Multichannel Audio in Premiere Pro
“You know, it’s a shame that Premiere Pro can’t output more than stereo audio.”
“What?? Are you kidding?? Premiere Pro handles multichannel audio output great. Up to 32 channels, depending on formats. Where’d you get that idea?”
“I’ve tried it. Even if I set my output to multiple channels, I end up with a stereo pair on A1 & A2, and a bunch of blank channels. It doesn’t matter how many tracks I have in my timeline, it all mixes down to Stereo.”
Does this conversation sound familiar?
It’s becoming more and more common for people to want/need to output more than a stereo mix down from a Premiere Pro sequence. Some need multiple languages in a single file. Others want to keep a discrete output of a music track, or a voiceover, so it can be updated later. Yet most people have trouble understanding how this is done in Premiere Pro, and it’s one of the biggest differences between Premiere Pro and FCP7.
It All Starts with the Sequence
Take a look at any existing sequence you may have, and scroll all the way to the bottom of the audio tracks. You’ll see something there called a Master track.
The Master track is the mixed-down version of all the other tracks in the sequence. It doesn’t matter if you have a single audio track or 99 audio tracks – they all are getting mixed down into this Master Track. It’s similar to the way an audio mixing board works – you have a slider for each input track, but you also have a Master slider at the far right of the mixing board. It’s one extra place you can make a final adjustment of the mix volume before going out. For example, if you like the overall mix, but it’s just a little too hot, you can use the master slider to nudge the volume down a bit. This preserves the overall mix, but lowers the final output volume.
Why is this important to multichannel output? Take a look at this icon on the Master track:
That’s a STEREO master track. Most of the sequence presets that come with Premiere Pro are set by default to use a Stereo Master track. If we want to output multichannel audio, we’ll need to use a multichannel audio track. There’s currently no way to change the Master audio track in a sequence, so it’s best to start with a new sequence, and copy/paste from your existing sequence into the new sequence.
Start by creating a new sequence (File-New-Sequence) and pick out the format that best suits your resolution and frame rate. But before you click OK, go to the Tracks tab at the top of the panel.
In order to output multichannel audio, you need to use a Multichannel Master Track. This will enable you to output up to 32 discrete channels of audio. And, it’s flexible, and the number of output channels can be changed at any time in the sequence or in the audio mixer.
For those who use a lot of multichannel output, be sure to set a new sequence preset using a multichannel master track, and take note of the default pan and channel assign controls found here in the Track tab of the New Sequence box – we’ll reference them later in this tutorial.
Using the Multichannel Master Track
The Multichannel master is really flexible – it can be set to 2-channel for output of stereo, and any other number of channels up to 32-channel. To change it, just click on the number in the track header here:
You can also adjust the number of output channels in the Audio Track Mixer here:
Notice that when you change the number of output channels, the VU meter to the right of the timeline also changes – it matches the number of output channels. There are Solo buttons at the bottom to listen to individual pairs of channels.
Let’s take a further look at the Audio Track Mixer, because this is also where you assign channels to the various output channels. Notice that by default, all of the audio tracks are assigned to output 1+2. This means that currently, the mixer is assigning all the output tracks to mix down into output channels 1 and 2. In the mixer, go to Track A2, and change the output assignment to 3+4. Notice that you need to uncheck 1+2 and check 3+4 to make this happen – it’s very easy to duplicate audio out to discrete tracks this way! For example, lets say you need to cut a promo with mixed music, SFX, and V/O tracks, but also want to keep discrete versions of all 3 tracks:
As this shows, I’ve assigned all the audio into 1+2, so this will be my mixed version. But I’ve also routed copies of each tracks into 3&4, 5&6, and 7&8, respectively. This way, the output file will still contain “clean” versions of the music, VO, and SFX. Someone else could recut the promo later with a different voiceover, or change out the music, just by using these extra tracks in the finished file. (and assuming the playout server knows to ignore these extra channels for play-to-air.)
The Pan knobs in the mixer also affect the output – If I have mono content in a track, and the pan knob is left as the default (center), then it will go to both assigned output channels equally. If I need it to go discretely into a single channel in the output, I need to pan the track either left or right, depending on which channel I want the audio to go to.
For example, if I have a mono V/O in A4, and I want it to ONLY be in A9 of my output file, I would do the following:
Assign A4 to output 9+10
Pan to -100 (left channel)
It should look like this (I labeled the track to Mono VO to avoid confusion):
Most people I know who use Multichannel audio like to set up the mixer the same way each time – don’t forget that the output channel assign AND the Pan control can be set to a default setting in the New Sequence box. Having the mixer output pre-set in the custom sequence is the key to using this quickly and efficiently. Don’t forget.
Out of the Pan, into the Output Settings
The output from Premiere Pro is also super-flexible – you can pare off unwanted channels for a specific output, add additional blank channels for file compatibility with playout servers, and more. But, with great power comes great responsibility. You’ll want to check to make sure your output settings match what you want, or else your rendered file may be different from what you’re looking for.
Select your sequence, and go to File-Export Media. Then click on the Audio tab.
The number of channels in the Export tab depends greatly on the file format chosen and the audio codec you’re using. Here, in this example, I’m using MXF OP1a as my output format, and I’m using AVC-Intra-100 as my video codec. This usually has uncompressed audio, and that’s what’s shown in the Audio tab.
The number of output channels can be limited sometimes by the video codec as well. Certain camera makers have specific numbers of channels that are supported. In AVC-Intra 100, I can’t choose 12-channel output. I have to choose 10-channel or 14-channel, or it wouldn’t be a valid AVC-Intra 100 file.
Another example would be IMX-50. This only supports 2, 4, or 8-channel audio.
For maximum flexibility for audio, QuickTime uncompressed audio is very open, with choices ranging from 1-32 tracks, and special output options for 5.1 sound as well.
So, what happens if my Master Audio track in my timeline and my Export settings don’t match?
Premiere and AME will use the Export settings, and add/remove tracks as necessary to make them match. For example:
If my Master Audio track is set for 16 channels, and I set the Export for 8 channels, the resulting output file will have the first 8 channels from my sequence. Anything assigned to channels 9-16 will NOT be in the output file.
If my Master Audio track is set for 8 channels, but my playout server needs 16 channels, I can set the Export Settings for 16 channels. The exported file will have the exact audio from my sequence – all 8 channels routed the way I assigned them – in channels 1-8. It will also have blank channels 9-16 so that the file will pass the QC system and play on my broadcast server.
The Master Audio track in the timeline determines the maximum number of discrete audio tracks that can be in the output file. For example, if the Master Audio track is a Multichannel track, and it’s set for 16 channels, that’s the maximum number of output channels available.
Routing of the tracks in the timeline is done in the Audio Track Mixer. Tracks on the timeline aren’t tied to particular output channels – it’s up to the editor to assign tracks to specific audio output channels.
The Audio tab in the Export Settings box has an additional choice for number of output tracks. The number of tracks depends on the format – some formats are much more rigid in the number of audio tracks. QuickTime AAC, for example, only supports 2-channel. QuickTime Uncompressed audio will support up to 32-channel. If the number of channels in the Export settings is different from the number of channels in the Multichannel Master track in the sequence, Premiere will either add blank tracks, or remove tracks. For example, if the Multichannel Master is set for 32 channels, but the export setting is only set to 16 channels, the exported file will only have the top 16 channels. Another example – if the Master track was set to 2 channels, but the export setting was set for 16 channels, the output file would have 2 channels with active audio, and 14 blank channels. (useful for playout server compatibility.)