Handle HW decode failures in RTCVideoDecoder

content/renderer/media/rtc_video_decoder.cc

Index: content/renderer/media/rtc_video_decoder.cc
diff --git a/content/renderer/media/rtc_video_decoder.cc b/content/renderer/media/rtc_video_decoder.cc
index 49f64362aa3622623d8b1c55688ebbe5cd6f7c63..88d1a5836811f351f92a244db671afafe6f090c0 100644
--- a/content/renderer/media/rtc_video_decoder.cc
+++ b/content/renderer/media/rtc_video_decoder.cc
@@ -28,6 +28,7 @@ namespace content {
 const int32_t RTCVideoDecoder::ID_LAST = 0x3FFFFFFF;
 const int32_t RTCVideoDecoder::ID_HALF = 0x20000000;
 const int32_t RTCVideoDecoder::ID_INVALID = -1;
+const uint32_t kNumVDAResetsBeforeSWFallback = 5;
 
 // Maximum number of concurrent VDA::Decode() operations RVD will maintain.
 // Higher values allow better pipelining in the GPU, but also require more
@@ -55,7 +56,8 @@ RTCVideoDecoder::BufferData::~BufferData() {}
 
 RTCVideoDecoder::RTCVideoDecoder(webrtc::VideoCodecType type,
                                  media::GpuVideoAcceleratorFactories* factories)
-    : video_codec_type_(type),
+    : num_vda_errors_(0),
+      video_codec_type_(type),
       factories_(factories),
       decoder_texture_target_(0),
       next_picture_buffer_id_(0),
@@ -160,6 +162,16 @@ int32_t RTCVideoDecoder::Decode(
 
   if (state_ == DECODE_ERROR) {
     LOG(ERROR) << "Decoding error occurred.";
+    // Try reseting the session |kNumVDAErrorsHandled| times.
+    if (num_vda_errors_ > kNumVDAResetsBeforeSWFallback) {
+      DLOG(ERROR) << num_vda_errors_
+                  << " errors reported by VDA, falling back to software decode";
+      return WEBRTC_VIDEO_CODEC_FALLBACK_SOFTWARE;

[hbos_chromium, 2016/03/29 12:28:19]

What if there is no SW decoder available? Would it continue to use this decoder
and get stuck in the DECODE_ERROR state?

Also, I don't know what causes decode errors, but if decode errors periodically
happen, for whatever reason, we might sooner or later always end up with SW
decoder for longer video sessions.
In a bug of mine (crbug.com/583704) decode errors happen seemingly randomly on
some machines, but not often enough that it wouldn't make sense to recover (if
possible).

[emircan, 2016/03/29 19:37:55]

That logic is handled in the WebRTC side:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...

AFAIU, it will try to use a SW encoder if there is and stop things with an error
message otherwise. 

If HW errors are happening periodically, maybe we can increase the limit of 5.
But, I think falling back to SW is a safer bet then?

[hbos_chromium, 2016/03/30 16:43:39]

Yeah, makes sense. Let's not assume HW errors occur periodically. Hopefully
there is a root cause that can be addressed. I'm still debugging my bug.
I wanted to try this out today in combination with my SW decoder but I've been
unable to reliably reproduce the decode error on my mac :/ I'll try again
tomorrow on my windows laptop.

+    }
+    state_ = RESETTING;
+    factories_->GetTaskRunner()->PostTask(
+        FROM_HERE, base::Bind(&RTCVideoDecoder::ResetInternal,
+                              weak_factory_.GetWeakPtr()));
     return WEBRTC_VIDEO_CODEC_ERROR;
   }
 
@@ -476,6 +488,7 @@ void RTCVideoDecoder::NotifyError(media::VideoDecodeAccelerator::Error error) {
 
   base::AutoLock auto_lock(lock_);
   state_ = DECODE_ERROR;
+  ++num_vda_errors_;
 }
 
 void RTCVideoDecoder::RequestBufferDecode() {
@@ -605,10 +618,13 @@ void RTCVideoDecoder::MovePendingBuffersToDecodeBuffers() {
 }
 
 void RTCVideoDecoder::ResetInternal() {
+  DVLOG(2) << __FUNCTION__;
   DCheckGpuVideoAcceleratorFactoriesTaskRunnerIsCurrent();
-  DVLOG(2) << "ResetInternal";
+
   if (vda_)
     vda_->Reset();
+  else
+    CreateVDA(vda_codec_profile_, nullptr);
 }
 
 // static
@@ -680,9 +696,11 @@ void RTCVideoDecoder::CreateVDA(media::VideoCodecProfile profile,
     media::VideoDecodeAccelerator::Config config(profile);
     if (vda_ && !vda_->Initialize(config, this))
       vda_.release()->Destroy();
+    vda_codec_profile_ = profile;
   }
 
-  waiter->Signal();
+  if (waiter)
+    waiter->Signal();
 }
 
 void RTCVideoDecoder::DestroyTextures() {
@@ -705,7 +723,14 @@ void RTCVideoDecoder::DestroyVDA() {
   if (vda_)
     vda_.release()->Destroy();
   DestroyTextures();
+
   base::AutoLock auto_lock(lock_);
+
+  // Put the buffers back in case we restart the decoder.
+  for (const auto& buffer : bitstream_buffers_in_decoder_)
+    PutSHM_Locked(scoped_ptr<base::SharedMemory>(buffer.second));
+  bitstream_buffers_in_decoder_.clear();
+
   state_ = UNINITIALIZED;
 }