案例研究:基于ios的手机实时交换流媒体

在本文中, 我给你介绍一下我的手机, iOS-driven, 多幅相机, 无线直播设置. It was designed around the need to push multiple live streams at an outdoor event where I needed to move everything around with me all day long. 没有AC或以太网馈电. 我用的所有东西都安装在两个三脚架上.

你可以很容易地将其调整为在汽车中进行多摄像头制作, 一艘船, or any other place where you need the flexibility and production value that a switched production delivers, 但仍然需要它完全移动.

为了这次拍摄, 我在德克萨斯州的旧金山艺术步行街, 为旧金山艺术协会做一系列Facebook直播. 我有三台相机. 在这篇文章附带的视频中, I do a visual walk through the gear I had with me and I used one of the cameras in the live-streaming kit because it was already set up for recording

这个工具包

我在视频中使用的相机展示了整个设置(下面的图1)是一款带有配件广角镜头的iPhone 5. I chose the 5 because I personally like the form factor of the 5 with the flat sides. +, 我为iPhone 5购买的配件也适用于iPhone SE, which is nearly identical to the iPhone 5 and is actually still a current and very affordable Apple product, 尽管iPhone 6和iPhone 6之间相隔多年, 7, 8, X). iPhone 5s也包括在iOS 11的升级中. iPhone 5已经成为iOS 10的“孤儿”.

图1. 在旧金山艺术步行街使用的移动流媒体设置

我有两个iPhone 5的保护套. One is a “glove”-type case that fits tightly, and has a metal mount for external lenses. 它没有任何安装附件或三脚架, but the case is only a millimeter bigger than the phone so it fits into any generic phone holder clamp. For the video I have a wide-angle lens on the camera that came as part of the kit. In the description of the video on YouTube, I have links to the items that I used.

我有第二台iPhone 5. It may be a 5s; to be honest, I can’t tell the difference between them. 第二款iPhone 5装在一个iOgrapher手机壳里. These are very common and also very handy in that they have handles to facilitate walking around with the phone without fumbling. 顶部还有冷鞋支架，用于放置麦克风和灯. The iOgrapher has a wide, flat base with a 1/4-20 threaded hole for tripod mounting. 在前面，有一个大的螺纹安装镜头. iOgrapher提供了一个广角镜头，一个长焦镜头和一个远程变焦镜头.

我有一台iPad Air，还是用了一个iOgrapher外壳(下面的图2). 在安装iPad的配件方面，你能做的真的很少. 我觉得照相机对塑料制品来说有点贵, 但话说回来, 它仍然比市场上的其他解决方案便宜得多. 它也做了它的设计，没有大惊小怪. I like the one I have because it’s flat, which makes it easy to slide into a laptop case.

图2. iPad Air在iOgrapher的情况下

Every time Apple makes the slightest change in the design of its devices—a millimeter longer, 更广泛的, 更厚或更薄, 圆, 更多的广场, 稍微移动一下按钮, or moves the camera a smidge—the existing cases don’t work and entirely new products need to be designed and molded for the new iOS device. 有一些产品是为“通用”平板电脑设计的, 用于三脚架安装, 牵手, 和accessory-mounting, 但那些更贵, 体积也大得多.

没有某种“包裹”，就没有真正的干净, 可靠的, 或者简单地将配件安装到iPad上, 或者将iPad安装在三脚架或其他支架上. 如果你只想用iPad来控制, 然后你可以使用桌面“文件夹”,但同时你也失去了其中一台相机的潜在用途.

For audio, I’ve investigated ingesting audio into the iPad via USB, and via a TRRS cable. 这是TRRS提示, 环, 环, sleeve) cable has the additional 环 where the microphone from a headset is fed back into the iOS or Android device (下面的图3). 当我在USB音频和模拟音频之间进行正面测试时, 到目前为止，USB音频更清晰，听起来也更好.

图3. 这条TRRS音频线是iDevice准备的, 但在与USB音频的面对面测试中表现不佳.

However, my USB audio mixer is bigger, it requires AC, and it uses a sizeable and heavy AC adapter. So I scoured the web and found the tiny USB audio mixer shown below the iOgrapher-mounted iPad in 图1, 声称它不仅可以通过USB输出音频, 但它也可以通过USB供电. 这个Maker Hart Just Mixer 5是一个很酷的小设备，但是, 不幸的是, iOS设备无法识别USB音频. 我就此事联系了创客哈特. 工作人员说，它的混频器是为线路级音频输出而设计的, 而iOS设备需要麦克风级别的输入. 显然这两个设备可以通信, 看到差异了吗, 并且完全不要传递音频, 即使我可以拒绝大师的邀请，让它成功.

尽管如此，这个轻量级的混合器的小形状因素仍然是可取的. 它的小, external USB battery pack was downright diminutive compared to the AC adapter for my bigger mixer. Maker Hart的混频器也有蓝牙音频在通道一, 这意味着它使我能够在音频混音中消除至少一根电缆. I was able to play some intro and outro music from an old iPhone 4 over Bluetooth into the mixer. 我把它设置在一个轨道上，让它循环播放，整个下午它都在循环播放.

Also feeding the audio mixer was my host’s wireless handheld microphone on input 2. 我在第三频道设置了第二个无线网络, 以防我们需要后援, 或者两个拿着麦克风的人. 但主要是, I planned on having the host point his handheld mic at the guest and manage the audio that way. 最后, 在第4频道, I added a powered short shotgun microphone (森海塞尔) mounted on the iPad that you can see in 图2 作为环境声音的备份，或者以防其他一切都有问题.

The output of the mixer goes into a special cable that feeds the TRRS of the iPad. I tried a cheap little adapter with two 1/8" sockets for headphone and microphone, 但适配器的使用不确定. 更贵的适配器总是工作可靠, 但它有一根15英尺长的电缆，我把它缠在了旅行箱的把手上. The cable adapter also has a headphone jack so I can hear what the application hears, but it's delayed by something like a half second so I cannot keep my headphones in while doing my own audio into the app.

The mixer features sunken sliders for each of the inputs (I used four of the five available), 这样就很难撞到它们了. 这也是为了确保当你把搅拌器扔进你的齿轮袋, 你不会把滑块弄坏的. 还有下沉的“低音/高音”控制. Honestly, these are sort of a weak point of the mixer as it's little more than a "tone" control. 你可以逆时针转动它来减少高音, 或者你可以顺时针转动它来降低低音(对风的噪音很有用). 但是你没有增加原始信号的任何部分. 它本质上是一个表盘上的可调带通滤波器.

The outputs include 1/8" stereo as well as L/R RCA jacks that use a common Master output slider, 还有一个耳机插孔，有自己的调节旋钮. There is also USB audio out which I have not tested as it does not work with iOS. The fact that it offers stereo outs from each input would benefit from a “pan” control on each input, 但是这个搅拌器没有锅控. 值得庆幸的是, I did not have any issue with a microphone not appea环 in the audio channel that was fed to the iPad.