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Limit size of initial keyframe in one-pass.

Rather than using a default size of 1/2 or 3/2 seconds for the first
frame, use a fraction of the initial buffer level to give the
application some control.

This will likely undergo further refinement as size limits on key
frames are currently under discussion on codec-devel@, but this gives
much better behavior for small buffer sizes as a starting point.

Change-Id: Ieba55b86517b81e51e6f0a9fe27aabba295acab0

--- a/vp8/encoder/onyx_if.c

+++ b/vp8/encoder/onyx_if.c

@@ -1459,10 +1459,6 @@

     cpi->avg_frame_qindex             = cpi->oxcf.worst_allowed_q;

     // Initialise the starting buffer levels

-    cpi->oxcf.starting_buffer_level =

-        rescale(cpi->oxcf.starting_buffer_level,

-                cpi->oxcf.target_bandwidth, 1000);

-

     cpi->buffer_level                 = cpi->oxcf.starting_buffer_level;

     cpi->bits_off_target              = cpi->oxcf.starting_buffer_level;

@@ -1635,6 +1631,10 @@

     // Convert target bandwidth from Kbit/s to Bit/s

     cpi->oxcf.target_bandwidth       *= 1000;

+    cpi->oxcf.starting_buffer_level =

+        rescale(cpi->oxcf.starting_buffer_level,

+                cpi->oxcf.target_bandwidth, 1000);

+

     // Set or reset optimal and maximum buffer levels.

     if (cpi->oxcf.optimal_buffer_level == 0)

         cpi->oxcf.optimal_buffer_level = cpi->oxcf.target_bandwidth / 8;

@@ -2661,16 +2661,17 @@

         if (cpi->pass == 2)

             vp8_calc_auto_iframe_target_size(cpi);

-        // 1 Pass there is no information on which to base size so use bandwidth per second * fixed fraction

         else

 #endif

-            cpi->this_frame_target = cpi->oxcf.target_bandwidth / 2;

-

-        // in error resilient mode the first frame is bigger since it likely contains

-        // all the static background

-        if (cpi->oxcf.error_resilient_mode == 1 || (cpi->compressor_speed == 2))

         {

-            cpi->this_frame_target *= 3;      // 5;

+            /* 1 Pass there is no information on which to base size so use

+             * bandwidth per second * fraction of the initial buffer

+             * level

+             */

+            cpi->this_frame_target = cpi->oxcf.starting_buffer_level / 2;

+

+            if(cpi->this_frame_target > cpi->oxcf.target_bandwidth * 3 / 2)

+                cpi->this_frame_target = cpi->oxcf.target_bandwidth * 3 / 2;

         }

         // Key frame from VFW/auto-keyframe/first frame

-- 

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