Excessive processor use decoding HEVC on iPhone X since v3.1.0

[Eversor]

Since version 3.1.0, the iPhone X has been heating up considerably when playing back HEVC videos - to the point of the device automatically dimming the screen in an attempt to reduce the power output.
This was definitely not an issue before 3.1.0, and seems to be related to the "Stability and performance improvements when decoding H.264/H.265 in hardware" line in the release notes for it. Can this please be reviewed? Many thanks!

[InTheWings]

Seems your video fallsback to software decoding

[retrojunkie]

Are you able to reproduce this with different HEVC videos (maybe from different sources)? If your video playback falls back to software encoding, then the CPU of your phone needs to do all the heavy work for encoding the video, which would explain the heat up.

Also, did you check if this happens with 3.1.1 too? I have no issues with HEVC videos on the recent version (but I don't have an iPhone X).

[InTheWings]

There was some fixes because Apple hw decoder is really "stable" under some circumstances (files that are not produced by Apple devices, bbecause they don't care, you're not supposed to use something out of their ecosystem...)
If you have a way to share file, that could help, but you probably hit the exception.

[Eversor]

Think I've found the cause of this; after a patch, the setting in Video->Deinterlace was blank (unset). When I changed this to Off, the phone stopped overheating while playing the videos. It must have read the blank value as 'Automatic', which translated to 'On' in my case. Maybe worth updating in the next Apple Store patch so that this value defaults to 'Off' if it is unset? iOS 11.4.1 btw