ExoPlayer ignores cached segments when adaptive streaming selects different quality

Version

Media3 1.5.1

More version details

No response

Devices that reproduce the issue

Google Pixel 3a with Android 11

Devices that do not reproduce the issue

not tested

Reproducible in the demo app?

Not tested

Reproduction steps

1. Set up two ExoPlayer instances:
   Player 0 for playback.
   Player 1 for preloading segments.

2. Videos are encoded using DASH with multiple representations (e.g., 240p, 480p, 720p). Each video has multiple .m4s segment files and init files per representation.

3. Use a custom CacheKeyFactory to unify segment keys across quality levels:

override fun buildCacheKey(dataSpec: DataSpec): String {    val url = dataSpec.uri.toString()
    val chunkRegex = Regex(".*/([^/]+)/chunk-stream\\d+-(\\d+)")
    val initRegex = Regex(".*/([^/]+)/init-stream(\\d+)")

    chunkRegex.find(url)?.let {
        val videoId = it.groupValues[1]
        val chunkId = it.groupValues[2]
        return "video-$videoId-chunk-$chunkId"
    }

    initRegex.find(url)?.let {
        val videoId = it.groupValues[1]
        val streamId = it.groupValues[2]
        return "video-$videoId-init-$streamId"
    }
    return url
}

4. Player 1 preloads the first few segments of video N+1 using this setup and stores them in the SimpleCache.

5. When the user scrolls, Player 0 plays video N+1 using the same CacheKeyFactory, expecting cache reuse for the first few segments, and then uses ABR to download the missing segments at the end.

Both players download videos based on

val mediaSource = DashMediaSource.Factory(cacheDataSourceFactory)
                .createMediaSource(mediaItem)
            exoPlayer.setMediaSource(mediaSource)

where mediaItem is based on an URL.

Expected result

Player 0 should detect and use the cached segments (from Player 1), even if they are of a different quality than what the adaptive logic would normally choose.

Playback should begin immediately without needing to redownload those segments in a different quality.

Actual result

Player 0 ignores the cached segments if their quality doesn't match the current ABR selection.

If the current ABR selection is not in the cache, it re-downloads the same segment index but in different quality, making the preloaded segments useless despite identical cache keys.

Media

Big Buck Bunny Dataset: https://ftp.itec.aau.at/datasets/DASHDataset2014/BigBuckBunny/4sec/

Bug Report

• You will email the zip file produced by adb bugreport to android-media-github@google.com after filing this issue.