commit eb3603bd5e72b3a941363c559ddea99ee71d510a
author aluebs <aluebs@webrtc.org> Wed Apr 20 15:27:58 2016 -0700
committer Commit bot <commit-bot@chromium.org> Wed Apr 20 22:28:01 2016 +0000
tree 4cd10e6f68bc712ed04a2973f8bdd3ff4243b1f2
parent 0a2c054f426104ed5364424d3ec88d6cffe203eb

Don't always downsample to 16kHz in the reverse stream in APM

The first approach landed here: https://codereview.webrtc.org/1773173002
But it was partially reverted, because it affected the AEC performance, here: https://codereview.webrtc.org/1867483003/
The main difference of this approach is that it doesn't use the 3-band splitting filter in the reverse stream, which seems to be the culprit of the AEC regression.
Also, the 2-band splitting filter has been used for the 32kHz case for a long time without any problem, and this is expanded in the CL to cover the 48kHz case as well.

BUG=webrtc:5725
TBR=tina.legrand@webrtc.org

Review URL: https://codereview.webrtc.org/1865633005

Cr-Commit-Position: refs/heads/master@{#12451}

webrtc/modules/audio_processing/audio_processing_impl.cc

diff --git a/webrtc/modules/audio_processing/audio_processing_impl.cc b/webrtc/modules/audio_processing/audio_processing_impl.cc
index 3a83d1c..af6d9b7 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.cc
+++ b/webrtc/modules/audio_processing/audio_processing_impl.cc
@@ -366,18 +366,20 @@
       std::min(formats_.api_format.input_stream().sample_rate_hz(),
                formats_.api_format.output_stream().sample_rate_hz())));
 
-  // We normally process the reverse stream at 16 kHz. Unless...
-  int rev_proc_rate = kSampleRate16kHz;
+  int rev_proc_rate = ClosestHigherNativeRate(std::min(
+      formats_.api_format.reverse_input_stream().sample_rate_hz(),
+      formats_.api_format.reverse_output_stream().sample_rate_hz()));
+  // TODO(aluebs): Remove this restriction once we figure out why the 3-band
+  // splitting filter degrades the AEC performance.
+  if (rev_proc_rate > kSampleRate32kHz) {
+    rev_proc_rate = is_rev_processed() ? kSampleRate32kHz : kSampleRate16kHz;
+  }
+  // If the forward sample rate is 8 kHz, the reverse stream is also processed
+  // at this rate.
   if (capture_nonlocked_.fwd_proc_format.sample_rate_hz() == kSampleRate8kHz) {
-    // ...the forward stream is at 8 kHz.
     rev_proc_rate = kSampleRate8kHz;
   } else {
-    if (formats_.api_format.reverse_input_stream().sample_rate_hz() ==
-        kSampleRate32kHz) {
-      // ...or the input is at 32 kHz, in which case we use the splitting
-      // filter rather than the resampler.
-      rev_proc_rate = kSampleRate32kHz;
-    }
+    rev_proc_rate = std::max(rev_proc_rate, static_cast<int>(kSampleRate16kHz));
   }
 
   // Always downmix the reverse stream to mono for analysis. This has been
@@ -1151,11 +1153,11 @@
 
 bool AudioProcessingImpl::rev_synthesis_needed() const {
   return (is_rev_processed() &&
-          formats_.rev_proc_format.sample_rate_hz() == kSampleRate32kHz);
+          is_multi_band(formats_.rev_proc_format.sample_rate_hz()));
 }
 
 bool AudioProcessingImpl::rev_analysis_needed() const {
-  return formats_.rev_proc_format.sample_rate_hz() == kSampleRate32kHz &&
+  return is_multi_band(formats_.rev_proc_format.sample_rate_hz()) &&
          (is_rev_processed() ||
           public_submodules_->echo_cancellation
               ->is_enabled_render_side_query() ||