–55 (the first 8 of the 16 NAL unit types that have "unspecified" usage) as "prefixes" (i.e. may start a new access unit) (reference notes for JCTVC-L0043).
Remove bit_rate_pic_rate_info( ) from VPS (reference notes for JCTVC-L0043).
Change the coding of the min_spatial_segmentation_idc syntax element from u(8) to ue(v), and specify the allowed value range as 0..4095 (reference notes for JCTVC-L0043).
Require that the TemporalId of any non-VCL NAL unit shall not be less than the TemporalId of the access unit containing the NAL unit (which implies that a VPS, SPS or PPS NAL unit is disallowed to be present in access units with TemporalId greater the TemporalId of the VPS, SPS or PPS NAL unit). (reference notes for JCTVC-L0043-v3)
Increase the length of general_reserved_zero_16bits and sub_layer_reserved_zero_16bits to 48 bits (and change its name accordingly, subtracting 4 bits to reflect other action noted below relating to JCTVC-L0046) (reference notes for JCTVC-L0363).
Requirement to set delta_poc_msb_present_flag[ i ] equal to 1 in a problematic corner case (option 2 of JCTVC-L0443).
Change the maximum value of num_ref_idx_lX_default_active_minus1 and num_ref_idx_lX_active_minus1 to 14 rather than 15, change the encoding of max_dec_pic_buffering to use the "_minus1" convention, correct uses of the value 0 for this syntax element, and change the range specification for num_negative_pics, num_positive_pics, num_long_term_sps and num_long_term_pics correspondingly (reference notes for JCTVC-L0323).
NAL unit header (primary section 6.2.2)
No action (other than as recorded above).
Parameter sets (primary section 6.2.3)
Move output_flag_present_flag and num_extra_slice_header_bits up to immediately after dependent_slice_segments_enabled_flag in the PPS (reference notes for JCTVC-L0255).
Add two flags to active parameter sets SEI message indicating presence of parameter sets in the CVS and lack of update (JCTVC-L0047-v2, as modified).
Suggestion relating to profile_tier_level( ) byte alignment in JCTVC-L0363-v5 "variant a" (sending 0 bytes or 2 bytes for sub-layer flags sent in loop).
Slices and slice header (primary section 6.2.4)
Apply the "_minus1" coding convention for entry_point_offset[ i ] syntax elements (reference notes for JCTVC-L0116).
Hypothetical reference decoder and associated syntax elements and SEI messages (primary section 6.2.5)
Signal clock tick value outside of HRD parameters (so that it will be available for use with indication of POC proportional to timing) and make the syntax structure for this the same in the VPS as in the SPS (nesting HRD parameters within the timing presence if statements, and adjusting semantics such that when POC is indicated to be proportional to timing in the VPS, this shall also be indicated in the SPS) (reference notes for JCTVC-L0043).
In the picture timing SEI message, fix the condition for the presence of some syntax elements on CpbDpbDelaysPresentFlag (editorial fix, listed here only to highlight the fix). (reference notes for JCTVC-L0045)
Fix aspects of semantics, constraints, and sub-bitstream extraction process relating to APS, BP, PT, and DU SEI messages and nuh_reserved_zero_6bits (which is expected to be called nuh_layer_id in SHVC) and nesting of SEI messages. (reference notes for JCTVC-L0045)
Condition the presence of the syntax elements (low_delay_hrd_flag[ i ] and cpb_cnt_minus1[ i ] to the case where the value is not required to be a particular value (conditioned on fixed_pic_rate_within_cvs_flag[ i ] and low_delay_hrd_flag[ i ], respectively, reference JCTVC-L0372).
Restrict buffering period SEI messages to be sent only for pictures with temporal ID equal to 0 that are not RASL, RADL or sub-layer non-reference pictures (reference notes for JCTVC-L0328).
Concatenation flag and associated CPB removal delay delta for bitstream splicing (reference notes for JCTVC-L0328)
Introduce two syntax elements in the buffering_period( ) SEI message to apply an adjustment to the CPB removal delay offset and a (separately-represented) adjustment to the DPB removal delay offset, to fix the support for the removal of RASL pictures. (reference JCTVC-L0044-v6 section 1.1)
Modify CPB removal time calculation to remove dependence of AU removal time on DU CPB parameters while maintaining alignment of nominal CPB removal time of AU and last DU. (reference JCTVC-L0044-v5 section 1.2)
Correct the description of (forward increment only) modulo wrapping calculation for CPB removal delay (reference notes for JCTVC-L0363).
Allow encoder to send a separate bit rate for sub-picture HRD operation (text in JCTVC-L0363-v2).
In bumping HRD operation, the bumping process should be invoked until there are no detected constraint violations rather than just until there is an empty frame buffer, and the checked conditions should checking immediately after decoding and should include checking both maximum picture reordering and maximum picture latency (reference notes for JCTVC-L0219)
Frame packing arrangement (primary section 6.2.6)
Remove frame packing arrangement types 0, 1, 2, 6, 7 (without renumbering the remaining ones) (reference notes for JCTVC-L0444 and JCTVC-L0454).
Four flags added to profile/tier/level syntax structures: progressive_source_flag, interlaced_source_flag, non_packed_constraint_flag, frame_only_constraint_flag (reference notes for JCTVC-L0046).
SEI messages (primary section 6.2.7)
Specify that an SEI message of a given type cannot be used as both a prefix and suffix SEI message in the same AU. (Post-meeting note: Should this be interpreted as applying to all SEI messages including reserved ones and filler data and user data? Presumably not, since for other similar aspects, we do not apply restrictions on these – e.g. see notes for JCTVC-L0325.) Allow suffix SEI NAL units between VCL NAL units of an AU (in general). If it's a prefix with whole-picture or higher scope, repetitions may be present between, but they must be repetitions. Similarly, if it's a suffix … it may be preceded by repetitions between VCL NAL units. (reference notes for JCTVC-L0045)
Allow the post-filter hint, user data registered, user data unregistered, progressive refinement segment end, and filler payload SEI messages to be suffix SEI messages (reference notes for JCTVC-L0363).
Establish constraints on the maximum number of repeated SEI messages within access units, generally with the constraint of a maximum of 8 messages with the same SEI payload data in an access unit (the constraint is specified per DU for the DU information SEI message, and the region refresh information SEI message is bounded to the number of slice segments rather than 8). (reference notes for JCTVC-L0325).
Modify the recovery point, region refresh, and progressive refinement SEI messages to fix their relationship with temporal scalability. (reference notes for JCTVC-L0045)
Clarify the scope of the post-filter hint SEI message applies only to the picture in the access unit that contains the SEI message. (reference notes for JCTVC-L0045)
For all five SEI message types that have a persistence repetition period, convert the "repetition period" into a persistence flag, such that the current semantics for the values 0 and 1 are supported and >1 is not. (reference notes for JCTVC-L0045)
Updated text of the SOP description SEI message (reference JCTVC-L0208)
Add a flag to the scene information SEI message to resolve a scope issue (reference JCTVC-L0431).
Post-meeting note: For SEI messages derived from AVC, must we retain the extension flags that are not needed in the HEVC context? Presumably not, since we have removed such extension flags in the other cases of SEI messages that were derived from AVC. HEVC has a different SEI payload extension mechanism. (reference JCTVC-L0444).
Temporal MV prediction "hook" in version 1 (primary section 6.3)
No action taken.
Other cleanup topics for version 1 (primary section 6.4)
Use POC (or equivalently, the identity of the referenced picture), rather than the reference index, in the motion vector derivation process (which only makes a difference when the same picture is at multiple reference index values in the reference picture list(s)) (reference notes for JCTVC-L0363).
Impact of extension plans on version 1 (RExt, SHVC, MHVC)
