shaka-player
Version:
DASH/EME video player library
867 lines (770 loc) • 30.8 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.device.DeviceFactory');
goog.require('shaka.log');
goog.require('shaka.util.BufferUtils');
goog.require('shaka.util.Error');
goog.require('shaka.util.Mp4BoxParsers');
goog.require('shaka.util.Mp4Generator');
goog.require('shaka.util.Mp4Parser');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* @summary
* A collection of methods to work around content issues on various platforms.
*/
shaka.media.ContentWorkarounds = class {
/**
* For EAC-3 audio, the "enca" box ChannelCount field
* MUST always be set to 2.
* See ETSI TS 102 366 V1.2.1 Sec F.3
*
* Clients SHOULD ignore this value; however, it has been discovered that
* some user agents don't, and instead, invalid values here can cause decoder
* failures to be thrown (this has been observed with Chromecast).
*
* Given that this value MUST be hard-coded to 2, and that clients "SHALL"
* ignore the value, it seems safe to manipulate the value to be 2 even when
* the packager has provided a different value.
* @param {!BufferSource} initSegmentBuffer
* @return {!Uint8Array}
*/
static correctEnca(initSegmentBuffer) {
const initSegment = shaka.util.BufferUtils.toUint8(initSegmentBuffer);
const modifiedInitSegment = initSegment;
/**
* Skip reserved bytes: 6
* Skip data_reference_index: 2
* Skip reserved bytes: 8
*/
const encaChannelCountOffset = 16;
/** @type {?DataView} */
let encaBoxDataView = null;
new shaka.util.Mp4Parser()
.boxes(shaka.util.Mp4Parser.SAMPLE_TABLE_PATH,
shaka.util.Mp4Parser.children)
.fullBox('stsd', shaka.util.Mp4Parser.sampleDescription)
.box('enca', (box) => {
encaBoxDataView = box.reader.getDataView();
return shaka.util.Mp4Parser.audioSampleEntry(box);
})
.box('sinf', shaka.util.Mp4Parser.children)
.box('frma', (box) => {
box.parser.stop();
const {codec} = shaka.util.Mp4BoxParsers.parseFRMA(box.reader);
if (codec === 'ec-3' &&
encaBoxDataView &&
encaBoxDataView.getUint16(encaChannelCountOffset) !== 2
) {
encaBoxDataView.setUint16(encaChannelCountOffset, 2);
}
})
.parse(initSegment);
return modifiedInitSegment;
}
/**
* Change the box type of the dvvC box from `dvvC` to `free`. This is a
* content workaround suggested by Dolby for Dolby Vision streams on some
* chromium-based devices.
* See https://professionalsupport.dolby.com/s/article/Guidelines-to-developers-building-DASH-HLS-player-apps-for-LG-WebOS-Chromecast-and-other-Chromium-based-app-development-platforms?language=en_US
* @param {!BufferSource} initSegmentBuffer
* @return {!Uint8Array}
*/
static freeDvvcBox(initSegmentBuffer) {
const initSegment = shaka.util.BufferUtils.toUint8(initSegmentBuffer);
/** @type {?DataView} */
let hvcDataView = null;
let hvcStart = -1;
new shaka.util.Mp4Parser()
.boxes(shaka.util.Mp4Parser.SAMPLE_TABLE_PATH,
shaka.util.Mp4Parser.children)
.fullBox('stsd', shaka.util.Mp4Parser.sampleDescription)
.box('hvc1', (box) => {
hvcDataView = box.reader.getDataView();
hvcStart = box.start;
return shaka.util.Mp4Parser.visualSampleEntry(box);
})
.box('dvvC', (box) => {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
box.parser.stop();
// box start - hvc1 box start - type size
const byteOffset = box.start - hvcStart - 4;
hvcDataView.setUint32(byteOffset, ContentWorkarounds.BOX_TYPE_FREE_);
})
.parse(initSegment);
return initSegment;
}
/**
* 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 {!shaka.extern.Stream} stream
* @param {!BufferSource} initSegmentBuffer
* @param {?string} uri
* @param {?string} keySystem
* @return {!Uint8Array}
* @see https://github.com/shaka-project/shaka-player/issues/2759
*/
static fakeEncryption(stream, initSegmentBuffer, uri, keySystem) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const initSegment = shaka.util.BufferUtils.toUint8(initSegmentBuffer);
let modifiedInitSegment = initSegment;
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;
box.parser.stop();
};
// 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 = [];
const pushEncv = (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCV_,
});
};
const pushEnca = (box) => {
boxesToModify.push({
box,
newType: ContentWorkarounds.BOX_TYPE_ENCA_,
});
};
new shaka.util.Mp4Parser()
.boxes(shaka.util.Mp4Parser.SAMPLE_TABLE_PATH, onSimpleAncestorBox)
.fullBox('stsd', (box) => {
stsdBox = box;
ancestorBoxes.push(box);
shaka.util.Mp4Parser.sampleDescription(box);
})
.boxes([
'encv',
'enca',
], onEncryptionMetadataBox)
.boxes(shaka.util.Mp4Parser.AVC_HEVC_VVC_DV, pushEncv)
.boxes([...shaka.util.Mp4Parser.GENERIC_AUDIO_SAMPLE_ENTRIES, 'mp4a'],
pushEnca)
.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,
uri);
}
// 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.`);
modifiedInitSegment = ContentWorkarounds.insertEncryptionMetadata_(
stream, modifiedInitSegment, stsdBox, workItem.box, ancestorBoxes,
workItem.newType, keySystem);
}
// Insert PSSH boxes as some platforms require it, i.e. NOS STBs.
modifiedInitSegment = ContentWorkarounds.insertPsshBoxes_(stream,
modifiedInitSegment);
// Edge Windows needs the unmodified init segment to be appended after the
// patched one, otherwise video element throws following error:
// CHUNK_DEMUXER_ERROR_APPEND_FAILED: Sample encryption info is not
// available.
const device = shaka.device.DeviceFactory.getDevice();
if (device.requiresClearAndEncryptedInitSegments(keySystem)) {
const doubleInitSegment = new Uint8Array(initSegment.byteLength +
modifiedInitSegment.byteLength);
doubleInitSegment.set(modifiedInitSegment);
doubleInitSegment.set(initSegment, modifiedInitSegment.byteLength);
return doubleInitSegment;
}
return modifiedInitSegment;
}
/**
* @param {!BufferSource} mediaSegmentBuffer
* @return {!Uint8Array}
*/
static fakeMediaEncryption(mediaSegmentBuffer) {
const mediaSegment = shaka.util.BufferUtils.toUint8(mediaSegmentBuffer);
const mdatBoxes = [];
new shaka.util.Mp4Parser()
.box('mdat', (box) => {
mdatBoxes.push(box);
})
.parse(mediaSegment);
const newSegmentChunks = [];
for (let i = 0; i < mdatBoxes.length; i++) {
const prevMdat = mdatBoxes[i - 1];
const currMdat = mdatBoxes[i];
const chunkStart = prevMdat ? prevMdat.start + prevMdat.size : 0;
const chunkEnd = currMdat.start + currMdat.size;
const chunk = mediaSegment.subarray(chunkStart, chunkEnd);
newSegmentChunks.push(
shaka.media.ContentWorkarounds.fakeMediaEncryptionInChunk_(chunk));
}
return shaka.util.Uint8ArrayUtils.concat(...newSegmentChunks);
}
/**
* @param {!Uint8Array} chunk
* @return {!Uint8Array}
* @private
*/
static fakeMediaEncryptionInChunk_(chunk) {
// Which track from stsd we want to use, 1-based.
const desiredSampleDescriptionIndex = 2;
let tfhdBox;
let trunBox;
let parsedTfhd;
let parsedTrun;
const ancestorBoxes = [];
const onSimpleAncestorBox = (box) => {
ancestorBoxes.push(box);
shaka.util.Mp4Parser.children(box);
};
const onTfhdBox = (box) => {
tfhdBox = box;
parsedTfhd = shaka.util.Mp4BoxParsers.parseTFHD(box.reader, box.flags);
};
const onTrunBox = (box) => {
trunBox = box;
parsedTrun = shaka.util.Mp4BoxParsers.parseTRUN(box.reader, box.version,
box.flags);
};
new shaka.util.Mp4Parser()
.boxes(shaka.util.Mp4Parser.FRAGMENT_PATH, onSimpleAncestorBox)
.fullBox('tfhd', onTfhdBox)
.fullBox('trun', onTrunBox)
.parse(chunk);
if (parsedTfhd && parsedTfhd.sampleDescriptionIndex !==
desiredSampleDescriptionIndex) {
const sdiPosition = tfhdBox.start +
shaka.util.Mp4Parser.headerSize(tfhdBox) +
4 + // track_id
(parsedTfhd.baseDataOffset !== null ? 8 : 0);
const dataview = shaka.util.BufferUtils.toDataView(chunk);
if (parsedTfhd.sampleDescriptionIndex !== null) {
dataview.setUint32(sdiPosition, desiredSampleDescriptionIndex);
} else {
const sdiSize = 4; // uint32
// first, update size & flags of tfhd
shaka.media.ContentWorkarounds.updateBoxSize_(chunk,
tfhdBox.start, tfhdBox.size + sdiSize);
const versionAndFlags = dataview.getUint32(tfhdBox.start + 8);
dataview.setUint32(tfhdBox.start + 8, versionAndFlags | 0x000002);
// second, update trun
if (parsedTrun && parsedTrun.dataOffset !== null) {
const newDataOffset = parsedTrun.dataOffset + sdiSize;
const dataOffsetPosition = trunBox.start +
shaka.util.Mp4Parser.headerSize(trunBox) +
4; // sample count
dataview.setInt32(dataOffsetPosition, newDataOffset);
}
const beforeSdi = chunk.subarray(0, sdiPosition);
const afterSdi = chunk.subarray(sdiPosition);
chunk = new Uint8Array(chunk.byteLength + sdiSize);
chunk.set(beforeSdi);
const bytes = [];
for (let byte = sdiSize - 1; byte >= 0; byte--) {
bytes.push((desiredSampleDescriptionIndex >> (8 * byte)) & 0xff);
}
chunk.set(new Uint8Array(bytes), sdiPosition);
chunk.set(afterSdi, sdiPosition + sdiSize);
for (const box of ancestorBoxes) {
shaka.media.ContentWorkarounds.updateBoxSize_(chunk, box.start,
box.size + sdiSize);
}
}
}
return chunk;
}
/**
* 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 {!shaka.extern.Stream} stream
* @param {!Uint8Array} initSegment
* @param {shaka.extern.ParsedBox} stsdBox
* @param {shaka.extern.ParsedBox} sourceBox
* @param {!Array<shaka.extern.ParsedBox>} ancestorBoxes
* @param {number} metadataBoxType
* @param {?string} keySystem
* @return {!Uint8Array}
* @private
*/
static insertEncryptionMetadata_(
stream, initSegment, stsdBox, sourceBox, ancestorBoxes, metadataBoxType,
keySystem) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const metadataBoxArray = ContentWorkarounds.createEncryptionMetadata_(
stream, 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 & Edge, 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 device = shaka.device.DeviceFactory.getDevice();
const cutPoint = device.insertEncryptionDataBeforeClear(keySystem) ?
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 {!shaka.extern.Stream} stream
* @param {!Uint8Array} initSegment
* @param {shaka.extern.ParsedBox} sourceBox
* @param {number} metadataBoxType
* @return {!Uint8Array}
* @private
*/
static createEncryptionMetadata_(stream, initSegment, sourceBox,
metadataBoxType) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const mp4Generator = new shaka.util.Mp4Generator();
const sinfBoxArray = mp4Generator.sinf(stream, sourceBox.name);
// Create a subarray which points to the source box data.
const sourceBoxArray = initSegment.subarray(
/* start= */ sourceBox.start,
/* end= */ sourceBox.start + sourceBox.size);
// 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);
// Now update the encryption metadata box size.
ContentWorkarounds.updateBoxSize_(
metadataBoxArray, /* boxStart= */ 0, metadataBoxArray.byteLength);
return metadataBoxArray;
}
/**
* @param {!shaka.extern.Stream} stream
* @param {!Uint8Array} initSegment
* @return {!Uint8Array}
* @private
*/
static insertPsshBoxes_(stream, initSegment) {
const psshs = new shaka.util.Mp4Generator().psshs(stream);
if (psshs.byteLength === 0) {
return initSegment;
}
let moovBoxStart = 0;
let moovBoxSize = 0;
new shaka.util.Mp4Parser()
.box('moov', (box) => {
moovBoxStart = box.start;
moovBoxSize = box.size;
box.parser.stop();
})
.parse(initSegment);
const updatedMoovBoxSize = moovBoxSize + psshs.byteLength;
const cutPoint = moovBoxStart + moovBoxSize;
shaka.media.ContentWorkarounds.updateBoxSize_(
initSegment, moovBoxStart, updatedMoovBoxSize);
const newInitSegment = new Uint8Array(initSegment.byteLength +
psshs.byteLength);
const beforeData = initSegment.subarray(0, cutPoint);
const afterData = initSegment.subarray(cutPoint);
newInitSegment.set(beforeData);
newInitSegment.set(psshs, cutPoint);
newInitSegment.set(afterData, cutPoint + psshs.byteLength);
return newInitSegment;
}
/**
* 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);
}
}
/**
* Transform the init segment into a new init segment buffer that indicates
* EC-3 as audio codec instead of AC-3. Even though any EC-3 decoder should
* be able to decode AC-3 streams, there are platforms that do not accept
* AC-3 as codec.
*
* Should only be called for MP4 init segments, and only on platforms that
* need this workaround. Returns a new buffer containing the modified init
* segment.
*
* @param {!BufferSource} initSegmentBuffer
* @return {!Uint8Array}
*/
static fakeEC3(initSegmentBuffer) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const initSegment = shaka.util.BufferUtils.toUint8(initSegmentBuffer);
const ancestorBoxes = [];
const onSimpleAncestorBox = (box) => {
ancestorBoxes.push({start: box.start, size: box.size});
shaka.util.Mp4Parser.children(box);
};
new shaka.util.Mp4Parser()
.boxes(shaka.util.Mp4Parser.SAMPLE_TABLE_PATH, onSimpleAncestorBox)
.box('stsd', (box) => {
ancestorBoxes.push({start: box.start, size: box.size});
const stsdBoxView = shaka.util.BufferUtils.toDataView(
initSegment, box.start);
// "size - 3" is because we immediately read a uint32.
for (let i = 0; i < box.size -3; i++) {
const codecTag = stsdBoxView.getUint32(i);
if (codecTag == ContentWorkarounds.BOX_TYPE_AC_3_) {
stsdBoxView.setUint32(i, ContentWorkarounds.BOX_TYPE_EC_3_);
} else if (codecTag == ContentWorkarounds.BOX_TYPE_DAC3_) {
stsdBoxView.setUint32(i, ContentWorkarounds.BOX_TYPE_DEC3_);
}
}
}).parse(initSegment);
return initSegment;
}
/**
* Some packagers produce broken I-frame only media segments: they clip the
* byte range down to the first I-frame but leave the moof/trun declaring the
* whole GOP (many samples) and the mdat declaring the full, un-clipped size.
* The demuxer then tries to decode samples whose data is not present and
* fails (e.g. "Failed to prepare video sample for decode").
*
* When the mdat is shorter than the trun/mdat headers declare, rewrite the
* fragment so that it only describes the single I-frame that is actually
* present, and extend that sample's duration to span the original segment so
* the buffered timeline stays continuous. Returns the segment untouched when
* it is well-formed or when the layout is not one we can safely rewrite.
*
* @param {!BufferSource} mediaSegmentBuffer
* @return {!Uint8Array}
*/
static fixBrokenIframes(mediaSegmentBuffer) {
const ContentWorkarounds = shaka.media.ContentWorkarounds;
const Mp4Parser = shaka.util.Mp4Parser;
const segment = shaka.util.BufferUtils.toUint8(mediaSegmentBuffer);
const moofBoxes = [];
const trafBoxes = [];
const tfhdBoxes = [];
const trunBoxes = [];
let hasEncryptionBoxes = false;
new Mp4Parser()
.box('moof', (box) => {
moofBoxes.push(box);
Mp4Parser.children(box);
})
.box('traf', (box) => {
trafBoxes.push(box);
Mp4Parser.children(box);
})
.fullBox('tfhd', (box) => {
tfhdBoxes.push(box);
})
.fullBox('trun', (box) => {
trunBoxes.push(box);
})
.boxes([
'senc',
'saiz',
'saio',
], () => {
hasEncryptionBoxes = true;
})
.parse(segment, /* partialOkay= */ false, /* stopOnPartial= */ true);
// Only handle a single, unencrypted movie fragment. Anything more complex
// is left untouched.
if (hasEncryptionBoxes || moofBoxes.length != 1 || trafBoxes.length != 1 ||
tfhdBoxes.length != 1 || trunBoxes.length != 1) {
return segment;
}
const moofBox = moofBoxes[0];
const trafBox = trafBoxes[0];
const tfhdBox = tfhdBoxes[0];
const trunBox = trunBoxes[0];
goog.asserts.assert(tfhdBox.flags != null, 'TFHD should have valid flags');
goog.asserts.assert(trunBox.flags != null, 'TRUN should have valid flags');
goog.asserts.assert(
trunBox.version != null, 'TRUN should have a valid version');
const trunFlags = trunBox.flags;
const parsedTfhd =
shaka.util.Mp4BoxParsers.parseTFHD(tfhdBox.reader, tfhdBox.flags);
const parsedTrun = shaka.util.Mp4BoxParsers.parseTRUN(
trunBox.reader, trunBox.version, trunBox.flags);
// A base_data_offset or an implicit data offset means the sample data is
// addressed in ways our byte removal would invalidate.
if (parsedTfhd.baseDataOffset != null ||
!(trunFlags & 0x000001) || parsedTrun.dataOffset == null) {
return segment;
}
const mdatStart = moofBox.start + moofBox.size;
const dataView = shaka.util.BufferUtils.toDataView(segment);
if (mdatStart + 8 > segment.byteLength ||
dataView.getUint32(mdatStart + ContentWorkarounds.BOX_TYPE_OFFSET_) !=
ContentWorkarounds.BOX_TYPE_MDAT_) {
return segment;
}
let mdatSize = dataView.getUint32(mdatStart);
const mdatHeaderSize = 8;
if (mdatSize == 1) {
// A 64-bit mdat size is not something we expect for I-frame segments.
return segment;
} else if (mdatSize == 0) {
mdatSize = segment.byteLength - mdatStart;
}
const availablePayload = segment.byteLength - (mdatStart + mdatHeaderSize);
const declaredPayload = mdatSize - mdatHeaderSize;
// If all the declared data is present, the fragment is well-formed.
if (availablePayload >= declaredPayload) {
return segment;
}
// Count how many whole samples fit in the bytes that are actually present.
let keptPayloadBytes = 0;
let keepCount = 0;
for (const sample of parsedTrun.sampleData) {
const size = sample.sampleSize != null ?
sample.sampleSize : parsedTfhd.defaultSampleSize;
if (size == null) {
return segment;
}
if (keptPayloadBytes + size > availablePayload) {
break;
}
keptPayloadBytes += size;
keepCount++;
}
// We only handle the case where exactly the first sample (the I-frame) is
// present out of a larger declared GOP.
if (keepCount != 1 || keepCount >= parsedTrun.sampleCount) {
return segment;
}
// Preserve the original segment duration so the single I-frame spans the
// whole slot and the buffered timeline stays continuous.
const hasPerSampleDuration = (trunFlags & 0x000100) != 0;
let originalTotalDuration = 0;
for (const sample of parsedTrun.sampleData) {
const duration = hasPerSampleDuration ?
sample.sampleDuration : parsedTfhd.defaultSampleDuration;
if (duration == null) {
return segment;
}
originalTotalDuration += duration;
}
const trunHeaderSize = Mp4Parser.headerSize(trunBox);
// trun payload layout: sample_count(4) [+ data_offset(4)]
// [+ first_sample_flags(4)] then the per-sample entries.
let sampleEntriesStart = trunBox.start + trunHeaderSize + 4;
sampleEntriesStart += 4; // data_offset, guaranteed present above.
if (trunFlags & 0x000004) {
sampleEntriesStart += 4; // first_sample_flags
}
let perSampleEntrySize = 0;
if (trunFlags & 0x000100) {
perSampleEntrySize += 4; // duration
}
if (trunFlags & 0x000200) {
perSampleEntrySize += 4; // size
}
if (trunFlags & 0x000400) {
perSampleEntrySize += 4; // flags
}
if (trunFlags & 0x000800) {
perSampleEntrySize += 4; // composition time offset
}
const removedSamples = parsedTrun.sampleCount - keepCount;
const bytesRemoved = removedSamples * perSampleEntrySize;
const keepEntriesEnd = sampleEntriesStart + keepCount * perSampleEntrySize;
// The removed sample entries must be the tail of the moof, immediately
// followed by the mdat, or the layout is more complex than we can rewrite.
if (keepEntriesEnd + bytesRemoved != mdatStart) {
return segment;
}
// Build the fixed fragment: patched moof header + kept sample entry,
// followed by an mdat that only holds the bytes we actually have.
const front = segment.slice(0, keepEntriesEnd);
const frontView = shaka.util.BufferUtils.toDataView(front);
// trun: sample_count -> keepCount, data_offset shifted by removed bytes.
frontView.setUint32(trunBox.start + trunHeaderSize, keepCount);
frontView.setInt32(trunBox.start + trunHeaderSize + 4,
parsedTrun.dataOffset - bytesRemoved);
// Extend the kept sample's duration to the original segment duration.
if (hasPerSampleDuration) {
// The duration is the first per-sample field.
frontView.setUint32(sampleEntriesStart, originalTotalDuration);
} else {
// The duration comes from tfhd's default_sample_duration.
let durationOffset =
tfhdBox.start + Mp4Parser.headerSize(tfhdBox) + 4; // track_ID
if (parsedTfhd.sampleDescriptionIndex != null) {
durationOffset += 4;
}
frontView.setUint32(durationOffset, originalTotalDuration);
}
// Shrink the container boxes to account for the removed sample entries.
ContentWorkarounds.updateBoxSize_(
front, trunBox.start, trunBox.size - bytesRemoved);
ContentWorkarounds.updateBoxSize_(
front, trafBox.start, trafBox.size - bytesRemoved);
ContentWorkarounds.updateBoxSize_(
front, moofBox.start, moofBox.size - bytesRemoved);
// Rebuild the mdat header with the corrected size, then append only the
// payload bytes that are actually present.
const mdatHeader = segment.slice(mdatStart, mdatStart + mdatHeaderSize);
ContentWorkarounds.updateBoxSize_(
mdatHeader, 0, mdatHeaderSize + keptPayloadBytes);
const mdatPayload = segment.subarray(mdatStart + mdatHeaderSize,
mdatStart + mdatHeaderSize + keptPayloadBytes);
return shaka.util.Uint8ArrayUtils.concat(front, mdatHeader, mdatPayload);
}
};
/**
* 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 "mdat".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_MDAT_ = 0x6d646174;
/**
* 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;
/**
* Box type for "ac-3".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_AC_3_ = 0x61632d33;
/**
* Box type for "dac3".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_DAC3_ = 0x64616333;
/**
* Box type for "ec-3".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_EC_3_ = 0x65632d33;
/**
* Box type for "free".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_FREE_ = 0x66726565;
/**
* Box type for "dec3".
*
* @const {number}
* @private
*/
shaka.media.ContentWorkarounds.BOX_TYPE_DEC3_ = 0x64656333;