package h264 import "github.com/AlexxIT/go2rtc/pkg/bits" // http://www.itu.int/rec/T-REC-H.264 // https://webrtc.googlesource.com/src/+/refs/heads/main/common_video/h264/sps_parser.cc //goland:noinspection GoSnakeCaseUsage type SPS struct { profile_idc uint8 profile_iop uint8 level_idc uint8 seq_parameter_set_id uint32 chroma_format_idc uint32 separate_colour_plane_flag byte bit_depth_luma_minus8 uint32 bit_depth_chroma_minus8 uint32 qpprime_y_zero_transform_bypass_flag byte seq_scaling_matrix_present_flag byte log2_max_frame_num_minus4 uint32 pic_order_cnt_type uint32 log2_max_pic_order_cnt_lsb_minus4 uint32 delta_pic_order_always_zero_flag byte offset_for_non_ref_pic int32 offset_for_top_to_bottom_field int32 num_ref_frames_in_pic_order_cnt_cycle uint32 num_ref_frames uint32 gaps_in_frame_num_value_allowed_flag byte pic_width_in_mbs_minus_1 uint32 pic_height_in_map_units_minus_1 uint32 frame_mbs_only_flag byte mb_adaptive_frame_field_flag byte direct_8x8_inference_flag byte frame_cropping_flag byte frame_crop_left_offset uint32 frame_crop_right_offset uint32 frame_crop_top_offset uint32 frame_crop_bottom_offset uint32 vui_parameters_present_flag byte aspect_ratio_info_present_flag byte aspect_ratio_idc byte sar_width uint16 sar_height uint16 overscan_info_present_flag byte overscan_appropriate_flag byte video_signal_type_present_flag byte video_format uint8 video_full_range_flag byte colour_description_present_flag byte colour_description uint32 chroma_loc_info_present_flag byte chroma_sample_loc_type_top_field uint32 chroma_sample_loc_type_bottom_field uint32 timing_info_present_flag byte num_units_in_tick uint32 time_scale uint32 fixed_frame_rate_flag byte } func (s *SPS) Width() uint16 { width := 16 * (s.pic_width_in_mbs_minus_1 + 1) crop := 2 * (s.frame_crop_left_offset + s.frame_crop_right_offset) return uint16(width - crop) } func (s *SPS) Height() uint16 { height := 16 * (s.pic_height_in_map_units_minus_1 + 1) crop := 2 * (s.frame_crop_top_offset + s.frame_crop_bottom_offset) if s.frame_mbs_only_flag == 0 { height *= 2 } return uint16(height - crop) } func DecodeSPS(sps []byte) *SPS { r := bits.NewReader(sps) hdr := r.ReadByte() if hdr&0x1F != NALUTypeSPS { return nil } s := &SPS{ profile_idc: r.ReadByte(), profile_iop: r.ReadByte(), level_idc: r.ReadByte(), seq_parameter_set_id: r.ReadUEGolomb(), } switch s.profile_idc { case 100, 110, 122, 244, 44, 83, 86, 118, 128, 138, 139, 134, 135: n := byte(8) s.chroma_format_idc = r.ReadUEGolomb() if s.chroma_format_idc == 3 { s.separate_colour_plane_flag = r.ReadBit() n = 12 } s.bit_depth_luma_minus8 = r.ReadUEGolomb() s.bit_depth_chroma_minus8 = r.ReadUEGolomb() s.qpprime_y_zero_transform_bypass_flag = r.ReadBit() s.seq_scaling_matrix_present_flag = r.ReadBit() if s.seq_scaling_matrix_present_flag != 0 { for i := byte(0); i < n; i++ { //goland:noinspection GoSnakeCaseUsage seq_scaling_list_present_flag := r.ReadBit() if seq_scaling_list_present_flag != 0 { if i < 6 { s.scaling_list(r, 16) } else { s.scaling_list(r, 64) } } } } } s.log2_max_frame_num_minus4 = r.ReadUEGolomb() s.pic_order_cnt_type = r.ReadUEGolomb() switch s.pic_order_cnt_type { case 0: s.log2_max_pic_order_cnt_lsb_minus4 = r.ReadUEGolomb() case 1: s.delta_pic_order_always_zero_flag = r.ReadBit() s.offset_for_non_ref_pic = r.ReadSEGolomb() s.offset_for_top_to_bottom_field = r.ReadSEGolomb() s.num_ref_frames_in_pic_order_cnt_cycle = r.ReadUEGolomb() for i := uint32(0); i < s.num_ref_frames_in_pic_order_cnt_cycle; i++ { _ = r.ReadSEGolomb() // offset_for_ref_frame[i] } } s.num_ref_frames = r.ReadUEGolomb() s.gaps_in_frame_num_value_allowed_flag = r.ReadBit() s.pic_width_in_mbs_minus_1 = r.ReadUEGolomb() s.pic_height_in_map_units_minus_1 = r.ReadUEGolomb() s.frame_mbs_only_flag = r.ReadBit() if s.frame_mbs_only_flag == 0 { s.mb_adaptive_frame_field_flag = r.ReadBit() } s.direct_8x8_inference_flag = r.ReadBit() s.frame_cropping_flag = r.ReadBit() if s.frame_cropping_flag != 0 { s.frame_crop_left_offset = r.ReadUEGolomb() s.frame_crop_right_offset = r.ReadUEGolomb() s.frame_crop_top_offset = r.ReadUEGolomb() s.frame_crop_bottom_offset = r.ReadUEGolomb() } s.vui_parameters_present_flag = r.ReadBit() if s.vui_parameters_present_flag != 0 { s.aspect_ratio_info_present_flag = r.ReadBit() if s.aspect_ratio_info_present_flag != 0 { s.aspect_ratio_idc = r.ReadByte() if s.aspect_ratio_idc == 255 { s.sar_width = r.ReadUint16() s.sar_height = r.ReadUint16() } } s.overscan_info_present_flag = r.ReadBit() if s.overscan_info_present_flag != 0 { s.overscan_appropriate_flag = r.ReadBit() } s.video_signal_type_present_flag = r.ReadBit() if s.video_signal_type_present_flag != 0 { s.video_format = r.ReadBits8(3) s.video_full_range_flag = r.ReadBit() s.colour_description_present_flag = r.ReadBit() if s.colour_description_present_flag != 0 { s.colour_description = r.ReadUint24() } } s.chroma_loc_info_present_flag = r.ReadBit() if s.chroma_loc_info_present_flag != 0 { s.chroma_sample_loc_type_top_field = r.ReadUEGolomb() s.chroma_sample_loc_type_bottom_field = r.ReadUEGolomb() } s.timing_info_present_flag = r.ReadBit() if s.timing_info_present_flag != 0 { s.num_units_in_tick = r.ReadUint32() s.time_scale = r.ReadUint32() s.fixed_frame_rate_flag = r.ReadBit() } //... } if r.EOF { return nil } return s } //goland:noinspection GoSnakeCaseUsage func (s *SPS) scaling_list(r *bits.Reader, sizeOfScalingList int) { lastScale := int32(8) nextScale := int32(8) for j := 0; j < sizeOfScalingList; j++ { if nextScale != 0 { delta_scale := r.ReadSEGolomb() nextScale = (lastScale + delta_scale + 256) % 256 } if nextScale != 0 { lastScale = nextScale } } }