Intra only encoder with MFX_RATECONTROL_VBR with lowpower:ON results in inaccurate bitrate (flat QP)

[kmawassi]

With lowpower mode is ON, and GopPicSize is 1, The VBR Target BitRate control method (MFX_RATECONTROL_VBR) results in very inaccurate file size and doesn't converge.

Repro command line:
sample_encode h265 -hw -nv12 -lowpower:on -f 30 -perf_opt 32 -n 512 -w 1920 -h 1080 -b 30000 -g 1 -r 1 -i crowdrun_NV12_1080p.yuv -o output.h265

When investigating the output h265, we observe that the Quantization Parameter for each picture is almost flat and is not modified to converge the file-size toward the target bitrate.

The obtained HEVC file looks to have a QP that is almost flat.

CPU model: 12th Gen Intel(R) Core(TM) i5-1235U (also reproduced on 13th Gen Inte(R) Core(TM) i5-1335u)
OS: Ubuntu 22.04 LTS
Kernel: 6.1.32-060132-generic
OneVPL runtime 2022Q3: 22.5.4

[SreedeviK_Intel]

Hi,

Thanks for posting in Intel communities.

This is a duplicate thread of https://community.intel.com/t5/forums/forumtopicpage/board-id/media-products/message-id/15153#M15153 

Hence we are closing this thread. Your issue would be addressed in the other thread mentioned .

Regards,

Sreedevi

[kmawassi]

Hi,
The duplicate thread link points to this same issue. Can you provide me the correct link please ?

Thanks,

[DiyaN_Intel]

Hi, 

Thank you for posting in Intel Communities.

Sorry for the inconvenience.

There was some technical issues from our end and we are working on the fix.

In the meantime could you please share the tool name / tool through which you got that quantized graph which will help us to investigate further?

Regards,

Diya

[kmawassi]

Hi,
I was using an evaluation version of the Elecard StreamEye tool.
Also, we can compute the file average bitrate to see that it is far from the specified target bitrate.
AvgBitrate (bits/s) = (FileSize_Bytes x 8 bits / Byte) / StreamDuration_Sec = FileSize_Bits / (NbFrames / FramesPerSec) = FileSize_Bits * FramesPerSec / NbFrames

Thanks,
Khalil

[DiyaN_Intel]

Hi,

Thanks for providing the valuable input.

We are working on this internally and get back to you with an update soon.

Thanks,

Diya Nandy