mirror of
https://github.com/arcodange-org/mediabunny.git
synced 2026-09-27 02:43:48 +02:00
Fix incomplete parsing and generation of AacAudioSpecificConfig (fixes #471)
This commit is contained in:
Vanilagy
+124
-41
@@ -10,10 +10,11 @@ import { Bitstream } from './bitstream';
|
||||
|
||||
export type AacAudioSpecificConfig = {
|
||||
objectType: number;
|
||||
coreObjectType: number;
|
||||
frequencyIndex: number;
|
||||
sampleRate: number | null;
|
||||
channelConfiguration: number;
|
||||
numberOfChannels: number | null;
|
||||
outputSampleRate: number | null;
|
||||
outputNumberOfChannels: number | null;
|
||||
};
|
||||
|
||||
export const aacFrequencyTable = [
|
||||
@@ -30,20 +31,8 @@ export const parseAacAudioSpecificConfig = (bytes: Uint8Array | null): AacAudioS
|
||||
|
||||
const bitstream = new Bitstream(bytes);
|
||||
|
||||
let objectType = bitstream.readBits(5);
|
||||
if (objectType === 31) {
|
||||
objectType = 32 + bitstream.readBits(6);
|
||||
}
|
||||
|
||||
const frequencyIndex = bitstream.readBits(4);
|
||||
let sampleRate: number | null = null;
|
||||
if (frequencyIndex === 15) {
|
||||
sampleRate = bitstream.readBits(24);
|
||||
} else {
|
||||
if (frequencyIndex < aacFrequencyTable.length) {
|
||||
sampleRate = aacFrequencyTable[frequencyIndex]!;
|
||||
}
|
||||
}
|
||||
const objectType = readAacObjectType(bitstream);
|
||||
const { frequencyIndex, sampleRate } = readAacSamplingFrequency(bitstream);
|
||||
|
||||
const channelConfiguration = bitstream.readBits(4);
|
||||
let numberOfChannels: number | null = null;
|
||||
@@ -51,61 +40,155 @@ export const parseAacAudioSpecificConfig = (bytes: Uint8Array | null): AacAudioS
|
||||
numberOfChannels = aacChannelMap[channelConfiguration]!;
|
||||
}
|
||||
|
||||
let coreObjectType = objectType;
|
||||
let psPresent = false;
|
||||
let outputSampleRate = sampleRate;
|
||||
|
||||
if (objectType === 5 || objectType === 29) {
|
||||
// Explicit hierarchical signaling: everything read so far describes the core coder, and the rate the
|
||||
// decoder actually outputs follows right here
|
||||
psPresent = objectType === 29;
|
||||
|
||||
outputSampleRate = readAacSamplingFrequency(bitstream).sampleRate;
|
||||
coreObjectType = readAacObjectType(bitstream);
|
||||
|
||||
if (coreObjectType === 22) {
|
||||
bitstream.skipBits(4); // extensionChannelConfiguration
|
||||
}
|
||||
} else {
|
||||
// There may be SBR/PS flags sitting behind a sync word after the config of the core coder. We find them by
|
||||
// scanning for the sync word, just like FFmpeg does.
|
||||
while (bitstream.getBitsLeft() > 15) {
|
||||
const searchStart = bitstream.pos;
|
||||
|
||||
if (bitstream.readBits(11) !== 0x2b7) {
|
||||
bitstream.pos = searchStart + 1;
|
||||
continue;
|
||||
}
|
||||
|
||||
if (readAacObjectType(bitstream) === 5 && bitstream.readBits(1)) {
|
||||
outputSampleRate = readAacSamplingFrequency(bitstream).sampleRate;
|
||||
|
||||
if (bitstream.getBitsLeft() > 11 && bitstream.readBits(11) === 0x548) {
|
||||
psPresent = !!bitstream.readBits(1);
|
||||
}
|
||||
}
|
||||
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
if (numberOfChannels !== null && numberOfChannels > 1) {
|
||||
// PS only ever upmixes a mono core. A stereo signal means whatever we read was bogus
|
||||
psPresent = false;
|
||||
}
|
||||
|
||||
return {
|
||||
objectType,
|
||||
coreObjectType,
|
||||
frequencyIndex,
|
||||
sampleRate,
|
||||
channelConfiguration,
|
||||
numberOfChannels,
|
||||
outputSampleRate,
|
||||
outputNumberOfChannels: psPresent && numberOfChannels === 1
|
||||
? 2
|
||||
: numberOfChannels,
|
||||
};
|
||||
};
|
||||
|
||||
const readAacObjectType = (bitstream: Bitstream) => {
|
||||
const objectType = bitstream.readBits(5);
|
||||
return objectType === 31 ? 32 + bitstream.readBits(6) : objectType;
|
||||
};
|
||||
|
||||
const readAacSamplingFrequency = (bitstream: Bitstream) => {
|
||||
const frequencyIndex = bitstream.readBits(4);
|
||||
|
||||
if (frequencyIndex === 15) {
|
||||
return {
|
||||
frequencyIndex,
|
||||
sampleRate: bitstream.readBits(24),
|
||||
};
|
||||
}
|
||||
|
||||
return {
|
||||
frequencyIndex,
|
||||
sampleRate: frequencyIndex < aacFrequencyTable.length
|
||||
? aacFrequencyTable[frequencyIndex]!
|
||||
: null,
|
||||
};
|
||||
};
|
||||
|
||||
export const buildAacAudioSpecificConfig = (config: {
|
||||
objectType: number;
|
||||
sampleRate: number;
|
||||
numberOfChannels: number;
|
||||
outputSampleRate: number;
|
||||
outputNumberOfChannels: number;
|
||||
}) => {
|
||||
let frequencyIndex = aacFrequencyTable.indexOf(config.sampleRate);
|
||||
let customSampleRate: number | null = null;
|
||||
const usesSbr = config.objectType === 5 || config.objectType === 29;
|
||||
const usesPs = config.objectType === 29;
|
||||
|
||||
if (frequencyIndex === -1) {
|
||||
frequencyIndex = 15;
|
||||
customSampleRate = config.sampleRate;
|
||||
}
|
||||
// SBR runs the core coder at half the output rate, and PS upmixes a mono core to stereo
|
||||
const coreSampleRate = usesSbr ? config.outputSampleRate / 2 : config.outputSampleRate;
|
||||
const coreNumberOfChannels = usesPs ? 1 : config.outputNumberOfChannels;
|
||||
|
||||
const channelConfiguration = aacChannelMap.indexOf(config.numberOfChannels);
|
||||
const channelConfiguration = aacChannelMap.indexOf(coreNumberOfChannels);
|
||||
if (channelConfiguration === -1) {
|
||||
throw new TypeError(`Unsupported number of channels: ${config.numberOfChannels}`);
|
||||
throw new TypeError(`Unsupported number of channels: ${config.outputNumberOfChannels}`);
|
||||
}
|
||||
|
||||
let bitCount = 5 + 4 + 4;
|
||||
// Object type, sampling frequency, channel configuration, then a bare GASpecificConfig
|
||||
let bitCount = 5 + 4 + 4 + 3;
|
||||
if (config.objectType >= 32) {
|
||||
bitCount += 6;
|
||||
}
|
||||
if (frequencyIndex === 15) {
|
||||
if (findAacFrequencyIndex(coreSampleRate) === 15) {
|
||||
bitCount += 24;
|
||||
}
|
||||
if (usesSbr) {
|
||||
bitCount += 4 + 5; // Extension sampling frequency and the object type of the core coder
|
||||
if (findAacFrequencyIndex(config.outputSampleRate) === 15) {
|
||||
bitCount += 24;
|
||||
}
|
||||
}
|
||||
|
||||
const byteCount = Math.ceil(bitCount / 8);
|
||||
const bytes = new Uint8Array(byteCount);
|
||||
const bitstream = new Bitstream(bytes);
|
||||
|
||||
if (config.objectType < 32) {
|
||||
bitstream.writeBits(5, config.objectType);
|
||||
} else {
|
||||
bitstream.writeBits(5, 31);
|
||||
bitstream.writeBits(6, config.objectType - 32);
|
||||
writeAacObjectType(bitstream, config.objectType);
|
||||
writeAacSamplingFrequency(bitstream, coreSampleRate);
|
||||
bitstream.writeBits(4, channelConfiguration);
|
||||
|
||||
if (usesSbr) {
|
||||
writeAacSamplingFrequency(bitstream, config.outputSampleRate);
|
||||
writeAacObjectType(bitstream, 2); // AAC-LC underneath
|
||||
}
|
||||
|
||||
bitstream.writeBits(3, 0); // frameLengthFlag, dependsOnCoreCoder, extensionFlag
|
||||
|
||||
return bytes;
|
||||
};
|
||||
|
||||
const writeAacObjectType = (bitstream: Bitstream, objectType: number) => {
|
||||
if (objectType < 32) {
|
||||
bitstream.writeBits(5, objectType);
|
||||
} else {
|
||||
bitstream.writeBits(5, 31);
|
||||
bitstream.writeBits(6, objectType - 32);
|
||||
}
|
||||
};
|
||||
|
||||
const writeAacSamplingFrequency = (bitstream: Bitstream, sampleRate: number) => {
|
||||
const frequencyIndex = findAacFrequencyIndex(sampleRate);
|
||||
bitstream.writeBits(4, frequencyIndex);
|
||||
|
||||
if (frequencyIndex === 15) {
|
||||
bitstream.writeBits(24, customSampleRate!);
|
||||
bitstream.writeBits(24, sampleRate);
|
||||
}
|
||||
};
|
||||
|
||||
bitstream.writeBits(4, channelConfiguration);
|
||||
|
||||
return bytes;
|
||||
const findAacFrequencyIndex = (sampleRate: number) => {
|
||||
const index = aacFrequencyTable.indexOf(sampleRate);
|
||||
return index === -1 ? 15 : index;
|
||||
};
|
||||
|
||||
export type AdtsHeaderTemplate = {
|
||||
@@ -117,8 +200,8 @@ export const buildAdtsHeaderTemplate = (config: AacAudioSpecificConfig): AdtsHea
|
||||
const header = new Uint8Array(7);
|
||||
const bitstream = new Bitstream(header);
|
||||
|
||||
const { objectType, frequencyIndex, channelConfiguration } = config;
|
||||
const profile = objectType - 1;
|
||||
const { coreObjectType, frequencyIndex, channelConfiguration } = config;
|
||||
const profile = coreObjectType - 1;
|
||||
|
||||
bitstream.writeBits(12, 0b1111_11111111); // Syncword
|
||||
bitstream.writeBits(1, 0); // MPEG Version
|
||||
|
||||
Reference in New Issue
Block a user