Adolfo Reyna
54 lines
2.0 KiB
JavaScript
54 lines
2.0 KiB
JavaScript
"use strict";
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// If an audio is of type, LPCM, the data structure will include 44100-48000 samples per second
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// We need to handle this case differently and treat each chunk as a sample instead
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.getGroupedSamplesPositionsFromMp4 = void 0;
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const traversal_1 = require("./containers/iso-base-media/traversal");
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// example video: mehmet.mov
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const getGroupedSamplesPositionsFromMp4 = ({ trakBox, bigEndian, }) => {
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const stscBox = (0, traversal_1.getStscBox)(trakBox);
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const stszBox = (0, traversal_1.getStszBox)(trakBox);
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const stcoBox = (0, traversal_1.getStcoBox)(trakBox);
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if (!stscBox) {
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throw new Error('Expected stsc box in trak box');
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}
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if (!stcoBox) {
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throw new Error('Expected stco box in trak box');
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}
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if (!stszBox) {
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throw new Error('Expected stsz box in trak box');
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}
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if (stszBox.countType !== 'fixed') {
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throw new Error('Only supporting fixed count type in stsz box');
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}
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const samples = [];
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let timestamp = 0;
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const stscKeys = Array.from(stscBox.entries.keys());
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for (let i = 0; i < stcoBox.entries.length; i++) {
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const entry = stcoBox.entries[i];
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const chunk = i + 1;
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const stscEntry = stscKeys.findLast((e) => e <= chunk);
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if (stscEntry === undefined) {
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throw new Error('should not be');
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}
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const samplesPerChunk = stscBox.entries.get(stscEntry);
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if (samplesPerChunk === undefined) {
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throw new Error('should not be');
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}
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samples.push({
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chunk,
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timestamp,
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decodingTimestamp: timestamp,
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offset: Number(entry),
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size: stszBox.sampleSize * samplesPerChunk,
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duration: samplesPerChunk,
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isKeyframe: true,
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bigEndian,
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chunkSize: stszBox.sampleSize,
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});
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timestamp += samplesPerChunk;
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}
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return samples;
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};
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exports.getGroupedSamplesPositionsFromMp4 = getGroupedSamplesPositionsFromMp4;
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