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This CL queries the driver for the encoding quality range and, if
available and the device is considered "low power" (celeron, pentium
and Core -Y devices), sets it to its maximum value, for highest speed
and lowest power consumption, albeit at lower encoding quality. The
quality difference should not be noticeable for video conference
scenarios.

I followed the code in both of Intel's VA backends.
For the legacy i965:
- VP8 supports values 1-2 [1]. (ENCODER_LOW_QUALITY is 2 so at least
 this CL can supersede the patch in [2] which is what it was set off to
 do).
- AVC1 and VP9 support 1-7 [3,4], ENCODER_QUALITY_RANGE_(AVC,VP9) == 7
 see [5], but this only on Gen9 [6a, 6b] (VP9 encoding is only
 available in Gen9+ FTR).

For the modern intel-media-driver iHD, values are configured with
names, 1 being TARGETUSAGE_BEST_QUALITY ([7] and its following lines).
By default, the TARGETUSAGE_RT_SPEED == 4 is used, and 7 would be
TARGETUSAGE_BEST_SPEED.

Improvements depend on the input content. I measured kohaku with
EncodeAccelPerf.h264_1080p_i420 and when ToT is ~204fps, 4.75W, with
this CL I see ~220 fps, 4.42W.

[1] https://github.com/intel/intel-vaapi-driver/blob/d87db2111a33b157d1913415f15d201cc5182850/src/i965_drv_video.c#L1151
[2] https://source.chromium.org/chromiumos/chromiumos/codesearch/+/master:src/third_party/chromiumos-overlay/x11-libs/libva-intel-driver/files/vp8-encoder-Workaround-to-force-perforamce-mode-enco.patch;l=36
[3] https://github.com/intel/intel-vaapi-driver/blob/d87db2111a33b157d1913415f15d201cc5182850/src/i965_drv_video.c#L1142
[4] https://github.com/intel/intel-vaapi-driver/blob/d87db2111a33b157d1913415f15d201cc5182850/src/i965_drv_video.c#L1149
[5] https://github.com/intel/intel-vaapi-driver/blob/021bcb79d1bd873bbd9fbca55f40320344bab866/src/i965_drv_video.h#L76
[6a] https://github.com/intel/intel-vaapi-driver/blob/021bcb79d1bd873bbd9fbca55f40320344bab866/src/i965_encoder.c#L1599
[6b] https://github.com/intel/intel-vaapi-driver/blob/021bcb79d1bd873bbd9fbca55f40320344bab866/src/i965_encoder.c#L1653
[7] https://github.com/intel/media-driver/blob/105f0341a21324ae3bc458cfa6c25c7df0517f3a/media_driver/agnostic/common/codec/shared/codec_def_common.h#L333

Bug: b:141147405
Change-Id: I7e5c54f1e5a7ac7a51c5503f37168db16f9e99f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2344526
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Reviewed-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Reviewed-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827439}