Playback failing on iPad without a transcode attempt

[flashls82 7]

When a user in my house tries to play a 4K file on a slightly older iPad, he gets a "no compatible streams available" error. This is on a file that plays fine on several other devices (a newer iPad, a new-ish iPhone, and a Roku TV). I also tried forcing transcoding on one of those devices just to make sure there wasn't some issue going on sever side there; it worked fine. The user has full access to all transcoding/remuxing. Why is the iOS client bailing out of the playback attempt entirely rather than trying to transcode to a compatible format? This happens even if I set the local streaming quality to something low enough to force a transcode from the start. Log of one playback attempt attached, relevant things I'm seeing:

• Bitrate exceeds DirectPlay/DirectStream limit fires (23,334,642 vs the 10,000,001 cap) — seems reasonable for this device, and I would think the trigger for transcoding.
• The very next PlaybackInfo call includes EnableDirectPlay=false&EnableDirectStream=false — the client asking for a transcode profile — and gets a 200 back.
• Then the client immediately calls ActiveEncodings/Delete and reports Sessions/Playing/Stopped at position 0 — no stream request, no ffmpeg process ever spawned, no ffmpeg log from the attempt.

 

ipad playback error.txt

[Luke 42814]

Hi, what version of iOS does it run?