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Zurab_T_1
Beginner
68 Views

mfx encoder strange behavior bitrate is upto 200mbps.

I am encoding raw yuv420 to avc 8mbps, but the result8ng videos bitrate is in range 20mbps to 200mbps. here is set5ings which I am using. 1280x720x50p nv12 yuv420 aspectratio=1÷1 use va-drm for memory allocation. asyncdepth=4. targetusage=best_speed, but changing this parameter to best_quality gives no changes. use vbr targetkbps=8000 cropx=cropy=0 cropw and croph are both aligned. gopsize=12 goprefdist=1 all other parameters are set to zero. can someone tell me what to check? the same va api implementation works fine when i use it in my transcoder.
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5 Replies
Zurab_T_1
Beginner
68 Views

Is there anybody? I really need help.
Zurab_T_1
Beginner
68 Views

It was my problem. I set framerate 50/1 instead of 1/50, but it is very interesting why this affect on the bitrate.

Surbhi_M_Intel
Employee
68 Views

Hi Zurab, 

Apologies for late response. Were you using sample - sample_encode to do so? Generally when bitrate(in Kbps) is less than 0 or not mentioned then it is passed through the function of Calculatedefaultbitrate() which consider height width and framerate to calculate frame rate. Check sample_utils.cpp in sample_encode for more details.  

    mfxF64 at = nWidth * nHeight * dFrameRate / 30.0;

    if (!at)
        return 0;

    switch (nTargetUsage)
    {
    case MFX_TARGETUSAGE_BEST_QUALITY :
        {
            bitrate = (&fnc)->at(at);
            break;
        }
    case MFX_TARGETUSAGE_BEST_SPEED :
        {
            bitrate = (&fnc)->at(at) * 0.5;
            break;
        }
    case MFX_TARGETUSAGE_BALANCED :
    default:
        {
            bitrate = (&fnc)->at(at) * 0.75;
            break;
        }
    }

    return (mfxU16)bitrate;
}

If I didn't get your question right, can you please provide us the reproduces and input in which you are seeing the issue, will be happy to debug. 

Thanks,
Surbhi

Zurab_T_1
Beginner
68 Views

I already solved the problem..

It was my mistake, but I will try describe the situation more detailed.

I was set targetkbps to 8000, targetusage to speed also I set ratecontrol to vbr, but the framerate I set not correctyl, except 1/50 it was 50/1.

and the resulting bitstream was very bad quality and the bitrate was up to 200mbps. by changing framerate to correct value it was fixed.

 

Thanx for the answer.

 

Surbhi_M_Intel
Employee
68 Views

I am glad you got it resolved! thanks for updating the post :)

-Surbhi

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