h264_qsv internal bug message on valid h264 video file

[jorgev]

Summary of the bug:

I've come across a video file which hits a decode error that looks like the following:

[h264_qsv @ 0x561849930140] Error during QSV decoding.: undefined behavior (-16)
Error while decoding stream #0:0: Internal bug, should not have happened

This error does not occur when decoding with libx264 and seems specific to running ffmpeg with -hwaccel qsv. Running ffmpeg with -c:v h264_qsv specified instead of hwaccel completes successuflly both when compiled with libmfx and libvpl.

How to reproduce:

Download the badfile-shorter.mp4 file and run ffmpeg (built with --enable-libmfx) like so:

% ffmpeg -report -loglevel debug -hwaccel qsv -i badfile-shorter.mp4 -f null -
...
[h264_qsv @ 0x55b72b9d4a40] Error during QSV decoding.: undefined behavior (-16)
Error while decoding stream #0:0: Internal bug, should not have happened
...

I've attached a full log of the ffmpeg output for this error, which unfortunately doesn't look very helpful.

Some additional pertinent details are:

Hardware:

Intel NUC 11
​https://www.intel.com/content/www/us/en/products/sku/205593/intel-nuc-11-pro-kit-nuc11tnki3/specifications.html

OS:

Ubuntu 20.04 with linux-oem installed as well as the driver packages provided by intel here:
​https://dgpu-docs.intel.com/installation-guides/ubuntu/ubuntu-focal.html

[Carl Eugen Hoyos]

Please reopen this ticket if you can provide an input sample that allows to reproduce the issue.

[jorgev]

I've added a sample file which reproduces the issue for me

[wenbin,chen]

Hi Jorge.
I can reproduce your problem. And I found the cause is that you are using a guide for Arc GPU.
You can try this guide ​https://dgpu-docs.intel.com/installation-guides/ubuntu/ubuntu-focal-legacy.html. After I switch to this guide, the problem is unseen.

[jorgev]

Ah thanks so much! Looks like user-error on my part, that incorrect driver seems to *mostly* work and I didn't see any indication on the guide that it was hardware-specific. Switching to the driver installation guide in the comments eliminates the bug for me.