AudioCodingModule: Add methods for injecting external encoder stacks

webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc

Index: webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
diff --git a/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc b/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
index a7d9df457c1133c79db9752116a106837ed99bf7..34bf87f0f2407706449fefa0128f9abe3133cd21 100644
--- a/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
+++ b/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
@@ -221,16 +221,28 @@ void AudioCodingModuleImpl::RegisterExternalSendCodec(
   encoder_stack_ = encoder_factory_->rent_a_codec.RentEncoderStack(sp);
 }
 
+void AudioCodingModuleImpl::VisitEncoder(const EncoderVisitor& ev) {

[hlundin-webrtc, 2016/02/10 09:45:46]

Rename function to ModifyEncoder, or something similar.

+  rtc::CritScope lock(&acm_crit_sect_);
+
+  // Wipe the encoder factory, so that everything that relies on it will fail.
+  // We don't want the complexity of supporting swapping back and forth.
+  encoder_factory_.reset();
+
+  encoder_stack_ = ev(encoder_stack_);
+}
+
 // Get current send codec.
 rtc::Optional<CodecInst> AudioCodingModuleImpl::SendCodec() const {
   rtc::CritScope lock(&acm_crit_sect_);
-  auto* ci = encoder_factory_->codec_manager.GetCodecInst();
-  if (ci) {
-    return rtc::Optional<CodecInst>(*ci);
+  if (encoder_factory_) {
+    auto* ci = encoder_factory_->codec_manager.GetCodecInst();
+    if (ci) {
+      return rtc::Optional<CodecInst>(*ci);
+    }
   }
-  auto* enc = encoder_factory_->codec_manager.GetStackParams()->speech_encoder;
-  if (enc) {
-    return rtc::Optional<CodecInst>(CodecManager::ForgeCodecInst(enc));
+  if (encoder_stack_) {
+    return rtc::Optional<CodecInst>(
+        CodecManager::ForgeCodecInst(encoder_stack_));
   }
   return rtc::Optional<CodecInst>();
 }
@@ -580,10 +592,22 @@ int AudioCodingModuleImpl::PlayoutFrequency() const {
   return receiver_.last_output_sample_rate_hz();
 }
 
-// Register possible receive codecs, can be called multiple times,
-// for codecs, CNG (NB, WB and SWB), DTMF, RED.
 int AudioCodingModuleImpl::RegisterReceiveCodec(const CodecInst& codec) {
   rtc::CritScope lock(&acm_crit_sect_);
+  auto* ef = encoder_factory_.get();
+  return RegisterReceiveCodecUnlocked(
+      codec, [ef] { return ef->rent_a_codec.RentIsacDecoder(); });
+}
+
+int AudioCodingModuleImpl::RegisterReceiveCodec(const CodecInst& codec,
+                                                const DecoderFactory& df) {
+  rtc::CritScope lock(&acm_crit_sect_);
+  return RegisterReceiveCodecUnlocked(codec, df);
+}
+
+int AudioCodingModuleImpl::RegisterReceiveCodecUnlocked(
+    const CodecInst& codec,
+    const DecoderFactory& df) {
   RTC_DCHECK(receiver_initialized_);
   if (codec.channels > 2) {
     LOG_F(LS_ERROR) << "Unsupported number of channels: " << codec.channels;
@@ -610,10 +634,7 @@ int AudioCodingModuleImpl::RegisterReceiveCodec(const CodecInst& codec) {
   // not own its decoder.
   return receiver_.AddCodec(
       *codec_index, codec.pltype, codec.channels, codec.plfreq,
-      STR_CASE_CMP(codec.plname, "isac") == 0
-          ? encoder_factory_->rent_a_codec.RentIsacDecoder()
-          : nullptr,
-      codec.plname);
+      STR_CASE_CMP(codec.plname, "isac") == 0 ? df() : nullptr, codec.plname);
 }
 
 int AudioCodingModuleImpl::RegisterExternalReceiveCodec(