shithub: libvpx

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vp8: Add extra conditon for overshoot-drop

For drop due to large overshoot feature (in 1 pass CBR):
add additional condition that current prediction error
is larger than that of last encoded frame. This make the
drop due to sudden overshoot more robust, and improves
rate convergence for steady hard content.

Change-Id: If20027d26b4dcd290e4f788ae8e2760d95b536a5

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

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

@@ -3950,6 +3950,7 @@

     if (cpi->pass == 0 && cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER) {

       if (vp8_drop_encodedframe_overshoot(cpi, Q)) return;

+      cpi->last_pred_err_mb = (int)(cpi->mb.prediction_error / cpi->common.MBs);

     }

     cpi->projected_frame_size -= vp8_estimate_entropy_savings(cpi);

--- a/vp8/encoder/onyx_int.h

+++ b/vp8/encoder/onyx_int.h

@@ -510,6 +510,7 @@

   int force_maxqp;

   int frames_since_last_drop_overshoot;

+  int last_pred_err_mb;

   // GF update for 1 pass cbr.

   int gf_update_onepass_cbr;

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

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

@@ -1484,7 +1484,8 @@

     if (cpi->drop_frames_allowed && pred_err_mb > (thresh_pred_err_mb << 4))

       thresh_rate = thresh_rate >> 3;

     if ((Q < thresh_qp && cpi->projected_frame_size > thresh_rate &&

-         pred_err_mb > thresh_pred_err_mb) ||

+         pred_err_mb > thresh_pred_err_mb &&

+         pred_err_mb > 2 * cpi->last_pred_err_mb) ||

         force_drop_overshoot) {

       unsigned int i;

       double new_correction_factor;