Audio resampling.

[shogo4405]

Description & motivation

• refs Audio enhancements #1276
• I have added a feature to maintain a constant sampling rate during the broadcast, as a consistent sampling rate and channel configuration are preferable during streaming.

Usage

stream.audioSettings = .init(
  bitRate: 64 * 1000,
  sampleRate: 44100.0,
  channels: 1
) 

/**
A value of 0 corresponds to the same sampling rate and channel count as the input data.
The maximum value is a sampling rate of 48kHz and a channel count of 2 channels.

stream.audioSettings = .init(
  bitRate: 64 * 1000,
  sampleRate: 0,
  channels: 0
) 
*/

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Tests

RTMP Streaming

iOS(iPhone14 Pro max iOS16.6)

• Built-In Microphone: <AVAudioFormat 0x283935a90: 1 ch, 44100 Hz, Int16> numSamples = 1024
  • sampleRate: 48000Hz
  • sampleRate: 16000Hz
• Built-In Microphone: <AVAudioFormat 0x283935a90: 2 ch, 44100 Hz, Int16> numSamples = 1024
  • sampleRate: 48000Hz
  • sampleRate: 16000Hz
• AirPods: <AVAudioFormat 0x2828fc690: 1 ch, 24000 Hz, Int16> numSamples = 1024
  • sampleRate: 48000Hz
  • sampleRate: 16000Hz
• ReplayKit appAudio: <AVAudioFormat 0x2826edae0: 2 ch, 44100 Hz, Int16, interleaved>
  • sampleRate: 48000Hz
  • sampleRate: 16000Hz
    iPadOS(IPadAit 5h/iOS17.0)
• ZOOM AMS-44: <AVAudioFormat 0x2826edae0: 4 ch, 44100 Hz, Int16, interleaved>
  • sampleRate: 48000Hz
  • sampleRate: 16000Hz

macOS(MacBook Pro 14inch 2021 Ventura 13.5.2)

• Built-In Microphone: <AVAudioFormat 0x283935a90: 1 ch, 44100 Hz, Float32> numSamples = 512
  • sampleRate: 48000Hz
  • sampleRate: 16000Hz
• Loopback audio: AVAudioFormat 0x6000026bd4a0: 6 ch, 48000 Hz, Float32, deinterleaved> numSamples = 512
  • sampleRate: 48000Hz, channel: 0
  • sampleRate: 16000Hz, channel: 1
• BOMGE BMG22 USB: <AVAudioFormat 0x600002825b80: 2 ch, 192000 Hz, Float32, deinterleaved>
  • sampleRate: 48000Hz, channel: 0

Recording

iOS

• Built-In Microphone: <AVAudioFormat 0x283935a90: 1 ch, 44100 Hz, Int16> numSamples = 1024

IPadOS

• ZOOM AMS-44: <AVAudioFormat 0x2826edae0: 4 ch, 44100 Hz, Int16, interleaved>

Screenshots: