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feat(HLS): Get resolution from TS when load a Media Playlist (#5058)
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/** | ||
* @license | ||
* Copyright Brightcove, Inc. | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
*/ | ||
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goog.provide('shaka.util.ExpGolomb'); | ||
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goog.require('shaka.util.DataViewReader'); | ||
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/** | ||
* @summary | ||
* Parser for exponential Golomb codes, a variable-bitwidth number encoding | ||
* scheme used by h264. | ||
* Based on https://github.com/videojs/mux.js/blob/main/lib/utils/exp-golomb.js | ||
* | ||
* @export | ||
*/ | ||
shaka.util.ExpGolomb = class { | ||
/** | ||
* @param {!Uint8Array} data | ||
*/ | ||
constructor(data) { | ||
/** @private {!Uint8Array} */ | ||
this.data_ = data; | ||
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/** @private {number} */ | ||
this.workingBytesAvailable_ = data.byteLength; | ||
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// the current word being examined | ||
/** @private {number} */ | ||
this.workingWord_ = 0; | ||
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// the number of bits left to examine in the current word | ||
/** @private {number} */ | ||
this.workingBitsAvailable_ = 0; | ||
} | ||
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/** | ||
* Load the next word | ||
* | ||
* @private | ||
*/ | ||
loadWord_() { | ||
const position = this.data_.byteLength - this.workingBytesAvailable_; | ||
const bytes = new Uint8Array(4); | ||
const availableBytes = Math.min(4, this.workingBytesAvailable_); | ||
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if (availableBytes === 0) { | ||
return; | ||
} | ||
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bytes.set(this.data_.subarray(position, position + availableBytes)); | ||
const dataView = new shaka.util.DataViewReader( | ||
bytes, shaka.util.DataViewReader.Endianness.BIG_ENDIAN); | ||
this.workingWord_ = dataView.readUint32(); | ||
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// track the amount of data that has been processed | ||
this.workingBitsAvailable_ = availableBytes * 8; | ||
this.workingBytesAvailable_ -= availableBytes; | ||
} | ||
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/** | ||
* Skip n bits | ||
* | ||
* @param {number} count | ||
*/ | ||
skipBits(count) { | ||
if (this.workingBitsAvailable_ <= count) { | ||
count -= this.workingBitsAvailable_; | ||
const skipBytes = Math.floor(count / 8); | ||
count -= (skipBytes * 8); | ||
this.workingBitsAvailable_ -= skipBytes; | ||
this.loadWord_(); | ||
} | ||
this.workingWord_ <<= count; | ||
this.workingBitsAvailable_ -= count; | ||
} | ||
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/** | ||
* Read n bits | ||
* | ||
* @param {number} size | ||
* @return {number} | ||
*/ | ||
readBits(size) { | ||
let bits = Math.min(this.workingBitsAvailable_, size); | ||
const valu = this.workingWord_ >>> (32 - bits); | ||
this.workingBitsAvailable_ -= bits; | ||
if (this.workingBitsAvailable_ > 0) { | ||
this.workingWord_ <<= bits; | ||
} else if (this.workingBytesAvailable_ > 0) { | ||
this.loadWord_(); | ||
} | ||
bits = size - bits; | ||
if (bits > 0) { | ||
return (valu << bits) | this.readBits(bits); | ||
} | ||
return valu; | ||
} | ||
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/** | ||
* Return the number of skip leading zeros | ||
* | ||
* @return {number} | ||
* @private | ||
*/ | ||
skipLeadingZeros_() { | ||
let i; | ||
for (i = 0; i < this.workingBitsAvailable_; ++i) { | ||
if ((this.workingWord_ & (0x80000000 >>> i)) !== 0) { | ||
// the first bit of working word is 1 | ||
this.workingWord_ <<= i; | ||
this.workingBitsAvailable_ -= i; | ||
return i; | ||
} | ||
} | ||
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// we exhausted workingWord and still have not found a 1 | ||
this.loadWord_(); | ||
return i + this.skipLeadingZeros_(); | ||
} | ||
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/** | ||
* Skip exponential Golomb | ||
*/ | ||
skipExpGolomb() { | ||
this.skipBits(1 + this.skipLeadingZeros_()); | ||
} | ||
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/** | ||
* Return unsigned exponential Golomb | ||
* | ||
* @return {number} | ||
*/ | ||
readUnsignedExpGolomb() { | ||
const clz = this.skipLeadingZeros_(); | ||
return this.readBits(clz + 1) - 1; | ||
} | ||
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/** | ||
* Return exponential Golomb | ||
* | ||
* @return {number} | ||
*/ | ||
readExpGolomb() { | ||
const valu = this.readUnsignedExpGolomb(); | ||
if (0x01 & valu) { | ||
// the number is odd if the low order bit is set | ||
// add 1 to make it even, and divide by 2 | ||
return (1 + valu) >>> 1; | ||
} | ||
// divide by two then make it negative | ||
return -1 * (valu >>> 1); | ||
} | ||
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/** | ||
* Read 1 bit as boolean | ||
* | ||
* @return {boolean} | ||
*/ | ||
readBoolean() { | ||
return this.readBits(1) === 1; | ||
} | ||
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/** | ||
* Read 8 bits | ||
* | ||
* @return {number} | ||
*/ | ||
readUnsignedByte() { | ||
return this.readBits(8); | ||
} | ||
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/** | ||
* The scaling list is optionally transmitted as part of a Sequence Parameter | ||
* Set (SPS). | ||
* | ||
* @param {number} count the number of entries in this scaling list | ||
* @see Recommendation ITU-T H.264, Section 7.3.2.1.1.1 | ||
*/ | ||
skipScalingList(count) { | ||
let lastScale = 8; | ||
let nextScale = 8; | ||
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for (let j = 0; j < count; j++) { | ||
if (nextScale !== 0) { | ||
const deltaScale = this.readExpGolomb(); | ||
nextScale = (lastScale + deltaScale + 256) % 256; | ||
} | ||
lastScale = (nextScale === 0) ? lastScale : nextScale; | ||
} | ||
} | ||
}; |
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