Allen & Heath Qu-16 in a Timecode sync environment?



It's a regular thing in this industry: A last minute call for a production that is happening in 2 days time or the other side of a weekend with requirements a little bit outside of what you can provide out of your own standard kit store.

I was asked recently to provide a mix and multitrack of eight inputs for a quiz panel show in just such circumstances. Thankfully I'd already made a vague plan about how to go about this ever since I'd picked up my Allen & Heath Qu-16 digital desk and had even thought of a few things that add functions which, on the face of things, aren't really part of its design remit.

Mixing on the Qu-16 is as simple as any other digital desk. It has all the lovely digital toys you could want for making a decent mix on location, HPF, EQ, Gates and Compressors on every channel and a whole lot more than any other desk that I'm aware of in this form factor. Not least it's neat dual USB connections for making recordings to a PC/Mac or direct "Qu-Drive" recording directly to a USB 2 HDD. I've written about it before and still find that this desk has an awful lot to offer, especially the regular firmware upgrades that make increasing use of the DSP chip at the heart of the desk. Highlights of which are its increasing compatibility with Windows based PCs and the Automatic Mic Mixer (AMM), which is incredibly useful.

So here's a our full usage case:

- Seven contributors. Two teams of three and a host/quizmaster.

- One room mic

- Open mic mix guide track

- Main LR mix track (controlled by manual mute groups and AMM)

- Mix Track routed to five cameras and my sound recorder

- Time Code sync

Getting extra radios is easy. Just ask around; in this case the production company was able to provide me with the four additional radios for the contributors that I requested.

Now the hard bit was trying to get the desk timecoded up...Timecode is a tricky thing to do when you don't really have a properly timecode enabled recorder... Will it drift? Won't it? It's difficult to say truly how the clock will hold when there is effectively no clocking sync point.

Here's my work around.

Timecode from camera sent to my 744T recorder. Timecode from the 744T out to a single channel of a stereo line input on the desk (keeping it as far from the mic preamps as possible to avoid bleed). In this particular case it was also daisy chained in a rig of five cameras, so I also split the TC out on a BNC splitter and sent it back to the camera teams remaining cameras.

The 744T took the AES output of the Qu-16, locking the sample clocks at 48kHz, and every camera took a mix feed from the AB168 stagebox (which gave me eight completely isolated outputs that can be routed as any mix output). This interlinking of Timecode and sample rate gave me some level of confidence in the clock sync for the whole process. Whether or not it worked 100% will be found in the edit...

Extracting the Timecode (UPDATE: See below for TentacleSync software method)

Get your multitrack onto your computer. This can take a while as the data transfer on disks formatted by the mixers can end up slower than usual. You'll also need a couple of bits of handy software for this process. One is a video encoder, the next is DaVinci Resolve and then finally Sound Devices Wave Agent.

I will point out now that the first process is to get around a limitation of DaVinci Resolve. It, somewhat bafflingly, can only read timecode from audio that is embedded in a video file. So you have to encode your one channel of timecode audio into a video. I used Adobe Media Encoder just because I have it and know how it works. There's loads of free transcoders out there.

Then once you have your blank video with one channel of timecode as audio bring it into DaVinci Resolve. You have to add folders and files through the built in media browser in the software rather than drag and drop. From here you can bring the file into the media bin and right click to "Update Timecode from Audio - LTC" this will update the number to the side of the clip with the start and end times of the timecode. Note this down.

Import your multitrack files into Sound Devices Wave Agent. This great bit of software allows you to edit the metadata of your wav files, adding track names, frame rates, timecode start time and a variety of other features like creating poly-wav files from the multiple wav files generated by the Qu series mixers. All you have to do to get the Timecode set in these files is to set the frame rate as a batch and then type the TC start time into the first file then copy it into the same box of the others. Then try and import into the Timecode enabled editor of your choice and you'll see it snap to the newly inferred timecode position straight away.

This is a complex workaround I know...

UPDATE: Thanks to the kind people at TentacleSync I've been able to try their PC software tool. It happily reads the timecode from the audio files and can add that timecode to the metadata of a number of files in a batch, allowing post production to sync the files in any NLE software. This removes the requirement for almost all of the above steps and replaces them with one single software suite!

But in the end there are better ways of doing this anyway...

How to do it properly

One simple addition to the rig above would have made it TC capable straight off the bat... A Mac Mini or MacBook Pro running software like Boom Recorder or Wave Tracks Live.

The there's the elegant way... In this case it would have been simply renting out a Sound Devices 688 mixer/recorder and the CL12 mix surface. This whole system could have been done in a vastly smaller footprint, especially with a full set of SuperSlot radio receivers in the SL6 bolt on pack (plus one more radio channel). That rig would have made the whole thing super simple and reduced the space required in my car for the associated kit by some not inconsiderable margin. Maybe next time.

So what have we learned?

Aren't I clever? Anything is possible? Could have done it better? It's possible to create needlessly complex workarounds when actually the kit required for the job is readily available from rental houses fairly local to me? Under a small budget it's possible to put together a rig that despite its limitations, is actually incredibly functional?

Yes all of those really. I surprised myself by figuring out the timecode workaround, but everything could have been a little more elegant had I been given a bit more budget and more time to get my stuff together in preparation for the job.


0 views

© Charlie Hurst 2017

07833 904825

Laleham, Staines, TW18, UK

  • facebook
  • twitter
  • instagram