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Question asked by vladimir on Dec 29, 2015

Hi. We trying to set CBR mode for VCE H264 encoder but can not figure out how to do this. It seems there no real CBR but some simulation that adjusts quality according with content and trying to keep more less stable average bitrate during some period. It seems our main issue is that period is very long. For example, we set 2.2mbit CBR, and if video initially was black and then we start some video file transcoding with a lot of motion, bitrate can go up form 2.2mbit to 13mbit, and then if we send black again, it can go down to 30kbit. Sometimes it can keep 6mbit instead of 2.2mbit. After some time it seems bitrate more stable but initially it can jump a lot.

You can see this video (bitrate in window title):

We using following settings:

[5376] VCE param log: BPICTURESDELTAQP = 4

[5376] VCE param log: BPICTURESPATTERN = 0

[5376] VCE param log: ENGINE = DX11

[5376] VCE param log: FILLERDATAENABLE = true

[5376] VCE param log: FRAMERATE = 60,1

[5376] VCE param log: GOPSIZE = 119

[5376] VCE param log: IDRPERIOD = 119

[5376] VCE param log: MAXQP = 51

[5376] VCE param log: MINQP = 18

[5376] VCE param log: PEAKBITRATE = 2200000

[5376] VCE param log: PROFILE = 100

[5376] VCE param log: PROFILELEVEL = 41

[5376] VCE param log: QUALITYPRESET = 1

[5376] VCE param log: RATECONTROLMETHOD = 1


[5376] VCE param log: TARGETBITRATE = 2200000

[5376] VCE param log: VBVBUFFERSIZE = 2200000


Can you please help us figure out what we do wrong? Or maybe recommend some settings?