How To Create Quality Audio for Your Live Video Stream

There no doubt that video streaming is now an everyday event on the web. No longer do you have to plan well in advance and use expensive equipment that requires rigging and meticulous operation.

Periscope and Facebook Live are two of the higher profile platforms to deliver a live video experience, whilst cameras and apps such as Mevo and RecoLive are two methods to capture the video content. The video manipulation is truly staggering. High pixel-count cameras allow zoom and close-ups from a wide shot, meaning for simple shoots multiple cameras are no longer required.

 

But from an audio perspective they all suffer from the same thing – the use of built-in microphones in the device to capture sound. The lens and image converter may allow quality close-ups, but sound doesn’t play that way. Built-in microphones will, by definition, always be from the wide-shot camera position and simply be un-able to get in close or capture more than the ambient overall sound of that wide image, with its attendant “bathroom effect” or unwanted sounds.

Mevo

The Mevo: Great pictures, but you see that grill below the lens?

The mics are there. 

If you are going to capture quality audio, either to discriminate against unwanted sounds (crowd noise at an event) or to capture everything, but in proportion, e.g. a band on stage (PA systems are designed to help the vocalist, not the drummer) then getting a microphone in close is what you will have to do.

Using the correct microphone(s) in the right way is, of course, the answer to capturing quality audio. Connected to a mixing desk they can be balanced for a pleasing result. The problem is feeding the mixed signal to the streaming device, because this is where things get tricky:

The iPhone 7 aside, all current phones and tablets capable of streaming live video use the 3.5mm, 4 pole mini-jack as its audio input connector.

Note the words “four pole”; you cannot use a standard stereo jack (known as a TRS – Tip, Ring, and Sleeve) like this as the connector.

It won’t work.

3 pole minijack 3

 Phones a tablets use a four pole mini-jack like this:

4 pole minijack 4

Known as a TR1R2S (Tip, Ring 1, Ring 2, Sleeve) connector. The connectors carry the following signals:

Tip: Audio output left
Ring 1: Audio output right
Ring 2: ground reference
Sleeve: microphone input

This is why a standard TRS jack won’t work as the Tip and Ring signals are outputs and we are trying to send a signal into the device.

But you cannot use an AV mini-jack lead like this.

TR1R2S Minijack 3 x Phono Lead

These do have the TR1R2S minijack connector we want.

But the contacts carry the following signals:
Tip: Audio input or output left
Ring 1: Audio input or output right
Ring 2: video input or output ground
Sleeve: ground reference

You can see that the wiring for Ring 2 and the Sleeve is the opposite of what is needed. Use this type of lead and the input signal will connect to the ground of the device so won’t go any further.

Once we have the right connector with the correct wiring the issue of audio levels arises. The device expects a microphone level signal on Ring 2. This is a much smaller signal level than the “line” level signals that mixers operate at. So the level will need to be reduced or “padded down”. How much depends upon whether your send device uses “domestic” or “professional” line levels. Although named the same the former is about 12dB lower than the latter. As a rough indication of what level your device works at, if connects with XLRs it’s professional, using phono (cinch) connectors or 3.5mm mini-jacks means it works at domestic line level.

But if it has quarter inch jacks it could be either!

Once all these hurdles are overcome we meet the real clincher: Telling the device it has must take audio from its mini-jack socket and not from the internal microphone.

This is not a setting in the software, but a specific value of resistor being connected across the microphone input and the ground contacts. To further complicate matters this resistor value will also affect the value of the resistors used to pad the signal down.

So to recap we need:
• The right type of connector
• Wired with three resistors
• To convert a stereo signal to a mono one
• Reduce this signal level
• Tell the device to accept it as a signal input and switch-off the internal microphone

Oh and, if you want to keep the lead design both simple and reliable all three resistors really need to fit inside the body of the mini-jack!

What a faff!

Fortunately you don’t have to go to all this effort as it’s already been done for you. It is here that, after describing what you need to do and thus saving all the trial and error, I make no apologies for the blatant promotion of:

The Smartphone Pro – Line Po lead.

IMG 1167

It’s one of the clever leads available from AV Resilience. Using a 4 pole mini-jack, wired to two phono connectors, it connect a stereo mixer to a Smartphone or tablet and does all of the signal conditioning described above.

So save yourself the effort and get a Smartphone Pro – Line Po lead from AV Resilience.

Click an on this link or the image to order one.

Trying to get quality audio to accompany your quality video?

Problem solved!

Iain Betson