Add support for external decoders in ACM

webrtc/modules/audio_coding/main/acm2/acm_receiver.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 458 matching lines @@
   }
 
   return 0;
 }
 
 int32_t AcmReceiver::AddCodec(int acm_codec_id,
                               uint8_t payload_type,
                               int channels,
                               int sample_rate_hz,
                               AudioDecoder* audio_decoder) {
-  assert(acm_codec_id >= 0);
-  NetEqDecoder neteq_decoder = ACMCodecDB::neteq_decoders_[acm_codec_id];
+  assert(acm_codec_id >= -1);  // -1 means external decoder
+  NetEqDecoder neteq_decoder = (acm_codec_id == -1)
+                                   ? kDecoderArbitrary
+                                   : ACMCodecDB::neteq_decoders_[acm_codec_id];
 
   // Make sure the right decoder is registered for Opus.
   if (neteq_decoder == kDecoderOpus && channels == 2) {
     neteq_decoder = kDecoderOpus_2ch;
   }
 
   CriticalSectionScoped lock(crit_sect_.get());
 
   // The corresponding NetEq decoder ID.
   // If this codec has been registered before.
   auto it = decoders_.find(payload_type);
   if (it != decoders_.end()) {
     const Decoder& decoder = it->second;
-    if (decoder.acm_codec_id == acm_codec_id && decoder.channels == channels &&
+    if (acm_codec_id != -1 && decoder.acm_codec_id == acm_codec_id &&
+        decoder.channels == channels &&
         decoder.sample_rate_hz == sample_rate_hz) {
       // Re-registering the same codec. Do nothing and return.
       return 0;
     }
 
-    // Changing codec or number of channels. First unregister the old codec,
-    // then register the new one.
+    // Changing codec. First unregister the old codec, then register the new
+    // one.
     if (neteq_->RemovePayloadType(payload_type) != NetEq::kOK) {
       LOG(LERROR) << "Cannot remove payload " << static_cast<int>(payload_type);
       return -1;
     }
 
     decoders_.erase(it);
   }
 
   int ret_val;
   if (!audio_decoder) {
@@ skipping 324 matching lines @@
 
 void AcmReceiver::GetDecodingCallStatistics(
     AudioDecodingCallStats* stats) const {
   CriticalSectionScoped lock(crit_sect_.get());
   *stats = call_stats_.GetDecodingStatistics();
 }
 
 }  // namespace acm2
 
 }  // namespace webrtc