Content for TS 26.253 Word version: 18.1.1
7 Functional description of the rendering, rendering control, and pre-rendering
7.1 Rendering overview
7.2 Rendering modes
7.3 Room acoustics rendering
7.4 Rendering control
7.5 Pre-rendering
7.6 Split rendering
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7 Functional description of the rendering, rendering control, and pre-rendering p. 679
7.1 Rendering overview p. 679
7.2 Rendering modes p. 680
7.2.1 Rendering for loudspeaker reproduction p. 680
7.2.1.1 Overview p. 680
7.2.1.2 Vector-base amplitude panning (VBAP) p. 680
7.2.1.3 Edge Fading Amplitude Panning (EFAP) p. 686
7.2.1.3.1 EFAP overview p. 686
7.2.1.3.2 EFAP initialization p. 686
7.2.1.3.3 EFAP gain computation p. 688
7.2.1.4 All-round ambisonic panning and decoding p. 689
7.2.2 Rendering for binaural headphone reproduction p. 690
7.2.2.1 Binaural rendering overview p. 690
7.2.2.2 Time Domain binaural renderer p. 690
7.2.2.2.1 General p. 690
7.2.2.2.2 HRIR model p. 691
7.2.2.2.3 Obtain standard spline sample values p. 695
7.2.2.2.4 Obtain periodic spline sample values p. 696
7.2.2.2.5 ITD model p. 697
7.2.2.2.6 ITD synthesis p. 698
7.2.2.2.7 Distance and Direction Gain p. 700
7.2.2.2.8 HRIR convolution p. 702
7.2.2.3 Parametric binauralizer and parametric stereo renderer p. 703
7.2.2.3.1 Overview p. 703
7.2.2.3.2 Pre-processing the transport audio signals based on head orientation p. 704
7.2.2.3.3 Determination of input and target covariance matrices p. 707
7.2.2.3.4 Determining processing matrices based on input and target covariance matrices p. 711
7.2.2.3.5 Processing audio signals with the processing matrices p. 712
7.2.2.3.6 Determining direct part gains p. 713
7.2.2.3.7 Determining regularization factor p. 715
7.2.2.3.8 Decorrelation in the parametric binauralizer p. 716
7.2.2.3.9 SPAR metadata to MASA metadata mapping p. 716
7.2.2.3.10 Prototype signal generation with SBA format input p. 719
7.2.2.4 Fast convolution binaural renderer p. 719
7.2.2.4.1 CLDFB-domain convolution p. 719
7.2.2.4.2 Filter conversion p. 720
7.2.2.4.3 Late reverb model p. 721
7.2.2.4.4 Head tracking p. 724
7.2.2.5 Crend binaural renderer p. 724
7.3 Room acoustics rendering p. 727
7.3.1 Introduction to room acoustics rendering p. 727
7.3.2 Room impulse response convolution p. 727
7.3.3 Sparse frequency-domain reverberator p. 727
7.3.4 Feedback-delay network reverberator p. 728
7.3.5 Early-reflection synthesis p. 732
7.3.5.1 General p. 732
7.3.5.2 Coordinate System p. 733
7.3.5.3 Source-receiver location correction p. 733
7.3.5.4 Reflections calculations p. 734
7.3.5.5 Process Loop p. 734
7.3.5.6 Low-complexity mode p. 736
7.4 Rendering control p. 736
7.4.1 Rendering control overview p. 736
7.4.2 Scene and listener orientation p. 737
7.4.2.1 Scene orientation p. 737
7.4.2.2 Listener orientation p. 737
7.4.3 Head tracking p. 737
7.4.3.1 Head tracking via scene displacement p. 737
7.4.3.2 Conversion from Euler angles to quaternions p. 738
7.4.3.3 Rotation matrix from quaternions p. 738
7.4.3.4 Application of rotations p. 738
7.4.4 Orientation tracking p. 739
7.4.4.1 Orientation tracking introduction p. 739
7.4.4.2 External reference orientation p. 740
7.4.4.3 External reference vector orientation p. 740
7.4.4.4 External reference levelled vector orientation p. 741
7.4.4.5 Adaptive long-term average reference orientation p. 741
7.4.5 External orientation input handling p. 743
7.4.6 Combined rotations for rendering p. 746
7.4.6.1 Combining head and external rotations p. 746
7.4.6.2 External rotation interpolation p. 747
7.4.6.3 Initial values for combined rotation variables p. 749
7.4.7 HRTF and BRIR sets p. 749
7.4.7.1 HRTF and BRIR latency p. 749
7.4.7.2 Parametrization of Binaural renderers using binary file p. 750
7.4.7.3 HRTFs and BRIR conversion methods p. 751
7.4.7.3.1 Conversion from spatial domain to spherical harmonics domain p. 751
7.4.7.3.2 Conversion from Time domain to CLDFB domain for HRIRs (Fast convolution binaural renderer) p. 753
7.4.7.3.3 Conversion from Time domain to CLDFB domain for BRIRs (Fast convolution binaural renderer) p. 754
7.4.7.3.4 Conversion from Time domain to HRIR/ITD model (Time Domain binaural renderer) p. 754
7.4.7.3.5 Conversion from HRTF/BRIR to Crend binaural renderer convolver parameters p. 760
7.4.7.3.6 Conversion from Time domain to SH CLDFB domain for parametric binauralizer p. 763
7.4.8 Room acoustics parameters p. 766
7.4.8.1 Overview p. 766
7.4.8.2 Late reverb parameters p. 767
7.4.8.3 Early reflections parameters p. 768
7.4.9 Use of custom loudspeaker layouts p. 768
7.4.9.1 General p. 768
7.4.9.2 MASA, OMASA, and McMASA p. 769
7.4.9.3 ParamMC and Parametric Upmix MC p. 769
7.4.9.4 Remaining formats p. 769
7.5 Pre-rendering p. 769
7.5.2 Pre-rendering into SBA format p. 770
7.5.2.1 ISM to SBA rendering p. 770
7.5.2.2 Channel-based audio to SBA rendering p. 770
7.5.2.3 MASA to SBA rendering p. 770
7.5.3 Pre-rendering into MASA format p. 770
7.5.3.1 Overview p. 770
7.5.3.2 ISM to MASA rendering p. 770
7.5.3.3 Multi-channel to MASA rendering p. 770
7.5.3.4 SBA to MASA rendering p. 771
7.5.3.5 Merging audio signals rendered into MASA format p. 771
7.5.4 Pre-rendering into Binaural format p. 772
7.5.4.1 SBA and MC to Binaural rendering p. 772
7.5.4.2 ISM to Binaural rendering p. 773
7.5.4.3 MASA to Binaural rendering p. 773
7.5.5 Pre-rendering into MC format p. 773
7.5.5.1 ISM to MC rendering p. 773
7.5.5.2 SBA to MC rendering p. 773
7.5.5.3 MASA to MC rendering p. 773
7.5.5.4 MC to MC rendering p. 773
7.6 Split rendering p. 773
7.6.1 Overview p. 773
7.6.2 Split pre-rendering p. 774
7.6.2.1 Overview p. 774
7.6.2.2 Supported Split Rendering bitrates with LCLD or LC3plus codec p. 776
7.6.2.3 Supported Split Rendering bitrates with PCM output p. 776
7.6.2.4 Split pre-rendering of SBA p. 776
7.6.2.5 Split pre-rendering of MASA p. 777
7.6.2.6 Split pre-rendering of CBA p. 777
7.6.2.7 Split pre-rendering of ISM p. 777
7.6.2.8 Split pre-rendering of OSBA p. 777
7.6.2.9 Split pre-rendering of OMASA p. 777
7.6.3 Intermediate split renderer metadata format p. 777
7.6.3.1 Overview p. 777
7.6.3.2 Metadata computation, quantization and coding p. 778
7.6.3.2.1 Metadata computation for deviations about Yaw axis p. 778
7.6.3.2.2 Quantization and coding of Yaw metadata p. 779
7.6.3.2.3 Metadata computation for deviations about Pitch axis p. 780
7.6.3.2.4 Quantization and coding of Pitch metadata p. 780
7.6.3.2.5 Metadata computation for deviations about Roll axis p. 781
7.6.3.2.6 Quantization and coding of Roll metadata p. 781
7.6.3.3 Common split rendering metadata quantization and coding strategies p. 781
7.6.3.4 Intermediate split renderer metadata decoder p. 782
7.6.3.5 Intermediate split renderer metadata loss concealment p. 783
7.6.4 LCLD coded intermediate split renderer binaural audio format p. 783
7.6.4.1 LCLD codec overview p. 783
7.6.4.2 LCLD encoder p. 783
7.6.4.2.1 Overview p. 783
7.6.4.2.2 Perceptual Banding p. 784
7.6.4.2.3 Joint Channel Coding p. 785
7.6.4.2.3.1 Overview p. 785
7.6.4.2.3.2 Bitstream Syntax p. 786
7.6.4.2.3.3 Parameter Computation and Quantization p. 787
7.6.4.2.3.4 Joint Coding Type Decision p. 788
7.6.4.2.3.5 Entropy Coding of Parameters p. 789
7.6.4.2.4 Temporal Grouping p. 789
7.6.4.2.5 RMS Envelope p. 794
7.6.4.2.5.1 RMS Envelope Calculation p. 794
7.6.4.2.5.2 Normalizing the CLDFB Coefficients with the RMS Envelope p. 794
7.6.4.2.5.3 RMS Envelope Transmission p. 794
7.6.4.2.6 Perceptual Model p. 795
7.6.4.2.7 Linear Prediction p. 804
7.6.4.2.7.1 Overview p. 804
7.6.4.2.7.2 Bitstream Syntax p. 804
7.6.4.2.7.3 Prediction for 20ms frames p. 804
7.6.4.2.7.4 Prediction for frames shorter than 20ms p. 805
7.6.4.2.7.5 Prediction Signalling p. 805
7.6.4.2.7.6 Quantization of Prediction Parameters p. 806
7.6.4.2.7.7 Estimation of Prediction Parameters p. 807
7.6.4.2.8 Bit Allocation p. 808
7.6.4.2.9 Quantization of the Normalized CLDFB Coefficients p. 808
7.6.4.2.9.1 Overview p. 808
7.6.4.2.9.2 Differential Coding of the Normalized CLDFB Coefficients p. 809
7.6.4.2.9.3 Quantization of Normalized CLDFB coefficients and Prediction Residuals p. 809
7.6.4.2.9.4 Huffman Coding of Quantized Normalized CLDFB coefficients and Quantized Prediction Residuals p. 810
7.6.4.3 LCLD decoder p. 812
7.6.4.3.1 Overview p. 812
7.6.4.3.2 Decoding Group Information p. 812
7.6.4.3.3 Decoding RMS Envelope Information p. 812
7.6.4.3.4 Perceptual Model p. 813
7.6.4.3.5 Bit Allocation p. 813
7.6.4.3.6 Normalized CLDFB Coefficient and Prediction Residual Huffman Decoding and Inverse Quantization p. 813
7.6.4.3.7 Inverse Prediction p. 814
7.6.4.3.8 Inverse RMS Envelope Normalization p. 815
7.6.4.3.9 Inverse Joint Stereo Processing p. 816
7.6.4.4 LCLD packet loss concealment p. 816
7.6.4.4.1 General p. 816
7.6.4.4.2 Synthesis model p. 816
7.6.4.4.3 Analysis and parameter estimation p. 817
7.6.4.4.4 Tonality determination p. 818
7.6.4.4.5 Sinusoidal extension p. 818
7.6.4.4.6 Predictive extension p. 818
7.6.4.4.7 Cross-fade p. 818
7.6.4.4.8 Burst-loss handling p. 819
7.6.5 LC3plus coded intermediate split renderer binaural audio format p. 820
7.6.5.1 Introduction (Informative) p. 820
7.6.5.2 Overview p. 820
7.6.5.3 Encoder p. 820
7.6.5.4 Decoder p. 820
7.6.5.5 Frame Structure p. 820
7.6.5.6 Packet Loss Concealment p. 820
7.6.5.7 LC3 interoperable mode p. 820
7.6.6 Split post-rendering p. 821
7.6.6.1 Overview p. 821
7.6.6.2 Post rendering with pose correction p. 821
7.6.6.2.1 Metadata decoding p. 821
7.6.6.2.2 Metadata interpolation or extrapolation p. 822
7.6.6.2.3 Matrix mixing p. 822
7.6.6.3 Post rendering in 0 DOF mode p. 822
7.6.7 Bit allocation for Split rendering p. 822
7.6.8 Interface for Split rendering p. 826
