h264-pps-parser/dist/index.js

Parse H.264 PPS NAL units

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.parse = void 0;
const h264_sps_parser_1 = require("h264-sps-parser");
function scaling_list(stream, sizeOfScalingList, use_default, i) {
    let lastScale = 8;
    let nextScale = 8;
    const scalingList = [];
    for (let j = 0; j < sizeOfScalingList; j++) {
        if (nextScale !== 0) {
            const deltaScale = stream.SignedExpGolomb();
            nextScale = (lastScale + deltaScale + 256) % 256;
            use_default[i] = +(j === 0 && nextScale === 0);
        }
        if (nextScale) {
            lastScale = nextScale;
        }
        scalingList[j] = lastScale;
    }
    return scalingList;
}
function parse(nalu, spss) {
    if ((nalu[0] & 0x1F) !== 8)
        throw new Error("Not a PPS unit");
    const stream = new h264_sps_parser_1.Bitstream(new DataView(nalu.buffer, nalu.byteOffset + 1));
    const pps_id = stream.ExpGolomb();
    const sps_id = stream.ExpGolomb();
    const entropy_coding_mode_flag = stream.readBit();
    const bottom_field_pic_order_in_frame_present_flag = stream.readBit();
    const num_slice_groups = stream.ExpGolomb() + 1;
    let slice_group_map_type = 0;
    let slice_group_change_direction_flag = 0;
    let slice_group_change_rate = 0;
    let pic_size_in_map_units = 0;
    const run_length = [];
    const top_left = [];
    const bottom_right = [];
    const slice_group_id = [];
    if (num_slice_groups > 1) {
        slice_group_map_type = stream.ExpGolomb();
        switch (slice_group_map_type) {
            case 0: {
                for (let i = 0; i < num_slice_groups; i++) {
                    run_length[i] = stream.ExpGolomb() + 1;
                }
                break;
            }
            case 2: {
                for (let i = 0; i < num_slice_groups; i++) {
                    top_left[i] = stream.ExpGolomb();
                    bottom_right[i] = stream.ExpGolomb();
                }
                break;
            }
            case 3:
            case 4:
            case 5: {
                slice_group_change_direction_flag = stream.readBit();
                slice_group_change_rate = stream.ExpGolomb() + 1;
                break;
            }
            case 6: {
                pic_size_in_map_units = stream.ExpGolomb() + 1;
                for (let i = 0; i < pic_size_in_map_units; i++) {
                    slice_group_id[i] = stream.ExpGolomb();
                }
            }
        }
    }
    const num_refs_idx_10_default_active = stream.ExpGolomb();
    const num_refs_idx_11_default_active = stream.ExpGolomb();
    const weighted_pred_flag = stream.readBit();
    const weighted_bipred_idc = (stream.readBit() << 1) | stream.readBit();
    const pic_init_qp = stream.SignedExpGolomb() + 26;
    const pic_init_qs = stream.SignedExpGolomb() + 26;
    const chroma_qp_index_offset = stream.SignedExpGolomb();
    const deblocking_filter_control_present_flag = stream.readBit();
    const constrained_intra_pred_flag = stream.readBit();
    const redundant_pic_cnt_present_flag = stream.readBit();
    let transform_8x8_mode_flag = 0;
    let pic_scaling_matrix_present_flag = 0;
    let second_chroma_qp_index_offset = 0;
    const pic_scaling_list_present_flag = [];
    const scaling_list_4x4 = [];
    const scaling_list_8x8 = [];
    const use_default_scaling_matrix_4x4_flag = [];
    const use_default_scaling_matrix_8x8_flag = [];
    if (stream.more_rbsp_data()) {
        transform_8x8_mode_flag = stream.readBit();
        pic_scaling_matrix_present_flag = stream.readBit();
        if (pic_scaling_matrix_present_flag) {
            for (let i = 0; i < 6; i++) {
                const f = stream.readBit();
                pic_scaling_list_present_flag[i] = f;
                if (f) {
                    scaling_list_4x4.push(scaling_list(stream, 16, use_default_scaling_matrix_4x4_flag, i));
                }
            }
            if (transform_8x8_mode_flag) {
                const { chroma_format_idc } = spss.get(sps_id);
                const limit = chroma_format_idc === 3 ? 6 : 2;
                for (let i = 0; i < limit; i++) {
                    const f = stream.readBit();
                    pic_scaling_list_present_flag[i + 6] = f;
                    if (f) {
                        scaling_list_8x8.push(scaling_list(stream, 64, use_default_scaling_matrix_8x8_flag, i));
                    }
                }
            }
        }
        second_chroma_qp_index_offset = stream.SignedExpGolomb();
    }
    return {
        pps_id, sps_id,
        entropy_coding_mode_flag,
        bottom_field_pic_order_in_frame_present_flag,
        num_slice_groups,
        slice_group_map_type,
        run_length,
        top_left,
        bottom_right,
        slice_group_change_direction_flag,
        slice_group_change_rate,
        pic_size_in_map_units,
        slice_group_id,
        num_refs_idx_10_default_active,
        num_refs_idx_11_default_active,
        weighted_pred_flag,
        weighted_bipred_idc,
        pic_init_qp,
        pic_init_qs,
        chroma_qp_index_offset,
        deblocking_filter_control_present_flag,
        constrained_intra_pred_flag,
        redundant_pic_cnt_present_flag,
        transform_8x8_mode_flag,
        pic_scaling_matrix_present_flag,
        pic_scaling_list_present_flag,
        scaling_list_4x4,
        scaling_list_8x8,
        use_default_scaling_matrix_4x4_flag,
        use_default_scaling_matrix_8x8_flag,
        second_chroma_qp_index_offset,
    };
}
exports.parse = parse;