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Pro Tools - Offline Bounce To QuickTime - What We Want

Alan Sallabank - Pro Tools Expert

Offline Bounce To Quicktime - How Good Is it?

There's no denying that Offline Bounce to QuickTime has absolutely revolutionised my workflow. However, when it comes to using Bounce to QuickTime in Pro Tools with multi-channel audio (5.1), things start going horribly wrong.

I've been chatting to several users in the Pro Tools community and have been finding various issues.

When you do an Offline Bounce to QuickTime with a 5.1 audio source, it only gives you the option of a 5.1 interleaved WAV or a mono-summed WAV. No Multiple Mono option. While some video codecs do not allow for discrete tracks, a lot do. 

Flag Waving

When you create an interleaved multi-channel WAV in Pro Tools, it gives each channel a flag or ident, which most software can interpret correctly on import. However, QuickTime and VLC go by the track order.

SMPTE Or Not SMPTE?

Pro Tools' internal 5.1 track designation is locked to the following -

  1. FRONT LEFT
  2. FRONT CENTRE
  3. FRONT RIGHT
  4. REAR LEFT
  5. REAR RIGHT
  6. LFE

And it exports interleaved WAV files in that order.

The SMPTE (Society of Motion Picture and Television Engineers) track order that the likes of QuickTime and VLC expect is this -

  1. FRONT LEFT
  2. FRONT RIGHT
  3. FRONT CENTRE
  4. LFE
  5. REAR LEFT
  6. REAR RIGHT

Historically in the days of DTRS and ADAT, it was deemed that only AES pairs were truly phase coherent, so they arranged the channels in an order that made sense for that.

So if you play a 5.1 movie file generated by Pro Tools, on Quicktime or VLC, the centre channel is coming out of the right, and all manner of other weirdness. If you play it on Windows Media Player, or import it into Premiere, it plays correctly. If you re-import that movie back into Pro Tools, it plays correctly.

The QuickTime Factor

Things get even worse if you want to embed an MP3 of your mix instead of a WAV in your video.

MP3 only supports stereo, so if you give it a 5.1 source, it does an internal fold-down to stereo. Firstly, we have no control over that fold down. Secondly, Pro Tools gives the task of encoding the MP3 to QuickTime, which is expecting the 5.1 mix in the SMPTE order, so routes the channels incorrectly and makes an incorrect fold down.

The blue track is the resulting fold down. The track above is the original source, in the Pro Tools internal config order of L,C,R,Ls,Rs,Lf.

You can clearly see (and hear) that the resulting stereo fold down is wrong.

This is because we users have no control over how Pro Tools interfaces with certain third party software and how Avid relying heavily on them affects us.

How Can It Be Done Better?

I've recently had the need to use Adobe Premiere Pro to make master delivery video files.

Armed with a delivery spec, I set about making a 14 channel HD video with the following audio spec -

  • Tracks 1&2 - Final Mix Stereo
  • Tracks 3&4 - M&E Stereo
  • Tracks 5-10 - Final Mix 5.1 - L,R,C,Lf,Ls,Rs
  • Track 11 -  Dialogue Stem Mono
  • Track 12 - Music Stem Mono
  • Track 13 - Effects Stem Mono
  • Track 14 - Mute

First I had to set up the Premiere sequence. This is a bit counter intuitive to us audio engineers, as we've got used, with Pro Tools at least, to being able to change our configuration after initial setup. I just find it a bit more complicated in Premiere, probably because I've got used to doing it the Pro Tools way.

I set that the session master output was "multichannel" and there were a total of 13 outputs, with one video track.

I then clicked on the output assignments buttons for each track and was able to set up which channels of the master outputs each type of channel routed to.

Just click on the Output Assignments button -

And you get this handy routing matrix

Routing is not exclusive - you can route simultaneously to multiple outputs.

This shows in particular how the 5.1 can be routed. We don't need to worry about re-assigning the 5.1 track order, as Premiere properly reads the track ident flags when importing interleaved multichannel WAVs.

As you can see, it has imported the 5.1 in the correct SMPTE order, and all the tracks are playing out of the correct master outputs.

Finally when it comes to exporting your master video file, you just need to set the video export configuration.

Premiere presents the commonly supported channel configs for the video codec you are using.

So What Does Avid Need To Do?

Simple. Unlock the full power of the Avid Video Engine in Pro Tools, and start weaning off the reliance on QuickTime. All these options are available in Media Composer.

Without this kind of flexibility and control, Offline Bounce to QuickTime is limited to Stereo use only, and even then only from a stereo source, and we Pro Tools HD owners are suffering from a piece of Avid software being held back, despite the premium we pay.

The ball's in your court Avid.