This change aims to prioritise tracks that have a 'smooth enough for
video' frame rate, without always selecting the track with the highest
frame rate.
In particular MP4 files extracted from motion photos sometimes have two
HEVC tracks, with the higher-res one having a very low frame rate (not
intended for use in video playback). Before this change
`DefaultTrackSelector` would pick the low-fps, high-res track.
This change adds a somewhat arbitrary 10fps threshold for "smooth video
playback", meaning any tracks above this threshold are selected in
preference to tracks below it. Within the tracks above the threshold
other attributes are used to select the preferred track. We deliberately
don't pick the highest-fps track (over pixel count and bitrate), because
most users would prefer to see a 30fps 4k track over a 60fps 720p track.
This change also includes a test MP4 file, extracted from the existing
`jpeg/pixel-motion-photo-2-hevc-tracks.jpg` file by logging
`mp4StartPosition` in
[`MotionPhotoDescription.getMotionPhotoMetadata`](b930b40a16/libraries/extractor/src/main/java/androidx/media3/extractor/jpeg/MotionPhotoDescription.java (L123))
and then using `dd`:
```
mp4StartPosition=2603594
$ dd if=jpeg/pixel-motion-photo-2-hevc-tracks.jpg \
of=mp4/pixel-motion-photo-2-hevc-tracks.mp4 \
bs=1 \
skip=2603594
```
----
This solution is in addition to the `JpegMotionPhotoExtractor` change
made specifically for these two-track motion photos in
5266c71b3a.
We will keep both changes, even though that change is not strictly
needed after this one, because adding the role flags helps to
communicate more clearly the intended usage of these tracks. This
change to consider FPS seems like a generally useful improvement to
`DefaultTrackSelector`, since it seems unlikely we would prefer a 5fps
video track over a 30fps one.
Issue: androidx/media#1051
PiperOrigin-RevId: 611015459
c7e00b12b4