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Update track selection to prefer content over technical preferences.

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Currently we prefer technical preferences set in the Parameters over
content preferences implied by the media. It proably makes more
sense in the opposite order to avoid the situation where a
non-default track (e.g. commentary) is selected just because it
better matches some technical criteria.

Also add comments explaining the track selection logic stages.

PiperOrigin-RevId: 412840962
This commit is contained in:
tonihei 2021-11-29 10:57:51 +00:00
parent 041c3e9971
commit 99eb35179d
2 changed files with 20 additions and 6 deletions
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4
RELEASENOTES.md
View file

@ -5,6 +5,10 @@
* Core library:
* Support preferred video role flags in track selection
((#9402)[https://github.com/google/ExoPlayer/issues/9402]).
* Prefer audio content preferences (for example, "default" audio track or
track matching system Locale language) over technical track selection
constraints (for example, preferred MIME type, or maximum channel
count).
* Extractors:
* Fix inconsistency with spec in H.265 SPS nal units parsing
((#9719)[https://github.com/google/ExoPlayer/issues/9719]).

22
library/core/src/main/java/com/google/android/exoplayer2/trackselection/DefaultTrackSelector.java
View file

@ -2558,14 +2558,18 @@ public class DefaultTrackSelector extends MappingTrackSelector {
: FORMAT_VALUE_ORDERING.reverse();
return ComparisonChain.start()
.compareFalseFirst(this.isWithinRendererCapabilities, other.isWithinRendererCapabilities)
// 1. Compare match with specific content preferences set by the parameters.
.compare(this.preferredRoleFlagsScore, other.preferredRoleFlagsScore)
// 2. Compare match with implicit content preferences set by the media.
.compareFalseFirst(this.hasMainOrNoRoleFlag, other.hasMainOrNoRoleFlag)
// 3. Compare match with technical preferences set by the parameters.
.compareFalseFirst(this.isWithinMaxConstraints, other.isWithinMaxConstraints)
.compareFalseFirst(this.isWithinMinConstraints, other.isWithinMinConstraints)
.compare(
this.preferredMimeTypeMatchIndex,
other.preferredMimeTypeMatchIndex,
Ordering.natural().reverse())
// 4. Compare technical quality.
.compare(
this.bitrate,
other.bitrate,
@ -2675,13 +2679,22 @@ public class DefaultTrackSelector extends MappingTrackSelector {
: FORMAT_VALUE_ORDERING.reverse();
return ComparisonChain.start()
.compareFalseFirst(this.isWithinRendererCapabilities, other.isWithinRendererCapabilities)
// 1. Compare match with specific content preferences set by the parameters.
.compare(
this.preferredLanguageIndex,
other.preferredLanguageIndex,
Ordering.natural().reverse())
.compare(this.preferredLanguageScore, other.preferredLanguageScore)
.compare(this.preferredRoleFlagsScore, other.preferredRoleFlagsScore)
// 2. Compare match with implicit content preferences set by the media or the system.
.compareFalseFirst(this.isDefaultSelectionFlag, other.isDefaultSelectionFlag)
.compareFalseFirst(this.hasMainOrNoRoleFlag, other.hasMainOrNoRoleFlag)
.compare(
this.localeLanguageMatchIndex,
other.localeLanguageMatchIndex,
Ordering.natural().reverse())
.compare(this.localeLanguageScore, other.localeLanguageScore)
// 3. Compare match with technical preferences set by the parameters.
.compareFalseFirst(this.isWithinConstraints, other.isWithinConstraints)
.compare(
this.preferredMimeTypeMatchIndex,
@ -2691,12 +2704,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
this.bitrate,
other.bitrate,
parameters.forceLowestBitrate ? FORMAT_VALUE_ORDERING.reverse() : NO_ORDER)
.compareFalseFirst(this.isDefaultSelectionFlag, other.isDefaultSelectionFlag)
.compare(
this.localeLanguageMatchIndex,
other.localeLanguageMatchIndex,
Ordering.natural().reverse())
.compare(this.localeLanguageScore, other.localeLanguageScore)
// 4. Compare technical quality.
.compare(this.channelCount, other.channelCount, qualityOrdering)
.compare(this.sampleRate, other.sampleRate, qualityOrdering)
.compare(
@ -2785,12 +2793,14 @@ public class DefaultTrackSelector extends MappingTrackSelector {
ComparisonChain.start()
.compareFalseFirst(
this.isWithinRendererCapabilities, other.isWithinRendererCapabilities)
// 1. Compare match with specific content preferences set by the parameters.
.compare(
this.preferredLanguageIndex,
other.preferredLanguageIndex,
Ordering.natural().reverse())
.compare(this.preferredLanguageScore, other.preferredLanguageScore)
.compare(this.preferredRoleFlagsScore, other.preferredRoleFlagsScore)
// 2. Compare match with implicit content preferences set by the media.
.compareFalseFirst(this.isDefault, other.isDefault)
.compare(
this.isForced,