[Fire HD 8 and HD 10 Original Android Development] topher587:
Here's an example of what is logged when trying video playback from Plex:

09-17 23:50:04.140 e: [ExoPlayer][EventLogger] playerFailed [eventTime=22.69, mediaPos=1977.00, window=0, period=0, errorCode=ERROR_CODE_DECODING_FAILED
com.google.android.exoplayer2.q: MediaCodecVideoRenderer error, index=1, format=Format(0, null, null, video/avc, h264, 9258000, null, [1280, 720, 23.976], [-1, -1]), format_supported=YES
at com.google.android.exoplayer2.t1.handleMessage(SourceFile:43)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:223)
at android.os.HandlerThread.run(HandlerThread.java:67)
Caused by: com.google.android.exoplayer2.video.h: Decoder failed: OMX.MTK.VIDEO.DECODER.AVC
at com.google.android.exoplayer2.video.i.m(Unknown Source:4)
at v2.o.render(SourceFile:27)
at com.google.android.exoplayer2.t1.q(SourceFile:14)
at com.google.android.exoplayer2.t1.handleMessage(SourceFile:25)
... 3 more
Caused by: java.lang.IllegalStateException
at android.media.MediaCodec.native_dequeueOutputBuffer(Native Method)
at android.media.MediaCodec.dequeueOutputBuffer(MediaCodec.java:3452)
at v2.x.l(SourceFile:1)
at v2.o.drainOutputBuffer(SourceFile:7)
at v2.o.render(SourceFile:16)
... 5 more
]
09-17 23:50:04.145 e: [Player][ExoPlayer] Playback error detected
09-17 23:50:04.148 i: [Player][Timeline] Handling player error
09-17 23:50:04.149 i: [Player][Timeline] Playback stopped (error: true)
09-17 23:50:04.151 i: [Player][Timeline] Player error not known by server, reporting original player error (or a playback interrupted one)
09-17 23:50:04.152 i: [Player] Error reported: UnknownError (null)
09-17 23:50:04.153 i: [Player][Timeline] Playback stopped (error: false)
09-17 23:50:04.154 e: An exception occurred: com.google.android.exoplayer2.q: MediaCodecVideoRenderer error, index=1, format=Format(0, null, null, video/avc, h264, 9258000, null, [1280, 720, 23.976], [-1, -1]), format_supported=YES
09-17 23:50:04.157 e: Stacktrace: com.google.android.exoplayer2.q: MediaCodecVideoRenderer error, index=1, format=Format(0, null, null, video/avc, h264, 9258000, null, [1280, 720, 23.976], [-1, -1]), format_supported=YES
at com.google.android.exoplayer2.t1.handleMessage(SourceFile:43)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:223)
at android.os.HandlerThread.run(HandlerThread.java:67)
Caused by: com.google.android.exoplayer2.video.h: Decoder failed: OMX.MTK.VIDEO.DECODER.AVC
at com.google.android.exoplayer2.video.i.m(Unknown Source:4)
at v2.o.render(SourceFile:27)
at com.google.android.exoplayer2.t1.q(SourceFile:14)
at com.google.android.exoplayer2.t1.handleMessage(SourceFile:25)
... 3 more
Caused by: java.lang.IllegalStateException
at android.media.MediaCodec.native_dequeueOutputBuffer(Native Method)
at android.media.MediaCodec.dequeueOutputBuffer(MediaCodec.java:3452)
at v2.x.l(SourceFile:1)
at v2.o.drainOutputBuffer(SourceFile:7)
at v2.o.render(SourceFile:16)
... 5 more

However, streaming video outside of android's exoplayer seems to work fine. The same file above which is failing will play successfully when using an external video player like VLC or other streaming content apps with their own players like Jellyfin.

You can use the youtube or youtube vanced app to view youtube content, but the same youtube content played via firefox will fail. Other streaming video sites a web browser also fail. No audio, no video, just an playback error thrown in the player to the user.