Failed to Capture System Audio with ScreenCaptureKit on macOS 15 (SCStreamErrorDomain -3805 or No Callbacks)

[yuelong3]

Environment:

• macOS Version: 15 (darwin 24.1.0)
• Python Version: 3.9.9 (via pyenv)
• PyObjC Version: 11.0 (installed via pip install pyobjc)

Problem Description:

We are trying to capture system audio output using ScreenCaptureKit with PyObjC, specifically without relying on external tools like BlackHole. We understand that ScreenCaptureKit's primary purpose is screen recording, but native Swift/Objective-C implementations have confirmed that capturing system audio is possible with this framework.

However, using PyObjC (version 11.0) on macOS 15, we consistently fail to achieve this. The main issues encountered are:

1. The SCStream starts but stops almost immediately, reporting Error Domain=com.apple.ScreenCaptureKit.SCStreamErrorDomain Code=-3805 "流播放期间，应用程序连接中断而导致失败" UserInfo={NSLocalizedDescription=流播放期间，应用程序连接中断而导致失败} (equivalent to SCStreamError.connectionInvalid).
2. Alternatively, the stream appears to start successfully ("流已成功启动！正在监听音频...") but the audio sample buffer callback (stream_didOutputSampleBuffer_ofType_ for SCStreamOutputTypeAudio) is never invoked, even when system
   Describe the bug
   A clear and concise description of what the bug is.

Platform information

• Python version
• How was python installed (python.org, anaconda, homebrew, ...)
• macOS version

To Reproduce
Steps to reproduce the behavior.

Expected behavior
A clear and concise description of what you expected to happen.

Additional context
Add any other context about the problem here.

[Alexandro1112]

Hello, do you have the code?

[yuelong3]

Thanks， i have solved the problem but now new problem come...
The application initializes correctly, but never receives any audio buffers.
This indicates that no audio buffers are being received by the delegate method. I've confirmed that:
YouTube is playing with audible sound
Screen Recording permissions are granted to both Python and Terminal
The application successfully starts the capture stream
The delegate is properly registeredimport tkinter as tk
from tkinter import ttk
import threading
import queue
import time
import numpy as np
import objc
from ctypes import c_void_p

PyObjC-specific imports

from AVFoundation import CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer
from CoreMedia import (
CMSampleBufferGetDataBuffer, CMSampleBufferGetNumSamples, CMSampleBufferGetFormatDescription
)
from ScreenCaptureKit import (
SCStream, SCShareableContent, SCStreamConfiguration, SCContentFilter,
SCStreamOutputTypeAudio, SCStreamOutputTypeScreen
)
from Foundation import NSObject, NSLog

Define the protocol

SCStreamDelegate = objc.protocolNamed("SCStreamDelegate")

class CaptureDelegate(NSObject):
"""Handles callbacks from the SCStream."""
capturer = objc.IBOutlet()

def initWithCapturer_(self, capturer_instance):
    self = objc.super(CaptureDelegate, self).init()
    if self is None:
        return None
    self.capturer = capturer_instance
    NSLog("CaptureDelegate initialized")
    return self

@objc.python_method
def stream_didOutputSampleBuffer_ofType_(self, stream, sampleBuffer, type):
    # Check if capturer is still valid
    if not self.capturer or not self.capturer.is_running:
        return

    # Log the type of buffer received
    if type == SCStreamOutputTypeAudio:
        NSLog("Audio buffer received")
    elif type == SCStreamOutputTypeScreen:
        # NSLog("Screen buffer received")
        pass
    else:
        NSLog(f"Unknown buffer type: {type}")
        
    # Only process audio buffers
    if type == SCStreamOutputTypeAudio:
        try:
            objc.retain(sampleBuffer)
            self.capturer.audio_queue.put(sampleBuffer)
            NSLog("Added audio buffer to queue")
        except Exception as e:
            NSLog(f"Error handling audio buffer: {e}")
            objc.release(sampleBuffer)

@objc.python_method
def stream_didStopWithError_(self, stream, error):
    if error:
        NSLog(f"Stream stopped with error: {error}")
    else:
        NSLog("Stream stopped normally")
    if self.capturer:
        self.capturer.stop_capture()

Register metadata

objc.registerMetaDataForSelector(
b"CaptureDelegate",
b"stream:didOutputSampleBuffer:ofType:",
dict(
arguments={
2+0: dict(type=b"@"),
2+1: dict(type=b"@"),
2+2: dict(type=objc._C_NSInteger)
}
)
)

objc.registerMetaDataForSelector(
b"CaptureDelegate",
b"stream:didStopWithError:",
dict(
arguments={
2+0: dict(type=b"@"),
2+1: dict(type=b"@")
}
)
)

class SystemAudioCapturer:
def init(self):
self.root = None
self.volume_bar = None
self.audio_queue = queue.Queue(maxsize=100)
self.stream = None
self.delegate = None
self.content_filter = None
self.stream_config = None
self.is_running = False
self.processing_thread = None
self._lock = threading.Lock()

def _process_audio_queue(self):
    """Worker thread to process audio buffers."""
    NSLog("Audio processing thread started")
    count = 0
    
    while self.is_running:
        try:
            if count % 10 == 0:
                NSLog(f"Processed {count} buffers, queue size: {self.audio_queue.qsize()}")
            
            sampleBuffer = self.audio_queue.get(block=True, timeout=0.2)
            count += 1
            
            if not self.is_running:
                if sampleBuffer: objc.release(sampleBuffer)
                break
            
            # Extract audio data and process...
            # (Implementation simplified for brevity)
            formatDesc = CMSampleBufferGetFormatDescription(sampleBuffer)
            if formatDesc:
                NSLog("Got format description")
                try:
                    asbd = formatDesc.audioStreamBasicDescription()
                    if asbd:
                        NSLog(f"Audio format: rate={asbd.mSampleRate}, channels={asbd.mChannelsPerFrame}")
                except:
                    pass
            
            # Update UI - simplified
            if self.root and self.is_running:
                self.root.after(0, lambda: self.volume_bar.config(value=50))
                
            # Release the buffer
            if sampleBuffer: objc.release(sampleBuffer)
            
        except queue.Empty:
            continue
        except Exception as e:
            NSLog(f"Error in processing thread: {e}")
            time.sleep(0.1)
            
    NSLog("Audio processing thread finished")

def setup_ui(self):
    """Sets up minimal UI."""
    self.root = tk.Tk()
    self.root.title("System Audio Capture")
    self.root.geometry("300x200")
    self.root.protocol("WM_DELETE_WINDOW", self.on_closing)
    
    self.status_label = tk.Label(self.root, text="Status: Idle")
    self.status_label.pack(pady=10)
    
    # Volume meter
    self.volume_bar = ttk.Progressbar(self.root, orient="horizontal", mode="determinate", maximum=100)
    self.volume_bar.pack(fill=tk.X, padx=20, pady=10)
    
    # Buttons
    button_frame = tk.Frame(self.root)
    button_frame.pack(pady=10)
    self.start_button = tk.Button(button_frame, text="Start Capture", command=self.start_capture)
    self.start_button.pack(side=tk.LEFT, padx=10)
    self.stop_button = tk.Button(button_frame, text="Stop Capture", command=self.stop_capture)
    self.stop_button.pack(side=tk.LEFT, padx=10)

def start_capture(self):
    """Starts the audio capture."""
    with self._lock:
        if self.is_running:
            return
        self.is_running = True
        
    NSLog("Starting capture")
    self.status_label.config(text="Status: Starting...")
    
    # Get shareable content 
    try:
        SCShareableContent.getShareableContentWithCompletionHandler_(self._handle_shareable_content)
    except Exception as e:
        NSLog(f"Error getting shareable content: {e}")
        self.is_running = False

def _handle_shareable_content(self, content, error):
    """Callback after getting shareable content."""
    if error:
        NSLog(f"Error: {error}")
        return
        
    if not content or not content.displays():
        NSLog("No displays found")
        return
    
    try:
        # Setup with primary display
        display = content.displays()[0]
        
        # Check for apps with audio
        for app in content.applications():
            if hasattr(app, 'hasAudio') and app.hasAudio():
                NSLog(f"App with audio: {app.applicationName()}")
        
        # Create filter
        self.content_filter = SCContentFilter.alloc().initWithDisplay_excludingApplications_exceptingWindows_(
            display, [], []
        )
        
        # Create stream configuration
        self.stream_config = SCStreamConfiguration.alloc().init()
        self.stream_config.setCapturesAudio_(True)
        self.stream_config.setExcludesCurrentProcessAudio_(False)
        self.stream_config.setSampleRate_(48000)
        self.stream_config.setChannelCount_(2)
        
        # Create delegate and stream
        self.delegate = CaptureDelegate.alloc().initWithCapturer_(self)
        self.stream = SCStream.alloc().initWithFilter_configuration_delegate_(
            self.content_filter, self.stream_config, self.delegate
        )
        
        # Add audio output
        success = self.stream.addStreamOutput_type_sampleHandlerQueue_error_(
            self.delegate, SCStreamOutputTypeAudio, None, None
        )
        
        if not success:
            NSLog("Failed to add audio output")
            return
            
        # Start capture
        self.stream.startCaptureWithCompletionHandler_(self._handle_start_completion)
        
    except Exception as e:
        NSLog(f"Setup error: {e}")
        self.is_running = False

def _handle_start_completion(self, error):
    """Callback after capture starts."""
    if error:
        NSLog(f"Start error: {error}")
        self.is_running = False
        return
        
    NSLog("Capture started successfully!")
    self.status_label.config(text="Status: Capturing")
    
    # Start processing thread
    self.processing_thread = threading.Thread(
        target=self._process_audio_queue, daemon=True
    )
    self.processing_thread.start()

def stop_capture(self):
    """Stops the capture."""
    with self._lock:
        if not self.is_running:
            return
        self.is_running = False
    
    NSLog("Stopping capture")
    self.status_label.config(text="Status: Stopping...")
    
    if self.stream:
        self.stream.stopCaptureWithCompletionHandler_(self._handle_stop_completion)
    else:
        self._handle_stop_completion(None)

def _handle_stop_completion(self, error):
    """Callback after capture stops."""
    if error:
        NSLog(f"Stop error: {error}")
    
    NSLog("Capture stopped")
    # Clean up resources
    self.stream = None
    self.delegate = None
    self.content_filter = None
    self.stream_config = None
    
    # Wait for processing thread
    if self.processing_thread and self.processing_thread.is_alive():
        self.processing_thread.join(timeout=1.0)
    
    self.status_label.config(text="Status: Idle")

def on_closing(self):
    """Handle window close."""
    self.stop_capture()
    self.root.after(500, self.root.destroy)

def run(self):
    """Start the application."""
    self.setup_ui()
    self.root.mainloop()
    NSLog("Application exiting")

if name == "main":
capturer = SystemAudioCapturer()
capturer.run()

[huangjunsen0406]

Thanks， i have solved the problem but now new problem come...谢谢，我已经解决了问题，但现在新问题来了...... The application initializes correctly, but never receives any audio buffers.应用程序正确初始化，但从不接收任何音频缓冲区。 This indicates that no audio buffers are being received by the delegate method. I've confirmed that:这表示委托方法未接收任何音频缓冲区。我已经确认： YouTube is playing with audible soundYouTube 正在播放有声音 Screen Recording permissions are granted to both Python and Terminal屏幕录制权限授予 Python 和终端 The application successfully starts the capture stream应用程序成功启动捕获流 The delegate is properly registeredimport tkinter as tk委托已正确注册 import tkinter as tk from tkinter import ttk从 tkinter 导入 ttk import threading  导入线程 import queue  导入队列 import time  导入时间 import numpy as np将 numpy 导入为 np import objc  导入 OBJC from ctypes import c_void_p从 ctypes 导入 c_void_p

PyObjC-specific imports  特定于 PyObjC 的导入

from AVFoundation import CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer从 AVFoundation 导入 CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer from CoreMedia import (从 CoreMedia 导入 （ CMSampleBufferGetDataBuffer, CMSampleBufferGetNumSamples, CMSampleBufferGetFormatDescriptionCMSampleBufferGetDataBuffer、CMSampleBufferGetNumSamples、CMSampleBufferGetFormat 说明 ) from ScreenCaptureKit import (从 ScreenCaptureKit 导入 （ SCStream, SCShareableContent, SCStreamConfiguration, SCContentFilter,SCStream、SCShareableContent、SCStreamConfiguration、SCContentFilter、 SCStreamOutputTypeAudio, SCStreamOutputTypeScreenSCStreamOutputTypeAudio、SCStreamOutputTypeScreen ) from Foundation import NSObject, NSLog来自 Foundation 导入 NSObject， NSLog

Define the protocol  定义协议

SCStreamDelegate = objc.protocolNamed("SCStreamDelegate")SCStreamDelegate = objc.protocolNamed（“SCStreamDelegate”）

class CaptureDelegate(NSObject):class CaptureDelegate（NSObject）： """Handles callbacks from the SCStream."""“”“处理来自 SCStream 的回调。 capturer = objc.IBOutlet()捕获器 = objc。IBOutlet（）

def initWithCapturer_(self, capturer_instance):
    self = objc.super(CaptureDelegate, self).init()
    if self is None:
        return None
    self.capturer = capturer_instance
    NSLog("CaptureDelegate initialized")
    return self

@objc.python_method
def stream_didOutputSampleBuffer_ofType_(self, stream, sampleBuffer, type):
    # Check if capturer is still valid
    if not self.capturer or not self.capturer.is_running:
        return

    # Log the type of buffer received
    if type == SCStreamOutputTypeAudio:
        NSLog("Audio buffer received")
    elif type == SCStreamOutputTypeScreen:
        # NSLog("Screen buffer received")
        pass
    else:
        NSLog(f"Unknown buffer type: {type}")
        
    # Only process audio buffers
    if type == SCStreamOutputTypeAudio:
        try:
            objc.retain(sampleBuffer)
            self.capturer.audio_queue.put(sampleBuffer)
            NSLog("Added audio buffer to queue")
        except Exception as e:
            NSLog(f"Error handling audio buffer: {e}")
            objc.release(sampleBuffer)

@objc.python_method
def stream_didStopWithError_(self, stream, error):
    if error:
        NSLog(f"Stream stopped with error: {error}")
    else:
        NSLog("Stream stopped normally")
    if self.capturer:
        self.capturer.stop_capture()

Register metadata  注册元数据

objc.registerMetaDataForSelector(objc.registerMetaDataForSelector（ b"CaptureDelegate",  b“捕获委托”， b"stream:didOutputSampleBuffer:ofType:",b“流：didOutputSampleBuffer：ofType：”， dict(  dict（ arguments={  参数={ 2+0: dict(type=b"@"),  2+0：dict（type=b“@”）， 2+1: dict(type=b"@"),  2+1：dict（type=b“@”）， 2+2: dict(type=objc._C_NSInteger)2+2：dict（type=objc._C_NSInteger） } ) )

objc.registerMetaDataForSelector(objc.registerMetaDataForSelector（ b"CaptureDelegate",  b“捕获委托”， b"stream:didStopWithError:",b“流：didStopWithError：”， dict(  dict（ arguments={  参数={ 2+0: dict(type=b"@"),  2+0：dict（type=b“@”）， 2+1: dict(type=b"@")  2+1：dict（type=b“@”） } ) )

class SystemAudioCapturer:类 SystemAudioCapturer： def init(self):  def init（self） 中： self.root = None  self.root = 无 self.volume_bar = None  self.volume_bar = 无 self.audio_queue = queue.Queue(maxsize=100)self.audio_queue = 队列。队列（maxsize=100） self.stream = None  self.stream = 无 self.delegate = None  self.delegate = 无 self.content_filter = Noneself.content_filter = 无 self.stream_config = Noneself.stream_config = 无 self.is_running = False  self.is_running = 错误 self.processing_thread = Noneself.processing_thread = 无 self._lock = threading.Lock()self._lock = 线程。锁（）

def _process_audio_queue(self):
    """Worker thread to process audio buffers."""
    NSLog("Audio processing thread started")
    count = 0
    
    while self.is_running:
        try:
            if count % 10 == 0:
                NSLog(f"Processed {count} buffers, queue size: {self.audio_queue.qsize()}")
            
            sampleBuffer = self.audio_queue.get(block=True, timeout=0.2)
            count += 1
            
            if not self.is_running:
                if sampleBuffer: objc.release(sampleBuffer)
                break
            
            # Extract audio data and process...
            # (Implementation simplified for brevity)
            formatDesc = CMSampleBufferGetFormatDescription(sampleBuffer)
            if formatDesc:
                NSLog("Got format description")
                try:
                    asbd = formatDesc.audioStreamBasicDescription()
                    if asbd:
                        NSLog(f"Audio format: rate={asbd.mSampleRate}, channels={asbd.mChannelsPerFrame}")
                except:
                    pass
            
            # Update UI - simplified
            if self.root and self.is_running:
                self.root.after(0, lambda: self.volume_bar.config(value=50))
                
            # Release the buffer
            if sampleBuffer: objc.release(sampleBuffer)
            
        except queue.Empty:
            continue
        except Exception as e:
            NSLog(f"Error in processing thread: {e}")
            time.sleep(0.1)
            
    NSLog("Audio processing thread finished")

def setup_ui(self):
    """Sets up minimal UI."""
    self.root = tk.Tk()
    self.root.title("System Audio Capture")
    self.root.geometry("300x200")
    self.root.protocol("WM_DELETE_WINDOW", self.on_closing)
    
    self.status_label = tk.Label(self.root, text="Status: Idle")
    self.status_label.pack(pady=10)
    
    # Volume meter
    self.volume_bar = ttk.Progressbar(self.root, orient="horizontal", mode="determinate", maximum=100)
    self.volume_bar.pack(fill=tk.X, padx=20, pady=10)
    
    # Buttons
    button_frame = tk.Frame(self.root)
    button_frame.pack(pady=10)
    self.start_button = tk.Button(button_frame, text="Start Capture", command=self.start_capture)
    self.start_button.pack(side=tk.LEFT, padx=10)
    self.stop_button = tk.Button(button_frame, text="Stop Capture", command=self.stop_capture)
    self.stop_button.pack(side=tk.LEFT, padx=10)

def start_capture(self):
    """Starts the audio capture."""
    with self._lock:
        if self.is_running:
            return
        self.is_running = True
        
    NSLog("Starting capture")
    self.status_label.config(text="Status: Starting...")
    
    # Get shareable content 
    try:
        SCShareableContent.getShareableContentWithCompletionHandler_(self._handle_shareable_content)
    except Exception as e:
        NSLog(f"Error getting shareable content: {e}")
        self.is_running = False

def _handle_shareable_content(self, content, error):
    """Callback after getting shareable content."""
    if error:
        NSLog(f"Error: {error}")
        return
        
    if not content or not content.displays():
        NSLog("No displays found")
        return
    
    try:
        # Setup with primary display
        display = content.displays()[0]
        
        # Check for apps with audio
        for app in content.applications():
            if hasattr(app, 'hasAudio') and app.hasAudio():
                NSLog(f"App with audio: {app.applicationName()}")
        
        # Create filter
        self.content_filter = SCContentFilter.alloc().initWithDisplay_excludingApplications_exceptingWindows_(
            display, [], []
        )
        
        # Create stream configuration
        self.stream_config = SCStreamConfiguration.alloc().init()
        self.stream_config.setCapturesAudio_(True)
        self.stream_config.setExcludesCurrentProcessAudio_(False)
        self.stream_config.setSampleRate_(48000)
        self.stream_config.setChannelCount_(2)
        
        # Create delegate and stream
        self.delegate = CaptureDelegate.alloc().initWithCapturer_(self)
        self.stream = SCStream.alloc().initWithFilter_configuration_delegate_(
            self.content_filter, self.stream_config, self.delegate
        )
        
        # Add audio output
        success = self.stream.addStreamOutput_type_sampleHandlerQueue_error_(
            self.delegate, SCStreamOutputTypeAudio, None, None
        )
        
        if not success:
            NSLog("Failed to add audio output")
            return
            
        # Start capture
        self.stream.startCaptureWithCompletionHandler_(self._handle_start_completion)
        
    except Exception as e:
        NSLog(f"Setup error: {e}")
        self.is_running = False

def _handle_start_completion(self, error):
    """Callback after capture starts."""
    if error:
        NSLog(f"Start error: {error}")
        self.is_running = False
        return
        
    NSLog("Capture started successfully!")
    self.status_label.config(text="Status: Capturing")
    
    # Start processing thread
    self.processing_thread = threading.Thread(
        target=self._process_audio_queue, daemon=True
    )
    self.processing_thread.start()

def stop_capture(self):
    """Stops the capture."""
    with self._lock:
        if not self.is_running:
            return
        self.is_running = False
    
    NSLog("Stopping capture")
    self.status_label.config(text="Status: Stopping...")
    
    if self.stream:
        self.stream.stopCaptureWithCompletionHandler_(self._handle_stop_completion)
    else:
        self._handle_stop_completion(None)

def _handle_stop_completion(self, error):
    """Callback after capture stops."""
    if error:
        NSLog(f"Stop error: {error}")
    
    NSLog("Capture stopped")
    # Clean up resources
    self.stream = None
    self.delegate = None
    self.content_filter = None
    self.stream_config = None
    
    # Wait for processing thread
    if self.processing_thread and self.processing_thread.is_alive():
        self.processing_thread.join(timeout=1.0)
    
    self.status_label.config(text="Status: Idle")

def on_closing(self):
    """Handle window close."""
    self.stop_capture()
    self.root.after(500, self.root.destroy)

def run(self):
    """Start the application."""
    self.setup_ui()
    self.root.mainloop()
    NSLog("Application exiting")

if name == "main":如果**名称 ** == “main”： capturer = SystemAudioCapturer()捕获器 = SystemAudioCapturer（） capturer.run()  capturer.run（）

hello,   I also encountered the same problem, ask how to solve, your side solved it?