@remotion/media-parser/dist/containers/webm/description.js

A pure JavaScript library for parsing video files

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.getAudioDescription = void 0;
const buffer_iterator_1 = require("../../iterator/buffer-iterator");
const traversal_1 = require("./traversal");
const getAudioDescription = (track) => {
    const codec = (0, traversal_1.getCodecSegment)(track);
    if (!codec || codec.value !== 'A_VORBIS') {
        return undefined;
    }
    // how to parse vorbis private
    // https://github.com/google/ExoPlayer/blob/dd430f7053a1a3958deea3ead6a0565150c06bfc/library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mkv/MatroskaExtractor.java#L2466
    const privateData = (0, traversal_1.getPrivateData)(track);
    if (!privateData) {
        return undefined;
    }
    if (privateData[0] !== 2) {
        throw new Error('Expected vorbis private data version 2');
    }
    let offset = 1;
    let vorbisInfoLength = 0;
    let vorbisSkipLength = 0;
    while ((privateData[offset] & 0xff) === 0xff) {
        vorbisInfoLength += 0xff;
        offset++;
    }
    vorbisInfoLength += privateData[offset++] & 0xff;
    while ((privateData[offset] & 0xff) === 0xff) {
        vorbisSkipLength += 0xff;
        offset++;
    }
    vorbisSkipLength += privateData[offset++] & 0xff;
    if (privateData[offset] !== 0x01) {
        throw new Error('Error parsing vorbis codec private');
    }
    const vorbisInfo = privateData.slice(offset, offset + vorbisInfoLength);
    offset += vorbisInfoLength;
    if (privateData[offset] !== 0x03) {
        throw new Error('Error parsing vorbis codec private');
    }
    const vorbisComments = privateData.slice(offset, offset + vorbisSkipLength);
    offset += vorbisSkipLength;
    if (privateData[offset] !== 0x05) {
        throw new Error('Error parsing vorbis codec private');
    }
    const vorbisBooks = privateData.slice(offset);
    const bufferIterator = (0, buffer_iterator_1.getArrayBufferIterator)(vorbisInfo.slice(0), vorbisInfo.length);
    // type
    bufferIterator.getUint8();
    // vorbis
    const vorbis = bufferIterator.getByteString(6, false);
    if (vorbis !== 'vorbis') {
        throw new Error('Error parsing vorbis codec private');
    }
    const vorbisVersion = bufferIterator.getUint32Le();
    if (vorbisVersion !== 0) {
        throw new Error('Error parsing vorbis codec private');
    }
    const vorbisDescription = new Uint8Array([
        // constructing the vorbis description
        // This format consists in the page_segments field
        /**
         * The number of segment entries to appear in the segment table.
         * The maximum number of 255 segments (255 bytes each) sets the maximum possible physical page size at 65307 bytes or just under 64kB (thus we know that a header corrupted so as destroy sizing/alignment information will not cause a runaway bitstream.
         * We'll read in the page according to the corrupted size information that's guaranteed to be a reasonable size regardless, notice the checksum mismatch, drop sync and then look for recapture).
         */
        2,
        // followed by the segment_table field
        // offset of the comments table
        vorbisInfo.length,
        // offset of the codebooks table
        vorbisComments.length,
        // followed by the three Vorbis header packets,
        // respectively the identification header,
        ...vorbisInfo,
        // the comments header,
        ...vorbisComments,
        // and the setup header, in this order, as described in section 4.2 of [VORBIS].
        ...vorbisBooks,
    ]);
    return vorbisDescription;
};
exports.getAudioDescription = getAudioDescription;