Add rc_max_intra_bitrate_pct control

Adds a control to limit the maximum size of a keyframe, as a function of
the per-frame bitrate. See this thread[1] for more detailed discussion:

[1]: http://groups.google.com/a/webmproject.org/group/codec-devel/browse_thread/thread/271b944a5e47ca38

Change-Id: I7337707642eb8041d1e593efc2edfdf66db02a94

vp8/common/onyx.h

diff --git a/vp8/common/onyx.h b/vp8/common/onyx.h
index 426b8fc..c586d0d 100644
--- a/vp8/common/onyx.h
+++ b/vp8/common/onyx.h
@@ -109,6 +109,7 @@
         int noise_sensitivity;   // parameter used for applying pre processing blur: recommendation 0
         int Sharpness;          // parameter used for sharpening output: recommendation 0:
         int cpu_used;
+        unsigned int rc_max_intra_bitrate_pct;
 
         // mode ->
         //(0)=Realtime/Live Encoding. This mode is optimized for realtim encoding (for example, capturing

vp8/encoder/onyx_if.c

diff --git a/vp8/encoder/onyx_if.c b/vp8/encoder/onyx_if.c
index 7461edc..cbaab5f 100644
--- a/vp8/encoder/onyx_if.c
+++ b/vp8/encoder/onyx_if.c
@@ -2704,6 +2704,19 @@
         }
     }
 
+    /* Apply limits on keyframe target.
+     *
+     * TODO: move this after consolidating
+     * vp8_calc_iframe_target_size() and vp8_calc_auto_iframe_target_size()
+     */
+    if (cm->frame_type == KEY_FRAME && cpi->oxcf.rc_max_intra_bitrate_pct)
+    {
+        unsigned int max_rate = cpi->av_per_frame_bandwidth
+                                * cpi->oxcf.rc_max_intra_bitrate_pct / 100;
+
+        if (cpi->this_frame_target > max_rate)
+            cpi->this_frame_target = max_rate;
+    }
     return 1;
 }
 

vp8/vp8_cx_iface.c

diff --git a/vp8/vp8_cx_iface.c b/vp8/vp8_cx_iface.c
index 973265c..17eb6a2 100644
--- a/vp8/vp8_cx_iface.c
+++ b/vp8/vp8_cx_iface.c
@@ -304,6 +304,7 @@
     }
 
     oxcf->target_bandwidth       = cfg.rc_target_bitrate;
+    oxcf->rc_max_intra_bitrate_pct = cfg.rc_max_intra_bitrate_pct;
 
     oxcf->best_allowed_q          = cfg.rc_min_quantizer;
     oxcf->worst_allowed_q         = cfg.rc_max_quantizer;
@@ -1083,7 +1084,7 @@
         {0},                /* rc_twopass_stats_in */
 #endif
         256,                /* rc_target_bandwidth */
-
+        0,                  /* rc_max_intra_bitrate_pct */
         4,                  /* rc_min_quantizer */
         63,                 /* rc_max_quantizer */
         95,                 /* rc_undershoot_pct */