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VPU performance in gray scale H.264 encode

Question asked by TETSUO MAEDA on Oct 25, 2016
Latest reply on Feb 8, 2017 by TETSUO MAEDA


We are trying to implement a gray scale H.264 encoder of 1920 x 1080 30fps using VPU.
Video source is a CMOS camera connected to CSI.

First, 30fps color encoding is successful at the following path.
CSI => DRAM => VPU (H.264 encode)


We are using IC (in IPU) to convert YUV to gray scale (U = V = 0) and the path is as follows.

CSI => DRAM => IC (IPU) => DRAM => VPU (H.264 encode)

Our engineer has modified the device driver of IPU to convert the YUV stream to gray scale.


In case of the resolution 1920 x 1080, the encoded frame rate is as low as around 10fps!
But, in case of the resolution 1280 x 720, 30fps encoding is successful. In this case, the resizing procedure in IC is added.

We have not found the reason of the above low frame rate.

Does any one know the reason of the above phenomena?

I'd appreciate any responses.


Best Regards,


Tetsuo Maeda