ios - 在 iOS 的 webrtc 上启用立体声

Question

我在 iOS 上使用 Opus 编解码器进行 webrtc 音频流 (libjingle_peerconnection)。如何为音频播放启用立体声？

我从这篇博客文章中借鉴了一些想法，希望我能让它发挥作用。我们能够为 Web 客户端而非 iOS 客户端启用立体声。

https://www.webrtcexample.com/blog/?go=all/how-to-support-stereo-in-a-webrtc-application/

我在这样的提议和对等连接约束的约束中禁用回声消除:

private func initializeConstraints() -> RTCMediaConstraints {
    let mandatoryConstraints = [
        RTCPair(key: "OfferToReceiveAudio", value: "true"),
        RTCPair(key: "OfferToReceiveVideo", value: "false"),
        RTCPair(key: "echoCancellation", value: "false"),
        RTCPair(key: "googEchoCancellation", value: "false")
    ]
    let optionalConstraints = [
        RTCPair(key: "internalSctpDataChannels", value: "true"),
        RTCPair(key: "DtlsSrtpKeyAgreement", value: "true")
    ]
    return RTCMediaConstraints(mandatoryConstraints: mandatoryConstraints, optionalConstraints: optionalConstraints)
}

我像这样为 Opus 音频编解码器启用立体声:

func peerConnection(peerConnection: RTCPeerConnection!, didCreateSessionDescription sdp: RTCSessionDescription!, error: NSError?) {
    LOGD("created sdp")

    guard error == nil else {
        LOGE("error creating session description: \(error!)")
        delegate.onError(self, description: "Error creating sdp")
        return
    }

    dispatch_async(dispatch_get_main_queue()) {
        let replaceThis = "fmtp:111 minptime=10; useinbandfec=1"
        let replaceWith = "fmtp:111 minptime=10; useinbandfec=1; stereo=1; sprop-stereo=1"
        let sdpDescriptionWithStereo = sdp.description.stringByReplacingOccurrencesOfString(replaceThis, withString: replaceWith)
        let sdpWithStereo = RTCSessionDescription(type: sdp.type, sdp: sdpDescriptionWithStereo)
        peerConnection.setLocalDescriptionWithDelegate(self, sessionDescription: sdpWithStereo)

        self.delegate.onLocalSDP(self, type: sdp.type, sdp: sdpDescriptionWithStereo)
    }
}

我在 sdpDescriptionWithStereo 中得到了想要的结果。但我仍然无法使用立体声。

(而且，是的，我知道 stringByReplacingOccurrencesOfString 完全是一个黑客，但我稍后会谈到)

Answer 1

您可以在通知中心捕获事件，然后切换它。

     NotificationCenter.default.addObserver(self, selector: #selector(JanusCommunicationManager.didSessionRouteChange), name: NSNotification.Name.AVAudioSessionRouteChange, object: nil)

     @objc func didSessionRouteChange(notification:Notification) {
        let dict = notification.userInfo
        let routeChangeReason = dict![AVAudioSessionRouteChangeReasonKey] as! UInt
        let error:Error? = nil
        switch routeChangeReason {
        case AVAudioSessionRouteChangeReason.categoryChange.rawValue:
            try? AVAudioSession.sharedInstance().overrideOutputAudioPort(.none)
            break
        default:
            break
        }

    }