MB Qp is discordant with slice Qp avg

[shan__quanyuan]

Hello,

I'm using mfxExtBRC, and encountering a problem that outputted H264 raw stream's MB Qp is discordant with slice Qp avg. For example, all MB Qp are 38, but slice Qp avg may be 37/36/35/34/33...... Or,  just the opposite. slice Qp avg is always equal to the return of GetFrameCtrl, but outputted MB Qp cannot match it as predescribed. 

system info：

windows 10 professional 1803 17134.950

Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz 3.19 GHz

 Microsoft Visual Studio professional 2015 14.0.25431.01 update 3

Intel(R) UHD Graphics 630 23.20.16.5018

Intel media sdk version[1.26 65562]

Thanks, and looking forward to your reply.

Regards,

Quanyuan

[Mark_L_Intel1]

Hi Quanyuan,

Sorry for the late response,

Are you using your own application or our sample?

If you are using your own sample, you should first check if CBR is turned off.

In our sample_multi_transcode, you can check to see if MB QP works, by enabled MB QP in ExtCBR, you apply "-extmbqp", then you should see the QP in the output stream with the following repeated pattern in the 16x16 blocks: 1, 2, ...51

The code is enabled here:

https://github.com/Intel-Media-SDK/MediaSDK/blob/master/samples/sample_multi_transcode/src/transcode_utils.cpp#L296

and implemented here:

https://github.com/Intel-Media-SDK/MediaSDK/blob/master/samples/sample_multi_transcode/src/pipeline_transcode.cpp#L1497

At the command line you should do:

sample_multi_transcode -i::h264 xxx -o:h264 xxx -extmpqp

Let me know if this works for you and solves your problem.

Mark