app/BlobFix.ts

/*
 * There is a bug where `navigator.mediaDevices.getUserMedia` + `MediaRecorder`
 * creates WEBM files without duration metadata. See:
 * - https://bugs.chromium.org/p/chromium/issues/detail?id=642012
 * - https://stackoverflow.com/a/39971175/13989043
 *
 * This file contains a function that fixes the duration metadata of a WEBM file.
 *  - Answer found: https://stackoverflow.com/a/75218309/13989043
 *  - Code adapted from: https://github.com/mat-sz/webm-fix-duration
 *    (forked from https://github.com/yusitnikov/fix-webm-duration)
 */

/*
 * This is the list of possible WEBM file sections by their IDs.
 * Possible types: Container, Binary, Uint, Int, String, Float, Date
 */
interface Section {
    name: string;
    type: string;
}

const sections: Record<number, Section> = {
    0xa45dfa3: { name: "EBML", type: "Container" },
    0x286: { name: "EBMLVersion", type: "Uint" },
    0x2f7: { name: "EBMLReadVersion", type: "Uint" },
    0x2f2: { name: "EBMLMaxIDLength", type: "Uint" },
    0x2f3: { name: "EBMLMaxSizeLength", type: "Uint" },
    0x282: { name: "DocType", type: "String" },
    0x287: { name: "DocTypeVersion", type: "Uint" },
    0x285: { name: "DocTypeReadVersion", type: "Uint" },
    0x6c: { name: "Void", type: "Binary" },
    0x3f: { name: "CRC-32", type: "Binary" },
    0xb538667: { name: "SignatureSlot", type: "Container" },
    0x3e8a: { name: "SignatureAlgo", type: "Uint" },
    0x3e9a: { name: "SignatureHash", type: "Uint" },
    0x3ea5: { name: "SignaturePublicKey", type: "Binary" },
    0x3eb5: { name: "Signature", type: "Binary" },
    0x3e5b: { name: "SignatureElements", type: "Container" },
    0x3e7b: { name: "SignatureElementList", type: "Container" },
    0x2532: { name: "SignedElement", type: "Binary" },
    0x8538067: { name: "Segment", type: "Container" },
    0x14d9b74: { name: "SeekHead", type: "Container" },
    0xdbb: { name: "Seek", type: "Container" },
    0x13ab: { name: "SeekID", type: "Binary" },
    0x13ac: { name: "SeekPosition", type: "Uint" },
    0x549a966: { name: "Info", type: "Container" },
    0x33a4: { name: "SegmentUID", type: "Binary" },
    0x3384: { name: "SegmentFilename", type: "String" },
    0x1cb923: { name: "PrevUID", type: "Binary" },
    0x1c83ab: { name: "PrevFilename", type: "String" },
    0x1eb923: { name: "NextUID", type: "Binary" },
    0x1e83bb: { name: "NextFilename", type: "String" },
    0x444: { name: "SegmentFamily", type: "Binary" },
    0x2924: { name: "ChapterTranslate", type: "Container" },
    0x29fc: { name: "ChapterTranslateEditionUID", type: "Uint" },
    0x29bf: { name: "ChapterTranslateCodec", type: "Uint" },
    0x29a5: { name: "ChapterTranslateID", type: "Binary" },
    0xad7b1: { name: "TimecodeScale", type: "Uint" },
    0x489: { name: "Duration", type: "Float" },
    0x461: { name: "DateUTC", type: "Date" },
    0x3ba9: { name: "Title", type: "String" },
    0xd80: { name: "MuxingApp", type: "String" },
    0x1741: { name: "WritingApp", type: "String" },
    // 0xf43b675: { name: 'Cluster', type: 'Container' },
    0x67: { name: "Timecode", type: "Uint" },
    0x1854: { name: "SilentTracks", type: "Container" },
    0x18d7: { name: "SilentTrackNumber", type: "Uint" },
    0x27: { name: "Position", type: "Uint" },
    0x2b: { name: "PrevSize", type: "Uint" },
    0x23: { name: "SimpleBlock", type: "Binary" },
    0x20: { name: "BlockGroup", type: "Container" },
    0x21: { name: "Block", type: "Binary" },
    0x22: { name: "BlockVirtual", type: "Binary" },
    0x35a1: { name: "BlockAdditions", type: "Container" },
    0x26: { name: "BlockMore", type: "Container" },
    0x6e: { name: "BlockAddID", type: "Uint" },
    0x25: { name: "BlockAdditional", type: "Binary" },
    0x1b: { name: "BlockDuration", type: "Uint" },
    0x7a: { name: "ReferencePriority", type: "Uint" },
    0x7b: { name: "ReferenceBlock", type: "Int" },
    0x7d: { name: "ReferenceVirtual", type: "Int" },
    0x24: { name: "CodecState", type: "Binary" },
    0x35a2: { name: "DiscardPadding", type: "Int" },
    0xe: { name: "Slices", type: "Container" },
    0x68: { name: "TimeSlice", type: "Container" },
    0x4c: { name: "LaceNumber", type: "Uint" },
    0x4d: { name: "FrameNumber", type: "Uint" },
    0x4b: { name: "BlockAdditionID", type: "Uint" },
    0x4e: { name: "Delay", type: "Uint" },
    0x4f: { name: "SliceDuration", type: "Uint" },
    0x48: { name: "ReferenceFrame", type: "Container" },
    0x49: { name: "ReferenceOffset", type: "Uint" },
    0x4a: { name: "ReferenceTimeCode", type: "Uint" },
    0x2f: { name: "EncryptedBlock", type: "Binary" },
    0x654ae6b: { name: "Tracks", type: "Container" },
    0x2e: { name: "TrackEntry", type: "Container" },
    0x57: { name: "TrackNumber", type: "Uint" },
    0x33c5: { name: "TrackUID", type: "Uint" },
    0x3: { name: "TrackType", type: "Uint" },
    0x39: { name: "FlagEnabled", type: "Uint" },
    0x8: { name: "FlagDefault", type: "Uint" },
    0x15aa: { name: "FlagForced", type: "Uint" },
    0x1c: { name: "FlagLacing", type: "Uint" },
    0x2de7: { name: "MinCache", type: "Uint" },
    0x2df8: { name: "MaxCache", type: "Uint" },
    0x3e383: { name: "DefaultDuration", type: "Uint" },
    0x34e7a: { name: "DefaultDecodedFieldDuration", type: "Uint" },
    0x3314f: { name: "TrackTimecodeScale", type: "Float" },
    0x137f: { name: "TrackOffset", type: "Int" },
    0x15ee: { name: "MaxBlockAdditionID", type: "Uint" },
    0x136e: { name: "Name", type: "String" },
    0x2b59c: { name: "Language", type: "String" },
    0x6: { name: "CodecID", type: "String" },
    0x23a2: { name: "CodecPrivate", type: "Binary" },
    0x58688: { name: "CodecName", type: "String" },
    0x3446: { name: "AttachmentLink", type: "Uint" },
    0x1a9697: { name: "CodecSettings", type: "String" },
    0x1b4040: { name: "CodecInfoURL", type: "String" },
    0x6b240: { name: "CodecDownloadURL", type: "String" },
    0x2a: { name: "CodecDecodeAll", type: "Uint" },
    0x2fab: { name: "TrackOverlay", type: "Uint" },
    0x16aa: { name: "CodecDelay", type: "Uint" },
    0x16bb: { name: "SeekPreRoll", type: "Uint" },
    0x2624: { name: "TrackTranslate", type: "Container" },
    0x26fc: { name: "TrackTranslateEditionUID", type: "Uint" },
    0x26bf: { name: "TrackTranslateCodec", type: "Uint" },
    0x26a5: { name: "TrackTranslateTrackID", type: "Binary" },
    0x60: { name: "Video", type: "Container" },
    0x1a: { name: "FlagInterlaced", type: "Uint" },
    0x13b8: { name: "StereoMode", type: "Uint" },
    0x13c0: { name: "AlphaMode", type: "Uint" },
    0x13b9: { name: "OldStereoMode", type: "Uint" },
    0x30: { name: "PixelWidth", type: "Uint" },
    0x3a: { name: "PixelHeight", type: "Uint" },
    0x14aa: { name: "PixelCropBottom", type: "Uint" },
    0x14bb: { name: "PixelCropTop", type: "Uint" },
    0x14cc: { name: "PixelCropLeft", type: "Uint" },
    0x14dd: { name: "PixelCropRight", type: "Uint" },
    0x14b0: { name: "DisplayWidth", type: "Uint" },
    0x14ba: { name: "DisplayHeight", type: "Uint" },
    0x14b2: { name: "DisplayUnit", type: "Uint" },
    0x14b3: { name: "AspectRatioType", type: "Uint" },
    0xeb524: { name: "ColourSpace", type: "Binary" },
    0xfb523: { name: "GammaValue", type: "Float" },
    0x383e3: { name: "FrameRate", type: "Float" },
    0x61: { name: "Audio", type: "Container" },
    0x35: { name: "SamplingFrequency", type: "Float" },
    0x38b5: { name: "OutputSamplingFrequency", type: "Float" },
    0x1f: { name: "Channels", type: "Uint" },
    0x3d7b: { name: "ChannelPositions", type: "Binary" },
    0x2264: { name: "BitDepth", type: "Uint" },
    0x62: { name: "TrackOperation", type: "Container" },
    0x63: { name: "TrackCombinePlanes", type: "Container" },
    0x64: { name: "TrackPlane", type: "Container" },
    0x65: { name: "TrackPlaneUID", type: "Uint" },
    0x66: { name: "TrackPlaneType", type: "Uint" },
    0x69: { name: "TrackJoinBlocks", type: "Container" },
    0x6d: { name: "TrackJoinUID", type: "Uint" },
    0x40: { name: "TrickTrackUID", type: "Uint" },
    0x41: { name: "TrickTrackSegmentUID", type: "Binary" },
    0x46: { name: "TrickTrackFlag", type: "Uint" },
    0x47: { name: "TrickMasterTrackUID", type: "Uint" },
    0x44: { name: "TrickMasterTrackSegmentUID", type: "Binary" },
    0x2d80: { name: "ContentEncodings", type: "Container" },
    0x2240: { name: "ContentEncoding", type: "Container" },
    0x1031: { name: "ContentEncodingOrder", type: "Uint" },
    0x1032: { name: "ContentEncodingScope", type: "Uint" },
    0x1033: { name: "ContentEncodingType", type: "Uint" },
    0x1034: { name: "ContentCompression", type: "Container" },
    0x254: { name: "ContentCompAlgo", type: "Uint" },
    0x255: { name: "ContentCompSettings", type: "Binary" },
    0x1035: { name: "ContentEncryption", type: "Container" },
    0x7e1: { name: "ContentEncAlgo", type: "Uint" },
    0x7e2: { name: "ContentEncKeyID", type: "Binary" },
    0x7e3: { name: "ContentSignature", type: "Binary" },
    0x7e4: { name: "ContentSigKeyID", type: "Binary" },
    0x7e5: { name: "ContentSigAlgo", type: "Uint" },
    0x7e6: { name: "ContentSigHashAlgo", type: "Uint" },
    0xc53bb6b: { name: "Cues", type: "Container" },
    0x3b: { name: "CuePoint", type: "Container" },
    0x33: { name: "CueTime", type: "Uint" },
    0x37: { name: "CueTrackPositions", type: "Container" },
    0x77: { name: "CueTrack", type: "Uint" },
    0x71: { name: "CueClusterPosition", type: "Uint" },
    0x70: { name: "CueRelativePosition", type: "Uint" },
    0x32: { name: "CueDuration", type: "Uint" },
    0x1378: { name: "CueBlockNumber", type: "Uint" },
    0x6a: { name: "CueCodecState", type: "Uint" },
    0x5b: { name: "CueReference", type: "Container" },
    0x16: { name: "CueRefTime", type: "Uint" },
    0x17: { name: "CueRefCluster", type: "Uint" },
    0x135f: { name: "CueRefNumber", type: "Uint" },
    0x6b: { name: "CueRefCodecState", type: "Uint" },
    0x941a469: { name: "Attachments", type: "Container" },
    0x21a7: { name: "AttachedFile", type: "Container" },
    0x67e: { name: "FileDescription", type: "String" },
    0x66e: { name: "FileName", type: "String" },
    0x660: { name: "FileMimeType", type: "String" },
    0x65c: { name: "FileData", type: "Binary" },
    0x6ae: { name: "FileUID", type: "Uint" },
    0x675: { name: "FileReferral", type: "Binary" },
    0x661: { name: "FileUsedStartTime", type: "Uint" },
    0x662: { name: "FileUsedEndTime", type: "Uint" },
    0x43a770: { name: "Chapters", type: "Container" },
    0x5b9: { name: "EditionEntry", type: "Container" },
    0x5bc: { name: "EditionUID", type: "Uint" },
    0x5bd: { name: "EditionFlagHidden", type: "Uint" },
    0x5db: { name: "EditionFlagDefault", type: "Uint" },
    0x5dd: { name: "EditionFlagOrdered", type: "Uint" },
    0x36: { name: "ChapterAtom", type: "Container" },
    0x33c4: { name: "ChapterUID", type: "Uint" },
    0x1654: { name: "ChapterStringUID", type: "String" },
    0x11: { name: "ChapterTimeStart", type: "Uint" },
    0x12: { name: "ChapterTimeEnd", type: "Uint" },
    0x18: { name: "ChapterFlagHidden", type: "Uint" },
    0x598: { name: "ChapterFlagEnabled", type: "Uint" },
    0x2e67: { name: "ChapterSegmentUID", type: "Binary" },
    0x2ebc: { name: "ChapterSegmentEditionUID", type: "Uint" },
    0x23c3: { name: "ChapterPhysicalEquiv", type: "Uint" },
    0xf: { name: "ChapterTrack", type: "Container" },
    0x9: { name: "ChapterTrackNumber", type: "Uint" },
    0x0: { name: "ChapterDisplay", type: "Container" },
    0x5: { name: "ChapString", type: "String" },
    0x37c: { name: "ChapLanguage", type: "String" },
    0x37e: { name: "ChapCountry", type: "String" },
    0x2944: { name: "ChapProcess", type: "Container" },
    0x2955: { name: "ChapProcessCodecID", type: "Uint" },
    0x50d: { name: "ChapProcessPrivate", type: "Binary" },
    0x2911: { name: "ChapProcessCommand", type: "Container" },
    0x2922: { name: "ChapProcessTime", type: "Uint" },
    0x2933: { name: "ChapProcessData", type: "Binary" },
    0x254c367: { name: "Tags", type: "Container" },
    0x3373: { name: "Tag", type: "Container" },
    0x23c0: { name: "Targets", type: "Container" },
    0x28ca: { name: "TargetTypeValue", type: "Uint" },
    0x23ca: { name: "TargetType", type: "String" },
    0x23c5: { name: "TagTrackUID", type: "Uint" },
    0x23c9: { name: "TagEditionUID", type: "Uint" },
    0x23c4: { name: "TagChapterUID", type: "Uint" },
    0x23c6: { name: "TagAttachmentUID", type: "Uint" },
    0x27c8: { name: "SimpleTag", type: "Container" },
    0x5a3: { name: "TagName", type: "String" },
    0x47a: { name: "TagLanguage", type: "String" },
    0x484: { name: "TagDefault", type: "Uint" },
    0x487: { name: "TagString", type: "String" },
    0x485: { name: "TagBinary", type: "Binary" },
};

class WebmBase<T> {
    source?: Uint8Array;
    data?: T;

    constructor(private name = "Unknown", private type = "Unknown") {}

    updateBySource() {}

    setSource(source: Uint8Array) {
        this.source = source;
        this.updateBySource();
    }

    updateByData() {}

    setData(data: T) {
        this.data = data;
        this.updateByData();
    }
}

class WebmUint extends WebmBase<string> {
    constructor(name: string, type: string) {
        super(name, type || "Uint");
    }

    updateBySource() {
        // use hex representation of a number instead of number value
        this.data = "";
        for (let i = 0; i < this.source!.length; i++) {
            const hex = this.source![i].toString(16);
            this.data += padHex(hex);
        }
    }

    updateByData() {
        const length = this.data!.length / 2;
        this.source = new Uint8Array(length);
        for (let i = 0; i < length; i++) {
            const hex = this.data!.substr(i * 2, 2);
            this.source[i] = parseInt(hex, 16);
        }
    }

    getValue() {
        return parseInt(this.data!, 16);
    }

    setValue(value: number) {
        this.setData(padHex(value.toString(16)));
    }
}

function padHex(hex: string) {
    return hex.length % 2 === 1 ? "0" + hex : hex;
}

class WebmFloat extends WebmBase<number> {
    constructor(name: string, type: string) {
        super(name, type || "Float");
    }

    getFloatArrayType() {
        return this.source && this.source.length === 4
            ? Float32Array
            : Float64Array;
    }
    updateBySource() {
        const byteArray = this.source!.reverse();
        const floatArrayType = this.getFloatArrayType();
        const floatArray = new floatArrayType(byteArray.buffer);
        this.data! = floatArray[0];
    }
    updateByData() {
        const floatArrayType = this.getFloatArrayType();
        const floatArray = new floatArrayType([this.data!]);
        const byteArray = new Uint8Array(floatArray.buffer);
        this.source = byteArray.reverse();
    }
    getValue() {
        return this.data;
    }
    setValue(value: number) {
        this.setData(value);
    }
}

interface ContainerData {
    id: number;
    idHex?: string;
    data: WebmBase<any>;
}

class WebmContainer extends WebmBase<ContainerData[]> {
    offset: number = 0;
    data: ContainerData[] = [];

    constructor(name: string, type: string) {
        super(name, type || "Container");
    }

    readByte() {
        return this.source![this.offset++];
    }
    readUint() {
        const firstByte = this.readByte();
        const bytes = 8 - firstByte.toString(2).length;
        let value = firstByte - (1 << (7 - bytes));
        for (let i = 0; i < bytes; i++) {
            // don't use bit operators to support x86
            value *= 256;
            value += this.readByte();
        }
        return value;
    }
    updateBySource() {
        let end: number | undefined = undefined;
        this.data = [];
        for (
            this.offset = 0;
            this.offset < this.source!.length;
            this.offset = end
        ) {
            const id = this.readUint();
            const len = this.readUint();
            end = Math.min(this.offset + len, this.source!.length);
            const data = this.source!.slice(this.offset, end);

            const info = sections[id] || { name: "Unknown", type: "Unknown" };
            let ctr: any = WebmBase;
            switch (info.type) {
                case "Container":
                    ctr = WebmContainer;
                    break;
                case "Uint":
                    ctr = WebmUint;
                    break;
                case "Float":
                    ctr = WebmFloat;
                    break;
            }
            const section = new ctr(info.name, info.type);
            section.setSource(data);
            this.data.push({
                id: id,
                idHex: id.toString(16),
                data: section,
            });
        }
    }
    writeUint(x: number, draft = false) {
        for (
            var bytes = 1, flag = 0x80;
            x >= flag && bytes < 8;
            bytes++, flag *= 0x80
        ) {}

        if (!draft) {
            let value = flag + x;
            for (let i = bytes - 1; i >= 0; i--) {
                // don't use bit operators to support x86
                const c = value % 256;
                this.source![this.offset! + i] = c;
                value = (value - c) / 256;
            }
        }

        this.offset += bytes;
    }

    writeSections(draft = false) {
        this.offset = 0;
        for (let i = 0; i < this.data.length; i++) {
            const section = this.data[i],
                content = section.data.source,
                contentLength = content!.length;
            this.writeUint(section.id, draft);
            this.writeUint(contentLength, draft);
            if (!draft) {
                this.source!.set(content!, this.offset);
            }
            this.offset += contentLength;
        }
        return this.offset;
    }

    updateByData() {
        // run without accessing this.source to determine total length - need to know it to create Uint8Array
        const length = this.writeSections(true);
        this.source = new Uint8Array(length);
        // now really write data
        this.writeSections();
    }

    getSectionById(id: number) {
        for (let i = 0; i < this.data.length; i++) {
            const section = this.data[i];
            if (section.id === id) {
                return section.data;
            }
        }

        return undefined;
    }
}

class WebmFile extends WebmContainer {
    constructor(source: Uint8Array) {
        super("File", "File");
        this.setSource(source);
    }

    fixDuration(duration: number) {
        const segmentSection = this.getSectionById(0x8538067) as WebmContainer;
        if (!segmentSection) {
            return false;
        }

        const infoSection = segmentSection.getSectionById(
            0x549a966,
        ) as WebmContainer;
        if (!infoSection) {
            return false;
        }

        const timeScaleSection = infoSection.getSectionById(
            0xad7b1,
        ) as WebmFloat;
        if (!timeScaleSection) {
            return false;
        }

        let durationSection = infoSection.getSectionById(0x489) as WebmFloat;
        if (durationSection) {
            if (durationSection.getValue()! <= 0) {
                durationSection.setValue(duration);
            } else {
                return false;
            }
        } else {
            // append Duration section
            durationSection = new WebmFloat("Duration", "Float");
            durationSection.setValue(duration);
            infoSection.data.push({
                id: 0x489,
                data: durationSection,
            });
        }

        // set default time scale to 1 millisecond (1000000 nanoseconds)
        timeScaleSection.setValue(1000000);
        infoSection.updateByData();
        segmentSection.updateByData();
        this.updateByData();

        return true;
    }

    toBlob(type = "video/webm") {
        return new Blob([this.source!.buffer], { type });
    }
}

/**
 * Fixes duration on MediaRecorder output.
 * @param blob Input Blob with incorrect duration.
 * @param duration Correct duration (in milliseconds).
 * @param type Output blob mimetype (default: video/webm).
 * @returns
 */
export const webmFixDuration = (
    blob: Blob,
    duration: number,
    type = "video/webm",
): Promise<Blob> => {
    return new Promise((resolve, reject) => {
        try {
            const reader = new FileReader();

            reader.addEventListener("loadend", () => {
                try {
                    const result = reader.result as ArrayBuffer;
                    const file = new WebmFile(new Uint8Array(result));
                    if (file.fixDuration(duration)) {
                        resolve(file.toBlob(type));
                    } else {
                        resolve(blob);
                    }
                } catch (ex) {
                    reject(ex);
                }
            });

            reader.addEventListener("error", () => reject());

            reader.readAsArrayBuffer(blob);
        } catch (ex) {
            reject(ex);
        }
    });
};