Add picture ID support in RtcVideoEncoder.

When Forward Error Correction (FEC) packets arrive, jitter buffer
will consider them missing. The jitter buffer needs to use the
picture ID to see if a new frame is continuous to the previous
frame. Without picture ID, the jitter buffer will not determine
any frame decodable after FEC. Video will hang until the jitter 
buffer drops all packets and requests a key frame.

BUG=347477
TEST=Run apprtc.appspot.com between Linux and CrOS.
Run apprtc.appspot.com loopback on CrOS.

Review URL: https://codereview.chromium.org/216793002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260269 0039d316-1c4b-4281-b951-d872f2087c98

content/renderer/media/rtc_video_encoder.cc

@@ -10,6 +10,7 @@
 #include "base/memory/scoped_vector.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/metrics/histogram.h"
+#include "base/rand_util.h"
 #include "base/synchronization/waitable_event.h"
 #include "media/base/bitstream_buffer.h"
 #include "media/base/video_frame.h"
@@ -152,6 +153,9 @@ class RTCVideoEncoder::Impl
   // encoder.
   int output_buffers_free_count_;
 
+  // 15 bits running index of the VP8 frames. See VP8 RTP spec for details.
+  uint16 picture_id_;
+
   DISALLOW_COPY_AND_ASSIGN(Impl);
 };
 
@@ -167,6 +171,8 @@ RTCVideoEncoder::Impl::Impl(
       input_next_frame_keyframe_(false),
       output_buffers_free_count_(0) {
   thread_checker_.DetachFromThread();
+  // Picture ID should start on a random number.
+  picture_id_ = static_cast<uint16_t>(base::RandInt(0, 0x7FFF));
 }
 
 void RTCVideoEncoder::Impl::CreateAndInitializeVEA(
@@ -378,7 +384,10 @@ void RTCVideoEncoder::Impl::BitstreamBufferReady(int32 bitstream_buffer_id,
       base::Bind(&RTCVideoEncoder::ReturnEncodedImage,
                  weak_encoder_,
                  base::Passed(&image),
-                 bitstream_buffer_id));
+                 bitstream_buffer_id,
+                 picture_id_));
+  // Picture ID must wrap after reaching the maximum.
+  picture_id_ = (picture_id_ + 1) & 0x7FFF;
 }
 
 void RTCVideoEncoder::Impl::NotifyError(
@@ -637,10 +646,12 @@ int32_t RTCVideoEncoder::SetRates(uint32_t new_bit_rate, uint32_t frame_rate) {
 }
 
 void RTCVideoEncoder::ReturnEncodedImage(scoped_ptr<webrtc::EncodedImage> image,
-                                         int32 bitstream_buffer_id) {
+                                         int32 bitstream_buffer_id,
+                                         uint16 picture_id) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(3) << "ReturnEncodedImage(): "
-              "bitstream_buffer_id=" << bitstream_buffer_id;
+           << "bitstream_buffer_id=" << bitstream_buffer_id
+           << ", picture_id=" << picture_id;
 
   if (!encoded_image_callback_)
     return;
@@ -649,7 +660,7 @@ void RTCVideoEncoder::ReturnEncodedImage(scoped_ptr<webrtc::EncodedImage> image,
   memset(&info, 0, sizeof(info));
   info.codecType = video_codec_type_;
   if (video_codec_type_ == webrtc::kVideoCodecVP8) {
-    info.codecSpecific.VP8.pictureId = -1;
+    info.codecSpecific.VP8.pictureId = picture_id;
     info.codecSpecific.VP8.tl0PicIdx = -1;
     info.codecSpecific.VP8.keyIdx = -1;
   }

content/renderer/media/rtc_video_encoder.h

@@ -69,7 +69,8 @@ class CONTENT_EXPORT RTCVideoEncoder
 
   // Return an encoded output buffer to WebRTC.
   void ReturnEncodedImage(scoped_ptr<webrtc::EncodedImage> image,
-                          int32 bitstream_buffer_id);
+                          int32 bitstream_buffer_id,
+                          uint16 picture_id);
 
   void NotifyError(int32_t error);