shithub: libvpx

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vp9-svc: Adjust some logic on gf temporal reference.

For the feature of using second temporal reference (when
inter-layer is off): move the buffer_idx assignement and
refresh flag settings further down to vp9_rc_get_svc_params(),
since is_key_frame is set there for every frame/layer.
Otherwise it was using the setting from the previous frame/layer.

This makes the refresh more consistent for both layers for
2 spatial layers case.

Small/negligible change in metrics.

Change-Id: I88279243bc27898448e8891dba38143d936cf6d5

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

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

@@ -1873,27 +1873,42 @@

     }

   }

   // If long term termporal feature is enabled, set the period of the update.

-  // The update/refresh of this reference frame  is always on base temporal

+  // The update/refresh of this reference frame is always on base temporal

   // layer frame.

-  if (svc->use_gf_temporal_ref_current_layer && svc->temporal_layer_id == 0) {

-    if (svc->layer_context[svc->temporal_layer_id].is_key_frame) {

-      // On key frame we update the buffer index used for long term reference.

-      // Use the alt_ref since it is not used or updated on key frames.

+  if (svc->use_gf_temporal_ref_current_layer) {

+    // Only use gf long-term prediction on non-key superframes.

+    if (!svc->layer_context[svc->temporal_layer_id].is_key_frame) {

+      // Use golden for this reference, which will be used for prediction.

       int index = svc->spatial_layer_id;

-      cpi->ext_refresh_alt_ref_frame = 1;

       if (svc->number_spatial_layers == 3) index = svc->spatial_layer_id - 1;

       assert(index >= 0);

-      cpi->alt_fb_idx = svc->buffer_gf_temporal_ref[index].idx;

-    } else if (rc->frames_till_gf_update_due == 0) {

-      // Set perdiod of next update. Make it a multiple of 10, as the cyclic

-      // refresh is typically ~10%, and we'd like the update to happen after

-      // a few cylces of the refresh (so it better quality frame). Note the

-      // cyclic refresh for SVC only operates on base temporal layer frames.

-      // Choose 20 as perdiod for now (2 cycles).

-      rc->baseline_gf_interval = 20;

-      rc->frames_till_gf_update_due = rc->baseline_gf_interval;

-      cpi->ext_refresh_golden_frame = 1;

-      rc->gfu_boost = DEFAULT_GF_BOOST;

+      cpi->gld_fb_idx = svc->buffer_gf_temporal_ref[index].idx;

+      // Enable prediction off LAST (last reference) and golden (which will

+      // generally be further behind/long-term reference).

+      cpi->ref_frame_flags = VP9_LAST_FLAG | VP9_GOLD_FLAG;

+    }

+    // Check for update/refresh of reference: only refresh on base temporal

+    // layer.

+    if (svc->temporal_layer_id == 0) {

+      if (svc->layer_context[svc->temporal_layer_id].is_key_frame) {

+        // On key frame we update the buffer index used for long term reference.

+        // Use the alt_ref since it is not used or updated on key frames.

+        int index = svc->spatial_layer_id;

+        if (svc->number_spatial_layers == 3) index = svc->spatial_layer_id - 1;

+        assert(index >= 0);

+        cpi->alt_fb_idx = svc->buffer_gf_temporal_ref[index].idx;

+        cpi->ext_refresh_alt_ref_frame = 1;

+      } else if (rc->frames_till_gf_update_due == 0) {

+        // Set perdiod of next update. Make it a multiple of 10, as the cyclic

+        // refresh is typically ~10%, and we'd like the update to happen after

+        // a few cylces of the refresh (so it better quality frame). Note the

+        // cyclic refresh for SVC only operates on base temporal layer frames.

+        // Choose 20 as perdiod for now (2 cycles).

+        rc->baseline_gf_interval = 20;

+        rc->frames_till_gf_update_due = rc->baseline_gf_interval;

+        cpi->ext_refresh_golden_frame = 1;

+        rc->gfu_boost = DEFAULT_GF_BOOST;

+      }

     }

   } else if (!svc->use_gf_temporal_ref) {

     rc->frames_till_gf_update_due = INT_MAX;

--- a/vp9/encoder/vp9_svc_layercontext.c

+++ b/vp9/encoder/vp9_svc_layercontext.c

@@ -744,16 +744,6 @@

       svc->spatial_layer_id >= svc->number_spatial_layers - 2) {

     // Enable the second (long-term) temporal reference at the frame-level.

     svc->use_gf_temporal_ref_current_layer = 1;

-    // Only used for prediction for on non-key superframes.

-    if (!svc->layer_context[svc->temporal_layer_id].is_key_frame) {

-      // Use golden for this reference which will be used for prediction.

-      int index = svc->spatial_layer_id;

-      if (svc->number_spatial_layers == 3) index = svc->spatial_layer_id - 1;

-      cpi->gld_fb_idx = svc->buffer_gf_temporal_ref[index].idx;

-      // Enable prediction off LAST (last reference) and golden (which will

-      // generally be further behind/long-term reference).

-      cpi->ref_frame_flags = VP9_LAST_FLAG | VP9_GOLD_FLAG;

-    }

   }

   // Reset the drop flags for all spatial layers, on the base layer.