Dear Champs,
My customer is testing H.264 CVBR (Constrained variable bitrate). They found the targetBitrate work but the maxBitrate did not work as expected.
Setting: targetBitRate 2.5Mbps, maxBitrateCVBR 5Mbps
Measured: targetBitRate 2.5Mbps, maxBitrateCVBR 3.25Mbps
Actually this issue has been addressed several times in E2E (links below) but no one provided solution.
http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/p/358060/1256807#1256807
http://e2e.ti.com/support/embedded/multimedia_software_codecs/f/356/t/365528
Below please see customer's setup
[H/W] DM368
[S/W] IPNC RDK v5.1, H.264 Encoder v2.3.0.6
[Detail Description]
We are doing some additional testing of the CVBR encoder settings as we are not seeing the bit rate response that we expect to see.
According to several E2E post, maxBitRateCVBR should be at least 1.5 x targetBitRate, so with the following configuration:
pObj->createPrm.bitrate 4000000
pObj->params.maxBitRate 12000000
pObj->dynamicParams_h264.maxBitrateCVBR 5000000
pObj->dynamicParams_h264.CVBRminbitrate 700000
pObj->dynamicParams.targetBitRate 25000000
pObj->params.rateControlPreset 5
pObj->dynamicParams_h264.CVBRsensitivity 8
pObj->dynamicParams_h264.maxHighCmpxIntCVBR 1
pObj->dynamicParams_h264.rcAlgo 3
pObj->dynamicParams_h264.rcQMax 42
pObj->dynamicParams_h264.rcQMin 8
pObj->dynamicParams_h264.rcQMaxI 42
pObj->dynamicParams_h264.rcQMinI 8
We would expect to see bitrate adjustments between 2Mbps and 5Mbps based on scene complexity, however we are only seeing adjustments between 2.5Mbps and 3.25Mbps.
Are there any other parameters that we should be setting differently from the default configuration to achieve the bitrate variations that we expect?
We would also like to verify that there is not a way to achieve a maximum bitrate configuration when we are using Fixed Quality / RCOFF configuration as the camera will crash in a dark scene in this configuration as the bitrate exceeds any reasonable bitrate that the hardware could support.
Best Regards,
Luke Lin
