Y.3 Immersive 360-Degree Video Support
26.1143GPPIP Multimedia Subsystem (IMS)Media handling and interactionMultimedia telephonyRelease 18TS
ITT4RT-Rx clients in terminals offering video communication shall support decoding capabilities based on:
– H.264 (AVC) [24] Constrained High Profile, Level 5.1 with the following additional restrictions and requirements on the bitstream:
– the maximum VCL Bit Rate is constrained to be 120 Mbps with cpbBrVclFactor and cpbBrNalFactor being fixed to be 1250 and 1500, respectively.
– the bitstream does not contain more than 10 slices per picture.
– H.265 (HEVC) [119] Main 10 Profile, Main Tier, Level 5.1.
In addition, ITT4RT-Rx clients in terminals may support:
– H.265 (HEVC) [119] Screen-Extended Main 10 Profile, Main Tier, Level 5.1.
– H.265 (HEVC) [119] Screen-Extended Main 4:4:4 10 Profile, Main Tier, Level 5.1.
ITT4RT-Tx clients in terminals offering video communication shall support encoding up to the maximum capabilities (e.g., color bit-depth, luma samples per second, luma picture size, frames per second) compatible with decoders compliant with the following on the bitstream:
– H.264 (AVC) [24] Constrained High Profile, Level 5.1 with the following additional restrictions and requirements:
– the maximum VCL Bit Rate is constrained to be 120 Mbps with cpbBrVclFactor and cpbBrNalFactor being fixed to be 1250 and 1500, respectively.
– the bitstream does not contain more than 10 slices per picture.
– H.265 (HEVC) [119] Main 10 Profile, Main Tier, Level 5.1.
In addition, ITT4RT-Tx clients in terminals may support:
– H.265 (HEVC) [119] Screen-Extended Main 10 Profile, Main Tier, Level 5.1.
– H.265 (HEVC) [119] Screen-Extended Main 4:4:4 10 Profile, Main Tier, Level 5.1.
Hence, for a Bitstream conforming to the H.264 (AVC) [24] Constrained High Profile, Level 5.1 delivered from an ITT4RT-Tx client to the ITT4RT-Rx client, the following restrictions apply:
– The profile_idc shall be set to 100 indicating the High profile.
– The constraint_set0_flag, constraint_set1_flag, constraint_set2_flag and constraint_set3_flag shall all be set to 0, and constraint_set4_flag and constraint_set5_flag shall be set to 1.
– The value of level_idc shall not be greater than 51 (corresponding to the level 5.1) and should indicate the lowest level to which the Bitstream conforms.
Furthermore, for a Bitstream conforming to the H.265 (HEVC) [119] Main 10 Profile, Main Tier, Level 5.1 delivered from an ITT4RT-Tx client to the ITT4RT-Rx client, the following restrictions apply:
– The general_profile_idc shall be set to 2 indicating the Main10 profile.
– The general_tier_flag shall be set to 0 indicating the Main tier.
– The value of level_idc shall not be greater than 153 (corresponding to the Level 5.1) and should indicate the lowest level to which the Bitstream conforms.
For 360-degree video delivery across ITT4RT clients, the following components are applicable:
– The RTP stream shall contain an HEVC or an AVC bitstream with possible presence of omnidirectional video specific SEI messages. In particular, the omnidirectional video specific SEI messages as defined in clause D.2.41 of ISO/IEC 23008-2 [119] or ISO/IEC 14496-10 [24] may be present for the respective HEVC or AVC bitstreams.
– The video elementary stream(s) shall be encoded following the requirements in the Omnidirectional Media Format (OMAF) specification ISO/IEC 23090-2 [179], clauses 10.1.2.2 (viewport-independent case) or 10.1.3.2 (viewport-dependent case) for HEVC bitstreams and clause 10.1.4.2 for AVC bitstreams. Furthermore, the general video codec requirements for AVC and HEVC in clause 5.2.2 of TS 26.114 also apply.
ITT4RT-Rx clients are expected to be able to process the VR metadata carried in SEI messages for rendering 360-degree video according to the relevant processes. Relevant SEI messages contained in the elementary stream(s) with decoder rendering metadata may include the following information for the relevant processes as per clause D.3.41 of ISO/IEC 23008-2 [119] and ISO/IEC 14496-10 [24]:
– Projection mapping information (indicating the projection format in use, e.g., Equirectangular projection (ERP) or Cubemap projection (CMP)), for the projection sample location remapping process as specified in clauses 7.5.1.3 and 5.2 of ISO/IEC 23090-2 [179]
– Region-wise packing information (carrying region-wise packing format indication, any coverage restrictions or padding/guard region information in ithe packed picture), for the inverse processes of the region-wise packing as specified in clauses 7.5.1.2 and 5.4 of ISO/IEC 23090-2 [179]
– Sphere rotation information (indicating the amount of sphere rotation, if any, applied to the sphere signal before projection and region-wise packing at the encoder side), for the coordinate axes conversion process as specified in clause 5.3 of ISO/IEC 23090-2 [179]
– Frame packing arrangement (indicating the frame packing format for stereoscopic content), for the processes as specified in D.3.16 of ISO/IEC 23008-2 [119]
– Fisheye video information (indicating that the picture is a fisheye video picture containing a number of active areas captured by fisheye camera lens), for the fisheye sample location remapping process as specified in clause D.3.41.7.5 of ISO/IEC 23008-2 [119]
The exchange of SEI messages carrying VR metadata for rendering 360-degree video or fisheye video shall be performed using bitstream-level signalling as follows.
SEI messages shall be present in the respective video elementary streams corresponding to the HEVC or AVC bitstreams carrying 360-degree video or fisheye video from the ITT4RT-Tx client to the ITT4RT-Rx client, as per ISO/IEC 23008-2 [119] or ISO/IEC 14496-10 [24]. As expressed more clearly below, the mandatory inclusion of the specific SEI messages in the bitstream by the ITT4RT-Tx client and their decoder and rendering processing by the ITT4RT-Rx client is conditional upon successful SDP-based negotiation of the corresponding 360-degree video or fisheye video capabilities.
In particular, the ITT4RT-Tx client supporting 360-degree video for viewport-independent processing shall signal in the bitstream the equirectangular projection SEI message (payloadType equal to 150) to the ITT4RT-Rx client, with the erp_guard_band_flag set to 0.
If viewport-dependent processing (VDP) capability is successfully negotiated by the ITT4RT-Tx client and ITT4RT-Rx client for the exchange of 360-degree video, then, the ITT4RT-Tx client shall signal in the bitstream to the ITT4RT-Rx client either:
– the equirectangular projection SEI message (payloadType equal to 150) with the erp_guard_band_flag set to 0, or
– the cubemap projection SEI message (payloadType equal to 151).
In order to optimize the spatial resolution of specific viewports, the ITT4RT-Tx client and ITT4RT-Rx client may negotiate the use of region-wise packing as part of the exchange of 360-degree video. If this is the case, the region-wise packing SEI message (payloadType equal to 155) shall also be signalled by the ITT4RT-Tx client to the ITT4RT-Rx client in the bitstream.
If stereoscopic video capability is successfully negotiated by the ITT4RT-Tx client and ITT4RT-Rx client as part of the exchange of 360-degree video, then the frame packing arrangement SEI message (payloadType equal to 45) shall also be signalled by the ITT4RT-Tx client to the ITT4RT-Rx client in the bitstream, with the following restrictions:
– The value of frame_packing_arrangement_cancel_flag is equal to 0.
– The value of frame_packing_arrangement_type is equal to 4.
– The value of quincunx_sampling_flag is equal to 0.
– The value of spatial_flipping_flag is equal to 0.
– The value of field_views_flag is equal to 0.
– The value of frame0_grid_position_x is equal to 0.
– The value of frame0_grid_position_y is equal to 0.
– The value of frame1_grid_position_x is equal to 0.
– The value of frame1_grid_position_y is equal to 0.
Furthermore, ITT4RT-Tx clients supporting 360-degree fisheye video shall signal the fisheye video information SEI message (payloadType equal to 152) to the ITT4RT-Rx clients in the bitstream.
The bitstream delivered from an ITT4RT-Tx client to the ITT4RT-Rx client shall contain the corresponding SEI message and ITT4RT-Rx client shall process the VR metadata carried in the signalled SEI message(s) for rendering 360-degree video (provided the successful SDP-based negotiation of the corresponding 360-degree video or fisheye video capabilities associated with the SEI messages).