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Added clipping of the buffer level to maximum_buffer_size

The buffer level was not being capped at the maximum decode
buffer size specified by the user.

In CBR mode this resulted in large files being generated
immediately after a dramatic reduction in the data rate
target. This fix should prevent this from happening.

Change-Id: Iaf01c9fb037cf51515217a5834d6ee4fbb0cb853

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

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

@@ -3490,6 +3490,9 @@

         {

             cpi->decimation_count --;

             cpi->bits_off_target += cpi->av_per_frame_bandwidth;

+            if (cpi->bits_off_target > cpi->oxcf.maximum_buffer_size)

+                cpi->bits_off_target = cpi->oxcf.maximum_buffer_size;

+

             cm->current_video_frame++;

             cpi->frames_since_key++;

@@ -4320,6 +4323,10 @@

         cpi->bits_off_target -= cpi->projected_frame_size;

     else

         cpi->bits_off_target += cpi->av_per_frame_bandwidth - cpi->projected_frame_size;

+

+    // Clip the buffer level to the maximum specified buffer size

+    if (cpi->bits_off_target > cpi->oxcf.maximum_buffer_size)

+        cpi->bits_off_target = cpi->oxcf.maximum_buffer_size;

     // Rolling monitors of whether we are over or underspending used to help regulate min and Max Q in two pass.

     cpi->rolling_target_bits = ((cpi->rolling_target_bits * 3) + cpi->this_frame_target + 2) / 4;

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

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

@@ -1029,6 +1029,8 @@

         {

             // Update the buffer level variable.

             cpi->bits_off_target += cpi->av_per_frame_bandwidth;

+            if (cpi->bits_off_target > cpi->oxcf.maximum_buffer_size)

+                cpi->bits_off_target = cpi->oxcf.maximum_buffer_size;

             cpi->buffer_level = cpi->bits_off_target;

         }

         else

-- 

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