Expose RTCAudioSource custom source API on iOS/macOS (parity with Windows/Linux builds)

[ihatebeans3000]

Summary

The iOS/macOS builds of this WebRTC fork currently do not expose the custom audio source API (CaptureFrame/OnData) that is available in the Windows/Linux builds (libwebrtc). This creates a platform inconsistency that prevents developers from implementing custom audio sources on Apple platforms.

Background

Current Platform Disparity

Windows/Linux (libwebrtc)

• Publicly exposes RTCAudioSource::CaptureFrame() API
• Supports SourceType::kCustom for custom audio sources
• Includes patch: custom_audio_source_m137.patch
• Header: include/rtc_audio_source.h

class RTCAudioSource : public RefCountInterface {
 public:
  enum SourceType { kMicrophone, kCustom };

  virtual void CaptureFrame(const void* audio_data,
                           int bits_per_sample,
                           int sample_rate,
                           size_t number_of_channels,
                           size_t number_of_frames) = 0;
};

iOS/macOS (CocoaPods WebRTC-SDK)

• Objective-C wrapper only exposes volume property
• No way to inject custom audio data
• Underlying webrtc::AudioSourceInterface not accessible

@interface RTCAudioSource : RTCMediaSource
@property(nonatomic, assign) double volume;
// No CaptureFrame or equivalent method
@end

Questions

1. Is there a specific reason this API is not exposed on Apple platforms?

I'm happy to contribute the implementation if this approach is acceptable.

Thank you for maintaining this valuable fork of WebRTC!

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