Enabling spatial layers in VP9Impl. Filter layers in the loopback test.

webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc b/webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc
index 64bd5aa25c07249f1c6e96fa4aea3a75fef6d784..b8410a64cdcc602d86cc11ed98133a8db4dc68ea 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc
@@ -578,7 +578,10 @@ bool RtpPacketizerVp9::NextPacket(uint8_t* buffer,
   if (!WriteHeaderAndPayload(packet_info, buffer, bytes_to_send)) {
     return false;
   }
-  *last_packet = packets_.empty();
+  // If SVC used, num_spatial_layers must be populated for each packet.

[sprang_webrtc, 2015/08/13 13:52:07]

This comment is a bit confusing. Do you mean that num_spatial_layers may change
from packet to packet? Or from frame to frame?

[ivica, 2015/08/13 15:20:30]

Yeah, it really is confusing. I removed it, it's clear from the code itself what
is going on.

+  *last_packet = packets_.empty() &&
+                 (hdr_.spatial_idx == kNoSpatialIdx ||
+                  hdr_.spatial_idx == hdr_.num_spatial_layers - 1);
   return true;
 }