If this is after resuming from suspend, I think this is a known issue where there is some SteamOS bug leading to the "unsuspend" animation still holding on to stuff even when it's no longer visible.
Try restarting your headset and then playing the video again. If you get the same error, it'd be very helpful if you shared what the codec and overall metadata is, it'd help a lot!
So a quick write up on some of the errors I got:
"reopen Iris decoder: Cannot allocate memory" - the original one, no sleep, video would play, usually happened after about 5ish minutes or seeking too far in
"Iris send packet: cannot allocate memory" - not sure what this one is, I got this while collecting data, and could not replicate it at all
"open native decoder: cannot allocate memory" - this is the error I get after waking from sleep, unsure if its the same one that others get, that you know about already
Video Codec: MPEG-H/HEVC H.265
Bitrate 122209kb/s
Res: 8192x4096
Frame rate: 59.94
Colorspace ITU-R BT.709 Range
Audio Codec: MPEG AAC Audio (mp4a)
Bitrate 320kb/s
Sample rate 48000Hz
Bits per sample: 16
Stereo
Memory usage hovered around 6.2 - 7.5g
GPU usage would fluctuate, but never got above 50%
