Become a Site Supporter and Never see Ads again!

Author Topic: To shrink or stretch?  (Read 5767 times)

0 Members and 1 Guest are viewing this topic.

Offline danny3

  • Trade Count: (10)
  • Taperssection Regular
  • **
  • Posts: 221
  • Gender: Male
To shrink or stretch?
« on: July 20, 2014, 02:30:23 PM »
It took me a while but I now have applied advice found on TS to mix files from two different recorders with Audacity. The method I use is to line up the files at the beginning, find a reference point at the end, divide longer sample by the lower sample, apply percentage in the Change Speed effect.

Currently working on a recording from last night, where I had 4 channels (stage mics / aud mics) going into a DR-680. I was sent the sbd by a fellow taper, and have entered that into my project. The sbd file is shorter, and using the above method I selected the two stereo files from the 680 and applied .00314 % with the Change Speed tool. The set was @ 58 minutes. (Set 2 is 1:42)

This worked fine, but I question if it would be better to change (stretch?) the sbd to match the other files? I don’t know how to do this yet, but will seek out how to do so. It was a pretty small adjustment, and I don’t know how much the pitch/tempo could be adversely affected. Any thoughts would be greatly appreciated. Thanks.

Offline dmonkey

  • Trade Count: (7)
  • Taperssection All-Star
  • ****
  • Posts: 1068
  • Gender: Male
Re: To shrink or stretch?
« Reply #1 on: July 20, 2014, 02:40:23 PM »
I've never noticed a difference and I've done both several times. My guess is that it doesn't matter in a practical sense (perhaps there's some theoretical argument to be made, though).
MK4's, KM140's or MC930's >  Tinybox or Aerco MP-2 > R-09, M-10, R-44 (Oade CM) or MixPre-6

Offline 2manyrocks

  • Trade Count: (12)
  • Taperssection All-Star
  • ****
  • Posts: 1662
Re: To shrink or stretch?
« Reply #2 on: July 20, 2014, 03:41:05 PM »
Another option is to split one of the audio files during a silent moment  as needed and then align each segment without shrinking or stretching anything.  Just listen to the recording and make your splits/adjustments between songs as needed. 


Offline danny3

  • Trade Count: (10)
  • Taperssection Regular
  • **
  • Posts: 221
  • Gender: Male
Re: To shrink or stretch?
« Reply #3 on: July 20, 2014, 04:04:15 PM »
Another option is to split one of the audio files during a silent moment  as needed and then align each segment without shrinking or stretching anything.  Just listen to the recording and make your splits/adjustments between songs as needed.

Aligning each song separately is the approach I used until I got my head around the speed change method, which is actually very easy, except for times when it is near impossible to find a good point of reference.


Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #4 on: July 20, 2014, 05:03:06 PM »
I would think with modern software shrinking or stretching would maintain accuracy much better than splicing and realigning.

To the original post I'd go with the "if it sounds good it probably is good" rule of thumb. Either stretching or shrinking should work just as well.

runonce

  • Guest
  • Trade Count: (0)
Re: To shrink or stretch?
« Reply #5 on: July 20, 2014, 05:35:45 PM »
I'd alter the source I'd be using the least of in the mix....

The chop and align method is flawed because the sources are slightly out of tune...avoid.

Offline page

  • Trade Count: (25)
  • Needs to get out more...
  • *****
  • Posts: 8392
  • Gender: Male
  • #TeamRetired
Re: To shrink or stretch?
« Reply #6 on: July 20, 2014, 05:47:43 PM »
I'd alter the source I'd be using the least of in the mix....

The chop and align method is flawed

Agreed. When I was doing this, I tweaked the source I was going to use the least amount of. And yes, the chop method sucks because all it takes is 4 or 5 minutes to hear even small changes in the soundstage where stuff smears due to time differences.
"This is a common practice we have on the bus; debating facts that we could easily find through printed material. It's like, how far is it today? I think it's four hours, and someone else comes in at 11 hours, and well, then we'll... just... talk about it..." - Jeb Puryear

"Nostalgia ain't what it used to be." - Jim Williams

Offline 2manyrocks

  • Trade Count: (12)
  • Taperssection All-Star
  • ****
  • Posts: 1662
Re: To shrink or stretch?
« Reply #7 on: July 20, 2014, 08:53:51 PM »
I see what you are both saying. 

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 13323
  • Gender: Male
Re: To shrink or stretch?
« Reply #8 on: July 20, 2014, 09:54:47 PM »
I doubt it makes much audible difference whether you stretch or shrink, if only because the degree of change is rather minimal given the overall length of the files.  Like the other fellows mentioned, probably best practice to modify the least significant source in the mix.

When I've done this in the past with two sources used more or less equally, I opted to shrink the longer file with the reasoning that condensing what information is already there (going from 'more' to 'less') may arguably be somewhat less artifact prone than stretching that existing limited information out (going from 'less' to 'more'). Sort of like a sample rate reduction recalculation or bit-depth reduction throws out some of the existing information, and a sample rate or bit-depth increase doesn't add any additional information beyond what was in the original file.

If you want to find out if one is actually better, at least for more significant changes, you could do a test and adjust two copies a clip by a large percentage both ways, maybe making the same clip twice and half as long.  Listen for which one withstands the time-manipulation algorithm with the least objectionable distortions.
« Last Edit: July 20, 2014, 09:57:13 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline montanamon

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 11
  • NeumannKM-184's (matched pair), EdirolR-4Pro (Oade
Re: To shrink or stretch?
« Reply #9 on: July 24, 2014, 10:33:52 AM »
I also doubt the shrink vs stretch has much audible difference when were making minimal adjustments over a longer length of time. I've generally used the SBD (the larger % of the mix) as the "baseline" for time and adjusted the AUD file to match using a similar adjustment in Audacity. The matmatical formula you mentioned also mentioned in past forums here on TS regarding post show matrix's i haven't found to be a perfect art. Often after the math was done i was finding small differences when i thought the math was solid. I have since that point been literally eyeing the final result ensuring they match exactly with phasing being the digitial artifact that i have found if you don't.

Has anyone used Sony Soundforge (version 10 or 11) for time stretching or matching up SBD vs AUD recorded on different recorders ? Or can anyone else recommend a better program that is spot on for stretching or shrinking as Audacity certainly works however, i just don't find very user friendly in this matter...

Any possible changes with pitch or tempo is really the question i have - is there anyone that could chime in on this topic in relation to a stretch or shrink ? I know Charlie Miller recordings (of Grateful Dead fame) are often checked for proper pitch but i don't know enough about the topic and how it could relate here.

Finally my own two cents (from personal experience) is that having chopped files to individually lay over a "baseline" file for a matrix still would require subtle shrink or stretch issues with the timeline and i have often had a few phasing issues with that. I also do not recommend that approach...

Offline bombdiggity

  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 2286
Re: To shrink or stretch?
« Reply #10 on: July 24, 2014, 12:10:01 PM »
^ I don't think which of shrink or stretch is employed will matter (assuming a digital realm since the net change there should be infinitesimal).  Of course by doing either of those one is changing the pitch (very subtly I'd presume).  Likely only a professional musician could say which of the sources is objectively at exactly the right speed and thus pitch (if either of them is actually spot on).  If dealing with fractions of cents the correct absolute pitch may not even be identifiable.  The rule of thumb from my golden eared music degreed friend (who is truly Mr. Wonder Pitch) is if a source is less than 10 cents off he doesn't fool with it (it's a rare ear that can hear that small a difference in absolute terms, though clearly if you're aligning sources that would be a huge variation that would be impossible to reconcile without the requisite change).  The possibility of any digital sources being anywhere near that far different from each other seems to be zero (unless DAT tape is played back at the wrong sample rate or malfunctioning). 

I would actually recommend against doing any pitch adjustment in Audacity.  My friend says he felt that program has unacceptable impacts on the quality when doing anything more than very basic processing (levels, tracking).  Pitch adjustment is a high end function that should be done in high end software.  Which seems a matter of choice or access, though people have their favorites, there are differences and workflows can be quite different. 

The "chopping" approach is very crude and will only result in memorializing any drift between the two sources (rather than getting it right it basically only ensures that the initial match points may match but nothing else will). 
Gear:
Audio:
Schoeps MK4V
Nak CM-100/CM-300 w/ CP-1's or CP-4's
SP-CMC-25
>
Oade C mod R-44  OR
Tinybox > Sony PCM-M10 (formerly Roland R-05) 
Video: Varied, with various outboard mics depending on the situation

Offline 2manyrocks

  • Trade Count: (12)
  • Taperssection All-Star
  • ****
  • Posts: 1662
Re: To shrink or stretch?
« Reply #11 on: July 24, 2014, 12:54:50 PM »
Which high end software does your friend find acceptable? 

Can you shrink or stretch in Reaper?  Is it any better than Audacity for this?

For all the trouble in aligning between different recorders, I'm sort of thinking of selling my Dr-2d and buying another M10.  Wondering if two M10s will record closely enough to avoid any alignment issues in recordings under an hour and a half?

Offline bombdiggity

  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 2286
Re: To shrink or stretch?
« Reply #12 on: July 24, 2014, 01:31:39 PM »
Which high end software does your friend find acceptable? 

Can you shrink or stretch in Reaper?  Is it any better than Audacity for this?

For all the trouble in aligning between different recorders, I'm sort of thinking of selling my Dr-2d and buying another M10.  Wondering if two M10s will record closely enough to avoid any alignment issues in recordings under an hour and a half?

My friend uses Audition but some complain about its work flow (I'm not a huge fan of the work flow but have come to learn it OK).  Reaper is well liked around here and I know one of the multichannel recordists relies on it.  Sound Forge, Wave Lab...  Basically any of the better retail software is going to be better (and probably easier to do this in).

I'd think similar recorders would align better but they may not be exact either.  Of course if you use the same recorders all the time you should be able to identify the exact offset between them.  I'd be shocked if the difference once you align the starting point was not always the same setting in absolute terms.  Of course if you're correcting by applying a % to varying length sets then you don't know what the absolute offset is and are likely going about it wrong (by applying a variable adjustment methodology to a fixed differential).  If Audition only lets you do % then it is a sign it is lacking in that area. 

Pitch correction should always be done in absolute terms (in cents/semi-tones) not by %.  Anyone who adjusts pitch and says they corrected it by such and such % isn't doing it right.  This is time alignment rather than pitch correction but I think the principle is the same.  The recorders should vary by an absolute amount (a certain number of milliseconds or samples per hour or whatever increment you choose).  Once you conclusively identify that offset you should be able to just apply that rate to every instance. 

The more obvious solution if you run multiple sources is to get a multichannel recorder, though the practical geography of that may not work if you're running mics and board since the sweet spot is rarely near the board. 
« Last Edit: July 24, 2014, 03:54:29 PM by bombdiggity »
Gear:
Audio:
Schoeps MK4V
Nak CM-100/CM-300 w/ CP-1's or CP-4's
SP-CMC-25
>
Oade C mod R-44  OR
Tinybox > Sony PCM-M10 (formerly Roland R-05) 
Video: Varied, with various outboard mics depending on the situation

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 13323
  • Gender: Male
Re: To shrink or stretch?
« Reply #13 on: July 24, 2014, 03:34:30 PM »
I'm doing it in Samplitude, using the most appropriate setting in their advanced algorithm which maintains pitch while adjusting the timebase, and that partly figured into my decision to shrink the longer instead of stretch the shorter.  Neither source is particularly dominant my case because these are Left/Right/Center/Surround recordings, L/R on one recorder, C/S on the other.  Sometimes these are mixed to 2-channel, though primarily synced and left as discrete channels which still need to be in phase alignment (at least the L/C/R channels do, the S channel is more forgiving by a few ms long as it doesn't lead).

It's pretty straightforward to do in Samplitude at the object level, using that algorithm.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline Fried Chicken Boy

  • Trade Count: (8)
  • Needs to get out more...
  • *****
  • Posts: 3003
Re: To shrink or stretch?
« Reply #14 on: July 24, 2014, 04:15:01 PM »
Good advice and suggestions in this thread.  Going to try putting together a matrix of two different sources and this should come in handy.  +T

Offline 2manyrocks

  • Trade Count: (12)
  • Taperssection All-Star
  • ****
  • Posts: 1662
Re: To shrink or stretch?
« Reply #15 on: July 25, 2014, 10:05:08 AM »
I gave shrinking a shot last night in Reaper to align two tracks from two different recorders by pulling the end of one track backwards to line up the peaks in the other track.  Although I was able to sync the two tracks this way, it was very "processed" sounding, and must not be the right way to do it as the result was awful sounding.   :(

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 13323
  • Gender: Male
Re: To shrink or stretch?
« Reply #16 on: July 25, 2014, 12:06:58 PM »
Quality of results depends on the algorithm. Here's a couple snippets from the section of the  Samplitude 11 user manual (the version previous to the current release) appropriate to what we are discussing.  It also includes other time-streching algorithm modes more appropriate for things like drums, loops, monophonic samples, and more extreme stretch factors which I've not included below.  Note that it mentions shrinking (length-reduction / time-compression) is less artifact prone than stretching.

I use the Universal HQ mode.

Resampling
Samplers and PCM synthesizers transpose samples using this procedure. Time factor and pitch are dependent upon each other: the shorter the audio material, the higher the pitch and vice versa. The effect is comparable with changing the playing speed of record players or tape recorders. The effect is relatively loss-free, the sound loss is smaller than with all Timestretching/Pitchshifting procedures. If a pitch change is wanted or justified by changing the speed, use this algorithm.
 
Pitchshifting/Timestretching
With all other algorithms, the time factor and pitch are independently adjustable. These algorithms may create artifacts, which can be balanced out using the anti-aliasing filter. The preset timestretching/pitchshifting algorithm can be saved via Timestretch / Pitchshift Patcher (view page 621) ("Tools" menu).
 
Standard
Here, an algorithm is used that usually delivers very good results with factors from 0.9 to 1.1, that works in phase-locked mode, and thereby keeps the room effect of stereo signals. This algorithm is only partially suitable for drum loops or other "beat heavy" audio material as it can change the groove.

Time compression (sample length is reduced) is more successful with this algorithm than timestretching, i.e. it is better to reduce the longer sample than vice versa. This algorithm is especially suited to complex audio material. The CPU load is light. At extreme settings, anti-aliasing effects may occur. An additional anti-aliasing filter can come to your aid. This filter is also available for all other algorithms that work internally with resampling.

Universal HQ
This algorithm serves as a high-quality timestretching/pitchshifting method and offers good audio quality with almost any audio material. Especially when it comes to complex audio recordings like orchestral recordings, this algorithm delivers especially good results. The stereo properties remain intact. The CPU load can become very high
« Last Edit: July 25, 2014, 12:08:45 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline jagraham

  • Trade Count: (20)
  • Needs to get out more...
  • *****
  • Posts: 2856
  • Gender: Male
Re: To shrink or stretch?
« Reply #17 on: August 03, 2014, 07:42:21 PM »
For all the trouble in aligning between different recorders, I'm sort of thinking of selling my Dr-2d and buying another M10.  Wondering if two M10s will record closely enough to avoid any alignment issues in recordings under an hour and a half?

If the M-10 is anything like the Tascam units, no. It's possible they are made with better aligned internal clocks but any Tascam units I have compared in the past have had .5-1 second drift per hour resulting in a huge echo. Anyone that's attempted this with 2 M-10s that could provide input here?

Just curious - Why wouldn't you just keep and use the DR-2d if you are doing 4ch with miniplug mics? That's exactly how I use it and I find it to be perfect for the function. Not to mention other mics it can be used with and SBD matrices. It makes 4ch audience recording very simple, no need to worry about alignment in post.

I'd alter the source I'd be using the least of in the mix....

The chop and align method is flawed because the sources are slightly out of tune...avoid.

^ Agreed with all this. There's no way it matters if you shrink or stretch, just make sure to edit the source less prominent (especially in a matrix where one source has an issue you are trying to cover up). I wouldn't even think about chop and align, as I would second guess the whole thing to the point of not being able to enjoy the recording. What about songs that are longer than others, they are just supposed to be out of alignment making the recording inconsistent? Perhaps there's an appropriate threshold of time before it can be noticed audibly but I just would avoid it period.

The only issue with the "math and stretch" method that I've encountered was once the files would not align due to some kind of digital issue. Used the same units other times and aligned successfully. Not sure how frequent this is but it happened, couldn't get that recording to align no matter what.
Mics: Nak CM-300s, Nak CM-100s, CP-1s, CP-2s, AT-853s(Cards, Hypers, Omnis) CA-14s(Cards, Omnis)
Pres: CA STC-9200, CA-UBB
Recorders: Tascam DR-70D, DR-2D, Edirol R-09

ISO: 1 Teac ME-120, CP-3 Caps, AT-853 Subcard Caps

Offline 2manyrocks

  • Trade Count: (12)
  • Taperssection All-Star
  • ****
  • Posts: 1662
Re: To shrink or stretch?
« Reply #18 on: August 04, 2014, 11:26:25 AM »
To answer your logical question why not to keep the Dr2d, based on the comparison testing I've done, it seems that the M10 runs at a speed that is closest to my Canon HF M500 video camera, the battery life on the M10 is longer, and I am more comfortable with the M10 controls.  However, a single DR2d would be easier to manage than two M10s and I already have the DR2d. 

For me to go back to using the DR2d, I'd have to get better at managing its battery life and need to understand how to best match up the DR2d audio to my camera audio without making it sound terrible in the process. 

short answer:  I need to learn how to shrink/stretch as I appear to be going at it the wrong way.   

 

Offline Scooter123

  • "I am not an alcoholic. I am a drunk. Drunks don't go to meetings."
  • Trade Count: (9)
  • Taperssection All-Star
  • ****
  • Posts: 1027
Re: To shrink or stretch?
« Reply #19 on: August 06, 2014, 11:28:16 AM »
The way I was taught--

It doesn't matter whether you shrink or stretch.  But you do need to pick the recorder which has the best time clock as your base.

Line up the files near the beginning with a sharp note, bass notes don't work so well.

Go out 30-45 minutes and select another sharp note and drop another marker on the  two files, separately. 

Get out of the digital time mode and display samples.

Subtract the difference in the samples between the two points and get the percentage, whether it is .999875 or 100,00123  Doesn't matter.  Stretch or Shrink

Time digital display is not accurate enough

I find working with most DAWs for this project to be annoying because when you place a marker, it does across all the files, which is not useful for time alignment.  So I use a two channel waveform editor to place the markers and go back and forth between the waveform editor and the DAW multi-track.  Adobe Audition either cc or 3 has some advantages in this regard in that it combines a two channel waveform editor with a multi-track and you can seamlessly pop between the two. 

Repeat the marker drill every 30-45 minutes. 

Problems may surface when the recorder malfunctions dropping a section even ever so small, and finding those write errors is, well, I just don't have the skill set to do that. 



Regards,

Scooter123

mk41 > N Box  > Sony M-10
mk4 > N Box > Sony M-10

Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #20 on: August 06, 2014, 01:37:36 PM »
ProTools' Elastic Audio feature makes this really easy. Markers are automatically inserted at all transients during the recordings. You line up the first transient, "lock" it into place, stretch or shrink the final transient as needed, and proceed with rendering. PT makes sure all the transients remain aligned throughout. I hope something like this will makes its way to Reaper eventually.
« Last Edit: August 06, 2014, 05:20:22 PM by Sloan Simpson »

Offline Scooter123

  • "I am not an alcoholic. I am a drunk. Drunks don't go to meetings."
  • Trade Count: (9)
  • Taperssection All-Star
  • ****
  • Posts: 1027
Re: To shrink or stretch?
« Reply #21 on: August 08, 2014, 11:06:35 AM »
Question on Pro Tools Method

From my review of the videos on this feature, ProTools automatically places the transient markers on the two tracks.  Do you know if that is by beat or areas in which ProTools spots similar distinct notes.  I assume it by the beat. 

Also stretching seems to be done manually, is that correct?

Regards,

Scooter123

mk41 > N Box  > Sony M-10
mk4 > N Box > Sony M-10

Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #22 on: August 09, 2014, 10:00:55 PM »
Question on Pro Tools Method

From my review of the videos on this feature, ProTools automatically places the transient markers on the two tracks.  Do you know if that is by beat or areas in which ProTools spots similar distinct notes.  I assume it by the beat. 

Also stretching seems to be done manually, is that correct?

By the beat, or whatever is producing the transient. The process of placing the transient markers is done separately for each track.

Then you move around whichever track necessary to align the markers for the first transient in the recording. You then "lock" that transient for the track you're going to shrink/stretch, so that it becomes an "end point" so to speak.  Then you go to the end of the file and manually drag the last transient so that it aligns with the other track. The process aligns the transients throughout the recording (though I couldn't explain the algorithm for this).

Offline Scooter123

  • "I am not an alcoholic. I am a drunk. Drunks don't go to meetings."
  • Trade Count: (9)
  • Taperssection All-Star
  • ****
  • Posts: 1027
Re: To shrink or stretch?
« Reply #23 on: August 12, 2014, 11:10:40 AM »
I doubt any automated placement of markers by the beat would be accurate enough for me.  The most accurate method to place markers is, in my judgment, by visual inspection of the waveform.   
Regards,

Scooter123

mk41 > N Box  > Sony M-10
mk4 > N Box > Sony M-10

Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #24 on: August 12, 2014, 04:47:30 PM »
I doubt any automated placement of markers by the beat would be accurate enough for me.  The most accurate method to place markers is, in my judgment, by visual inspection of the waveform.   

I'm probably not explaining it very well but it has worked flawlessly for me. I personally wouldn't sync two separate sources any other way.

Offline montanamon

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 11
  • NeumannKM-184's (matched pair), EdirolR-4Pro (Oade
Re: To shrink or stretch?
« Reply #25 on: August 12, 2014, 06:48:23 PM »
I doubt any automated placement of markers by the beat would be accurate enough for me.  The most accurate method to place markers is, in my judgment, by visual inspection of the waveform.   

I absolutely agree Scooter123 - after MUCH trial an error with the "math" and automated attempts - visably lining it up is the best recommendation i could also make. I have no doubt there maybe a program (or 10) that works perfectly - i just have yet to use it.... anyhoo great little forum for those trying to sync up multiple sources and not using a 4 channel+ recorder! I recorded many SBDs and AUDs on different recorders to later sync and that is why this forum is valuable personally however, after purchasing my R-4Pro i would never go back and do it that way again - the first Matrix i did with my R-4Pro i had synced perfectly (b/c of the same time clock running all 4 channels) in minutes vs HOURS 'n HOURS! All i have to do is pull the AUD into sync with the SBD due to how much delay i had recording (due to the length away fromt the PA my mics were). Anyhoo great post :) cheers from MT

runonce

  • Guest
  • Trade Count: (0)
Re: To shrink or stretch?
« Reply #26 on: August 12, 2014, 07:47:26 PM »
I doubt any automated placement of markers by the beat would be accurate enough for me.  The most accurate method to place markers is, in my judgment, by visual inspection of the waveform.   

I took his explanation as another approach to correcting for clock drift - and not as a means of making the final time sync - I would think you could still slide the tracks around in time after correcting for drift...

Offline hoserama

  • Trade Count: (0)
  • Taperssection Member
  • ***
  • Posts: 307
  • Gender: Male
Re: To shrink or stretch?
« Reply #27 on: August 13, 2014, 09:52:41 AM »
Scooter123 is using my approach--putting in sync markers between different feeds, then finding the difference between the different markers, then time stretching it with the resultant ratio. No need to slide it around. If you do it right, in theory, they should be completely matched the whole way through.

I would think the automated version would work for a project not needing a lot of precision, but when you have projects that have only a margin of error between +/- 2 samples, then I wouldn't trust it at all. It would probably work okay with a clean aud/sbd, although have to be careful that claps on a drum/transient wouldn't throw it off.
Audio: Countryman B3 + SBD feeds
Wireless Receivers: Lots of those
Antennas: Lots of those
Cables: Lots of those
Recorders: Cymatic Utrack24, Cymatic LR16, RME Multiface, Zoom F8, (3) Tascam 680, (2) Tascam 2D, Zoom H6, Zoom H4n, and a graveyard of irivers/nomads/minidiscs.

Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #28 on: August 13, 2014, 05:43:39 PM »
Here's an example screenshot (only one file obviously). Looks pretty thorough to me. If you guys are inserting this many markers manually I'm impressed  ;D


Offline hoserama

  • Trade Count: (0)
  • Taperssection Member
  • ***
  • Posts: 307
  • Gender: Male
Re: To shrink or stretch?
« Reply #29 on: August 13, 2014, 08:08:59 PM »
I would just question the accuracy of those markers. Like I said, it's gotta be within +/- two samples. But who knows--it could do it. I might play around with it.
Audio: Countryman B3 + SBD feeds
Wireless Receivers: Lots of those
Antennas: Lots of those
Cables: Lots of those
Recorders: Cymatic Utrack24, Cymatic LR16, RME Multiface, Zoom F8, (3) Tascam 680, (2) Tascam 2D, Zoom H6, Zoom H4n, and a graveyard of irivers/nomads/minidiscs.

Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #30 on: August 13, 2014, 08:24:29 PM »
I would just question the accuracy of those markers. Like I said, it's gotta be within +/- two samples. But who knows--it could do it. I might play around with it.
Just out of curiosity, why would you doubt them? I would doubt a human before I'd doubt ProTools  :)

Offline hoserama

  • Trade Count: (0)
  • Taperssection Member
  • ***
  • Posts: 307
  • Gender: Male
Re: To shrink or stretch?
« Reply #31 on: August 15, 2014, 10:04:18 AM »
Because I know how precise they need to be. My main experience is time aligning with monitor mixes from different recorders. So it's generally a pretty clear soundboard-type pull. So any sort of issues with the time alignment and you start getting phasing VERY fast. However, the mixes are sometimes wildly different, so you need to use your common sense to figure out if a sync point is truly a sync point, and not just a similar looking wave form.

See the attached picture. Here's a time alignment that my friend did and I looked over. The dotted lines are the sync markers that he put in, because it looked like that was the start of the snare hit. However, if you look at the whole wave form, at least in that 1/50th of a second view, you'll see the dotted lines don't work. Instead, the correct sync point would be something like where the cursor is, and a majority of the peaks/valleys line up.

I don't really trust an automated program to not get tripped up on minor instances like that, and would end up checking every sync point before processing. That said--if it has some other functionality like ability to move/recalibrate sync points, it could be useful.
Audio: Countryman B3 + SBD feeds
Wireless Receivers: Lots of those
Antennas: Lots of those
Cables: Lots of those
Recorders: Cymatic Utrack24, Cymatic LR16, RME Multiface, Zoom F8, (3) Tascam 680, (2) Tascam 2D, Zoom H6, Zoom H4n, and a graveyard of irivers/nomads/minidiscs.

Offline bombdiggity

  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 2286
Re: To shrink or stretch?
« Reply #32 on: August 15, 2014, 10:36:07 AM »
^ Interesting example. 

Other than a truly mono recording aligning channels can be very tricky.  Apparently even with monitor mixes/SBD tracks. 

My experience in dealing with suboptimal L/R stereo sorts of configuration has been that you do need to look at the overall average (lots of reference points) since the discrete channels do not have the same perspective on every event within the overall soundstage.  Aligning an apparent "start" point would not necessarily be the proper alignment for the totality (as the above illustrates). 

The easier aspect is that a L/R stereo or a multitrack where all channels are on the same time clock means shrinking/stretching is not part of the equation, so there is an absolute alignment though slight offsets at almost any point along the timeline are likely (which provides the stereo image).   There's a lot more room for error in the realm of shrinking/stretching. 
Gear:
Audio:
Schoeps MK4V
Nak CM-100/CM-300 w/ CP-1's or CP-4's
SP-CMC-25
>
Oade C mod R-44  OR
Tinybox > Sony PCM-M10 (formerly Roland R-05) 
Video: Varied, with various outboard mics depending on the situation

Offline Sloan Simpson

  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 3696
  • Gender: Male
    • Southern Shelter
Re: To shrink or stretch?
« Reply #33 on: August 15, 2014, 01:16:33 PM »
Elastic Audio does allow you to reposition the markers if you wish. When syncing a stereo room track with a stereo soundboard track I've never needed to though, it's worked perfectly.


 

RSS | Mobile
Page created in 0.22 seconds with 75 queries.
© 2002-2019 Taperssection.com
Powered by SMF