教程:混合, 切换, and Streaming Live with the Roland VR-3EX All-in-One A/V Mixer

An A/V mixer is very different from a standard video mixer in that it has an audio component to it. 罗兰VR-3EX也不例外. On the left side, it has a full audio console with many inputs, including XLR inputs, 1/4” inputs， RCA立体声输入，mini 3.5mm立体声输入. 3.5mm inputs means you can take in an analog computer input and you can also take audio from embedded HDMI signals as well. 这是一个非常多功能，功能齐全的音频混音器.

至于视频方面, 我想从一开始就讲的一个问题是, “Why is the VR-3EX a standard-definition video switcher in the year 2014?“这有一个很好的理由. There’s still a need for video switchers that operate in standard-definition.

What’s more, the up-res 1080p output on this video switcher is exceptionally high quality. 这是, 很大程度上, 因为我们使用的是HDMI数字输入, 与模拟输入相反. 模拟合成和VGA输入可在此开关, 但如果你能避免使用它们, please do so because the digital-to-digital conversion is not a conversion per se. 这里涉及到缩放，从480p到1080p (下面的图1), but it provides much higher-quality output than you’d get if you started out with analog video inputs.

图1. 480p SD HDMI信号在Roland VR-3EX上转换为1080p. 单击图像以查看1920x1080分辨率的图像.

那, 本身, is one of the main reasons why Roland updated the VR3 with the VR-3EX video switcher: to add HDMI digital video input that wasn’t available on the VR3, making the VR-3EX a full-fledged digital video switcher with a digital-to-digital workflow, while retaining the ability to de-embed the audio from those HDMI video inputs and bring it in from a different audio source.

音频功能

Let’s delve a bit further into the audio functionality of this A/V mixer. 首先，你可以看到 图2(下面) that there’s an array of knobs and sliders, just as you’d expect to see in any audio mixer. 罗兰拥有丰富的音频混频器遗产, so it should come as no surprise that they’ve done a really good job of laying out the audio controls on this A/V mixer. There are 4 primary sliders that correspond to the XLR/TRS inputs that you’ll find on the side. 在我为本文制作的视频教程中, 我用无线电视里的XLR给自己装上了麦克风, 哪些插头插入VR-3EX设备的侧面. 对于每个4个XLR输入有一个增益旋钮在顶部, 以及一个3波段均衡器的高点, mids, 和低点. VR-3EX还具有2个内部麦克风, 位于控制台的左上方和右上方.

图2. The Roland VR-3EX has volume sliders for each input and the main, as well as ¼” and 3.5mm耳机输出. 

The first input I’m going to adjust is the XLR input for my lav microphone. We start off by adjusting the slider by raising it to the parity mark, which is about midway point where there’s no volume gain or attenuation. 这样我就可以自由调整增益了. If I adjust the gain too high, I’ll get some clipping that will be visible in the audio monitor.

使用音频设置菜单

The tendency to clip suggests the need to tweak some items in the setup menu (下面的图3). To address that, I click the SETUP button under the appropriate audio input. This brings up a menu where I’ll see two adjustments, Gate and 压缩机. 这是两个非常有用的音频级别工具. The Gate enables you to eliminate any hum or other noise in the background by setting a noise floor level. Anything that falls under than noise floor threefold will be attenuated. The 压缩机 allows you to attenuate audio once it reaches a certain threshold. 如果我调整音阶，我可以确保我没有剪辑我的音频. Other controls used in tandem with the Gate and 压缩机 allow you to extend your usable audio range.

图3. The audio channel setup menu adds additional audio features like Gate, 压缩机, 音频延迟, 高通滤波器, 和潘.

在音频设置和测试阶段, the Solo and Mute buttons allow me to isolate individual audio inputs so I don’t have to adjust the sliders; I can just toggle between them.

Finally, in the bottom-right corner of the Audio Setup menu is the Delay. 音频并不总是与视频同时到达. This may be due to the fact that the speed of light is faster than the speed of sound; or, 由于音频处理, 一些音频信号可能会比其他信号早一点到达. 当我在制作这篇文章的视频教程时, the HDMI audio came in with a little delay compared to the XLR audio source plugged directly into the switcher, 在混音中两个声源都会产生一点回声. 为了弥补这一点, I add a slight delay to the XLR audio source to match the delay on the HDMI source. 那’s one of the techniques you can use if you experience this type of echo effect. It’s nice that the Roland VR-3EX has that type of audio delay functionality built right into the video switcher.

One really nice audio feature that Roland has added to the VR-3EX is the availability of an AUX send for audio. You’ve got 1/4” and RCA outputs, and for audio monitoring there’s a 3.5mm耳机输出以及1/4“输出.

On the program monitor, you can see the individual audio levels for each of your inputs and outputs. It’s really useful when you’re trying to get the right audio level mix. You can see what inputs are working and have levels, and which ones don’t.