I can't reproduce this (it happens seemingly at random), but sometimes there are problems with the HEVC decoder and it just refuses to work, it requires a reboot. This might have been introduced recently, but I can't be sure. I managed to play a h264 video in this state and that worked well.
I have the kernel logs for this:
$this->bbcode_second_pass_code('', '
Dec 21 23:11:35 kodi kernel: rpivid feb10000.codec: rpivid_h265_start: (1920x1040)
Dec 21 23:11:35 kodi kernel: VideoPlayer: page allocation failure: order:4, mode:0x40cc0(GFP_KERNEL|__GFP_COMP), nodemask=(null),cpuset=/,mems_allowed=0
Dec 21 23:11:35 kodi kernel: CPU: 2 PID: 1814 Comm: VideoPlayer Tainted: G C 5.10.83-1-rpi-ARCH #1
Dec 21 23:11:35 kodi kernel: Hardware name: BCM2711
Dec 21 23:11:35 kodi kernel: [<c020f0d8>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
Dec 21 23:11:35 kodi kernel: [<c020ae58>] (show_stack) from [<c0e0a18c>] (dump_stack+0xa4/0xc4)
Dec 21 23:11:35 kodi kernel: [<c0e0a18c>] (dump_stack) from [<c03f91e0>] (warn_alloc+0xe0/0x170)
Dec 21 23:11:35 kodi kernel: [<c03f91e0>] (warn_alloc) from [<c03fa338>] (__alloc_pages_nodemask+0x10c8/0x1164)
Dec 21 23:11:35 kodi kernel: [<c03fa338>] (__alloc_pages_nodemask) from [<c03cd88c>] (kmalloc_order+0x34/0xf0)
Dec 21 23:11:35 kodi kernel: [<c03cd88c>] (kmalloc_order) from [<c03cd964>] (kmalloc_order_trace+0x1c/0xcc)
Dec 21 23:11:35 kodi kernel: [<c03cd964>] (kmalloc_order_trace) from [<bf6664f4>] (rpivid_h265_start+0x134/0xc40 [rpivid_hevc])
Dec 21 23:11:35 kodi kernel: [<bf6664f4>] (rpivid_h265_start [rpivid_hevc]) from [<bf661ae0>] (rpivid_start_streaming+0x88/0x1a8 [rpivid_hevc])
Dec 21 23:11:35 kodi kernel: [<bf661ae0>] (rpivid_start_streaming [rpivid_hevc]) from [<bf3eda08>] (vb2_start_streaming+0x5c/0x16c [videobuf2_common])
Dec 21 23:11:35 kodi kernel: [<bf3eda08>] (vb2_start_streaming [videobuf2_common]) from [<bf3edb98>] (vb2_core_streamon+0x80/0x170 [videobuf2_common])
Dec 21 23:11:35 kodi kernel: [<bf3edb98>] (vb2_core_streamon [videobuf2_common]) from [<bf219f10>] (v4l2_m2m_ioctl_streamon+0x20/0x50 [v4l2_mem2mem])
Dec 21 23:11:35 kodi kernel: [<bf219f10>] (v4l2_m2m_ioctl_streamon [v4l2_mem2mem]) from [<bf26f518>] (__video_do_ioctl+0x238/0x490 [videodev])
Dec 21 23:11:35 kodi kernel: [<bf26f518>] (__video_do_ioctl [videodev]) from [<bf27040c>] (video_usercopy+0x184/0x5d8 [videodev])
Dec 21 23:11:35 kodi kernel: [<bf27040c>] (video_usercopy [videodev]) from [<c044b564>] (sys_ioctl+0x34c/0x904)
Dec 21 23:11:35 kodi kernel: [<c044b564>] (sys_ioctl) from [<c0200214>] (__sys_trace_return+0x0/0x2c)
Dec 21 23:11:35 kodi kernel: Exception stack(0xc16c1fa8 to 0xc16c1ff0)
Dec 21 23:11:35 kodi kernel: 1fa0: af2b7f78 00000000 00000034 40045612 7c4047b8 0000000a
Dec 21 23:11:35 kodi kernel: 1fc0: af2b7f78 00000000 7c4047b8 00000036 02e0a234 af247db8 02e0a20c 9ea16970
Dec 21 23:11:35 kodi kernel: 1fe0: 02e8e048 7c4047ac 025c8998 b5a579fc
Dec 21 23:11:35 kodi kernel: Mem-Info:
Dec 21 23:11:35 kodi kernel: active_anon:161 inactive_anon:65585 isolated_anon:0
active_file:15174 inactive_file:44334 isolated_file:0
unevictable:26610 dirty:1 writeback:0
slab_reclaimable:4112 slab_unreclaimable:8563
mapped:56528 shmem:26783 pagetables:678 bounce:0
free:1836118 free_pcp:371 free_cma:116703
Dec 21 23:11:35 kodi kernel: Node 0 active_anon:644kB inactive_anon:262340kB active_file:60696kB inactive_file:177680kB unevictable:106440kB isolated(anon):0kB isolated(file):0>
Dec 21 23:11:35 kodi kernel: DMA free:478940kB min:7228kB low:8008kB high:8788kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:21128kB inactive_file:780>
Dec 21 23:11:35 kodi kernel: lowmem_reserve[]: 0 0 7284 7284
Dec 21 23:11:35 kodi kernel: HighMem free:6865028kB min:512kB low:10016kB high:19520kB reserved_highatomic:0KB active_anon:644kB inactive_anon:262340kB active_file:39764kB inac>
Dec 21 23:11:35 kodi kernel: lowmem_reserve[]: 0 0 0 0
Dec 21 23:11:35 kodi kernel: DMA: 1268*4kB (UEC) 493*8kB (UME) 180*16kB (UEC) 12*32kB (UE) 1*64kB (E) 0*128kB 1*256kB (C) 1*512kB (C) 1*1024kB (C) 1*2048kB (C) 113*4096kB (C) =>
Dec 21 23:11:35 kodi kernel: HighMem: 3049*4kB (UM) 1745*8kB (UM) 1425*16kB (UM) 552*32kB (UM) 161*64kB (UM) 142*128kB (UM) 115*256kB (UM) 76*512kB (UM) 31*1024kB (UM) 17*2048k>
Dec 21 23:11:35 kodi kernel: Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
Dec 21 23:11:35 kodi kernel: 86333 total pagecache pages
Dec 21 23:11:35 kodi kernel: 0 pages in swap cache
Dec 21 23:11:35 kodi kernel: Swap cache stats: add 0, delete 0, find 0/0
Dec 21 23:11:35 kodi kernel: Free swap = 0kB
Dec 21 23:11:35 kodi kernel: Total swap = 0kB
Dec 21 23:11:35 kodi kernel: 2061312 pages RAM
Dec 21 23:11:35 kodi kernel: 1864704 pages HighMem/MovableOnly
Dec 21 23:11:35 kodi kernel: 40913 pages reservedfree
Dec 21 23:11:35 kodi kernel: 131072 pages cma reserved
Dec 21 23:11:35 kodi kernel: rpivid feb10000.codec: Failed to allocate decode envs
Dec 21 23:11:35 kodi kernel: rpivid feb10000.codec: rpivid_start_streaming: qtype=10: FAIL
')
A few seconds later I tried again and got basically the same logs. After rebooting, it works, with some minor warnings:
$this->bbcode_second_pass_code('', '
Dec 21 23:14:49 kodi kernel: rpivid feb10000.codec: rpivid_h265_start: (1920x1040)
Dec 21 23:14:49 kodi kernel: rpivid feb10000.codec: SPS changed
Dec 21 23:14:49 kodi kernel: rpivid feb10000.codec: PPS changed
Dec 21 23:45:03 kodi kernel: rpivid feb10000.codec: Missing DPB ent 0, timestamp=0, index=-1
Dec 21 23:45:03 kodi kernel: rpivid feb10000.codec: Missing DPB ent 1, timestamp=0, index=-1
Dec 21 23:45:03 kodi kernel: rpivid feb10000.codec: Missing DPB ent 2, timestamp=0, index=-1
Dec 21 23:45:03 kodi kernel: rpivid feb10000.codec: Missing DPB ent 3, timestamp=0, index=-1
')
As I said, I can't really reproduce this. Not sure if this is lack of RAM, I had just refreshed Kodi's database a few minutes before.
I'm running all vanilla packages from the repos.
$this->bbcode_second_pass_code('', '
$ cat /boot/config.txt
# See /boot/overlays/README for all available options
dtoverlay=vc4-kms-v3d
initramfs initramfs-linux.img followkernel
[pi4]
# Run as fast as firmware / board allows
arm_boost=1
[all]
include kodi.config.txt
$ uname -a
Linux kodi 5.10.83-1-rpi-ARCH #1 SMP Tue Dec 7 15:22:25 UTC 2021 armv7l GNU/Linux
')