Stereo Mixdown of Projects

In last month's Performer Notes, I discussed the first stage of getting a MIDI and audio project out of DP and into the real world. This involves 'printing' or 'rendering' any external audio sources, such as synths and external effects processors, as audio tracks within DP so that they're all 'under one roof', as it were. It also allows any final EQ, dynamics or effects to be applied to these tracks prior to the final two-track 'mastering' stage, the subject of this month's article.

Quick Tips When you 'record in' your external sound sources and software synths as separate tracks in DP, it's possible that some won't play back at all, for no apparent reason. The prime suspect for this is nearly always the Configure Studio Size settings, in the Setup/Configure Audio System menu. Make sure you've assigned enough mono and stereo voices for your project there. Although Bounce To Disk has become a stable and reliable operation under DP4, it's still worth making a quick save of your Project before you do a bounce, as some third-party plug-ins can misbehave when asked to perform 'offline' faster-than-real-time processing.

Bounce To Disk

Assuming that you've recorded all your software and software synths, as well as external effects, to audio tracks in DP, and you're happy with your mix, the obvious way to produce a stereo version of it is to use DP's own dedicated 'mixdown' feature — Bounce To Disk. This, for the most part, generates a split stereo file from any tracks in your mix being directed to a single hardware output pair or buss pair. If you have your studio's monitoring speakers being driven from a hardware output pair in DP called 'Analogue 1-2' (for example), this same output pair will be available in Bounce To Disk's dialogue box, which should then create a stereo mix that's exactly the same as what you hear through your monitors.

Bounce To Disk is a process that runs faster than real time, so DP can often produce a stereo file of quite long multitrack mixes in a matter of seconds, providing they don't use too many processor-intensive effects. While this is often a boon when you're up against a deadline, it does mean that Bounce To Disk can't (at least for the time being) gather the output of software synths running in DP — you'll still need to record them as audio tracks first. And it certainly can't deal with any external audio coming in from outboard effects processors, hence the need to record the signals from these first of all, too.

DP's Bounce to Disk dialogue box. This bounce uses the hardware output pair 'Analogue 1-2' from a MOTU 896 interface as its source. DP's Bounce to Disk dialogue box. This bounce uses the hardware output pair 'Analogue 1-2' from a MOTU 896 interface as its source.

Before I run through how to do a Bounce To Disk, note that DP will only bounce those parts of your project that you've selected, allowing you to mix down anything from your entire project to just a couple of bars of it using a few tracks. If you're bouncing down the whole thing:

Go to the Tracks Window and hit Apple-A to Select All. Then trim the selection, if necessary, by using the selection number fields at the upper left of the window, or the dedicated fold-out Selection pane in the Control Panel, and shift-clicking track names to deselect any you don't need.

Now choose 'Bounce To Disk...' from the Audio menu. In the dialogue box that appears, make sure the Channels pop-up menu is set to 'Split Stereo (two mono files)', and choose an appropriate Source to match the outputs you've been using for monitoring (often 'Analogue 1-2' or similar).

Under 'Resolution', you'd normally choose 16-bit if you were producing a mixdown ready for burning to CD or for producing an MP3 or other file for web distribution. You might choose 24-bit if your project was recorded in 24-bit and you were intending to do some more work on your bounce, or were sending it off to a mastering engineer. You'd probably only choose 8-bit if you were bouncing for very low-quality web-distribution formats, such as low-bandwidth Real Audio, for example.

The Import setting determines what DP does with the Split Stereo format file it creates. 'Add to Sequence' causes a new stereo audio track to be created in your project and the bounced file to be placed on it. 'Do not Import' is a roundabout way of saying 'Export', in the sense that DP just creates the bounced file and doesn't attempt to reference it from any of its editing windows (though you could always re-import it). The final option, 'Add to Soundbites Window', causes the bounced files to be listed in the Project's Soundbites Window, which is more often than not the most useful option, as we'll see.

When the Split Stereo format files that a Bounce To Disk produces aren't much use to you, use the Soundbite Window's more flexible export feature instead. When the Split Stereo format files that a Bounce To Disk produces aren't much use to you, use the Soundbite Window's more flexible export feature instead.

In all cases, after you've made the appropriate settings, and optionally defined a new destination folder for the files that Bounce To Disk produces, hitting the OK button causes the bounce to take place, and a Split Stereo file in Sound Designer II format to be produced.

Split Stereo files are actually two mono files with the same filename but different 'L' and 'R' file extensions, and while they're the native format for stereo in DP, they're not widely compatible with other software, especially more consumer-level stuff. You'd need something like Roxio's Jam to burn a CD directly from a Split Stereo file, and if you've only got Toast or iTunes, you're a bit stuck.

This is where Bounce to Disk's 'Add to Soundbite Window' option comes in handy. First, make sure your stereo bounce shows up in the Soundbites window, then select it there and use the extended exporting capabilities the window offers to produce a more widely-compatible stereo file. In the mini-menu, choose 'Export Selected Bites...', specify an export location for the file, and select from an altogether more helpful selection of formats, including Interleaved Sound Designer II, Windows WAV, or — probably most compatible of all on the Mac — AIFF.

At this stage I should mention a caveat concerning the use of Bounce To Disk. Much has been written on various Internet chat rooms and email distribution lists about the audio quality of stereo files produced in this way, calling into question Bounce To Disk's ability to produce a mix that sounds exactly the same as the project played in real time. Personally, I've never had any problems with this, but if you suspect all is not well, or you're experiencing problems with third-party plug-ins that are not playing ball with the Bounce To Disk process, you can always do a 'real-time' bounce inside DP, though it's a lot more labour intensive than a Bounce To Disk operation. Basically, what you need to do is the following:

Set up a new stereo audio track and choose as its input a buss pair that hasn't been used for anything else in your Project.

Now re-route every track whose output is your normal 'monitoring' pair (eg. 'Analogue 1-2') to use the new buss pair as an output.

Record-enable the new stereo track and hit Record.

Although fiddly, and not as fast, there's much to commend this approach to bouncing, as you can hear the bounce as it happens, and of course you don't need to have 'recorded in' external audio sources or soft synths beforehand, as they'll play back as normal during the bounce. You'll also end up with the new 'mixdown' soundbite listed in the Soundbites window, and you can export it as an AIFF just as if you'd done an 'Add to Soundbites Window' Bounce To Disk.

Quick & Dirty Bounces Although there's a lot to be said for 'recording in' all your hardware synths and external audio sources, then using Bounce To Disk to produce a mixdown of your Project, an entirely different method stands out above all others in terms of simplicity and speed, but might seem like sacrilege to anyone who's spent the last few years perfecting an all-digital workflow. It relies on using an external mixer to co-ordinate the outputs of your audio interface(s), synths and other sound sources, as many people do (but you can still make it work if you've committed to the 'mixerless' studio concept). Rogue Amoeba's excellent Audio Hijack Pro is a quick and easy way to produce MP3 bounces from DP 4 projects. Rogue Amoeba's excellent Audio Hijack Pro is a quick and easy way to produce MP3 bounces from DP 4 projects. When you're ready to make your master recording, use your mixer to route your interface's output, along with any external synths and effects, back to a single pair of its inputs, and hence back into your Mac. In DP, create a new stereo track with the same inputs, record-enable it, and hit record. Your sequence should play back whilst simultaneously making a master recording of exactly what you can hear through your monitors. The clear advantage of this method is predominantly its speed and ease of setting up. The disadvantages, however, are obvious, especially to audio purists. By taking the trip through your external mixer, any signals originating within DP pass through an additional D-A conversion stage, probably a few metres of cable, the gain stage, EQ and mix buss of your mixer, before finally re-entering through another set of A-D converters. Only you can decide whether this introduces an unacceptable amount of signal degradation, although it's obviously not much different from when everyone was using DAT machines to make their two-track masters. If you're not using any external sound sources at all, or you always route them into DP via aux tracks, there's yet another mixdown option: Audio Hijack Pro. This OS X audio-recording application can make AIFF or MP3 recordings of the outputs of other applications, including DP. You simply set it up to 'listen' to the output of DP and start it recording, and whilst it feels a little haphazard it's a tremendously useful tool for making quick 'working' bounces as you go along, without generating more soundbites within DP.

The Final Stage

Blacktree's iTunes-LAME encoder allows iTunes to access the LAME MP3-encoding algorithm. Blacktree's iTunes-LAME encoder allows iTunes to access the LAME MP3-encoding algorithm.

If you were only ever planning to burn a CD of your project, you may already have what you need, as both Toast and iTunes will happily work with AIFFs, as will virtually any other Mac audio application. But if you want to produce an MP3 you still have work to do, as DP can't help you in this area. MP3s can be produced in iTunes, of course, but amongst MP3 aficionados iTunes' MP3 encoding is not considered one of the best — for any given bit-rate there are different algorithms available that could give better results. One of these is LAME, and (using the donationware script from http://blacktree.com/apps/iTunes-LAME/) you can use it in iTunes. There's also Lamebrain, a pretty serious front end for the LAME algorithm that allows all sorts of encoding settings to be made and batch encoding to take place. This is also donationware and can be found at www.funkatron.com

Amongst the many other options for web distribution, one of the most useful is Real Audio. Perhaps the easiest and cheapest way to produce files in this format nowadays is to use the free Real Export plug-in for Quicktime Pro, downloadable from www.realnetworks.com/products/realexport

Further Bouncing Considerations If you're using Bounce To Disk to bounce a 24-bit project down to a 16-bit file, you'll ideally want to use some dither to mask any low-level distortion introduced by the digital quantisation process, especially on classical or acoustic material. Despite what you may have heard elsewhere, DP's Audio menu Dither option does not apply to Bounces To Disk, so the easiest way to apply it is to create a new Master Fader track (if you don't have one already) with the same output pair as the main pair you're using to derive the bounce, leave its fader to 0dB, and add a bit-depth reduction plug-in. Use the simple Quan Jr if you're not ready to 'master' just yet, but consider one of the final limiter plug-ins I discussed last month (MasterWorks Limiter, Waves L2, etc) if you also want to maximise loudness. There's more on dither in DP in April 2002's Performer Notes.