# Bug: Windows Audio processes less samples then the samplerate when not selecting any outputs **URL:** \ **Category:** General JUCE discussion\ **Created:** [November 26, 2025, 3:07pm UTC](https://forum.juce.com/t/bug-windows-audio-processes-less-samples-then-the-samplerate-when-not-selecting-any-outputs/67689 "2025-11-26T15:07:43Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![haroldgroenenboom](https://avatars.discourse-cdn.com/v4/letter/h/8c91f0/32.png) [@haroldgroenenboom](https://forum.juce.com/u/haroldgroenenboom)\ **Post date:** [November 26, 2025, 3:07pm UTC](https://forum.juce.com/t/bug-windows-audio-processes-less-samples-then-the-samplerate-when-not-selecting-any-outputs/67689/1 "2025-11-26T15:07:43Z")
Hi, When using `AudioDeviceManager` with input-only configuration and a non-default buffer size, the audio callback does not receive the expected number of samples per second, despite the device reporting a sample rate of 44100 Hz. ### Details ##### Expected Behavior: At 44100 Hz sample rate, the audio callback should receive 44100 samples per second. ##### Actual Behavior: The actual number of samples received per second is significantly less than the reported sample rate, proportional to the selected buffer size ##### Preconditions - No output channels enabled - Windows Audio device type - Buffer size is smaller than the device’s default buffer size ##### Environment: - OS: Windows - Latest JUCE ### Minimal Reproducible Example ```cpp #include class AudioExample : private juce::AudioIODeviceCallback, private juce::Timer { public: AudioExample () { deviceManager.initialiseWithDefaultDevices (1, 0); deviceManager.addAudioCallback (this); // after 10 seconds, change the buffer size to a lower buffersize juce::Timer::callAfterDelay (10000, [&] { auto setup = deviceManager.getAudioDeviceSetup(); setup.bufferSize = 224; setup.inputChannels = 1; setup.outputChannels = 0; if (const auto err = deviceManager.setAudioDeviceSetup(setup, true); err.isNotEmpty()) { DBG (err); jassertfalse; } }); startTimerHz (1); } ~AudioExample() override { deviceManager.removeAudioCallback (this); } private: juce::AudioDeviceManager deviceManager; void audioDeviceIOCallbackWithContext (const float* const* inputChannelData, int numInputChannels, float* const* outputChannelData, int numOutputChannels, int numSamples, const juce::AudioIODeviceCallbackContext&) override { juce::ignoreUnused (inputChannelData, numInputChannels, outputChannelData, numOutputChannels); sampleCount += numSamples; } void audioDeviceAboutToStart (juce::AudioIODevice* audioDevice) override { DBG("Started device " + audioDevice->getName() + " (" + audioDevice->getTypeName() + ") with sampleRate and buffer size: " << audioDevice->getCurrentSampleRate() << ", " << audioDevice->getCurrentBufferSizeSamples()); } void audioDeviceStopped() override { DBG ("Stopped"); } void audioDeviceError (const juce::String& errorMessage) override { DBG (errorMessage); jassertfalse; } std::atomic sampleCount { 0 }; void timerCallback() override { // when the buffesize is changed to 224, we should see around 44100 samples processed per second // but on average we receive around 22400 samples per second DBG("Samples processed in one second: " << sampleCount.exchange(0)); } }; int main() { const juce::ScopedJuceInitialiser_GUI _guiInitializer; const auto mm = juce::MessageManager::getInstance(); AudioExample example; mm->runDispatchLoop(); return 0; } ``` See logs: ```auto Started device Analog (1+2) (RME Fireface UCX II) (Windows Audio) with sampleRate and buffer size: 44100, 441 Samples processed in one second: 44100 Samples processed in one second: 44100 Samples processed in one second: 44100 Samples processed in one second: 44100 Samples processed in one second: 44541 Samples processed in one second: 44100 Samples processed in one second: 44100 Samples processed in one second: 44100 Samples processed in one second: 44100 Stopped The thread 'JUCE v8.0.10: WASAPI' (37296) has exited with code 0 (0x0). 'AudioBugExample.exe' (Win32): Loaded 'C:\Windows\System32\avrt.dll'. Symbol loading disabled by Include/Exclude setting. 'AudioBugExample.exe' (Win32): Unloaded 'C:\Windows\System32\avrt.dll' Started device Analog (1+2) (RME Fireface UCX II) (Windows Audio) with sampleRate and buffer size: 44100, 224 Samples processed in one second: 43659 Samples processed in one second: 22400 Samples processed in one second: 22624 Samples processed in one second: 22400 ``` CMake used: ```auto cmake_minimum_required(VERSION 3.15) set(CMAKE_CXX_STANDARD 23) project(AudioBugExample VERSION 0.0.1) file( DOWNLOAD https://github.com/cpm-cmake/CPM.cmake/releases/latest/download/CPM.cmake ${CMAKE_CURRENT_BINARY_DIR}/cmake/CPM.cmake ) include(${CMAKE_CURRENT_BINARY_DIR}/cmake/CPM.cmake) CPMAddPackage( NAME JUCE GITHUB_REPOSITORY juce-framework/JUCE GIT_TAG master ) juce_add_console_app(AudioBugExample) target_sources(AudioBugExample PRIVATE AudioBugExample.cpp) target_link_libraries(AudioBugExample PRIVATE juce::juce_audio_utils PUBLIC juce::juce_recommended_config_flags juce::juce_recommended_lto_flags juce::juce_recommended_warning_flags ) ``` ---
**Author:** ![reuk](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.juce.com/reuk/32/21494_2.png) [@reuk](https://forum.juce.com/u/reuk)\ **Post date:** [December 16, 2025, 1:43pm UTC](https://forum.juce.com/t/bug-windows-audio-processes-less-samples-then-the-samplerate-when-not-selecting-any-outputs/67689/3 "2025-12-16T13:43:00Z")
Thanks for reporting. We’ve pushed a fix for this issue here: > > > In shared mode (i.e. non-low-latency, non-exclusive) the driver has sole > respons…ibility for setting the wakeup period, and this cannot be changed > by the application. This change ensures that the audio device always > uses the buffer size reported by the audio hardware, even when that > differs from the buffer size that was requested by the program. Please note that, in shared mode, changing the audio block size does not seem to be possible. Therefore, the actual block size may not end up matching the requested block size. ---
**Author:** ![haroldgroenenboom](https://avatars.discourse-cdn.com/v4/letter/h/8c91f0/32.png) [@haroldgroenenboom](https://forum.juce.com/u/haroldgroenenboom)\ **Post date:** [December 18, 2025, 8:41am UTC](https://forum.juce.com/t/bug-windows-audio-processes-less-samples-then-the-samplerate-when-not-selecting-any-outputs/67689/4 "2025-12-18T08:41:08Z")
Amazing thanks!