AppRTCDemo(WebRTC)+ iOS on iPhone 6 (iOS9)：当我设置约束时，本地RTCMediaStream无法工作

Question

我使用pod 'libjingle_peerconnection'，'~> 11142.2.0'

当我设置约束时

NSArray *mandatoryConstraints = @[
                                  [[RTCPair alloc] initWithKey:@"maxWidth" value:@"320"],
                                  [[RTCPair alloc] initWithKey:@"maxHeight" value:@"240"],
                                  [[RTCPair alloc] initWithKey:@"maxFrameRate" value:@"15"]
                                  ];
RTCMediaConstraints* mediaConstraints = [[RTCMediaConstraints alloc] initWithMandatoryConstraints:mandatoryConstraints
                                                                         optionalConstraints:nil];

下一步

RTCAVFoundationVideoSource *source =
[[RTCAVFoundationVideoSource alloc] initWithFactory:_factory
                                        constraints:mediaConstraints];
localVideoTrack =
[[RTCVideoTrack alloc] initWithFactory:_factory
                                source:source
                               trackId:@"ARDAMSv0"];

或

RTCVideoCapturer *capturer = [RTCVideoCapturer capturerWithDeviceName:cameraID];
RTCVideoSource *videoSource = [_factory videoSourceWithCapturer:capturer constraints:mediaConstraints];
localVideoTrack = [_factory videoTrackWithID:@"ARDAMSv0" source:videoSource];

然后结果是“黑色”本地流。也是当我开始

RTCMediaConstraints* constraints = [[RTCMediaConstraints alloc] initWithMandatoryConstraints:nil
                                                                         optionalConstraints:nil];

它正常工作；我如何创建带有一些约束的流？

Answer 1

这是我的约束初始化代码：

- (void) initMediaConstraints {
    if (!mediaConstraints) {
        // retrieve system information and set device name
        struct utsname systemInfo;
        uname(&systemInfo);
        NSString *deviceName = [NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding];
        if ([deviceName isEqualToString:@"iPad1,1"] || [deviceName isEqualToString:@"iPad2,1"] || [deviceName isEqualToString:@"iPad2,2"] || [deviceName isEqualToString:@"iPad2,3"] || [deviceName isEqualToString:@"iPad2,4"]) {
            // use these constraints on crappy devices
            mediaConstraints = [[RTCMediaConstraints alloc] initWithMandatoryConstraints:@[
                    [[RTCPair alloc] initWithKey:@"minWidth" value:@"192"],
                    [[RTCPair alloc] initWithKey:@"minHeight" value:@"144"],
                    [[RTCPair alloc] initWithKey:@"maxWidth" value:@"352"],
                    [[RTCPair alloc] initWithKey:@"maxHeight" value:@"288"]
            ]                                                        optionalConstraints:@[]];
        } else {
            mediaConstraints = [[RTCMediaConstraints alloc] initWithMandatoryConstraints:@[
                [[RTCPair alloc] initWithKey:@"minWidth" value:@"640"],
                [[RTCPair alloc] initWithKey:@"minHeight" value:@"480"],
                [[RTCPair alloc] initWithKey:@"maxWidth" value:@"1280"],
                [[RTCPair alloc] initWithKey:@"maxHeight" value:@"760"]]
                                                                     optionalConstraints:@[]];
        }
    }
}

然后我在这里用它们：

- (void) initVideoSource {
    // create a capturer and video source
    if (!localVideoCapturer) {
        localVideoCapturer = [RTCVideoCapturer capturerWithDeviceName:cameraId];
    }
    if (!localVideoSource) {
        localVideoSource = [peerConnectionFactory videoSourceWithCapturer:localVideoCapturer constraints:mediaConstraints];
    }
}

它检测应用程序是否运行在较旧的iOS设备上，如果运行，则设置较低的约束(我忘记了哪些设备，但我们在广泛的设备上进行了相当彻底的测试，以找到这些值)。如果它运行在更好的设备上，它会设置更高的分辨率约束(同样，为了找到这些值，我们进行了大量的测试)。

据我所知，max设置最大帧速率并不适用于本机iOS库，至少对我来说从未如此。相反，我实现了自己的最大fps检查如前所述。这并不限制发送到远程对等端的帧的数量，但它确实限制了呈现的帧数量，这已经极大地提高了性能。

为了完整起见，下面是我的整个呈现程序和相关的视图控制器代码