Allow encoders to fall back dynamically to software.

webrtc/video/video_encoder.cc

Index: webrtc/video/video_encoder.cc
diff --git a/webrtc/video/video_encoder.cc b/webrtc/video/video_encoder.cc
index 3e6ce634f8e9022442bab86e15250119e4639e35..d116a1ea6728c30391fceaaae931633c5eea0154 100644
--- a/webrtc/video/video_encoder.cc
+++ b/webrtc/video/video_encoder.cc
@@ -50,34 +50,67 @@ VideoEncoder::EncoderType CodecToEncoderType(VideoCodecType codec_type) {
 VideoEncoderSoftwareFallbackWrapper::VideoEncoderSoftwareFallbackWrapper(
     VideoCodecType codec_type,
     webrtc::VideoEncoder* encoder)
-    : encoder_type_(CodecToEncoderType(codec_type)),
+    : rates_set_(false),
+      channel_parameters_set_(false),
+      encoder_type_(CodecToEncoderType(codec_type)),
       encoder_(encoder),
-      callback_(nullptr) {
+      callback_(nullptr) {}
+
+bool VideoEncoderSoftwareFallbackWrapper::InitFallbackEncoder() {
+  RTC_CHECK(encoder_type_ != kUnsupportedCodec)
+      << "Encoder requesting fallback to codec not supported in software.";
+  fallback_encoder_.reset(VideoEncoder::Create(encoder_type_));
+  if (fallback_encoder_->InitEncode(&codec_settings_, number_of_cores_,
+                                    max_payload_size_) !=
+      WEBRTC_VIDEO_CODEC_OK) {
+    LOG(LS_ERROR) << "Failed to initialize software-encoder fallback.";
+    fallback_encoder_->Release();
+    fallback_encoder_.reset();
+    return false;
+  }
+  // Replay callback, rates, and channel parameters.
+  if (callback_)
+    fallback_encoder_->RegisterEncodeCompleteCallback(callback_);
+  if (rates_set_)
+    fallback_encoder_->SetRates(bitrate_, framerate_);
+  if (channel_parameters_set_)
+    fallback_encoder_->SetChannelParameters(packet_loss_, rtt_);
+
+  // Since we're switching to the fallback encoder, Release the real encoder. It
+  // may be re-initialized via InitEncode later, and it will continue to get
+  // Set calls for rates and channel parameters in the meantime.
+  encoder_->Release();
+  return true;
 }
 
 int32_t VideoEncoderSoftwareFallbackWrapper::InitEncode(
     const VideoCodec* codec_settings,
     int32_t number_of_cores,
     size_t max_payload_size) {
+  // Store settings, in case we need to dynamically switch to the fallback
+  // encoder after a failed Encode call.
+  codec_settings_ = *codec_settings;
+  number_of_cores_ = number_of_cores;
+  max_payload_size_ = max_payload_size;
+  // Clear stored rate/channel parameters.
+  rates_set_ = false;
+  channel_parameters_set_ = false;
+
   int32_t ret =
       encoder_->InitEncode(codec_settings, number_of_cores, max_payload_size);
   if (ret == WEBRTC_VIDEO_CODEC_OK || encoder_type_ == kUnsupportedCodec) {
+    if (fallback_encoder_)
+      fallback_encoder_->Release();
     fallback_encoder_.reset();
     if (callback_)
       encoder_->RegisterEncodeCompleteCallback(callback_);
     return ret;
   }
   // Try to instantiate software codec.
-  fallback_encoder_.reset(VideoEncoder::Create(encoder_type_));
-  if (fallback_encoder_->InitEncode(codec_settings, number_of_cores,
-                                    max_payload_size) ==
-      WEBRTC_VIDEO_CODEC_OK) {
-    if (callback_)
-      fallback_encoder_->RegisterEncodeCompleteCallback(callback_);
+  if (InitFallbackEncoder()) {
     return WEBRTC_VIDEO_CODEC_OK;
   }
-  // Software encoder failed, reset and use original return code.
-  fallback_encoder_.reset();
+  // Software encoder failed, use original return code.
   return ret;
 }
 
@@ -91,6 +124,9 @@ int32_t VideoEncoderSoftwareFallbackWrapper::RegisterEncodeCompleteCallback(
 }
 
 int32_t VideoEncoderSoftwareFallbackWrapper::Release() {
+  // If the fallback_encoder_ is non-null, it means it was created via
+  // InitFallbackEncoder which has Release()d encoder_, so we should only ever
+  // need to Release() whichever one is active.
   if (fallback_encoder_)
     return fallback_encoder_->Release();
   return encoder_->Release();
@@ -102,12 +138,21 @@ int32_t VideoEncoderSoftwareFallbackWrapper::Encode(
     const std::vector<FrameType>* frame_types) {
   if (fallback_encoder_)
     return fallback_encoder_->Encode(frame, codec_specific_info, frame_types);
-  return encoder_->Encode(frame, codec_specific_info, frame_types);
+  int32_t ret = encoder_->Encode(frame, codec_specific_info, frame_types);
+  // If requested, try a software fallback.
+  if (ret == WEBRTC_VIDEO_CODEC_FALLBACK_SOFTWARE && InitFallbackEncoder()) {
+    // Fallback was successful, so start using it with this frame.
+    return fallback_encoder_->Encode(frame, codec_specific_info, frame_types);
+  }
+  return ret;
 }
 
 int32_t VideoEncoderSoftwareFallbackWrapper::SetChannelParameters(
     uint32_t packet_loss,
     int64_t rtt) {
+  channel_parameters_set_ = true;
+  packet_loss_ = packet_loss;
+  rtt_ = rtt;
   int32_t ret = encoder_->SetChannelParameters(packet_loss, rtt);
   if (fallback_encoder_)
     return fallback_encoder_->SetChannelParameters(packet_loss, rtt);
@@ -116,6 +161,9 @@ int32_t VideoEncoderSoftwareFallbackWrapper::SetChannelParameters(
 
 int32_t VideoEncoderSoftwareFallbackWrapper::SetRates(uint32_t bitrate,
                                                       uint32_t framerate) {
+  rates_set_ = true;
+  bitrate_ = bitrate;
+  framerate_ = framerate;
   int32_t ret = encoder_->SetRates(bitrate, framerate);
   if (fallback_encoder_)
     return fallback_encoder_->SetRates(bitrate, framerate);