Audio Coding Module: Use separate instances for 16 kHz and 32 kHz iSAC decoder

webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc

 /*
  *  Copyright (c) 2012 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 701 matching lines @@
 
   // Check if the payload-type is valid.
   if (!RentACodec::IsPayloadTypeValid(codec.pltype)) {
     LOG_F(LS_ERROR) << "Invalid payload type " << codec.pltype << " for "
                     << codec.plname;
     return -1;
   }
 
   AudioDecoder* isac_decoder = nullptr;
   if (STR_CASE_CMP(codec.plname, "isac") == 0) {
-    if (!isac_decoder_) {
-      isac_decoder_ = isac_factory();
+    std::unique_ptr<AudioDecoder>& saved_isac_decoder =
+        codec.plfreq == 16000 ? isac_decoder_16k_ : isac_decoder_32k_;
+    if (!saved_isac_decoder) {
+      saved_isac_decoder = isac_factory();
     }
-    isac_decoder = isac_decoder_.get();
+    isac_decoder = saved_isac_decoder.get();
   }
   return receiver_.AddCodec(*codec_index, codec.pltype, codec.channels,
                             codec.plfreq, isac_decoder, codec.plname);
 }
 
 int AudioCodingModuleImpl::RegisterExternalReceiveCodec(
     int rtp_payload_type,
     AudioDecoder* external_decoder,
     int sample_rate_hz,
     int num_channels,
@@ skipping 200 matching lines @@
   return receiver_.LeastRequiredDelayMs();
 }
 
 void AudioCodingModuleImpl::GetDecodingCallStatistics(
       AudioDecodingCallStats* call_stats) const {
   receiver_.GetDecodingCallStatistics(call_stats);
 }
 
 }  // namespace acm2
 }  // namespace webrtc