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MP3extractor

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This commit is contained in:
n1073645 2020-03-19 16:10:22 +00:00
parent ff585584f6
commit b69e4567c0
1 changed files with 30 additions and 8 deletions
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38
src/core/lib/FileSignatures.mjs
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@ -3077,17 +3077,39 @@ export function extractWAV(bytes, offset) {
export function extractMP3(bytes, offset) {
const stream = new Stream(bytes.slice(offset));
if (stream.readInt(1) === 0xff) {
console.log("gggg");
} else if (stream.getBytes(3) === [0x49, 0x44, 0x33]) {
const bitRateIndexes = ["free", 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000, "bad"];
const samplingRateFrequencyIndex = [44100, 48000, 32000, "reserved"];
if ((stream.getBytes(3).toString() === [0x49, 0x44, 0x33].toString())) {
stream.moveTo(6);
const tagSize = (stream.readInt(1)<<23) | (stream.readInt(1)<<15) | (stream.readInt(1)<<7) | stream.readInt(1);
const tagSize = (stream.readInt(1) << 21) | (stream.readInt(1) << 14) | (stream.readInt(1) << 7) | stream.readInt(1);
stream.moveForwardsBy(tagSize);
if (stream.getBytes(4) !== [0xff, 0xfb, 0x30, 0xc4])
console.log("always bad");
} else {
stream.moveTo(0);
}
while (stream.hasMore()) {
if (stream.getBytes(2).toString() !== [0xff, 0xfb].toString()) {
stream.moveBackwardsBy(2);
break;
}
const flags = stream.readInt(1);
const bitRate = bitRateIndexes[flags >> 4];
const sampleRate = samplingRateFrequencyIndex[(flags & 0x0f) >> 2];
const padding = (flags & 0x02) >> 1;
if (bitRate === "free" || bitRate === "bad" || sampleRate === "reserved") {
stream.moveBackwardsBy(1);
break;
}
const frameSize = Math.floor(((144 * bitRate) / sampleRate) + padding);
if ((stream.position + frameSize) > stream.length) {
stream.moveTo(stream.length);
break;
} else {
stream.moveForwardsBy(frameSize - 3);
}
}
return stream.carve();
}