[Libva] Is there a limit on number of parallel encoders?

[Torbjorn tyridal]

I have the following case on a haswell 4770R  (gigabyte brix)

A libva based encoder reads raw 1920x1088 nv12 frames from file on
ramfs. Encoding set to 10 slices, fixed qp (26). cpu governor set to
performance.

if I run two of the above in parallel, each goes along at 230fps, 18%
cpu (top). ie a total of 460 fps/36% cpu
If I then add a third instance the frame rate drops to 72fps (total 216)
and the cpu load jumps to 86 / 198%.

Is there an explanation for the above in libva? 

Decoder scales nicely: 1 * 926 fps, 2 * 626 fps, 3 * 411 fps, 4 * 288
fps, 5 * 229 fps ...


Cheers, T.

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