Fix decoder handling of intra-only frames

This patch fixes bug 633:
https://code.google.com/p/webm/issues/detail?id=633

The first decoded frame does not have to be a keyframe,
it could be an inter-frame that is coded intra-only.

This patch fixes the handling of intra-only frames.

A test vector has also been added that encodes 3
intra-only frames at the start of the clip. The
test vector was generated using the code in the
following patch:
https://gerrit.chromium.org/gerrit/#/c/70680/

Change-Id: Ib40b1dbf91aae2bc047e23c626eaef09d1860147

1 files changed, 13 insertions, 4 deletions

diff --git a/vp9/decoder/vp9_decoder.c b/vp9/decoder/vp9_decoder.c
index d154e9d81..6f1f21fc8 100644
--- a/vp9/decoder/vp9_decoder.c
+++ b/vp9/decoder/vp9_decoder.c
@@ -267,7 +267,10 @@ int vp9_receive_compressed_data(VP9Decoder *pbi,
 
   vp9_decode_frame(pbi, source, source + size, psource);
 
-  swap_frame_buffers(pbi);
+  if (!cm->show_existing_frame)
+    swap_frame_buffers(pbi);
+  else
+    cm->frame_to_show = get_frame_new_buffer(cm);
 
   vp9_clear_system_state();
 
@@ -291,6 +294,7 @@ int vp9_receive_compressed_data(VP9Decoder *pbi,
 
 int vp9_get_raw_frame(VP9Decoder *pbi, YV12_BUFFER_CONFIG *sd,
                       vp9_ppflags_t *flags) {
+  VP9_COMMON *const cm = &pbi->common;
   int ret = -1;
 #if !CONFIG_VP9_POSTPROC
   (void)*flags;
@@ -300,15 +304,20 @@ int vp9_get_raw_frame(VP9Decoder *pbi, YV12_BUFFER_CONFIG *sd,
     return ret;
 
   /* no raw frame to show!!! */
-  if (pbi->common.show_frame == 0)
+  if (!cm->show_frame)
     return ret;
 
   pbi->ready_for_new_data = 1;
 
 #if CONFIG_VP9_POSTPROC
-  ret = vp9_post_proc_frame(&pbi->common, sd, flags);
+  if (!cm->show_existing_frame) {
+    ret = vp9_post_proc_frame(cm, sd, flags);
+  } else {
+    *sd = *cm->frame_to_show;
+    ret = 0;
+  }
 #else
-  *sd = *pbi->common.frame_to_show;
+  *sd = *cm->frame_to_show;
   ret = 0;
 #endif /*!CONFIG_POSTPROC*/
   vp9_clear_system_state();