[RWP] Time alignment of audio from multiple sources

[Scott Chesworth]

Awesome, thanks for the level of detail you went into there Jim! I
don't have Sound Forge here, but seems like the concept would apply
anyway if I use Reaper to adjust the sample rates.

Cheers

Scott

On 12/18/14, Jim Snowbarger <snowman at snowmanradio.com> wrote:
> I would guess that, even though they will be quoted as being identical,
> the
> frame rates actually are different.  The fact is that they were recorded
> with devices each of which had it's own time base crystal, and thus it's
> own
> idea of the actual length of a microsecond.  One always has this problem in
> sinking recordings that were made on separate devices.  They don't have a
> common time base.
> You might be able to eventually tame that down by taking one of them into
> sound forge and changing the sample rate, setting the sample rate only.
> The hard part is how much to change the sampel rate, and in what direction,
> in order to get compliance.  The way I do it is to position them so they
> start in sink, and then go to the end, are try to judge how much time lag
> has developed, over how long an interval.
> That workks ok for long clips, but not so well for short ones.
> But then, it is the long one's that give you enough time for the mismatch
> to
> become apparent.
> Once a significant mismatch has developed, you can often learn to judge the
> number of milliseconds involved just by the sound of the composite mix.
> Make one signal louder thant the other.  So, you can tell just by
> listening,
> whether the lould signal comes first, or the soft one.  The later is a bit
> like reverse reverb effect.  So, now you know who is slow and who is fast.
> Next, is to estimate the number of milliseconds involved.  A handy place to
> judge that might be where there is a sharp edge, like a wood blick hit, or
> other sharp percussive,  listen to how the sharp edge is spattered by the
> two competing signals.  If you guess right, then divide that estimate to
> the
> total length of the sample, and that will tell you by what percent the
> clocks differ.  Change the sample rate by that percentage, setting the
> sample rate only, and see what happens.  Your results will vary.
>
>
>
>
>
> -----Original Message-----
> From: RWP [mailto:rwp-bounces at reaaccess.com] On Behalf Of Scott Chesworth
> Sent: Wednesday, December 17, 2014 6:22 PM
> To: Reapers Without Peepers
> Subject: [RWP] Time alignment of audio from multiple sources
>
> Hey folks,
>
> I'm sat here mixing a multitracked live recording. There are a bunch of
> close mics and a couple of DI sources that were tracked with a Zoom R16,
> and
> the band would like me to use the audio from a Zoom Q3 camera as ambient
> mics. But here's the thing, I'm having no luck at all getting the audio
> from
> the Q3 synced with the audio from the R16, and I've not struggled with this
> task before, so thought I'd ask whether anyone here had a decent workflow
> for getting the job done. At the moment I'm just nudging in small
> increments
> and listening. I can get the alignment so that it sounds fine on one part
> of
> a song, but then skipping forward a minute or so I'm hearing flamming on
> pronounced drum fills etc. It's almost like the frame rates of the two
> sources are different or something.
>
> Any thoughts or advice?
>
> Scott
>
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