shithub: libvpx

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Remove the frame rate factor for key frame size.

When temporal layers is used (i.e., number_of_layers > 1),
we don't use the frame rate boost for setting the key
frame target size. The factor was forcing the target size to be
always at its minimum (2* per_frame_bandwidth) for low frame rates
(i.e., base layer frame rate).

Generally we should modify or remove this frame rate factor;
for now we turn if off for number_of_layers > 1.

Change-Id: Ia5acf406c9b2f634d30ac2473adc7b9bf2e7e6c6

--- a/vp8/encoder/ratectrl.c

+++ b/vp8/encoder/ratectrl.c

@@ -392,10 +392,16 @@

         int Q = (cpi->common.frame_flags & FRAMEFLAGS_KEY)

                 ? cpi->avg_frame_qindex : cpi->ni_av_qi;

-        // Boost depends somewhat on frame rate

-        kf_boost = (int)(2 * cpi->output_frame_rate - 16);

+        // Boost depends somewhat on frame rate: only used for 1 layer case.

+        if (cpi->oxcf.number_of_layers == 1) {

+          kf_boost = (int)(2 * cpi->output_frame_rate - 16);

+        }

+        else {

+          // Initial factor: set target size to: |2.5 * per_frame_bandwidth|.

+          kf_boost = 24;

+        }

-        // adjustment up based on q

+        // adjustment up based on q: this factor ranges from ~1.2 to 2.2.

         kf_boost = kf_boost * kf_boost_qadjustment[Q] / 100;

         // frame separation adjustment ( down)

@@ -403,6 +409,7 @@

             kf_boost = (int)(kf_boost

                        * cpi->frames_since_key / (cpi->output_frame_rate / 2));

+        // Minimal target size is |2* per_frame_bandwidth|.

         if (kf_boost < 16)

             kf_boost = 16;

-- 

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