shaka-player
Version:
DASH/EME video player library
235 lines (220 loc) • 7.73 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
// cspell:ignore lavfi aevalsrc libfdk hexdump
goog.provide('shaka.transmuxer.ADTS');
/**
* ADTS utils
*/
shaka.transmuxer.ADTS = class {
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {?{headerLength: number, frameLength: number}}
*/
static parseHeader(data, offset) {
const ADTS = shaka.transmuxer.ADTS;
// The protection skip bit tells us if we have 2 bytes of CRC data at the
// end of the ADTS header
const headerLength = ADTS.getHeaderLength(data, offset);
if (offset + headerLength <= data.length) {
// retrieve frame size
const frameLength = ADTS.getFullFrameLength(data, offset) - headerLength;
if (frameLength > 0) {
return {
headerLength,
frameLength,
};
}
}
return null;
}
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {?{sampleRate: number, channelCount: number, codec: string}}
*/
static parseInfo(data, offset) {
const adtsSamplingRates = [
96000,
88200,
64000,
48000,
44100,
32000,
24000,
22050,
16000,
12000,
11025,
8000,
7350,
];
const adtsSamplingIndex = (data[offset + 2] & 0x3c) >>> 2;
if (adtsSamplingIndex > adtsSamplingRates.length - 1) {
return null;
}
const adtsObjectType = ((data[offset + 2] & 0xc0) >>> 6) + 1;
let adtsChannelConfig = (data[offset + 2] & 0x01) << 2;
adtsChannelConfig |= (data[offset + 3] & 0xc0) >>> 6;
return {
sampleRate: adtsSamplingRates[adtsSamplingIndex],
channelCount: adtsChannelConfig,
codec: 'mp4a.40.' + adtsObjectType,
};
}
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {boolean}
*/
static isHeaderPattern(data, offset) {
return data[offset] === 0xff && (data[offset + 1] & 0xf6) === 0xf0;
}
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {number}
*/
static getHeaderLength(data, offset) {
return data[offset + 1] & 0x01 ? 7 : 9;
}
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {number}
*/
static getFullFrameLength(data, offset) {
return ((data[offset + 3] & 0x03) << 11) |
(data[offset + 4] << 3) |
((data[offset + 5] & 0xe0) >>> 5);
}
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {boolean}
*/
static isHeader(data, offset) {
const ADTS = shaka.transmuxer.ADTS;
// Look for ADTS header | 1111 1111 | 1111 X00X | where X can be
// either 0 or 1
// Layer bits (position 14 and 15) in header should be always 0 for ADTS
// More info https://wiki.multimedia.cx/index.php?title=ADTS
return offset + 1 < data.length && ADTS.isHeaderPattern(data, offset);
}
/**
* @param {!Uint8Array} data
* @param {!number} offset
* @return {boolean}
*/
static probe(data, offset) {
const ADTS = shaka.transmuxer.ADTS;
// same as isHeader but we also check that ADTS frame follows last ADTS
// frame or end of data is reached
if (ADTS.isHeader(data, offset)) {
// ADTS header Length
const headerLength = ADTS.getHeaderLength(data, offset);
if (offset + headerLength >= data.length) {
return false;
}
// ADTS frame Length
const frameLength = ADTS.getFullFrameLength(data, offset);
if (frameLength <= headerLength) {
return false;
}
const newOffset = offset + frameLength;
return newOffset === data.length || ADTS.isHeader(data, newOffset);
}
return false;
}
/**
* @param {!number} samplerate
* @return {number}
*/
static getFrameDuration(samplerate) {
return (shaka.transmuxer.ADTS.AAC_SAMPLES_PER_FRAME * 90000) / samplerate;
}
/**
* @param {string} codec
* @param {number} channelCount
* @return {?Uint8Array}
*/
static getSilentFrame(codec, channelCount) {
switch (codec) {
case 'mp4a.40.2':
if (channelCount === 1) {
return new Uint8Array([0x00, 0xc8, 0x00, 0x80, 0x23, 0x80]);
} else if (channelCount === 2) {
return new Uint8Array([
0x21, 0x00, 0x49, 0x90, 0x02, 0x19, 0x00, 0x23, 0x80,
]);
} else if (channelCount === 3) {
return new Uint8Array([
0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
0x00, 0x8e,
]);
} else if (channelCount === 4) {
return new Uint8Array([
0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
0x00, 0x80, 0x2c, 0x80, 0x08, 0x02, 0x38,
]);
} else if (channelCount === 5) {
return new Uint8Array([
0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x38,
]);
} else if (channelCount === 6) {
return new Uint8Array([
0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x00, 0xb2,
0x00, 0x20, 0x08, 0xe0,
]);
}
break;
// handle HE-AAC below (mp4a.40.5 / mp4a.40.29)
default:
if (channelCount === 1) {
// eslint-disable-next-line @stylistic/max-len
// ffmpeg -y -f lavfi -i "aevalsrc=0:d=0.05" -c:a libfdk_aac -profile:a aac_he -b:a 4k output.aac && hexdump -v -e '16/1 "0x%x," "\n"' -v output.aac
return new Uint8Array([
0x1, 0x40, 0x22, 0x80, 0xa3, 0x4e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
0x0, 0x1c, 0x6, 0xf1, 0xc1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5e,
]);
} else if (channelCount === 2) {
// eslint-disable-next-line @stylistic/max-len
// ffmpeg -y -f lavfi -i "aevalsrc=0|0:d=0.05" -c:a libfdk_aac -profile:a aac_he_v2 -b:a 4k output.aac && hexdump -v -e '16/1 "0x%x," "\n"' -v output.aac
return new Uint8Array([
0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5e,
]);
} else if (channelCount === 3) {
// eslint-disable-next-line @stylistic/max-len
// ffmpeg -y -f lavfi -i "aevalsrc=0|0|0:d=0.05" -c:a libfdk_aac -profile:a aac_he_v2 -b:a 4k output.aac && hexdump -v -e '16/1 "0x%x," "\n"' -v output.aac
return new Uint8Array([
0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
0x5a, 0x5e,
]);
}
break;
}
return null;
}
};
/**
* @const {number}
*/
shaka.transmuxer.ADTS.AAC_SAMPLES_PER_FRAME = 1024;