h264-sps-parser/src/vui.ts

Parse H.264 SPS NAL units

import { Bitstream } from "./bitstream";

type HRDParams = {
  cpb_cnt: number;
  bit_rate_scale: number;
  cpb_size_scale: number;
  bit_rate_value: number[];
  cpb_size_value: number[];
  cbr_flag: (0|1)[];
  initial_cpb_removal_delay_length: number;
  cpb_removal_delay_length: number;
  dpb_output_delay_length: number;
  time_offset_length: number;
};

export type VUIParams = {
  aspect_ratio_info_present_flag: 0|1;
  aspect_ratio_idc: number;
  sar_width: number;
  sar_height: number;
  overscan_info_present_flag: 0|1;
  overscan_appropriate_flag: 0|1;
  video_signal_type_present_flag: 0|1;
  video_format: number;
  video_full_range_flag: 0|1;
  colour_description_present_flag: 0|1;
  colour_primaries: number;
  transfer_characteristics: number;
  matrix_coefficients: number;
  chroma_loc_info_present_flag: 0|1;
  chroma_sample_loc_type_top_field: number;
  chroma_sample_loc_type_bottom_field: number;
  timing_info_present_flag: 0|1;
  num_units_in_tick: number;
  time_scale: number;
  fixed_frame_rate_flag: 0|1;
  nal_hrd_parameters_present_flag: 0|1;
  vcl_hrd_parameters_present_flag: 0|1;
  hrd_params: HRDParams;
  low_delay_hrd_flag: 0|1;
  pic_struct_present_flag: 0|1;
  bitstream_restriction_flag: 0|1;
  motion_vectors_over_pic_boundaries_flag: number;
  max_bytes_per_pic_denom: number;
  max_bits_per_mb_denom: number;
  log2_max_mv_length_horizontal: number;
  log2_max_mv_length_vertical: number;
  num_reorder_frames: number;
  max_dec_frame_buffering: number;
};

function hrd_parameters(hrd: HRDParams, stream: Bitstream): void {
  const cpb_cnt_minus1 = stream.ExpGolomb();
  hrd.cpb_cnt = cpb_cnt_minus1 + 1;
  hrd.bit_rate_scale = stream.readNibble();
  hrd.cpb_size_scale = stream.readNibble();
  for (let i = 0; i <= cpb_cnt_minus1; i++) {
    hrd.bit_rate_value[i] = stream.ExpGolomb() + 1;
    hrd.cpb_size_value[i] = stream.ExpGolomb() + 1;
    hrd.cbr_flag[i] = stream.readBit();
  }
  hrd.initial_cpb_removal_delay_length = stream.read5() + 1;
  hrd.cpb_removal_delay_length = stream.read5() + 1;
  hrd.dpb_output_delay_length = stream.read5() + 1;
  hrd.time_offset_length = stream.read5();
}

export function getVUIParams(flag: 0|1, stream: Bitstream): VUIParams {
  const vp: VUIParams = {
    aspect_ratio_info_present_flag: 0,
    aspect_ratio_idc: 0,
    sar_width: 0,
    sar_height: 0,
    overscan_info_present_flag: 0,
    overscan_appropriate_flag: 0,
    video_signal_type_present_flag: 0,
    video_format: 0,
    video_full_range_flag: 0,
    colour_description_present_flag: 0,
    colour_primaries: 0,
    transfer_characteristics: 0,
    matrix_coefficients: 0,
    chroma_loc_info_present_flag: 0,
    chroma_sample_loc_type_top_field: 0,
    chroma_sample_loc_type_bottom_field: 0,
    timing_info_present_flag: 0,
    num_units_in_tick: 0,
    time_scale: 0,
    fixed_frame_rate_flag: 0,
    nal_hrd_parameters_present_flag: 0,
    vcl_hrd_parameters_present_flag: 0,
    hrd_params: {
      cpb_cnt: 0,
      bit_rate_scale: 0,
      cpb_size_scale: 0,
      bit_rate_value: [],
      cpb_size_value: [],
      cbr_flag: [],
      initial_cpb_removal_delay_length: 0,
      cpb_removal_delay_length: 0,
      dpb_output_delay_length: 0,
      time_offset_length: 0,
    },
    low_delay_hrd_flag: 0,
    pic_struct_present_flag: 0,
    bitstream_restriction_flag: 0,
    motion_vectors_over_pic_boundaries_flag: 0,
    max_bytes_per_pic_denom: 0,
    max_bits_per_mb_denom: 0,
    log2_max_mv_length_horizontal: 0,
    log2_max_mv_length_vertical: 0,
    num_reorder_frames: 0,
    max_dec_frame_buffering: 0,
  };

  if (!flag) return vp;

  vp.aspect_ratio_info_present_flag = stream.readBit();
  if (vp.aspect_ratio_info_present_flag) {
    vp.aspect_ratio_idc = stream.ExpGolomb();
    if (vp.aspect_ratio_idc === 255) { // Extended_SAR
      vp.sar_width = stream.readByte();
      vp.sar_height = stream.readByte();
    }
  }
  
  vp.overscan_info_present_flag = stream.readBit();
  if (vp.overscan_info_present_flag) {
    vp.overscan_appropriate_flag = stream.readBit();
  }

  vp.video_signal_type_present_flag = stream.readBit();

  if (vp.video_signal_type_present_flag) {
    vp.video_format = (stream.readBit() << 2) |
                      (stream.readBit() << 1) |
                        stream.readBit();
    vp.video_full_range_flag = stream.readBit();
    vp.colour_description_present_flag = stream.readBit();
    if (vp.colour_description_present_flag) {
      vp.colour_primaries = stream.readByte();
      vp.transfer_characteristics = stream.readByte();
      vp.matrix_coefficients = stream.readByte();
    }
  }
  
  vp.chroma_loc_info_present_flag = stream.readBit();

  if (vp.chroma_loc_info_present_flag) {
    vp.chroma_sample_loc_type_top_field = stream.ExpGolomb();
    vp.chroma_sample_loc_type_bottom_field = stream.ExpGolomb();
  }

  vp.timing_info_present_flag = stream.readBit();
  if (vp.timing_info_present_flag) {
    vp.num_units_in_tick = stream.readWord();
    vp.time_scale = stream.readWord();
    vp.fixed_frame_rate_flag = stream.readBit();
  }

  vp.nal_hrd_parameters_present_flag = stream.readBit();
  if (vp.nal_hrd_parameters_present_flag) {
    hrd_parameters(vp.hrd_params, stream);
  }

  vp.vcl_hrd_parameters_present_flag = stream.readBit();
  if (vp.vcl_hrd_parameters_present_flag) {
    hrd_parameters(vp.hrd_params, stream);
  }

  if (vp.nal_hrd_parameters_present_flag || vp.vcl_hrd_parameters_present_flag) {
    vp.low_delay_hrd_flag = stream.readBit();
  }

  vp.pic_struct_present_flag = stream.readBit();
  vp.bitstream_restriction_flag = stream.readBit();

  if (vp.bitstream_restriction_flag) {
    vp.motion_vectors_over_pic_boundaries_flag = stream.readBit();
    vp.max_bytes_per_pic_denom = stream.ExpGolomb();
    vp.max_bits_per_mb_denom = stream.ExpGolomb();
    vp.log2_max_mv_length_horizontal = stream.ExpGolomb();
    vp.log2_max_mv_length_vertical = stream.ExpGolomb();
    vp.num_reorder_frames = stream.ExpGolomb();
    vp.max_dec_frame_buffering = stream.ExpGolomb();
  }

  return vp;
}