ios - libjingle iOS : Don't ask for mic permission

Question

我正在开发 WebRTC iOS 应用程序以从网络摄像头接收视频/音频。只有网络摄像头发送视频和音频，移动设备不发送任何内容。

我正在使用来自 CocoaPods (v11177.2.0) 的 libjingle_peerconnection 库。

一切正常，我可以正常接收视频和音频，但我遇到了设备权限问题。我第一次使用该应用程序时，当我想从网络摄像头接收视频时，iOS 应用程序要求获得麦克风许可。这很重要，因为设备不发送音频，而我的客户说“为什么应用程序要求麦克风？？”

这很奇怪，因为对于相机，该应用不需要任何许可。

我已经检查了 SDP，似乎两者都可以(提供和回答)。

这是我创建 peerconnection 对象的方式没有附加流:

RTCICEServer *stunServer = [[RTCICEServer alloc]initWithURI:[NSURL URLWithString:@"stun:stun.l.google.com:19302"] username:@"" password:@""];
    NSMutableArray *iceServers = [NSMutableArray arrayWithObject:stunServer];

RTCPeerConnectionFactory *factory = [[RTCPeerConnectionFactory alloc]init];

NSArray *peerConnectionConstraints = @[[[RTCPair alloc] initWithKey:@"DtlsSrtpKeyAgreement" value:@"true"]];
RTCMediaConstraints *peerConnectionConstraints = [[RTCMediaConstraints alloc]initWithMandatoryConstraints:peerConnectionConstraints optionalConstraints:nil];

RTCPeerConnection *pConnection = [factory peerConnectionWithICEServers:iceServers constraints:peerConnectionConstraints delegate:self];

NSArray *sdpConstraints = @[[[RTCPair alloc] initWithKey:@"OfferToReceiveAudio" value:@"true"],
                            [[RTCPair alloc] initWithKey:@"OfferToReceiveVideo" value:@"true"]];

RTCMediaConstraints* sdpConstraints = [[RTCMediaConstraints alloc] initWithMandatoryConstraints:sdpConstraints optionalConstraints:nil];
[pConnection createOfferWithDelegate:self constraints:sdpConstraints];

这是生成的 SDP Offer:

v=0
o=- 6528383367639880158 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE audio video
a=msid-semantic: WMS
m=audio 9 RTP/SAVPF 111 103 104 9 102 0 8 127 126
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:0QOsaBCKhCBBcHz5
a=ice-pwd:/y5snrrO3Qmq37m2aejRbK1E
a=mid:audio
a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=recvonly
a=rtcp-mux
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:x1lfnVdo9lCRa9ykH6759WhY1SnI+dbLjKNbkTl+
a=rtpmap:111 opus/48000/2
a=fmtp:111 minptime=10; useinbandfec=1
a=rtpmap:103 ISAC/16000
a=rtpmap:104 ISAC/32000
a=rtpmap:9 G722/8000
a=rtpmap:102 ILBC/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:127 red/8000
a=rtpmap:126 telephone-event/8000
a=maxptime:60
m=video 9 RTP/SAVPF 100 101 116 117 96
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:0QOsaBCKhCBBcHz5
a=ice-pwd:/y5snrrO3Qmq37m2aejRbK1E
a=mid:video
a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=extmap:4 urn:3gpp:video-orientation
a=recvonly
a=rtcp-mux
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:x1lfnVdo9lCRa9ykH6759WhY1SnI+dbLjKNbkTl+
a=rtpmap:100 VP8/90000
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=rtcp-fb:100 goog-remb
a=rtcp-fb:100 transport-cc
a=rtpmap:101 VP9/90000
a=rtcp-fb:101 ccm fir
a=rtcp-fb:101 nack
a=rtcp-fb:101 nack pli
a=rtcp-fb:101 goog-remb
a=rtcp-fb:101 transport-cc
a=rtpmap:116 red/90000
a=rtpmap:117 ulpfec/90000
a=rtpmap:96 rtx/90000
a=fmtp:96 apt=100

这是来自网络摄像头的 SDP 回答:

v=0
o=- 3699612909 3699612909 IN IP4 0.0.0.0
s=-
c=IN IP4 0.0.0.0
t=0 0
a=msid-semantic: WMS
a=group:BUNDLE audio video
m=audio 1 RTP/SAVPF 111 0
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=mid:audio
a=rtcp:9 IN IP4 0.0.0.0
a=rtpmap:111 opus/48000/2
a=rtpmap:0 PCMU/8000
a=sendonly
a=rtcp-mux
a=fmtp:111 minptime=10; useinbandfec=1
a=maxptime:60
a=ssrc:3192391506 cname:user604422501@host-6a96398f
a=ice-ufrag:r2kq
a=ice-pwd:6VJu/y0Kbc4iUDQB/1ZrnE
a=fingerprint:sha-256 57:26:29:A5:DD:CD:42:74:C9:A3:BB:C4:67:D1:1C:24:E9:4B:4C:86:6F:93:32:03:52:6B:2B:77:B3:C4:E8:88
m=video 1 RTP/SAVPF 100
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=mid:video
a=rtcp:9 IN IP4 0.0.0.0
a=rtpmap:100 VP8/90000
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=rtcp-fb:100 goog-remb
a=sendonly
a=rtcp-mux
a=ssrc:455461391 cname:user604422501@host-6a96398f
a=ice-ufrag:r2kq
a=ice-pwd:6VJu/y0Kbc4iUDQB/1ZrnE
a=fingerprint:sha-256 57:26:29:A5:DD:CD:42:74:C9:A3:BB:C4:67:D1:1C:24:E9:4B:4C:86:6F:93:32:03:52:6B:2B:77:B3:C4:E8:88

如您所见，在 SDP 报价中，两种媒体(音频和视频)都是“receiveOnly”，在 SDP 中回答“sendOnly”，所以我认为没有与 SDP 相关的问题。

有人知道为什么要请求麦克风许可吗？如果您需要更多信息，请告诉我。

谢谢!

Answer 1

我没有使用过您的代码/库，对于那部分我无能为力，但是来自 Apple documentation我们可以阅读:

The first time your app’s audio session attempts to use an audio input route while using a category that enables recording, the system automatically prompts the user for permission. You can explicitly ask earlier by calling the request​Record​Permission(_:​) method. Until the user grants your app permission to record, your app can record only silence.

这可能会给您一些线索，说明某处(可能在 libjingle 中)正在访问 iOS Audio Session，并且可能是什么触发了麦克风权限。