1 files changed, 578 insertions, 0 deletions
diff --git a/media/libcubeb/test/test_loopback.cpp b/media/libcubeb/test/test_loopback.cpp
new file mode 100644
index 0000000000..9977f6f934
--- /dev/null
+++ b/media/libcubeb/test/test_loopback.cpp
@@ -0,0 +1,578 @@
+/*
+ * Copyright © 2017 Mozilla Foundation
+ *
+ * This program is made available under an ISC-style license.  See the
+ * accompanying file LICENSE for details.
+ */
+
+ /* libcubeb api/function test. Requests a loopback device and checks that
+    output is being looped back to input. NOTE: Usage of output devices while
+    performing this test will cause flakey results! */
+#include "gtest/gtest.h"
+#if !defined(_XOPEN_SOURCE)
+#define _XOPEN_SOURCE 600
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <algorithm>
+#include <memory>
+#include <mutex>
+#include <string>
+#include "cubeb/cubeb.h"
+//#define ENABLE_NORMAL_LOG
+//#define ENABLE_VERBOSE_LOG
+#include "common.h"
+const uint32_t SAMPLE_FREQUENCY = 48000;
+const uint32_t TONE_FREQUENCY = 440;
+const double OUTPUT_AMPLITUDE = 0.25;
+const int32_t NUM_FRAMES_TO_OUTPUT = SAMPLE_FREQUENCY / 20; /* play ~50ms of samples */
+
+template<typename T> T ConvertSampleToOutput(double input);
+template<> float ConvertSampleToOutput(double input) { return float(input); }
+template<> short ConvertSampleToOutput(double input) { return short(input * 32767.0f); }
+
+template<typename T> double ConvertSampleFromOutput(T sample);
+template<> double ConvertSampleFromOutput(float sample) { return double(sample); }
+template<> double ConvertSampleFromOutput(short sample) { return double(sample / 32767.0); }
+
+/* Simple cross correlation to help find phase shift. Not a performant impl */
+std::vector<double> cross_correlate(std::vector<double> & f,
+                                    std::vector<double> & g,
+                                    size_t signal_length)
+{
+  /* the length we sweep our window through to find the cross correlation */
+  size_t sweep_length = f.size() - signal_length + 1;
+  std::vector<double> correlation;
+  correlation.reserve(sweep_length);
+  for (size_t i = 0; i < sweep_length; i++) {
+    double accumulator = 0.0;
+    for (size_t j = 0; j < signal_length; j++) {
+      accumulator += f.at(j) * g.at(i + j);
+    }
+    correlation.push_back(accumulator);
+  }
+  return correlation;
+}
+
+/* best effort discovery of phase shift between output and (looped) input*/
+size_t find_phase(std::vector<double> & output_frames,
+                  std::vector<double> & input_frames,
+                  size_t signal_length)
+{
+  std::vector<double> correlation = cross_correlate(output_frames, input_frames, signal_length);
+  size_t phase = 0;
+  double max_correlation = correlation.at(0);
+  for (size_t i = 1; i < correlation.size(); i++) {
+    if (correlation.at(i) > max_correlation) {
+      max_correlation = correlation.at(i);
+      phase = i;
+    }
+  }
+  return phase;
+}
+
+std::vector<double> normalize_frames(std::vector<double> & frames) {
+  double max = abs(*std::max_element(frames.begin(), frames.end(),
+                                     [](double a, double b) { return abs(a) < abs(b); }));
+  std::vector<double> normalized_frames;
+  normalized_frames.reserve(frames.size());
+  for (const double frame : frames) {
+    normalized_frames.push_back(frame / max);
+  }
+  return normalized_frames;
+}
+
+/* heuristic comparison of aligned output and input signals, gets flaky if TONE_FREQUENCY is too high */
+void compare_signals(std::vector<double> & output_frames,
+                     std::vector<double> & input_frames)
+{
+  ASSERT_EQ(output_frames.size(), input_frames.size()) << "#Output frames != #input frames";
+  size_t num_frames = output_frames.size();
+  std::vector<double> normalized_output_frames = normalize_frames(output_frames);
+  std::vector<double> normalized_input_frames = normalize_frames(input_frames);
+
+  /* calculate mean absolute errors */
+  /* mean absolute errors between output and input */
+  double io_mas = 0.0;
+  /* mean absolute errors between output and silence */
+  double output_silence_mas = 0.0;
+  /* mean absolute errors between input and silence */
+  double input_silence_mas = 0.0;
+  for (size_t i = 0; i < num_frames; i++) {
+    io_mas += abs(normalized_output_frames.at(i) - normalized_input_frames.at(i));
+    output_silence_mas += abs(normalized_output_frames.at(i));
+    input_silence_mas += abs(normalized_input_frames.at(i));
+  }
+  io_mas /= num_frames;
+  output_silence_mas /= num_frames;
+  input_silence_mas /= num_frames;
+
+  ASSERT_LT(io_mas, output_silence_mas)
+    << "Error between output and input should be less than output and silence!";
+  ASSERT_LT(io_mas, input_silence_mas)
+    << "Error between output and input should be less than output and silence!";
+
+  /* make sure extrema are in (roughly) correct location */
+  /* number of maxima + minama expected in the frames*/
+  const long NUM_EXTREMA = 2 * TONE_FREQUENCY * NUM_FRAMES_TO_OUTPUT / SAMPLE_FREQUENCY;
+  /* expected index of first maxima */
+  const long FIRST_MAXIMUM_INDEX = SAMPLE_FREQUENCY / TONE_FREQUENCY / 4;
+  /* Threshold we expect all maxima and minima to be above or below. Ideally
+     the extrema would be 1 or -1, but particularly at the start of loopback
+     the values seen can be significantly lower. */
+  const double THRESHOLD = 0.5;
+
+  for (size_t i = 0; i < NUM_EXTREMA; i++) {
+    bool is_maximum = i % 2 == 0;
+    /* expected offset to current extreme: i * stide between extrema */
+    size_t offset = i * SAMPLE_FREQUENCY / TONE_FREQUENCY / 2;
+    if (is_maximum) {
+      ASSERT_GT(normalized_output_frames.at(FIRST_MAXIMUM_INDEX + offset), THRESHOLD)
+        << "Output frames have unexpected missing maximum!";
+      ASSERT_GT(normalized_input_frames.at(FIRST_MAXIMUM_INDEX + offset), THRESHOLD)
+        << "Input frames have unexpected missing maximum!";
+    } else {
+      ASSERT_LT(normalized_output_frames.at(FIRST_MAXIMUM_INDEX + offset), -THRESHOLD)
+        << "Output frames have unexpected missing minimum!";
+      ASSERT_LT(normalized_input_frames.at(FIRST_MAXIMUM_INDEX + offset), -THRESHOLD)
+        << "Input frames have unexpected missing minimum!";
+    }
+  }
+}
+
+struct user_state_loopback {
+  std::mutex user_state_mutex;
+  long position = 0;
+  /* track output */
+  std::vector<double> output_frames;
+  /* track input */
+  std::vector<double> input_frames;
+};
+
+template<typename T>
+long data_cb_loop_duplex(cubeb_stream * stream, void * user, const void * inputbuffer, void * outputbuffer, long nframes)
+{
+  struct user_state_loopback * u = (struct user_state_loopback *) user;
+  T * ib = (T *) inputbuffer;
+  T * ob = (T *) outputbuffer;
+
+  if (stream == NULL || inputbuffer == NULL || outputbuffer == NULL) {
+    return CUBEB_ERROR;
+  }
+
+  std::lock_guard<std::mutex> lock(u->user_state_mutex);
+  /* generate our test tone on the fly */
+  for (int i = 0; i < nframes; i++) {
+    double tone = 0.0;
+    if (u->position + i < NUM_FRAMES_TO_OUTPUT) {
+      /* generate sine wave */
+      tone = sin(2 * M_PI*(i + u->position) * TONE_FREQUENCY / SAMPLE_FREQUENCY);
+      tone *= OUTPUT_AMPLITUDE;
+    }
+    ob[i] = ConvertSampleToOutput<T>(tone);
+    u->output_frames.push_back(tone);
+    /* store any looped back output, may be silence */
+    u->input_frames.push_back(ConvertSampleFromOutput(ib[i]));
+  }
+
+  u->position += nframes;
+
+  return nframes;
+}
+
+template<typename T>
+long data_cb_loop_input_only(cubeb_stream * stream, void * user, const void * inputbuffer, void * outputbuffer, long nframes)
+{
+  struct user_state_loopback * u = (struct user_state_loopback *) user;
+  T * ib = (T *) inputbuffer;
+
+  if (outputbuffer != NULL) {
+    // Can't assert as it needs to return, so expect to fail instead
+    EXPECT_EQ(outputbuffer, (void *) NULL) << "outputbuffer should be null in input only callback";
+    return CUBEB_ERROR;
+  }
+
+  if (stream == NULL || inputbuffer == NULL) {
+    return CUBEB_ERROR;
+  }
+
+  std::lock_guard<std::mutex> lock(u->user_state_mutex);
+  for (int i = 0; i < nframes; i++) {
+    u->input_frames.push_back(ConvertSampleFromOutput(ib[i]));
+  }
+
+  return nframes;
+}
+
+template<typename T>
+long data_cb_playback(cubeb_stream * stream, void * user, const void * inputbuffer, void * outputbuffer, long nframes)
+{
+  struct user_state_loopback * u = (struct user_state_loopback *) user;
+  T * ob = (T *) outputbuffer;
+
+  if (stream == NULL || outputbuffer == NULL) {
+    return CUBEB_ERROR;
+  }
+
+  std::lock_guard<std::mutex> lock(u->user_state_mutex);
+  /* generate our test tone on the fly */
+  for (int i = 0; i < nframes; i++) {
+    double tone = 0.0;
+    if (u->position + i < NUM_FRAMES_TO_OUTPUT) {
+      /* generate sine wave */
+      tone = sin(2 * M_PI*(i + u->position) * TONE_FREQUENCY / SAMPLE_FREQUENCY);
+      tone *= OUTPUT_AMPLITUDE;
+    }
+    ob[i] = ConvertSampleToOutput<T>(tone);
+    u->output_frames.push_back(tone);
+  }
+
+  u->position += nframes;
+
+  return nframes;
+}
+
+void state_cb_loop(cubeb_stream * stream, void * /*user*/, cubeb_state state)
+{
+  if (stream == NULL)
+    return;
+
+  switch (state) {
+  case CUBEB_STATE_STARTED:
+    fprintf(stderr, "stream started\n"); break;
+  case CUBEB_STATE_STOPPED:
+    fprintf(stderr, "stream stopped\n"); break;
+  case CUBEB_STATE_DRAINED:
+    fprintf(stderr, "stream drained\n"); break;
+  default:
+    fprintf(stderr, "unknown stream state %d\n", state);
+  }
+
+  return;
+}
+
+void run_loopback_duplex_test(bool is_float)
+{
+  cubeb * ctx;
+  cubeb_stream * stream;
+  cubeb_stream_params input_params;
+  cubeb_stream_params output_params;
+  int r;
+  uint32_t latency_frames = 0;
+
+  r = common_init(&ctx, "Cubeb loopback example: duplex stream");
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb library";
+
+  std::unique_ptr<cubeb, decltype(&cubeb_destroy)>
+    cleanup_cubeb_at_exit(ctx, cubeb_destroy);
+
+  input_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  input_params.rate = SAMPLE_FREQUENCY;
+  input_params.channels = 1;
+  input_params.layout = CUBEB_LAYOUT_MONO;
+  input_params.prefs = CUBEB_STREAM_PREF_LOOPBACK;
+  output_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  output_params.rate = SAMPLE_FREQUENCY;
+  output_params.channels = 1;
+  output_params.layout = CUBEB_LAYOUT_MONO;
+  output_params.prefs = CUBEB_STREAM_PREF_NONE;
+
+  std::unique_ptr<user_state_loopback> user_data(new user_state_loopback());
+  ASSERT_TRUE(!!user_data) << "Error allocating user data";
+
+  r = cubeb_get_min_latency(ctx, &output_params, &latency_frames);
+  ASSERT_EQ(r, CUBEB_OK) << "Could not get minimal latency";
+
+  /* setup a duplex stream with loopback */
+  r = cubeb_stream_init(ctx, &stream, "Cubeb loopback",
+                        NULL, &input_params, NULL, &output_params, latency_frames,
+                        is_float ? data_cb_loop_duplex<float> : data_cb_loop_duplex<short>,
+                        state_cb_loop, user_data.get());
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb stream";
+
+  std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
+    cleanup_stream_at_exit(stream, cubeb_stream_destroy);
+
+  cubeb_stream_start(stream);
+  delay(300);
+  cubeb_stream_stop(stream);
+
+  /* access after stop should not happen, but lock just in case and to appease sanitization tools */
+  std::lock_guard<std::mutex> lock(user_data->user_state_mutex);
+  std::vector<double> & output_frames = user_data->output_frames;
+  std::vector<double> & input_frames = user_data->input_frames;
+  ASSERT_EQ(output_frames.size(), input_frames.size())
+    << "#Output frames != #input frames";
+
+  size_t phase = find_phase(user_data->output_frames, user_data->input_frames, NUM_FRAMES_TO_OUTPUT);
+
+  /* extract vectors of just the relevant signal from output and input */
+  auto output_frames_signal_start = output_frames.begin();
+  auto output_frames_signal_end = output_frames.begin() + NUM_FRAMES_TO_OUTPUT;
+  std::vector<double> trimmed_output_frames(output_frames_signal_start, output_frames_signal_end);
+  auto input_frames_signal_start = input_frames.begin() + phase;
+  auto input_frames_signal_end = input_frames.begin() + phase + NUM_FRAMES_TO_OUTPUT;
+  std::vector<double> trimmed_input_frames(input_frames_signal_start, input_frames_signal_end);
+
+  compare_signals(trimmed_output_frames, trimmed_input_frames);
+}
+
+TEST(cubeb, loopback_duplex)
+{
+  run_loopback_duplex_test(true);
+  run_loopback_duplex_test(false);
+}
+
+void run_loopback_separate_streams_test(bool is_float)
+{
+  cubeb * ctx;
+  cubeb_stream * input_stream;
+  cubeb_stream * output_stream;
+  cubeb_stream_params input_params;
+  cubeb_stream_params output_params;
+  int r;
+  uint32_t latency_frames = 0;
+
+  r = common_init(&ctx, "Cubeb loopback example: separate streams");
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb library";
+
+  std::unique_ptr<cubeb, decltype(&cubeb_destroy)>
+    cleanup_cubeb_at_exit(ctx, cubeb_destroy);
+
+  input_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  input_params.rate = SAMPLE_FREQUENCY;
+  input_params.channels = 1;
+  input_params.layout = CUBEB_LAYOUT_MONO;
+  input_params.prefs = CUBEB_STREAM_PREF_LOOPBACK;
+  output_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  output_params.rate = SAMPLE_FREQUENCY;
+  output_params.channels = 1;
+  output_params.layout = CUBEB_LAYOUT_MONO;
+  output_params.prefs = CUBEB_STREAM_PREF_NONE;
+
+  std::unique_ptr<user_state_loopback> user_data(new user_state_loopback());
+  ASSERT_TRUE(!!user_data) << "Error allocating user data";
+
+  r = cubeb_get_min_latency(ctx, &output_params, &latency_frames);
+  ASSERT_EQ(r, CUBEB_OK) << "Could not get minimal latency";
+
+  /* setup an input stream with loopback */
+  r = cubeb_stream_init(ctx, &input_stream, "Cubeb loopback input only",
+                        NULL, &input_params, NULL, NULL, latency_frames,
+                        is_float ? data_cb_loop_input_only<float> : data_cb_loop_input_only<short>,
+                        state_cb_loop, user_data.get());
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb stream";
+
+  std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
+    cleanup_input_stream_at_exit(input_stream, cubeb_stream_destroy);
+
+  /* setup an output stream */
+  r = cubeb_stream_init(ctx, &output_stream, "Cubeb loopback output only",
+                        NULL, NULL, NULL, &output_params, latency_frames,
+                        is_float ? data_cb_playback<float> : data_cb_playback<short>,
+                        state_cb_loop, user_data.get());
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb stream";
+
+  std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
+    cleanup_output_stream_at_exit(output_stream, cubeb_stream_destroy);
+
+  cubeb_stream_start(input_stream);
+  cubeb_stream_start(output_stream);
+  delay(300);
+  cubeb_stream_stop(output_stream);
+  cubeb_stream_stop(input_stream);
+
+  /* access after stop should not happen, but lock just in case and to appease sanitization tools */
+  std::lock_guard<std::mutex> lock(user_data->user_state_mutex);
+  std::vector<double> & output_frames = user_data->output_frames;
+  std::vector<double> & input_frames = user_data->input_frames;
+  ASSERT_LE(output_frames.size(), input_frames.size())
+    << "#Output frames should be less or equal to #input frames";
+
+  size_t phase = find_phase(user_data->output_frames, user_data->input_frames, NUM_FRAMES_TO_OUTPUT);
+
+  /* extract vectors of just the relevant signal from output and input */
+  auto output_frames_signal_start = output_frames.begin();
+  auto output_frames_signal_end = output_frames.begin() + NUM_FRAMES_TO_OUTPUT;
+  std::vector<double> trimmed_output_frames(output_frames_signal_start, output_frames_signal_end);
+  auto input_frames_signal_start = input_frames.begin() + phase;
+  auto input_frames_signal_end = input_frames.begin() + phase + NUM_FRAMES_TO_OUTPUT;
+  std::vector<double> trimmed_input_frames(input_frames_signal_start, input_frames_signal_end);
+
+  compare_signals(trimmed_output_frames, trimmed_input_frames);
+}
+
+TEST(cubeb, loopback_separate_streams)
+{
+  run_loopback_separate_streams_test(true);
+  run_loopback_separate_streams_test(false);
+}
+
+void run_loopback_silence_test(bool is_float)
+{
+  cubeb * ctx;
+  cubeb_stream * input_stream;
+  cubeb_stream_params input_params;
+  int r;
+  uint32_t latency_frames = 0;
+
+  r = common_init(&ctx, "Cubeb loopback example: record silence");
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb library";
+
+  std::unique_ptr<cubeb, decltype(&cubeb_destroy)>
+    cleanup_cubeb_at_exit(ctx, cubeb_destroy);
+
+  input_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  input_params.rate = SAMPLE_FREQUENCY;
+  input_params.channels = 1;
+  input_params.layout = CUBEB_LAYOUT_MONO;
+  input_params.prefs = CUBEB_STREAM_PREF_LOOPBACK;
+
+  std::unique_ptr<user_state_loopback> user_data(new user_state_loopback());
+  ASSERT_TRUE(!!user_data) << "Error allocating user data";
+
+  r = cubeb_get_min_latency(ctx, &input_params, &latency_frames);
+  ASSERT_EQ(r, CUBEB_OK) << "Could not get minimal latency";
+
+  /* setup an input stream with loopback */
+  r = cubeb_stream_init(ctx, &input_stream, "Cubeb loopback input only",
+                        NULL, &input_params, NULL, NULL, latency_frames,
+                        is_float ? data_cb_loop_input_only<float> : data_cb_loop_input_only<short>,
+                        state_cb_loop, user_data.get());
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb stream";
+
+  std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
+    cleanup_input_stream_at_exit(input_stream, cubeb_stream_destroy);
+
+  cubeb_stream_start(input_stream);
+  delay(300);
+  cubeb_stream_stop(input_stream);
+
+  /* access after stop should not happen, but lock just in case and to appease sanitization tools */
+  std::lock_guard<std::mutex> lock(user_data->user_state_mutex);
+  std::vector<double> & input_frames = user_data->input_frames;
+
+  /* expect to have at least ~50ms of frames */
+  ASSERT_GE(input_frames.size(), SAMPLE_FREQUENCY / 20);
+  double EPISILON = 0.0001;
+  /* frames should be 0.0, but use epsilon to avoid possible issues with impls
+  that may use ~0.0 silence values. */
+  for (double frame : input_frames) {
+    ASSERT_LT(abs(frame), EPISILON);
+  }
+}
+
+TEST(cubeb, loopback_silence)
+{
+  run_loopback_silence_test(true);
+  run_loopback_silence_test(false);
+}
+
+void run_loopback_device_selection_test(bool is_float)
+{
+  cubeb * ctx;
+  cubeb_device_collection collection;
+  cubeb_stream * input_stream;
+  cubeb_stream * output_stream;
+  cubeb_stream_params input_params;
+  cubeb_stream_params output_params;
+  int r;
+  uint32_t latency_frames = 0;
+
+  r = common_init(&ctx, "Cubeb loopback example: device selection, separate streams");
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb library";
+
+  std::unique_ptr<cubeb, decltype(&cubeb_destroy)>
+    cleanup_cubeb_at_exit(ctx, cubeb_destroy);
+
+  r = cubeb_enumerate_devices(ctx, CUBEB_DEVICE_TYPE_OUTPUT, &collection);
+  if (r == CUBEB_ERROR_NOT_SUPPORTED) {
+    fprintf(stderr, "Device enumeration not supported"
+            " for this backend, skipping this test.\n");
+    return;
+  }
+
+  ASSERT_EQ(r, CUBEB_OK) << "Error enumerating devices " << r;
+  /* get first preferred output device id */
+  std::string device_id;
+  for (size_t i = 0; i < collection.count; i++) {
+    if (collection.device[i].preferred) {
+      device_id = collection.device[i].device_id;
+      break;
+    }
+  }
+  cubeb_device_collection_destroy(ctx, &collection);
+  if (device_id.empty()) {
+    fprintf(stderr, "Could not find preferred device, aborting test.\n");
+    return;
+  }
+
+  input_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  input_params.rate = SAMPLE_FREQUENCY;
+  input_params.channels = 1;
+  input_params.layout = CUBEB_LAYOUT_MONO;
+  input_params.prefs = CUBEB_STREAM_PREF_LOOPBACK;
+  output_params.format = is_float ? CUBEB_SAMPLE_FLOAT32NE : CUBEB_SAMPLE_S16LE;
+  output_params.rate = SAMPLE_FREQUENCY;
+  output_params.channels = 1;
+  output_params.layout = CUBEB_LAYOUT_MONO;
+  output_params.prefs = CUBEB_STREAM_PREF_NONE;
+
+  std::unique_ptr<user_state_loopback> user_data(new user_state_loopback());
+  ASSERT_TRUE(!!user_data) << "Error allocating user data";
+
+  r = cubeb_get_min_latency(ctx, &output_params, &latency_frames);
+  ASSERT_EQ(r, CUBEB_OK) << "Could not get minimal latency";
+
+  /* setup an input stream with loopback */
+  r = cubeb_stream_init(ctx, &input_stream, "Cubeb loopback input only",
+                        device_id.c_str(), &input_params, NULL, NULL, latency_frames,
+                        is_float ? data_cb_loop_input_only<float> : data_cb_loop_input_only<short>,
+                        state_cb_loop, user_data.get());
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb stream";
+
+  std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
+    cleanup_input_stream_at_exit(input_stream, cubeb_stream_destroy);
+
+  /* setup an output stream */
+  r = cubeb_stream_init(ctx, &output_stream, "Cubeb loopback output only",
+                        NULL, NULL, device_id.c_str(), &output_params, latency_frames,
+                        is_float ? data_cb_playback<float> : data_cb_playback<short>,
+                        state_cb_loop, user_data.get());
+  ASSERT_EQ(r, CUBEB_OK) << "Error initializing cubeb stream";
+
+  std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
+    cleanup_output_stream_at_exit(output_stream, cubeb_stream_destroy);
+
+  cubeb_stream_start(input_stream);
+  cubeb_stream_start(output_stream);
+  delay(300);
+  cubeb_stream_stop(output_stream);
+  cubeb_stream_stop(input_stream);
+
+  /* access after stop should not happen, but lock just in case and to appease sanitization tools */
+  std::lock_guard<std::mutex> lock(user_data->user_state_mutex);
+  std::vector<double> & output_frames = user_data->output_frames;
+  std::vector<double> & input_frames = user_data->input_frames;
+  ASSERT_LE(output_frames.size(), input_frames.size())
+    << "#Output frames should be less or equal to #input frames";
+
+  size_t phase = find_phase(user_data->output_frames, user_data->input_frames, NUM_FRAMES_TO_OUTPUT);
+
+  /* extract vectors of just the relevant signal from output and input */
+  auto output_frames_signal_start = output_frames.begin();
+  auto output_frames_signal_end = output_frames.begin() + NUM_FRAMES_TO_OUTPUT;
+  std::vector<double> trimmed_output_frames(output_frames_signal_start, output_frames_signal_end);
+  auto input_frames_signal_start = input_frames.begin() + phase;
+  auto input_frames_signal_end = input_frames.begin() + phase + NUM_FRAMES_TO_OUTPUT;
+  std::vector<double> trimmed_input_frames(input_frames_signal_start, input_frames_signal_end);
+
+  compare_signals(trimmed_output_frames, trimmed_input_frames);
+}
+
+TEST(cubeb, loopback_device_selection)
+{
+  run_loopback_device_selection_test(true);
+  run_loopback_device_selection_test(false);
+}