shithub: libvpx

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vp9-svc: Modify logic for frame dropping with spatial layers.

In the constrained framedrop mode for svc: modify the buffer check
condition relative to (non-zero) dropmark to include uppper spatial layers,
in addition to the current spatial layer.

But keep the single layer check if the buffer goes below zero, since
in this case (buffer underflow) we should force drop of that layer
regardless of upper layers.

Change-Id: Id277f0b4a3ae6275effdd5f5f0c80e3229c17424

--- a/vp9/encoder/vp9_ratectrl.c

+++ b/vp9/encoder/vp9_ratectrl.c

@@ -393,6 +393,29 @@

   rc->baseline_gf_interval = (rc->min_gf_interval + rc->max_gf_interval) / 2;

 }

+static int check_buffer(VP9_COMP *cpi, int drop_mark) {

+  SVC *svc = &cpi->svc;

+  if (!cpi->use_svc || !cpi->svc.framedrop_mode) {

+    RATE_CONTROL *const rc = &cpi->rc;

+    return (rc->buffer_level <= drop_mark);

+  } else {

+    int i;

+    // For SVC in the constrained framedrop mode (svc->framedrop_mode = 1):

+    // the condition on buffer (to drop frame) is checked on current and

+    // upper spatial layers.

+    for (i = svc->spatial_layer_id; i < svc->number_spatial_layers; ++i) {

+      const int layer = LAYER_IDS_TO_IDX(i, svc->temporal_layer_id,

+                                         svc->number_temporal_layers);

+      LAYER_CONTEXT *lc = &svc->layer_context[layer];

+      RATE_CONTROL *lrc = &lc->rc;

+      const int drop_mark_layer =

+          (int)(cpi->svc.framedrop_thresh[i] * lrc->optimal_buffer_level / 100);

+      if (!(lrc->buffer_level <= drop_mark_layer)) return 0;

+    }

+    return 1;

+  }

+}

+

 int vp9_rc_drop_frame(VP9_COMP *cpi) {

   const VP9EncoderConfig *oxcf = &cpi->oxcf;

   RATE_CONTROL *const rc = &cpi->rc;

@@ -413,7 +436,7 @@

           (int)(drop_frames_water_mark * rc->optimal_buffer_level / 100);

       if ((rc->buffer_level > drop_mark) && (rc->decimation_factor > 0)) {

         --rc->decimation_factor;

-      } else if (rc->buffer_level <= drop_mark && rc->decimation_factor == 0) {

+      } else if (check_buffer(cpi, drop_mark) && rc->decimation_factor == 0) {

         rc->decimation_factor = 1;

       }

       if (rc->decimation_factor > 0) {