I'm developing a WebRTC iOS application to receive video/audio from a webcam. Only the webcam sends video and audio, the mobile device doesn't send anything.
I am using the libjingle_peerconnection library from CocoaPods (v11177.2.0).
Everything is working, I receive video and audio properly but I have an issue with device permissions. First time I use the application, when I want to receive video from the webcam, the iOS app ask for microphone permission. This is important because the device does not send audio, and my client is saying "Why the app is asking for the microphone??"
It is weird because for the camera the app does not require any permission.
I've checked the SDP and it seems that are ok both (offer and answer).
This is the way I create the peerconnection object with no streams attached:
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];
Here is the SDP Offer generated:
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
And here is the SDP answer from the webcam:
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
As you can see, in the SDP offer, both medias (audio and video) are "receiveOnly" and in the SDP answer "sendOnly", so I suppose that there is no problem related with the SDP.
Anyone knows why is asking for microphone permission? If you need more info please, let me know.
Thanks!
I have not worked with your code/libraries, for that part I can't help, but from the Apple documentation we can read:
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 requestRecordPermission(_:) method. Until the user grants your app permission to record, your app can record only silence.
That might give you a clue to that something, somewhere (probably in the libjingle) is accessing the iOS Audio Session and probably what is firing off the microphone permission.