Converting a single track selection to stream keys is only possible if the output
is independent from other track selections being made.
This is not the case for DASH and HLS embedded track groups which should select the
already selected primary track if possible (and thus needs to know whether a primary
track group is selected).
Also, update the test method to take a period index.
PiperOrigin-RevId: 231385490
1. Pull up all subclasses of DownloadAction into DownloadAction
2. Add DownloaderFactory for Downloader instantiation, and DefaultDownloaderFactory
to replace the instantiation logic being removed from the DownloadAction
subclasses.
This change will upgrade existing action files gracefully (i.e. it does not
lose compatibility with the existing offline implementation, other than some
minor breaking changes to the API).
TODOs:
1. Move test methods from the XDownloadActionTest classes into DownloadActionTest.
This will be done in a subsequent CL. There's a lot of consolidation that can
be done here, including de-duplicating some of the test code added in this CL.
2. Look at merging DownloaderConstructorHelper into DefaultDownloaderFactory.
3. Use customCacheKey in DASH/HLS/SS Downloaders, for completeness.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=222258983
Also moved shared code to SegmentDownloadAction between its subclasses.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=202294880
Also convert them to exposing periods and track groups, like
regular MediaSources do. This gets us much closer to being
able to use standard track selection components during offline
initialization. The helper is responsible for reverse mapping
selected tracks onto physical streams when generating the
download action. This is trivial except for the HLS case, which
is a TODO for now.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=195500826
These don't seem to be needed anymore. All tests run without them in gradle
and Blaze.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=191867518
