shithub: libvpx

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Delay decreasing reference count in frame-parallel decoding.

The current decoding scheme will decrease the reference count
of the output frame when finish decoding. Then the application
could copy the frame from the decoder buffer to application buffer.
In frame-parallel decoding, a decoded frame will not be outputted
until several frames later which depends on thread numbers. So
the decoded frame's reference count should be decreased only
after application finish copying the frame out. But due to the
limitation of vpx_codec_get_frame, decoder could not know when
application finish decoding. So use a index last_show_frame to
release the last output frame's reference count.

Change-Id: I403ee0d01148ac1182e5a2d87cf7dcc302b51e63

--- a/vp9/decoder/vp9_decoder.c

+++ b/vp9/decoder/vp9_decoder.c

@@ -211,8 +211,11 @@

   }

   cm->frame_to_show = get_frame_new_buffer(cm);

-  cm->frame_bufs[cm->new_fb_idx].ref_count--;

+  if (!pbi->frame_parallel_decode || !cm->show_frame) {

+    --cm->frame_bufs[cm->new_fb_idx].ref_count;

+  }

+

   // Invalidate these references until the next frame starts.

   for (ref_index = 0; ref_index < 3; ref_index++)

     cm->frame_refs[ref_index].idx = INT_MAX;

@@ -240,7 +243,9 @@

   }

   // Check if the previous frame was a frame without any references to it.

-  if (cm->new_fb_idx >= 0 && cm->frame_bufs[cm->new_fb_idx].ref_count == 0)

+  // Release frame buffer if not decoding in frame parallel mode.

+  if (!pbi->frame_parallel_decode && cm->new_fb_idx >= 0 &&

+         cm->frame_bufs[cm->new_fb_idx].ref_count == 0)

     cm->release_fb_cb(cm->cb_priv,

                       &cm->frame_bufs[cm->new_fb_idx].raw_frame_buffer);

   cm->new_fb_idx = get_free_fb(cm);

--- a/vp9/vp9_dx_iface.c

+++ b/vp9/vp9_dx_iface.c

@@ -40,6 +40,7 @@

   vpx_image_t             img;

   int                     invert_tile_order;

   int                     frame_parallel_decode;  // frame-based threading.

+  int                     last_show_frame;  // Index of last output frame.

   // External frame buffer info to save for VP9 common.

   void *ext_priv;  // Private data associated with the external frame buffers.

@@ -238,6 +239,7 @@

   ctx->pbi->max_threads = ctx->cfg.threads;

   ctx->pbi->inv_tile_order = ctx->invert_tile_order;

   ctx->pbi->frame_parallel_decode = ctx->frame_parallel_decode;

+  ctx->last_show_frame = -1;

   // If postprocessing was enabled by the application and a

   // configuration has not been provided, default it.

@@ -430,6 +432,15 @@

       ctx->img.fb_priv = cm->frame_bufs[cm->new_fb_idx].raw_frame_buffer.priv;

       img = &ctx->img;

       *iter = img;

+      // Decrease reference count of last output frame in frame parallel mode.

+      if (ctx->frame_parallel_decode && ctx->last_show_frame >= 0) {

+        --cm->frame_bufs[ctx->last_show_frame].ref_count;

+        if (cm->frame_bufs[ctx->last_show_frame].ref_count == 0) {

+          cm->release_fb_cb(cm->cb_priv,

+              &cm->frame_bufs[ctx->last_show_frame].raw_frame_buffer);

+        }

+      }

+      ctx->last_show_frame = ctx->pbi->common.new_fb_idx;

     }

   }