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Mixing Separate Multitrack and Stereo Recordings

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Re: Mixing Separate Multitrack and Stereo Recordings

Postby tk76 » Mon Jul 08, 2019 5:26 am

Bob Bickerton wrote:
tk76 wrote:The performance I'm recording is a 6 day non-stop kirtan festival in India;

So I’ve just had a look at what a ‘kirtan festival’ entails....... acoustic instruments - probably amplified. If this is the case have you had a conversation with the sound engineer about taking a split off the mixing desk for the MixPre? Is there always 8 mics being used on stage?

If it is unamplified, then we might be able to offer alternative solutions.

Bob

Thanks Bob. I’ll be doing the sound for the event. After attending last year I offered to help out this year as the equipment was so bad and the ‘sound engineer’ almost entirely absent! The instruments are amplified. There are one sometimes two harmoniums, 2 khol drums (2 mics each), 2 lead vocalists. The rest is unamplified loud percussion; brass kartals and tambourine shakers. It’s traditional ‘call and response’ kirtan where the crowd repeats the chanting of the lead singers. Due to the dominance of the amplified vocals the effect of the crowd’s response is often diminished however, something I hope to deal with at the mix stage using the stereo room take. I’ll be using a Midas DM12 with a mic splitter to feed 8 separate signals into the mixer and mixpre.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby CS70 » Mon Jul 08, 2019 10:26 am

To avoid slippages, if you have easy access to the recorders and the performance has natural break points - say a live concert - you could try and stop/restart the machines every two or three tracks. I do that when recording long video with multiple cameras, via wireless control. Crossfading a couple seconds break or so isn't gonna be noticeable - and having multiple short segments as opposite to one gigantic one helps with the editing (to me at least, and with video more than audio probably, but nevertheless). You won't have the clapping at start for each segment but in my experience most material has enough natural transients that it's easy to align things anyways. Unless it's Cage. :)

Of course this is only if you can't rent a recorder which you can sync to the mixpre, which is definitely your best option. That's because there is always a risk of a snafu in doing that kind of operations "live" (you have no fallback) and you have to physically configure the two recorders near you so that's it's very quick to stop/start them or use wireless (and probably spend some time training so that it becomes natural). In my case I never use the live audio as I make music videos, so losing a little bit would be no drama - even if it hasn't happened so far.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Bob Bickerton » Mon Jul 08, 2019 12:26 pm

OK. Sounds like you’ll be in control of the situation, which is good.

Pity your mixer doesn’t have another couple of preamps as you could have used that to send to the aux in of the MixPre.

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Re: Mixing Separate Multitrack and Stereo Recordings

Postby James Perrett » Mon Jul 08, 2019 9:25 pm

Bob Bickerton wrote:Pity your mixer doesn’t have another couple of preamps as you could have used that to send to the aux in of the MixPre.

Can you monitor the mic inputs of the DR100 recorder in real time? If so, could it be used as a mic preamp with its outputs feeding the aux in of the MixPre?
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby tk76 » Mon Jul 08, 2019 10:36 pm

James Perrett wrote:
Bob Bickerton wrote:Pity your mixer doesn’t have another couple of preamps as you could have used that to send to the aux in of the MixPre.

Can you monitor the mic inputs of the DR100 recorder in real time? If so, could it be used as a mic preamp with its outputs feeding the aux in of the MixPre?

This is what I'm hoping to do. Will let you know how it goes.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby blinddrew » Fri Aug 16, 2019 4:23 pm

Just thought I'd lob up a case in point with regards to the drift of different digital machines.
I've been working on a series of videos for work, all shot over the same 4 hour period using three Canon DSLRs and a Zoom H4n. The longest individual take was about 17 minutes.
We're pulling these into five separate videos and working on the first two of the morning has been relatively plain sailing.
Working on the third however I've suddenly got a huge amount of timing drift between the cameras and the audio recorder - around 2 seconds/minute. It's been 'interesting' working around that level of shift.
What I've been struggling with is what's caused this sudden shift, and all I can think of is that by the time we'd started working on the third video, the batteries in the cameras were beginning to get a bit tired. Very tired by the end of it. The audio recorder was running from the mains though.
So in summary, digital drift is real, and significant even for short durations.
I shall know this next time...
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Martin Walker » Fri Aug 16, 2019 5:44 pm

blinddrew wrote:Working on the third however I've suddenly got a huge amount of timing drift between the cameras and the audio recorder - around 2 seconds/minute. It's been 'interesting' working around that level of shift.
What I've been struggling with is what's caused this sudden shift, and all I can think of is that by the time we'd started working on the third video, the batteries in the cameras were beginning to get a bit tired. Very tired by the end of it. The audio recorder was running from the mains though.

Hopefully you'll have enough visual/audio cues to let you re-sync the audio to the slightly longer video tracks.

I'm surprised at 2 seconds/minute though - that's around 3% video speed drop :shock:


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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Hugh Robjohns » Fri Aug 16, 2019 5:51 pm

blinddrew wrote:What I've been struggling with is what's caused this sudden shift, and all I can think of is that by the time we'd started working on the third video, the batteries in the cameras were beginning to get a bit tired. Very tired by the end of it.

Yes -- tired and dying batteries are a very common cause of sample-rate drift. The same problem is well known in professional circles for affecting the accuracy of the real-time clock for the timecode generators in most video camcorders too.

Temperature could also be an issue -- if the equipment/room started out quite cool but became much hotter through the shoot duration...

There's a good reason why high-quality professional digital equipment places the clock oscillator crystals in an 'oven' to ensure stable operating temperature!

H
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Martin Walker » Fri Aug 16, 2019 6:03 pm

Hugh Robjohns wrote:There's a good reason why high-quality professional digital equipment places the clock oscillator crystals in an 'oven' to ensure stable operating temperature!

Some synth oscillators/filters use this approach too - keeping the associated circuitry at a constant temperature, rather than relying on temperature compensation to adjust tuning as the ambient temperature varies :ugeek:


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Re: Mixing Separate Multitrack and Stereo Recordings

Postby blinddrew » Fri Aug 16, 2019 6:27 pm

Martin Walker wrote:Hopefully you'll have enough visual/audio cues to let you re-sync the audio to the slightly longer video tracks.
Yep, all sorted now but turned a 1hr job into 3.
Fortunately it's what i'm paid for. :) sort of...

Martin Walker wrote:I'm surprised at 2 seconds/minute though - that's around 3% video speed drop :shock:
Martin
Yep, i was pretty amazed as well. My first thought was that someone had managed to reset the sample rate somehow.

I hadn't considered heat as a factor Hugh, it was fairly constant in the room but obviously the kit will have heated up in use.
More stuff to bear in mind.
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