Switch to using new ACM methods for encoder management

webrtc/modules/audio_coding/acm2/codec_manager.h

Index: webrtc/modules/audio_coding/acm2/codec_manager.h
diff --git a/webrtc/modules/audio_coding/acm2/codec_manager.h b/webrtc/modules/audio_coding/acm2/codec_manager.h
index fbd3a18b188efa203949159bf0e0b8c9bde353b3..a92c9c3b7d853be0fdcb2aa0397f72180db5d5f3 100644
--- a/webrtc/modules/audio_coding/acm2/codec_manager.h
+++ b/webrtc/modules/audio_coding/acm2/codec_manager.h
@@ -55,6 +55,25 @@ class CodecManager final {
 
   bool SetCodecFEC(bool enable_codec_fec);
 
+  // Uses the provided Rent-A-Codec to create a new encoder stack, if we have a
+  // complete specification; if so, it is then passed to set_encoder. On error,
+  // returns false.
+  template <typename F>
+  bool MakeEncoder(RentACodec* rac, F set_encoder) {
+    if (!codec_stack_params_.speech_encoder && send_codec_inst_) {
+      // We have no speech encoder, but we have a specification for making one.
+      auto enc = rac->RentEncoder(*send_codec_inst_);
+      if (!enc)
+        return false;
+      codec_stack_params_.speech_encoder = std::move(enc);
+    }
+    auto stack = rac->RentEncoderStack(&codec_stack_params_);
+    if (stack) {
+      set_encoder(std::move(stack));
+    }
+    return true;

[hlundin-webrtc, 2016/03/29 20:23:32]

If we did not get a stack, we still return true. Does that not count as an
error?

[kwiberg-webrtc, 2016/03/29 23:25:32]

No, because callers may call this method before a speech encoder has been
set—e.g. if CN and RED are registered first.

If the logic seems unduly complex, that’s because it is. What we have currently
(and still have as of this CL) is VoE/libjingle sending configuration data to
the ACM in pieces (such as single CodecInst objects, requests to enable VAD,
etc.), and the ACM must rebuild the encoder stack to the best of its ability
upon receiving each piece. What we hope to get eventually is a complete
specification presented all at once.

[hlundin-webrtc, 2016/03/30 08:36:10]

Acknowledged.

+  }
+
  private:
   rtc::ThreadChecker thread_checker_;
   rtc::Optional<CodecInst> send_codec_inst_;