SDK / exoplayer

Logic and some code is copied from V1.

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Created by MOE: https://github.com/google/moe
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Created by MOE: https://github.com/google/moe
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- Invoked --> Called
- Gets --> Returns
- "True if X. False otherwise." --> "Whether X."
- Removed some @returns where the Javadoc is in "Returns X" form

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Created by MOE: https://github.com/google/moe
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This is in preparation for allowing MediaSources to skip over periods when one
period ends, which is needed for starting to play a multi-period live stream
that is concatenated on to another period at the live edge.

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- Suppress spurious resource type warnings.
- Make AS happy by making private method non-final.

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As per the spec of MediaPeriod.getDurationUs, when a live
stream ends we need to start returning the correct final
duration.

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We were forgetting to reset renderers during track
selections where muxed media is used.

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Created by MOE: https://github.com/google/moe
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It's only "needed" for HLS, and this requirement will
go away soon. It's safe to remove the flag ahead of
this because a TrackSelector can/should not attempt to
adapt between multiple audio/text tracks.

Also remove unnecessary restrictions on TrackGroups
being non-empty and only of known types.

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Created by MOE: https://github.com/google/moe
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Created by MOE: https://github.com/google/moe
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Created by MOE: https://github.com/google/moe
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- Remove null checks (never happens).
- Use "const".equals(Util.CONST) where possible.

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Created by MOE: https://github.com/google/moe
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The classes these tests are written for have changed
so much we'll have to write them again. We can refer
to V1 if we want to look at what the old tests did, so
there's no need to keep this file in the V2 tree at
the moment.

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Created by MOE: https://github.com/google/moe
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- TrackSelection now exposes the selected formats, ordered
  by decreasing bandwidth. This removes the need for DASH,
  SS and HLS to do the sorting individually.
- The change also removes the need to reconstruct TrackSelection
  instances with a different group index in various places
  (e.g. MergingMediaPeriod).
- This is also a step toward potentially packaging the
  FormatEvaluator inside of the TrackSelection (TBD).

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According to the spec, there is no mandatory relation between segments'
sequence numbers of different variants. This CL ignores sequence numbers
when switching variants:

* In vod, the switching playback position is obtained by adding the
    duration of previous segments.
* In live playback this is not possible. It is assumed that the
    different live media playlists do not drift apart too much, so
    the playback position is obtained by subtracting the duration
    in reverse order.

In later CLs, the described mechanisms will become the fallback methods
by replacing them with the use of EXT-X-PROGRAM-DATE-TIME information
or more reliable sources.

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ISSUE: #1681

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It's the only place that uses it.

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Created by MOE: https://github.com/google/moe
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SmoothStreaming -> Ss
MediaPresentationDescription -> DashManifest
DashSingleSegmentIndex -> SingleSegmentIndex

Moved DASH and Ss manifest classes to matching
manifest packages for consistency. For Hls the
package is called playlist still, since that's
what they're widely known as.

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Created by MOE: https://github.com/google/moe
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This also removes direct use of HttpURLConnection and
allows use of any HttpDataSource for license requests,
which means those using OkHttp can finally use the
same network stack for license requests as they're using
for everything else, without having to implement their
own callback.

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Issue: #548

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With this change, MediaCodecRenderer acquires a session
from its DrmSessionManager whenever the DrmInitData in
the format changes. The DrmSessionManager is permitted
to return the same session if it can be re-used.

This plumbing adds support for:

1. Key-rotation, in the case that a key-rotation-aware
   DrmSessionManager is used. Such an implementation will
   return the same DrmSession for every aquisition, but
   will be making use of multiple MediaDrm instances within
   that session to enable the rotation.

2. Playlists with mixed clear and protected content. One
   final piece to this will be to have each MediaPeriod
   provide its own license URL. We could also allow each
   MediaPeriod to specify the DRM UUID, but switching from
   PlayReady to Widevine in a playlist seems like quite a
   hypothetical thing.

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