shaka-player
Version:
DASH/EME video player library
425 lines (364 loc) • 13.6 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.media.ContentWorkarounds');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.BufferUtils');
goog.require('shaka.util.Error');
goog.require('shaka.util.Lazy');
goog.require('shaka.util.Mp4Parser');
goog.require('shaka.util.Platform');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* @summary
* A collection of methods to work around content issues on various platforms.
*/
shaka.media.ContentWorkarounds = class {
/**
* Transform the init segment into a new init segment buffer that indicates
* encryption. If the init segment already indicates encryption, return the
* original init segment.
*
* Should only be called for MP4 init segments, and only on platforms that
* need this workaround.
*
* @param {!BufferSource} initSegmentBuffer
* @return {!Uint8Array}
* @see https://github.com/shaka-project/shaka-player/issues/2759
*/
static fakeEncryption(initSegmentBuffer) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
let initSegment = shaka.util.BufferUtils.toUint8(initSegmentBuffer);
let isEncrypted = false;
/** @type {shaka.extern.ParsedBox} */
let stsdBox;
const ancestorBoxes = [];
const onSimpleAncestorBox = (box) => {
ancestorBoxes.push(box);
shaka.util.Mp4Parser.children(box);
};
const onEncryptionMetadataBox = (box) => {
isEncrypted = true;
};
// Multiplexed content could have multiple boxes that we need to modify.
// Add to this array in order of box offset. This will be important later,
// when we process the boxes.
/** @type {!Array.<{box: shaka.extern.ParsedBox, newType: number}>} */
const boxesToModify = [];
new shaka.util.Mp4Parser()
.box('moov', onSimpleAncestorBox)
.box('trak', onSimpleAncestorBox)
.box('mdia', onSimpleAncestorBox)
.box('minf', onSimpleAncestorBox)
.box('stbl', onSimpleAncestorBox)
.fullBox('stsd', (box) => {
stsdBox = box;
ancestorBoxes.push(box);
shaka.util.Mp4Parser.sampleDescription(box);
})
.fullBox('encv', onEncryptionMetadataBox)
.fullBox('enca', onEncryptionMetadataBox)
.fullBox('hev1', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCV_,
});
})
.fullBox('hvc1', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCV_,
});
})
.fullBox('avc1', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCV_,
});
})
.fullBox('avc3', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCV_,
});
})
.fullBox('ac-3', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCA_,
});
})
.fullBox('ec-3', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCA_,
});
})
.fullBox('mp4a', (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCA_,
});
}).parse(initSegment);
if (isEncrypted) {
shaka.log.debug('Init segment already indicates encryption.');
return initSegment;
}
if (boxesToModify.length == 0 || !stsdBox) {
shaka.log.error('Failed to find boxes needed to fake encryption!');
shaka.log.v2('Failed init segment (hex):',
shaka.util.Uint8ArrayUtils.toHex(initSegment));
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.CONTENT_TRANSFORMATION_FAILED);
}
// Modify boxes in order from largest offset to smallest, so that earlier
// boxes don't have their offsets changed before we process them.
boxesToModify.reverse(); // in place!
for (const workItem of boxesToModify) {
const insertedBoxType =
shaka.util.Mp4Parser.typeToString(workItem.newType);
shaka.log.debug(`Inserting "${insertedBoxType}" box into init segment.`);
initSegment = ContentWorkarounds.insertEncryptionMetadata_(
initSegment, stsdBox, workItem.box, ancestorBoxes, workItem.newType);
}
return initSegment;
}
/**
* Insert an encryption metadata box ("encv" or "enca" box) into the MP4 init
* segment, based on the source box ("mp4a", "avc1", etc). Returns a new
* buffer containing the modified init segment.
*
* @param {!Uint8Array} initSegment
* @param {shaka.extern.ParsedBox} stsdBox
* @param {shaka.extern.ParsedBox} sourceBox
* @param {!Array.<shaka.extern.ParsedBox>} ancestorBoxes
* @param {number} metadataBoxType
* @return {!Uint8Array}
* @private
*/
static insertEncryptionMetadata_(
initSegment, stsdBox, sourceBox, ancestorBoxes, metadataBoxType) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const metadataBoxArray = ContentWorkarounds.createEncryptionMetadata_(
initSegment, sourceBox, metadataBoxType);
// Construct a new init segment array with room for the encryption metadata
// box we're adding.
const newInitSegment =
new Uint8Array(initSegment.byteLength + metadataBoxArray.byteLength);
// For Xbox One, we cut and insert at the start of the source box. For
// other platforms, we cut and insert at the end of the source box. It's
// not clear why this is necessary on Xbox One, but it seems to be evidence
// of another bug in the firmware implementation of MediaSource & EME.
const cutPoint = shaka.util.Platform.isXboxOne() ?
sourceBox.start :
sourceBox.start + sourceBox.size;
// The data before the cut point will be copied to the same location as
// before. The data after that will be appended after the added metadata
// box.
const beforeData = initSegment.subarray(0, cutPoint);
const afterData = initSegment.subarray(cutPoint);
newInitSegment.set(beforeData);
newInitSegment.set(metadataBoxArray, cutPoint);
newInitSegment.set(afterData, cutPoint + metadataBoxArray.byteLength);
// The parents up the chain from the encryption metadata box need their
// sizes adjusted to account for the added box. These offsets should not be
// changed, because they should all be within the first section we copy.
for (const box of ancestorBoxes) {
goog.asserts.assert(box.start < cutPoint,
'Ancestor MP4 box found in the wrong location! ' +
'Modified init segment will not make sense!');
ContentWorkarounds.updateBoxSize_(
newInitSegment, box.start, box.size + metadataBoxArray.byteLength);
}
// Add one to the sample entries field of the "stsd" box. This is a 4-byte
// field just past the box header.
const stsdBoxView = shaka.util.BufferUtils.toDataView(
newInitSegment, stsdBox.start);
const stsdBoxHeaderSize = shaka.util.Mp4Parser.headerSize(stsdBox);
const numEntries = stsdBoxView.getUint32(stsdBoxHeaderSize);
stsdBoxView.setUint32(stsdBoxHeaderSize, numEntries + 1);
return newInitSegment;
}
/**
* Create an encryption metadata box ("encv" or "enca" box), based on the
* source box ("mp4a", "avc1", etc). Returns a new buffer containing the
* encryption metadata box.
*
* @param {!Uint8Array} initSegment
* @param {shaka.extern.ParsedBox} sourceBox
* @param {number} metadataBoxType
* @return {!Uint8Array}
* @private
*/
static createEncryptionMetadata_(initSegment, sourceBox, metadataBoxType) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const sinfBoxArray = ContentWorkarounds.CANNED_SINF_BOX_.value();
// Create a subarray which points to the source box data.
const sourceBoxArray = initSegment.subarray(
/* start= */ sourceBox.start,
/* end= */ sourceBox.start + sourceBox.size);
// Create a view on the source box array.
const sourceBoxView = shaka.util.BufferUtils.toDataView(sourceBoxArray);
// Create an array to hold the new encryption metadata box, which is based
// on the source box.
const metadataBoxArray = new Uint8Array(
sourceBox.size + sinfBoxArray.byteLength);
// Copy the source box into the new array.
metadataBoxArray.set(sourceBoxArray, /* targetOffset= */ 0);
// Change the box type.
const metadataBoxView = shaka.util.BufferUtils.toDataView(metadataBoxArray);
metadataBoxView.setUint32(
ContentWorkarounds.BOX_TYPE_OFFSET_, metadataBoxType);
// Append the "sinf" box to the encryption metadata box.
metadataBoxArray.set(sinfBoxArray, /* targetOffset= */ sourceBox.size);
// Update the "sinf" box's format field (in the child "frma" box) to reflect
// the format of the original source box.
const sourceBoxType = sourceBoxView.getUint32(
ContentWorkarounds.BOX_TYPE_OFFSET_);
metadataBoxView.setUint32(
sourceBox.size + ContentWorkarounds.CANNED_SINF_BOX_FORMAT_OFFSET_,
sourceBoxType);
// Now update the encryption metadata box size.
ContentWorkarounds.updateBoxSize_(
metadataBoxArray, /* boxStart= */ 0, metadataBoxArray.byteLength);
return metadataBoxArray;
}
/**
* Modify an MP4 box's size field in-place.
*
* @param {!Uint8Array} dataArray
* @param {number} boxStart The start position of the box in dataArray.
* @param {number} newBoxSize The new size of the box.
* @private
*/
static updateBoxSize_(dataArray, boxStart, newBoxSize) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const boxView = shaka.util.BufferUtils.toDataView(dataArray, boxStart);
const sizeField = boxView.getUint32(ContentWorkarounds.BOX_SIZE_OFFSET_);
if (sizeField == 0) { // Means "the rest of the box".
// No adjustment needed for this box.
} else if (sizeField == 1) { // Means "use 64-bit size box".
// Set the 64-bit int in two 32-bit parts.
// The high bits should definitely be 0 in practice, but we're being
// thorough here.
boxView.setUint32(ContentWorkarounds.BOX_SIZE_64_OFFSET_,
newBoxSize >> 32);
boxView.setUint32(ContentWorkarounds.BOX_SIZE_64_OFFSET_ + 4,
newBoxSize & 0xffffffff);
} else { // Normal 32-bit size field.
// Not checking the size of the value here, since a box larger than 4GB is
// unrealistic.
boxView.setUint32(ContentWorkarounds.BOX_SIZE_OFFSET_, newBoxSize);
}
}
};
/**
* A canned "sinf" box for use when adding fake encryption metadata to init
* segments.
*
* @const {!shaka.util.Lazy.<!Uint8Array>}
* @private
* @see https://github.com/shaka-project/shaka-player/issues/2759
*/
shaka.media.ContentWorkarounds.CANNED_SINF_BOX_ =
new shaka.util.Lazy(() => new Uint8Array([
// sinf box
// Size: 0x50 = 80
0x00, 0x00, 0x00, 0x50,
// Type: sinf
0x73, 0x69, 0x6e, 0x66,
// Children of sinf...
// frma box
// Size: 0x0c = 12
0x00, 0x00, 0x00, 0x0c,
// Type: frma (child of sinf)
0x66, 0x72, 0x6d, 0x61,
// Format: filled in later based on the source box ("avc1", "mp4a", etc)
0x00, 0x00, 0x00, 0x00,
// end of frma box
// schm box
// Size: 0x14 = 20
0x00, 0x00, 0x00, 0x14,
// Type: schm (child of sinf)
0x73, 0x63, 0x68, 0x6d,
// Version: 0, Flags: 0
0x00, 0x00, 0x00, 0x00,
// Scheme: cenc
0x63, 0x65, 0x6e, 0x63,
// Scheme version: 1.0
0x00, 0x01, 0x00, 0x00,
// end of schm box
// schi box
// Size: 0x28 = 40
0x00, 0x00, 0x00, 0x28,
// Type: schi (child of sinf)
0x73, 0x63, 0x68, 0x69,
// Children of schi...
// tenc box
// Size: 0x20 = 32
0x00, 0x00, 0x00, 0x20,
// Type: tenc (child of schi)
0x74, 0x65, 0x6e, 0x63,
// Version: 0, Flags: 0
0x00, 0x00, 0x00, 0x00,
// Reserved fields
0x00, 0x00,
// Default protected: true
0x01,
// Default per-sample IV size: 8
0x08,
// Default key ID: all zeros (dummy)
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
// end of tenc box
// end of schi box
// end of sinf box
]));
/**
* The location of the format field in the "frma" box inside the canned "sinf"
* box above.
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.CANNED_SINF_BOX_FORMAT_OFFSET_ = 0x10;
/**
* Offset to a box's size field.
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_SIZE_OFFSET_ = 0;
/**
* Offset to a box's type field.
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_OFFSET_ = 4;
/**
* Offset to a box's 64-bit size field, if it has one.
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_SIZE_64_OFFSET_ = 8;
/**
* Box type for "encv".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_ENCV_ = 0x656e6376;
/**
* Box type for "enca".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_ENCA_ = 0x656e6361;