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Group Streams Before Downloading
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To make it easier to understand, we collect all the streams within a
period using a map. This ensures that we will have a set of streams.

We then download each stream in the map. Since the map is indexed by
stream id, we can easily connect the variants and streams.

Issue #1248

Change-Id: I65ae01733b5d9dbf8b6d73c37f802320fffa03d1
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@vaage @joeyparrish
vaage authored and joeyparrish committed May 9, 2018
1 parent b7cd984 commit 7a60119
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Showing 2 changed files with 88 additions and 63 deletions.
139 changes: 82 additions & 57 deletions lib/offline/storage.js
View file
Expand Up @@ -34,6 +34,7 @@ goog.require('shaka.util.Functional');
goog.require('shaka.util.IDestroyable');
goog.require('shaka.util.LanguageUtils');
goog.require('shaka.util.ManifestParserUtils');
goog.require('shaka.util.MapUtils');
goog.require('shaka.util.StreamUtils');


Expand Down Expand Up @@ -838,67 +839,66 @@ shaka.offline.Storage.prototype.createPeriod_ = function(
'Multiple tracks of the same type/kind/language given.');
}

let streams = [];

for (let i = 0; i < chosenTracks.length; i++) {
let variant = StreamUtils.findVariantForTrack(period, chosenTracks[i]);
if (variant) {
// Make a rough estimation of the streams' bandwidth so the download
// manager can track the progress of the download.
let bandwidthEstimation;
if (variant.audio) {
// If the audio stream has already been added to the DB as part of
// another variant, add the ID to the list. Otherwise, add it to the DB.
let stream = streams.filter(function(s) {
return s.id == variant.audio.id;
})[0];
if (stream) {
stream.variantIds.push(variant.id);
} else {
// If the variant has both audio and video, roughly estimate them
// both to be 1/2 of the variant's bandwidth.
// If the variant only has one stream, that stream's bandwidth equals
// the bandwidth of the variant.
bandwidthEstimation =
variant.video ? variant.bandwidth / 2 : variant.bandwidth;
streams.push(this.createStream_(
manifest,
period,
variant.audio,
bandwidthEstimation,
variant.id));
}
}
if (variant.video) {
let stream = streams.filter(function(s) {
return s.id == variant.video.id;
})[0];
if (stream) {
stream.variantIds.push(variant.id);
} else {
bandwidthEstimation =
variant.audio ? variant.bandwidth / 2 : variant.bandwidth;
streams.push(this.createStream_(
manifest,
period,
variant.video,
bandwidthEstimation,
variant.id));
}
}
} else {
let textStream =
StreamUtils.findTextStreamForTrack(period, chosenTracks[i]);
goog.asserts.assert(
textStream, 'Could not find track with id ' + chosenTracks[i].id);
streams.push(this.createStream_(
manifest, period, textStream, 0 /* estimatedStreamBandwidth */));
let bandwidth = {};
chosenTracks.forEach((track) => {
if (track.type == 'text') {
// We assume that text has no bandwidth.
bandwidth[track.id] = 0;
}
}

if (track.type == 'variant') {
let variant = StreamUtils.findVariantForTrack(period, track);
let streams = [variant.audio, variant.video].filter((stream) => !!stream);

let bandwidthPerStream = variant.bandwidth / streams.length;
streams.forEach((stream) => {
bandwidth[stream.id] = bandwidth[stream.id] || bandwidthPerStream;
});
}
});

// Need a way to look up which streams should be downloaded. Use a map so
// that we can easily lookup if a stream should be downloaded just by
// checking if its id is in the map.
let idMap = {};
chosenTracks.forEach((track) => {
if (track.type == 'variant' && track.audioId != null) {
idMap[track.audioId] = true;
}
if (track.type == 'variant' && track.videoId != null) {
idMap[track.videoId] = true;
}
if (track.type == 'text') {
idMap[track.id] = true;
}
});

// Find the streams we want to download and create a stream db instance
// for each of them.
let streamDBs = {};
shaka.offline.Storage.getStreamSet_(manifest)
.filter((stream) => !!idMap[stream.id])
.forEach((stream) => {
streamDBs[stream.id] = this.createStream_(
manifest,
period,
stream,
bandwidth[stream.id]);
});

// Connect streams and variants together.
chosenTracks.forEach((track) => {
if (track.type == 'variant' && track.audioId != null) {
streamDBs[track.audioId].variantIds.push(track.id);
}
if (track.type == 'variant' && track.videoId != null) {
streamDBs[track.videoId].variantIds.push(track.id);
}
});

return {
startTime: period.startTime,
streams: streams
streams: shaka.util.MapUtils.values(streamDBs)
};
};

Expand Down Expand Up @@ -1108,4 +1108,29 @@ shaka.offline.Storage.lookForSimilarTracks_ = function(tracks) {
};


/**
* Get a collection of streams that are in the manifest. This collection will
* only have one instance of each stream (similar to a set).
*
* @param {shakaExtern.Manifest} manifest
* @return {!Array.<shakaExtern.Stream>}
* @private
*/
shaka.offline.Storage.getStreamSet_ = function(manifest) {
// Use a map so that we don't store duplicates. Since a stream's id should
// be unique within the manifest, we can use that as the key.
let map = {};

manifest.periods.forEach((period) => {
period.textStreams.forEach((text) => { map[text.id] = text; });
period.variants.forEach((variant) => {
if (variant.audio) { map[variant.audio.id] = variant.audio; }
if (variant.video) { map[variant.video.id] = variant.video; }
});
});

return shaka.util.MapUtils.values(map);
};


shaka.Player.registerSupportPlugin('offline', shaka.offline.Storage.support);
12 changes: 6 additions & 6 deletions test/offline/storage_unit.js
View file
Expand Up @@ -584,19 +584,19 @@ describe('Storage', function() {
return fakeStorageEngine.getManifest(0);
})
.then(function(manifest) {
let stream1 = manifest.periods[0].streams[0];
let stream1 = manifest.periods[0].streams[1];
expect(stream1.initSegmentKey).toBe(null);
expect(stream1.segments.length).toBe(5);
expect(stream1.segments).toContain(makeSegment(0, 1, id1));
expect(stream1.segments).toContain(makeSegment(0, 1, id2));
expect(stream1.segments).toContain(makeSegment(1, 2, id3));
expect(stream1.segments).toContain(makeSegment(2, 3, id4));
expect(stream1.segments).toContain(makeSegment(3, 4, id5));
expect(stream1.segments).toContain(makeSegment(4, 5, id6));

let stream2 = manifest.periods[0].streams[1];
let stream2 = manifest.periods[0].streams[0];
expect(stream2.initSegmentKey).toBe(null);
expect(stream2.segments.length).toBe(1);
expect(stream2.segments).toContain(makeSegment(0, 1, id2));
expect(stream2.segments).toContain(makeSegment(0, 1, id1));

return fakeStorageEngine.getSegment(id4);
})
Expand Down Expand Up @@ -660,7 +660,7 @@ describe('Storage', function() {
expect(netEngine.request.calls.count()).toBe(1);
return fakeStorageEngine.getManifest(0);
}).then((manifest) => {
let stream = manifest.periods[0].streams[0];
let stream = manifest.periods[0].streams[1];
expect(stream.contentType).toBe('audio');
expect(stream.segments.length).toBe(0);
expect(stream.initSegmentKey).toBe(0);
Expand Down Expand Up @@ -692,7 +692,7 @@ describe('Storage', function() {
return fakeStorageEngine.getManifest(0);
})
.then(function(manifest) {
let stream = manifest.periods[0].streams[0];
let stream = manifest.periods[0].streams[1];
expect(stream.segments.length).toBe(3);
})
.catch(fail)
Expand Down

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