realview.js/dist/lib/video.js

RealView.js - High-performance video decoder for the browser

import { parseSPS } from "./SPSParser";
import { parseNALStream } from "./nalstream";
// Merge NAL Units from all packets into a single
// continuous buffer, separated by 4-byte length headers
function mergeNALUs(nalus, length) {
    const arr = new Uint8Array(length);
    const view = new DataView(arr.buffer);
    for (let i = 0, offset = 0; offset < length; i++) {
        const unit = nalus[i];
        view.setUint32(offset, unit.byteLength);
        arr.set(unit, offset + 4);
        offset += unit.byteLength + 4;
    }
    return arr;
}
export class VideoStream {
    constructor() {
        this.last_packet = null;
        this.nalus = [];
        this.pps = null;
        this.sps = null;
        this.samples = [];
        this.duration = 0;
        this.frame_sum = 0;
        this.frame_count = 0;
        this.zeroes = 0;
        this.byteLength = 0;
    }
    process(packet) {
        if (!this.last_packet) {
            this.last_packet = packet;
            return;
        }
        const { nalus } = this;
        const next = packet;
        packet = this.last_packet;
        let size = 0;
        let isIDR = false;
        for (const nalUnit of parseNALStream(packet.data)) {
            switch (nalUnit[0] & 0x1f) {
                case 7:
                    this.sps = nalUnit;
                    break;
                case 8:
                    this.pps = nalUnit;
                    break;
                case 5:
                    isIDR = true;
                    size += nalUnit.length + 4;
                    nalus.push(nalUnit);
                    break;
                default: // eslint-disable-line no-fallthrough
                    size += nalUnit.length + 4;
                    nalus.push(nalUnit);
            }
        }
        const dts_delta = next.dts - packet.dts;
        this.samples.push({
            size,
            isIDR,
            offset: this.byteLength,
            pts: packet.pts,
            dts: packet.dts,
            cts: packet.pts - packet.dts,
            duration: dts_delta,
        });
        if (dts_delta) {
            this.duration += dts_delta;
            this.frame_sum += dts_delta;
            this.frame_count++;
        }
        else {
            this.zeroes++;
        }
        this.byteLength += size;
        this.last_packet = next;
    }
    getTrack() {
        const { frame_count, frame_sum, zeroes, samples, sps, pps, nalus, byteLength, } = this;
        const frame_rate = Math.round(frame_sum / frame_count);
        const duration = this.duration + zeroes * frame_rate;
        if (!sps) {
            return null;
        }
        const spsInfo = parseSPS(sps);
        const cropping = spsInfo.frame_cropping;
        let track = {
            type: "video",
            pps,
            sps,
            spsInfo,
            width: spsInfo.pic_width_in_mbs * 16 - (cropping.left + cropping.right) * 2,
            height: (2 - spsInfo.frame_mbs_only_flag) *
                (spsInfo.pic_height_in_map_units * 16) -
                (cropping.top + cropping.bottom) * 2,
            samples,
            duration,
            byte_offset: 0,
            data: mergeNALUs(nalus, byteLength),
        };
        this.samples = [];
        this.nalus = [];
        this.byteLength = 0;
        return track;
    }
}