There are a variety of audio issues possible as part of a stream. In case you aren't familiar with the terms, audio and sound mean roughly the same thing and can be used interchangeably. This article covers several different possible audio issues and resolutions for each.
No audio / sound
Check your computer audio output
First, you'll want to check that the computer you are watching your broadcast on, you actually have the sound turned on and the volume up. You can test this by going to your computers audio settings and pressing the test sounds, or navigating to another video on the web and making sure you can hear audio through your computer speakers or headphones.
If you hear audio on other videos on the web and not on IBM Watson Media, check the volume in the player and make sure it is turned up.
If you have already established that the IBM Watson Media player and your computer have the volume turned up but you still aren't hearing any audio on your broadcast, next you need to check the audio settings in your encoding / broadcasting software. Every encoding software might have slightly different controls. We will cover the issue in the IBM Watson Media Web Broadcaster and Producer and if you are using something different, try to find the audio controls in the encoder you are using.
Audio too quiet
General tips if your audio volume is too quiet
- Make sure you are using a microphone as close to your sound source as possible. Most microphones only can pick up sound within a few inches. A microphone that is 20 feet away from the person speaking will not pick them up very well and your levels will be too quiet.
- Make sure you aren't accidentally using the built-in mic on your computer when you mean to be using an external mic. Follow the instructions for the IBM Watson Media's Web Broadcaster or check the audio settings in the encoding software you are using.
- Check your gain (gain is also sometimes called "level") on your microphone, your audio mixer, your camera and your encoding software. Make sure your levels are adequately turned up on every step of the way.
Audio too Loud
You'll know your levels are too loud if you hear distortion on your audio signal. Distortion will sound like an unpleasant degradation of the sound, particularly when somone is speaking loudly or when there are loud music sections.
Check mic / line input sensitivity and camera input gain
One of the most common causes of distortion in your audio signal is when you feed a mic level input a line level signal. If you are routing the signal from an audio mixer through your camera, make sure you set the camera to accept a line level signal and not a mic level signal. Additionally, most cameras have a gain control for the incoming audio. This might either be physical dials / switches on the body of the camera, or a setting inside a menu in the digital display. Locate these settings and adjust accordingly.
Check gain staging on every device in your audio signal path
Check your gain (gain is also sometimes called "level") on your microphone, your audio mixer, your camera and your encoding software. Each piece of gear you are using should have a meter. If the level is too loud, it will clip, or hit red on the meter. If your meters look like this, this is very bad and you should turn your volume down.
Audio echo or double
Echo or feedback while broadcasting
If you are using your built in mic or your microphone or camera is located close to a computer you are also monitoring / listening to the broadcast on, you might experience audio feedback. Audio feedback starts out like an echo, but can also sound like a "robot voice" a repeat, or can turn into a horrible loud screeching noise. Its very easy to prevent audio feedback by using headphones to listen to the broadcast and make sure your headphones are not turned up too loud.
There is secondary audio or an echo coming from my computer while I'm watching a broadcast. How can I turn it off?
If you are viewing a broadcast and hear secondary audio, you may be hearing audio from another source on your computer, for example you have the same broadcast playing on Twitter and also watching it on the channel page. Or you are watching another video on the web and that is playing at the same time as the video. Make sure that all other open internet browser windows and tabs on your computer are closed or muted prior to viewing your desired IBM Watson Media broadcast.
Buzz, hum or other artifacts in the audio
There is a buzz or hum in the audio signal
Buzzes and hums are generally analog audio problems, which means they are not caused by anything in your encoder or anything on the IBM Watson Media platform. Two common causes of buzzes and hums are grounding issues or radio frequency interference (RFI). When RFI is really bad, sometimes you are hearing radio stations or people talking through your audio wires. These problems can be difficult to solve since sometimes they are caused by the electrical wiring of the building you are in. Here are some potential solutions to fix a buzz or hum in your audio.
Try switching your cables
If you are experiencing a hum or a buzz it is worth it to try to switch which kinds of cables you are using to see if you can reduce the hum or noise you are hearing. Buzzes and hums can be caused by a faulty cable with loose connections, or by using the wrong type of cables.
XLR Balanced Audio Cables
XLR or Mic cables are generally balanced cables because they have three connections in them: positive, negative and ground. These types of connections are used in most professional productions and are more resistant to hum and other noises.
RCA cables are unbalanced connections and are more likely to introduce hum or noise, particularly if they travel a longer distance. RCA connections are usually used on the cheapest consumer-grade gear.
1/4 inch Cables
1/4 inch cables can be either balanced or unbalanced. If you see one line on the end of the cable it means it is unbalanced, two lines means it is balanced. Balanced 1/4 inch cables have three connections, similar to an XLR cable: positive, negative and ground.
If you are experiencing hums or buzzes, trying swapping around cables and consider investing in gear that uses balanced and not unbalanced connections.
Adjust your lighting
Sometimes lighting circuits can introduce hums or buzzes into your audio. Try plugging your lights into a separate circuit, or turn off any overhead flourescent lights that are not essential to your video production.
Try a hum eliminator
Hum eliminators are boxes that you plug into your audio signal path which can sometimes kill a hum or buzz. Shop for hum eliminators at B&H.
Other audio artifacts: clicks, "glitches", strange noises
A clicking sound or glitchy sounds or other inexplicable noises are typically caused by something wrong in the digital signal path.
Check for sample rate mismatches
If you notice clicking sounds or have no audio at all, check your audio sample rate settings in your encoding software. If you have two digital audio components, the sample rate between the two must match. The most common sample rates are 44.1k and 48k. Typical video workflows have a 48k sample rate. Make sure you set the sample rates so they match.
Use high quality AAC audio encoding at at least 96Kbps
The other potential cause is a poor quality audio encoding, or too low of a bitrate on your audio encoding. We recommend AAC audio encoding at 96-160kbps.
Audio and video out of sync
Most audio / video sync problems are caused by your audio and your video travelling down two different paths and having a difference in the processing time between the two.
Embed your audio into your video signal
One way to fix audio sync issues is to route your audio through your camera's audio input so that it gets embedded into the video signal and processed the same way in the encoder, rather than going into a separate interface.
Use an audio sync delay
Another way to fix audio sync issues is to utilize an audio sync delay. Audio sync delays usually allow you to set in milliseconds the amount of delay you want to add to the audio signal. You watch someone speaking while adjusting the control and stop when it looks like the audio and video are in sync. Some virtual or hardware encoders have built in audio sync delay for this purpose.
You can also utilize a hardware audio delay unit. Here is an example of a hardware audio delay unit at B&H: Datavideo AD-100 Audio Delay Box
Restart the encoder or viewer application
It is much less common, but occasionally there can be audio video sync issues caused by the video encoder, in the stream itself, or audio and video can get out of sync for a single viewer. The most common way to resolve these issues is to restart the encoder or restart the viewing application.