[Libva] vaEndPicture execution time

[Pierluigi Passaro]

Hi all,
I'm developing a H264 streaming server relying on VA-API.

The machine is an Intel Celeron J1900 running Lubuntu 15.04 (64bit) with 
libva 1.6.0, libva-intel 1.6.0 and gstreamer-vaapi 0.6.0.

I'm using gstreamer-vaapi to get rid of the NAL header management and 
I'm using a reference video available on youtube at the following link:
https://www.youtube.com/watch?v=h9FL_FclLuU

I'm able to sample the video at 1920x1080 at 30fps with a dedicated HW 
providing YUV420 raw images.

The chain works fine encoding in "Constant QP" mode (the actual bitrate 
rises up to 24 Mbps).
The whole frame processing time is around 2.7 ms and the vaEndPicture 
execution time is around 2.6 ms.

However if I encode in "Constant bitrate" mode (let's say 4Mbps), the 
whole frame processing time rises up to 29.3 ms and the vaEndPicture 
execution time rises up to 29.2 ms.

Such a time prevent me to switch at 1920x1080 at 60fps (16.7 ms per frame) 
with constant bitrate.

Is there any tweak or suggestion you could provide?


Thanks
Regards
Pierluigi