[Bug]: Intel Quick Sync HEVC Encoding Labels P Frames as B Frames

[quamt]

Which component impacted?

No response

Is it regression? Good in old configuration?

No, this issue exist a long time

What happened?

Description
When using Intel Quick Sync to encode HEVC video, P frames are incorrectly labelled as B.
This behaviour persists across various configurations and significantly impacts the expected frame type structure in the encoded video.
It appears that Low Delay B-frames (LDB) or Generalized P/B (GPB) frames are used instead of traditional P frames.

Steps to Reproduce
Use Intel Quick Sync to encode a video to HEVC format.
Inspect the frame types in the encoded video using tools like "ffprobe".
Observe that P frames are labelled as B frames, even when the encoding configuration is set to produce P frames.
Expected Behavior
P frames should be correctly labelled as P frames in the encoded HEVC video.

Actual Behavior
P frames are labelled as B frames, which can cause confusion and potential issues with playback and editing software that relies on correct frame type identification.

Environment
CPU: Intel Core i7-1065G7 @ 1.30GHz [TB: 3.49GHz] (4C/8T)
GPU: Intel Iris(R) Plus Graphics (64EU) 300-1100MHz [15W] (31.0.101.2127)
Operating System: Windows 11 x64 (22631) [UTF-8]
Driver Version: 31.0.101.2127
Media SDK: QuickSyncVideo API v1.35

2nd environment
CPU Info 13th Gen Intel Core i5-13600 [4.71GHz] (6P+8E,14C/20T)
GPU Info Intel UHD Graphics 770 (32EU) 300-1550MHz [65W] (31.0.101.5186)
OS Windows 11 x64 (22631) [UTF-8]
Media SDK QuickSyncVideo API v2.10

Additional Information
This behaviour has been observed consistently across different videos and configurations.
The issue explicitly affects iGPUs.
The iGPU supports the NO GPB setting, but it is not honoured when activated.

What's the usage scenario when you are seeing the problem?

Video Analytics

What impacted?

No response

Debug Information

No response

Do you want to contribute a patch to fix the issue?

No.

[intel-mediadev]

Auto Created VSMGWL-74557 for further analysis.

[OttoYang]

Hi @quamt ,
As far as I know, these platforms for iGPU do not support p-frame encoding on HEVC until MTL.

[quamt]

Hi @OttoYang

To clarify MLT - Meteor Lake.
Will iGPUs before MLT write Low Delay B-frames (LDB) or Generalized P/B (GPB) frames instead of the P-frames?