VMix and VMode

If you're familiar with Axia mixing consoles, then you already know about VMix and VMode, the virtual mixing and stream manipulation utilities that are built into these products.

That same functionality is available with Zephyr iPort PLUS. VMix (short for Virtual Mixer) provides up to 8 channels of “virtual mixing”, which can be used to pre-mix up to 5 audio sources each for presentation as a single. VMix works completely independently of the rest of your iPort. In addition to static control of VMix through its web pages, Axia’s Pathfinder routing control tools can also be used to dynamically control VMix and create mixing functions based on a variety of system-wide parameters.

VMode (short for Virtual Mode) can be used to convert channel count, channel order, and/or channel content between audio streams at their input and output. For example, passing some channels while cutting others, summing stereo to mono, upmixing or downmixing between stereo and multi-channel, combining channels from two inputs into one output. Select audio as input, define the “Mode” (conversion type, or in other words, the routing within an internal matrix), and define the output as a network source into the AoIP network. There are 8 VMode instances in an iPort engine. Normally, these would be used to manipulate Livewire audio channels before or after the iPort's inputs or outputs.

Virtual Mixing with VMix

What’s it all about?

VMix is a 40-input “virtual” mixer accessed using the Zephyr iPort PLUS web browser. This mixer consists of 40 stereo input channels, a direct output for each channel, 8 submixer outputs, and one master out. The 40 channels are divided equally among the 8 subgroups, providing 5 stereo channels in each subgroup mixer. Using these, you can combine multiple Livewire audio channels into a single summed channel, which can then be sent to a receiving Zephyr iPort PLUS.

The various VMix outputs described above are sources that can feed your Livewire network and they can be manipulated in the same manner as any other audio source. A VMix source can be applied to a console fader, assigned to an audio node destination, or monitored by Pathfinder.

To understand this concept, think of VMix as a standalone piece of hardware. If you visualize wiring an external line mixer to your network, Livewire audio sources would be connected to the mixer inputs; your VMix outputs then become mixdowns that you can use anywhere else on the network, just like any other audio source.

To access VMix setup, open a browser on a computer connected to your Axia network and browse to the IP Address assigned to Zephyr iPort PLUS or, if you have Axia iProbe, open the UI page by right-clicking on the device’s icon in the left pane. Then, choose the V-Mixer and V-Mode item from the navigation bar.

The following image is an excerpt of the VMode setup screen. It shows the VMix Main and Sub-Mixer 1 controls. These sub-mix controls are duplicated for all 8 VMix submixers.

Note that adjustments made to VMix take effect as soon as you apply them — so changes saved “on the fly” will affect your output streams immediately.

VMix Main Controls

The VMix Main output provides a summed mix of all 8 submixes. Unless you need a single output that combines the audio from of all the submixes, you may leave this disabled — it doesn’t need to be enabled for the submixers to work. There are only a few settings for this control:

Out Name - You can enter a friendly name for the VMix Main output, which will be displayed as a source name on your Axia network.

Out Stream Type - Choose from Live Stereo or Standard Stereo, or leave it Disabled if no Main stream is desired.

The Status window will normally display “OK” when the stream is enabled.

The Audio box will be green when audio is present.

VMix Submixer Controls

In most cases, the VMix Subs are the only channels you will need to enable, since each Sub has its own direct output. Only enable Submixes you intend to actively use; active submixes without any activity clutter up your network with empty streams.

First, you’ll want to enable the Submixer you’re working with. At the top of the section, you’ll see (in this case) Submix 1 displayed on the screen. Next to that are controls for:

Gain. Set this at whatever output level you want the submix output stream volume to be.

Channel. All Livewire audio streams are assigned a Channel number; put a unique value in this box.

Out Stream Type. Choose from Live Stereo or Standard Stereo. Disabled turns off the submixer.

Each VMix Sub submixer input includes an on/off setting, a gain setting, and automatic fade-up/fade-down time parameters. Using one is easy; let’s walk through the steps:

In the Src Name box, enter the name of the source you’ll be assigning to the input.

In the Channel box, enter the unique Livewire channel number of your audio source.

In Stream Type will normally be set to “From Source”, meaning that the source itself (a mic, CD player, etc.) will be providing the audio. However, you can select “To Source” to use the source’s automatically generated Backfeed (mix-minus audio) as in input.

Example: Selecting “From Source” when a phone hybrid is assigned as a VMix Sub input would use the caller audio; selecting “To Source” would instead use the Mix Minus sent to the hybrid.

Select the Enable box next to the input to turn the Submixer input on.

Leave the Fade Time boxes set at their default.

The Fade Time function won’t be used in normal operation, but can be used to create cross fades between sources when Pathfinder is dynamically making changes to the VMix.

If, say, 1.0 is entered in the first box, the submixer channel’s audio will rise from -∞ to the Gain value set in the next field in 1.0 seconds. If the field is set to 0, the audio will simply turn on at the gain value specified.

The second box works the same way, but controls the ON to OFF fade time.

In the Gain box, enter the setting, in dB, that you want for the Submixer input. Each input has its own individual Gain setting.

That’s all you need to do to configure a VMix Submixer input stream. You can configure up to 5 input streams per VMix Submixer.

At the bottom of each of the submix sections is an Apply button. Any changes you make will be saved when this button is pressed. Be sure to save the changes for each submixer as they are configured.

VMIx Submixer Advanced Options

There are some additional options provided for advanced users.

In most cases only the Submix output itself needs a unique channel number, but if you so desire, each VMix input can also be sent back to the network as a unique source, post the ON/OFF and gain stage of the VMix. Some users find this useful for constructing “cascaded” mix channels to suit unique situations. To do so, enter values for these controls:

Out Name: The name you give the post-on/off submix channel to send back to the Axia network.

Channel: the channel number you assign to the post-on/off submix channel to send back to the Axia network.

Out Stream Type. Choose from Live Stereo or Standard Stereo to enable the direct output stream for this VMix “fader”. Disabled means no stream will be generated.

Be sure to click Apply after you’ve finished making any options changes.

Some VMix Examples

Now that you know how to enable and set up VMix submixers, what might you do with it? The possibilities are limited only by your imagination. To get your creative juices flowing, here are some examples.

A Mix of Sources to Monitor

Some facilities may need to monitor one or more sources in addition to program audio, like the “squawk channel” some satellite feed providers use to relay announcements.

If you wanted to monitor this “squawk” audio on your Preview speaker without taking up a fader assignment, you could create a mix of the “squawk” source and the Preview mix from the engine. The VMix Sub Channel would be the audio source that you would route to the Preview speaker.

Virtual VMix Control

With a User Panel created in the Pathfinder Core Pro, you can remotely control the VMix channels in Zephyr iPort High Density. This gives studio talent or producers direct control of iPort's Vmix, without the need for a physical console. The computer running the User Panel must have access to the AoIP network to which the iPort High Density is connected.

GPIO control of your VMIX with Pathfinder

Imagine that you have a night jock that should monitor all four radio stations in your cluster. To help make sure this actually happens, you could send all four off-air signals as sources into a VMix submixer, and take the output of that submix to a monitor. A Fusion accessory panel or external button wired to a GPIO port could then provide a “press and hold” function to allow the jock to monitor the sources momentarily. (This example is only possible with Pathfinder control of VMix.)

Manipulating Streams With VMode

VMode Application

Each of the 8 VMode instances supports audio streams with up to 8 channels at input and up to 8 channels at output. Between the input and output, there is a matrix, where the conversion is performed, according to the selected audio routing option (“Mode”). Livewire 8-channel streams carry 5.1 content in channels 1-6, and stereo content in channels 7 and 8, and the matrix is partitioned the same way, to fit them natively:

• Channels 1 to 6 of the matrix form a multi-channel part

• Channels 7 and 8 of the matrix form a stereo part

Routing option (“Mode”) names refer to the parts of the matrix and conversions performed between them. They do not refer to channel maps of the input/output streams.

For receiving and transmitting, two stream classes are distinguished:

• Class “mono/stereo”: streams with 1 or 2 channels

• Class “multi-channel”: streams with 3 to 8 channels

Input streams put their content into, and output streams take their content from, the stereo or multi-channel parts of the matrix, according to their mono/stereo or multi-channel classes. Multi-channel streams with 7 and 8 channels span across the both parts of the matrix, starting from channel 1, in the natural order. Livewire 8-channel “Surround” streams fit the matrix mapping without reordering.

The VMode view provides status of the current configuration.

To change the configuration, select the far right “Configure…” button.

SDP file: If the input stream to the VMode is an AES67 stream, an SDP file may be supplied and uploaded using the “Choose File” and “Import” buttons.

SDP document: Alternatively, the textual content of an SDP file may be copied and pasted in to this box and applied by clicking “Import”

Input Selector: used to select any source that is native to the iPort engine or to select an “EXTERNAL” source from the network.

Source Name: Text field used to describe the input

Address: This is used to manually define an EXTERNAL source. Note that this supports Livewire, AES67, Unicast and AES67 SIP. Usage is shown in this screen shot and on the Web UI.

Notes regarding SIP ports used:

Default start port for SIP audio is 16384

Valid range for RTP stream protocol is from 16384 to 65535

SIP URI protocol supports ports from 1 to 65534 (CPSIP Stack does not allow port 65535)

Default SIP port is 5060

Mode: The manipulation within the matrix is referred to as rouging and is configured by selecting a Mode from the list.

Pass stereo: passes the stereo part of the matrix transparently, and blocks the multi-channel part.

Pass multi-channel: passes all 8 matrix inputs to the corresponding outputs.

Transpose options: These options move two channels between the stereo part of the matrix and channels 1 and 2 of the multi-channel part, as indicated in the name of the option.

Upmix and Downmix options: These options mix, copy, and/or apply gains to input channels, to obtain output channels. Only the stereo part of the matrix is involved in transformations, where both inputs and outputs are of the mono/stereo class. Both parts of the matrix are involved in transformations between the mono/stereo and multi-channel classes. All "Upmix …" options output silence in the LFE (sub woofer) channel.

Split Options: These options create a mono sum from a stereo input, apply the specified attenuation, and send it to either Left or Right output channel as indicated in the name of the option, while sending no signal to the other. For example, “Split L –6dB” sums Left and Right, reduces by 6dB, and places the mix on the Left channel.

Combine Options: These options are special in that they work with a pair of inputs. All 8 Vmode inputs are arranged in 4 fixed pairs – [1,2], [3,4], etc. When a “combine” option is selected on a Vmode instance, it takes input channels from the two inputs (designated A and B) of its pair, as indicated in the name of the option. For example, "Combine Left,Left" takes the Left channel from the A input and passes it to the Left channel of the output, and the Left channel from the B input and passes it to the Right channel of the output.

Additional details, with examples, can be obtained by following the “click here” link from the iPort while selecting your Mode.

SDP File: An SDP file may be supplied and uploaded using the “Choose File” and “Import” buttons.

SDP document: Alternatively, the textual content of an SDP file may be copied and pasted in to this box and applied by clicking “Import”

Source Name: Text field used to describe the input

Address: This is used to manually define the Livewire source channel or AES67 address. Note that this supports Livewire, AES67, Unicast and AES67 SIP. Usage is shown in this screen shot and on the Web UI.

Stream Type: This defines the type of stream to be generated from the matrix output. Similar to the input type field, there are many options available. Common AES67 and Livewire types are listed. The most common is L24 2ch (Livewire From source).

Packet time: This defines the latency and bandwidth consumption of the stream. Livewire has historically given this field a user-friendly name such as Live or Standard stereo. Packet times are now listed with their more common names referenced in parenthesis.

What's Next?

VMix and VMode are two of the features that make Zephyr iPort PLUS an even more versatile product. We've explained the fundamentals of each, and given you some examples of what to do with them. Hopefully, we've also brought out your inner hacker, and you'll develop something that solves an issue that is unique to your installation. If so, be sure to tell us about it.