diff --git a/modules/audio_processing/aec_dump/aec_dump_impl.cc b/modules/audio_processing/aec_dump/aec_dump_impl.cc
index db61b36c29..4497d575a4 100644
--- a/modules/audio_processing/aec_dump/aec_dump_impl.cc
+++ b/modules/audio_processing/aec_dump/aec_dump_impl.cc
@@ -155,7 +155,7 @@ void AecDumpImpl::WriteRenderStreamMessage(
 
   audioproc::ReverseStream* msg = event->mutable_reverse_stream();
 
-  for (size_t i = 0; i < src.num_channels(); ++i) {
+  for (int i = 0; i < src.num_channels(); ++i) {
     const auto& channel_view = src.channel(i);
     msg->add_channel(channel_view.begin(), sizeof(float) * channel_view.size());
   }
diff --git a/modules/audio_processing/aec_dump/capture_stream_info.cc b/modules/audio_processing/aec_dump/capture_stream_info.cc
index 907cd97793..efdda2570f 100644
--- a/modules/audio_processing/aec_dump/capture_stream_info.cc
+++ b/modules/audio_processing/aec_dump/capture_stream_info.cc
@@ -23,7 +23,7 @@ void CaptureStreamInfo::AddInput(const AudioFrameView<const float>& src) {
   RTC_DCHECK(task_);
   auto* stream = task_->GetEvent()->mutable_stream();
 
-  for (size_t i = 0; i < src.num_channels(); ++i) {
+  for (int i = 0; i < src.num_channels(); ++i) {
     const auto& channel_view = src.channel(i);
     stream->add_input_channel(channel_view.begin(),
                               sizeof(float) * channel_view.size());
@@ -34,7 +34,7 @@ void CaptureStreamInfo::AddOutput(const AudioFrameView<const float>& src) {
   RTC_DCHECK(task_);
   auto* stream = task_->GetEvent()->mutable_stream();
 
-  for (size_t i = 0; i < src.num_channels(); ++i) {
+  for (int i = 0; i < src.num_channels(); ++i) {
     const auto& channel_view = src.channel(i);
     stream->add_output_channel(channel_view.begin(),
                                sizeof(float) * channel_view.size());
diff --git a/modules/audio_processing/agc2/BUILD.gn b/modules/audio_processing/agc2/BUILD.gn
index 4e6daec826..734e98f6c2 100644
--- a/modules/audio_processing/agc2/BUILD.gn
+++ b/modules/audio_processing/agc2/BUILD.gn
@@ -91,6 +91,7 @@ rtc_library("fixed_digital") {
     "../../../rtc_base:checks",
     "../../../rtc_base:gtest_prod",
     "../../../rtc_base:rtc_base_approved",
+    "../../../rtc_base:safe_conversions",
     "../../../rtc_base:safe_minmax",
     "../../../system_wrappers:metrics",
   ]
diff --git a/modules/audio_processing/agc2/adaptive_digital_gain_applier.cc b/modules/audio_processing/agc2/adaptive_digital_gain_applier.cc
index 526ef06e24..deb03b074a 100644
--- a/modules/audio_processing/agc2/adaptive_digital_gain_applier.cc
+++ b/modules/audio_processing/agc2/adaptive_digital_gain_applier.cc
@@ -106,7 +106,7 @@ void CopyAudio(AudioFrameView<const float> src,
   RTC_DCHECK_GT(src.num_channels(), 0);
   RTC_DCHECK_GT(src.samples_per_channel(), 0);
   RTC_DCHECK_EQ(dst.size(), src.num_channels());
-  for (size_t c = 0; c < src.num_channels(); ++c) {
+  for (int c = 0; c < src.num_channels(); ++c) {
     rtc::ArrayView<const float> channel_view = src.channel(c);
     RTC_DCHECK_EQ(channel_view.size(), src.samples_per_channel());
     RTC_DCHECK_EQ(dst[c].size(), src.samples_per_channel());
diff --git a/modules/audio_processing/agc2/fixed_digital_level_estimator.cc b/modules/audio_processing/agc2/fixed_digital_level_estimator.cc
index eb8a64a9b5..8223a7395f 100644
--- a/modules/audio_processing/agc2/fixed_digital_level_estimator.cc
+++ b/modules/audio_processing/agc2/fixed_digital_level_estimator.cc
@@ -57,7 +57,7 @@ std::array<float, kSubFramesInFrame> FixedDigitalLevelEstimator::ComputeLevel(
 
   // Compute max envelope without smoothing.
   std::array<float, kSubFramesInFrame> envelope{};
-  for (size_t channel_idx = 0; channel_idx < float_frame.num_channels();
+  for (int channel_idx = 0; channel_idx < float_frame.num_channels();
        ++channel_idx) {
     const auto channel = float_frame.channel(channel_idx);
     for (int sub_frame = 0; sub_frame < kSubFramesInFrame; ++sub_frame) {
diff --git a/modules/audio_processing/agc2/gain_applier.cc b/modules/audio_processing/agc2/gain_applier.cc
index 8c437177e3..a777cf3165 100644
--- a/modules/audio_processing/agc2/gain_applier.cc
+++ b/modules/audio_processing/agc2/gain_applier.cc
@@ -25,7 +25,7 @@ bool GainCloseToOne(float gain_factor) {
 }
 
 void ClipSignal(AudioFrameView<float> signal) {
-  for (size_t k = 0; k < signal.num_channels(); ++k) {
+  for (int k = 0; k < signal.num_channels(); ++k) {
     rtc::ArrayView<float> channel_view = signal.channel(k);
     for (auto& sample : channel_view) {
       sample = rtc::SafeClamp(sample, kMinFloatS16Value, kMaxFloatS16Value);
@@ -45,7 +45,7 @@ void ApplyGainWithRamping(float last_gain_linear,
 
   // Gain is constant and different from 1.
   if (last_gain_linear == gain_at_end_of_frame_linear) {
-    for (size_t k = 0; k < float_frame.num_channels(); ++k) {
+    for (int k = 0; k < float_frame.num_channels(); ++k) {
       rtc::ArrayView<float> channel_view = float_frame.channel(k);
       for (auto& sample : channel_view) {
         sample *= gain_at_end_of_frame_linear;
@@ -58,8 +58,8 @@ void ApplyGainWithRamping(float last_gain_linear,
   const float increment = (gain_at_end_of_frame_linear - last_gain_linear) *
                           inverse_samples_per_channel;
   float gain = last_gain_linear;
-  for (size_t i = 0; i < float_frame.samples_per_channel(); ++i) {
-    for (size_t ch = 0; ch < float_frame.num_channels(); ++ch) {
+  for (int i = 0; i < float_frame.samples_per_channel(); ++i) {
+    for (int ch = 0; ch < float_frame.num_channels(); ++ch) {
       float_frame.channel(ch)[i] *= gain;
     }
     gain += increment;
@@ -93,7 +93,7 @@ void GainApplier::SetGainFactor(float gain_factor) {
   current_gain_factor_ = gain_factor;
 }
 
-void GainApplier::Initialize(size_t samples_per_channel) {
+void GainApplier::Initialize(int samples_per_channel) {
   RTC_DCHECK_GT(samples_per_channel, 0);
   samples_per_channel_ = static_cast<int>(samples_per_channel);
   inverse_samples_per_channel_ = 1.f / samples_per_channel_;
diff --git a/modules/audio_processing/agc2/gain_applier.h b/modules/audio_processing/agc2/gain_applier.h
index d9aa19d1aa..ba8a4a4cd2 100644
--- a/modules/audio_processing/agc2/gain_applier.h
+++ b/modules/audio_processing/agc2/gain_applier.h
@@ -25,7 +25,7 @@ class GainApplier {
   float GetGainFactor() const { return current_gain_factor_; }
 
  private:
-  void Initialize(size_t samples_per_channel);
+  void Initialize(int samples_per_channel);
 
   // Whether to clip samples after gain is applied. If 'true', result
   // will fit in FloatS16 range.
diff --git a/modules/audio_processing/agc2/limiter.cc b/modules/audio_processing/agc2/limiter.cc
index ed7d3ee5f2..57580924dc 100644
--- a/modules/audio_processing/agc2/limiter.cc
+++ b/modules/audio_processing/agc2/limiter.cc
@@ -18,6 +18,7 @@
 #include "modules/audio_processing/agc2/agc2_common.h"
 #include "modules/audio_processing/logging/apm_data_dumper.h"
 #include "rtc_base/checks.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/numerics/safe_minmax.h"
 
 namespace webrtc {
@@ -29,14 +30,14 @@ namespace {
 // sub-frame, linear interpolation is replaced with a power function which
 // reduces the chances of over-shooting (and hence saturation), however reducing
 // the fixed gain effectiveness.
-constexpr float kAttackFirstSubframeInterpolationPower = 8.f;
+constexpr float kAttackFirstSubframeInterpolationPower = 8.0f;
 
 void InterpolateFirstSubframe(float last_factor,
                               float current_factor,
                               rtc::ArrayView<float> subframe) {
-  const auto n = subframe.size();
-  constexpr auto p = kAttackFirstSubframeInterpolationPower;
-  for (size_t i = 0; i < n; ++i) {
+  const int n = rtc::dchecked_cast<int>(subframe.size());
+  constexpr float p = kAttackFirstSubframeInterpolationPower;
+  for (int i = 0; i < n; ++i) {
     subframe[i] = std::pow(1.f - i / n, p) * (last_factor - current_factor) +
                   current_factor;
   }
@@ -44,10 +45,10 @@ void InterpolateFirstSubframe(float last_factor,
 
 void ComputePerSampleSubframeFactors(
     const std::array<float, kSubFramesInFrame + 1>& scaling_factors,
-    size_t samples_per_channel,
+    int samples_per_channel,
     rtc::ArrayView<float> per_sample_scaling_factors) {
-  const size_t num_subframes = scaling_factors.size() - 1;
-  const size_t subframe_size =
+  const int num_subframes = scaling_factors.size() - 1;
+  const int subframe_size =
       rtc::CheckedDivExact(samples_per_channel, num_subframes);
 
   // Handle first sub-frame differently in case of attack.
@@ -59,12 +60,12 @@ void ComputePerSampleSubframeFactors(
             per_sample_scaling_factors.subview(0, subframe_size)));
   }
 
-  for (size_t i = is_attack ? 1 : 0; i < num_subframes; ++i) {
-    const size_t subframe_start = i * subframe_size;
+  for (int i = is_attack ? 1 : 0; i < num_subframes; ++i) {
+    const int subframe_start = i * subframe_size;
     const float scaling_start = scaling_factors[i];
     const float scaling_end = scaling_factors[i + 1];
     const float scaling_diff = (scaling_end - scaling_start) / subframe_size;
-    for (size_t j = 0; j < subframe_size; ++j) {
+    for (int j = 0; j < subframe_size; ++j) {
       per_sample_scaling_factors[subframe_start + j] =
           scaling_start + scaling_diff * j;
     }
@@ -73,18 +74,18 @@ void ComputePerSampleSubframeFactors(
 
 void ScaleSamples(rtc::ArrayView<const float> per_sample_scaling_factors,
                   AudioFrameView<float> signal) {
-  const size_t samples_per_channel = signal.samples_per_channel();
+  const int samples_per_channel = signal.samples_per_channel();
   RTC_DCHECK_EQ(samples_per_channel, per_sample_scaling_factors.size());
-  for (size_t i = 0; i < signal.num_channels(); ++i) {
-    auto channel = signal.channel(i);
-    for (size_t j = 0; j < samples_per_channel; ++j) {
+  for (int i = 0; i < signal.num_channels(); ++i) {
+    rtc::ArrayView<float> channel = signal.channel(i);
+    for (int j = 0; j < samples_per_channel; ++j) {
       channel[j] = rtc::SafeClamp(channel[j] * per_sample_scaling_factors[j],
                                   kMinFloatS16Value, kMaxFloatS16Value);
     }
   }
 }
 
-void CheckLimiterSampleRate(size_t sample_rate_hz) {
+void CheckLimiterSampleRate(int sample_rate_hz) {
   // Check that per_sample_scaling_factors_ is large enough.
   RTC_DCHECK_LE(sample_rate_hz,
                 kMaximalNumberOfSamplesPerChannel * 1000 / kFrameDurationMs);
@@ -92,7 +93,7 @@ void CheckLimiterSampleRate(size_t sample_rate_hz) {
 
 }  // namespace
 
-Limiter::Limiter(size_t sample_rate_hz,
+Limiter::Limiter(int sample_rate_hz,
                  ApmDataDumper* apm_data_dumper,
                  const std::string& histogram_name)
     : interp_gain_curve_(apm_data_dumper, histogram_name),
@@ -104,7 +105,8 @@ Limiter::Limiter(size_t sample_rate_hz,
 Limiter::~Limiter() = default;
 
 void Limiter::Process(AudioFrameView<float> signal) {
-  const auto level_estimate = level_estimator_.ComputeLevel(signal);
+  const std::array<float, kSubFramesInFrame> level_estimate =
+      level_estimator_.ComputeLevel(signal);
 
   RTC_DCHECK_EQ(level_estimate.size() + 1, scaling_factors_.size());
   scaling_factors_[0] = last_scaling_factor_;
@@ -113,7 +115,7 @@ void Limiter::Process(AudioFrameView<float> signal) {
                    return interp_gain_curve_.LookUpGainToApply(x);
                  });
 
-  const size_t samples_per_channel = signal.samples_per_channel();
+  const int samples_per_channel = signal.samples_per_channel();
   RTC_DCHECK_LE(samples_per_channel, kMaximalNumberOfSamplesPerChannel);
 
   auto per_sample_scaling_factors = rtc::ArrayView<float>(
@@ -136,7 +138,7 @@ InterpolatedGainCurve::Stats Limiter::GetGainCurveStats() const {
   return interp_gain_curve_.get_stats();
 }
 
-void Limiter::SetSampleRate(size_t sample_rate_hz) {
+void Limiter::SetSampleRate(int sample_rate_hz) {
   CheckLimiterSampleRate(sample_rate_hz);
   level_estimator_.SetSampleRate(sample_rate_hz);
 }
diff --git a/modules/audio_processing/agc2/limiter.h b/modules/audio_processing/agc2/limiter.h
index f8eec3dc79..f8894a308d 100644
--- a/modules/audio_processing/agc2/limiter.h
+++ b/modules/audio_processing/agc2/limiter.h
@@ -24,7 +24,7 @@ class ApmDataDumper;
 
 class Limiter {
  public:
-  Limiter(size_t sample_rate_hz,
+  Limiter(int sample_rate_hz,
           ApmDataDumper* apm_data_dumper,
           const std::string& histogram_name_prefix);
   Limiter(const Limiter& limiter) = delete;
@@ -40,7 +40,7 @@ class Limiter {
   // * below kMaximalNumberOfSamplesPerChannel*1000/kFrameDurationMs
   //   so that samples_per_channel fit in the
   //   per_sample_scaling_factors_ array.
-  void SetSampleRate(size_t sample_rate_hz);
+  void SetSampleRate(int sample_rate_hz);
 
   // Resets the internal state.
   void Reset();
diff --git a/modules/audio_processing/agc2/noise_level_estimator.cc b/modules/audio_processing/agc2/noise_level_estimator.cc
index 3d9aa1a4ae..9fb1c24b65 100644
--- a/modules/audio_processing/agc2/noise_level_estimator.cc
+++ b/modules/audio_processing/agc2/noise_level_estimator.cc
@@ -27,7 +27,7 @@ constexpr int kFramesPerSecond = 100;
 
 float FrameEnergy(const AudioFrameView<const float>& audio) {
   float energy = 0.0f;
-  for (size_t k = 0; k < audio.num_channels(); ++k) {
+  for (int k = 0; k < audio.num_channels(); ++k) {
     float channel_energy =
         std::accumulate(audio.channel(k).begin(), audio.channel(k).end(), 0.0f,
                         [](float a, float b) -> float { return a + b * b; });
diff --git a/modules/audio_processing/include/audio_frame_view.h b/modules/audio_processing/include/audio_frame_view.h
index 9786cd9d9d..164784a7cc 100644
--- a/modules/audio_processing/include/audio_frame_view.h
+++ b/modules/audio_processing/include/audio_frame_view.h
@@ -22,12 +22,13 @@ class AudioFrameView {
   // `num_channels` and `channel_size` describe the T**
   // `audio_samples`. `audio_samples` is assumed to point to a
   // two-dimensional |num_channels * channel_size| array of floats.
-  AudioFrameView(T* const* audio_samples,
-                 size_t num_channels,
-                 size_t channel_size)
+  AudioFrameView(T* const* audio_samples, int num_channels, int channel_size)
       : audio_samples_(audio_samples),
         num_channels_(num_channels),
-        channel_size_(channel_size) {}
+        channel_size_(channel_size) {
+    RTC_DCHECK_GE(num_channels_, 0);
+    RTC_DCHECK_GE(channel_size_, 0);
+  }
 
   // Implicit cast to allow converting Frame<float> to
   // Frame<const float>.
@@ -39,17 +40,17 @@ class AudioFrameView {
 
   AudioFrameView() = delete;
 
-  size_t num_channels() const { return num_channels_; }
+  int num_channels() const { return num_channels_; }
 
-  size_t samples_per_channel() const { return channel_size_; }
+  int samples_per_channel() const { return channel_size_; }
 
-  rtc::ArrayView<T> channel(size_t idx) {
+  rtc::ArrayView<T> channel(int idx) {
     RTC_DCHECK_LE(0, idx);
     RTC_DCHECK_LE(idx, num_channels_);
     return rtc::ArrayView<T>(audio_samples_[idx], channel_size_);
   }
 
-  rtc::ArrayView<const T> channel(size_t idx) const {
+  rtc::ArrayView<const T> channel(int idx) const {
     RTC_DCHECK_LE(0, idx);
     RTC_DCHECK_LE(idx, num_channels_);
     return rtc::ArrayView<const T>(audio_samples_[idx], channel_size_);
@@ -59,8 +60,8 @@ class AudioFrameView {
 
  private:
   T* const* audio_samples_;
-  size_t num_channels_;
-  size_t channel_size_;
+  int num_channels_;
+  int channel_size_;
 };
 }  // namespace webrtc