What software can correct constant pitch increase (CLV recording) ? - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

jamesperrett · 28th Jul 2010, 01:05 PM

Cool Edit Pro is now Adobe Audition and isn't free - although they have a limited time free demo.

Reaper has a play rate function that can be automated. If the play rate change is linear you can adjust it so that it is right at the start and then again at the end and the play rate will gradually change between the start and the end. It even comes with a basic spectrum analyser that can show you the frequency of your mains hum. The latest version can be found at http://www.reaper.fm

Cheers

James.

dseymo1 · 28th Jul 2010, 04:17 PM

You can achieve the desired effect in Audacity by adding a new time track, then using the envelope tool to adjust this track. Doing so will affect both the pitch and speed of the audio tracks, which is, of course, what's neded.

david winter · 28th Jul 2010, 05:43 PM

This is not exactly what I want. Changing both speed and pitch will never generate a file at accurate speed. I need to change the speed only, not the pitch. But we're getting closer !

Dave Moll · 28th Jul 2010, 05:52 PM

Surely, changing the speed without changing the pitch would fail to compensate for the physical change of speed - where the pitch would have changed in proportion to the speed.

Michael Maurice · 28th Jul 2010, 07:58 PM

It would normally yes, but in this case the speed and pitch would have changed when you playback on the revox. Adjusted the speed in audacity will automatically change the pitch.

If I was doing it, I'd use a varispeed machine and try and get the analogue output as close to the original as possible.

Perhaps if David could lay his hands on a Revox B77 Mk2 that has got varispeed and may prove the best solution to his problem.

david winter · 28th Jul 2010, 08:09 PM

I also have a B77MK2 machine, it's the 2-track in 19/38 speeds. The 2-track head would not have been a problem, quite in the contrary. But playing 10 tapes at 19cm/s when they're originally recorded at +/- 4.75cm/s would not have been very practical (insufficient sampling rate of my ADS InstantMusic Line-to-USB box which won't do over 96KHz) and much larger files taking longer to process any modification.

Quite honestly, it's not that a problem to work on those files manually. But I have to send them tomorrow, or at least a few, so if there's a software option to fix the speed automatically that would be much preferred.

TIMTAPE · 29th Jul 2010, 12:34 AM

David,
I know you are in a hurry to get these tapes done but you mentioned you have a B77.
At least in the MkII model there is an optional variable speed control unit which connects via a DIN plug to the back. I seem to remember it gives a much wider range of variable speeds than does the inbuilt front panel pot. This would be handy to accomodate the range of speeds encountered from beginning to end of a small rim drive tape.

The circuit is quite simple, using one IC and a few other cheap components. Next time I'm given a rim drive tape, I'll definitely be constructing such a unit. Will make life a lot easier.
The circuit details are in the B77 service manual.

I suppose one might also be lucky and pick up such a unit second hand.

Cheers Tim

david winter · 29th Jul 2010, 08:55 AM

Tim:

I have the original B77 service manual but got used to manually pitch the files section by section.

I found that the tapes had a slightly different length of +/- 1 minute.
What I did for 4 of them so far is simple:
- Playing at the begining and at the end to find the accurate percentages of pitch. They all start at 50%, and all finish at 60% to 62%.
- Dividing the recording in 11 to 13 sections depending on the pitch determined at the end (11 for 60%, 13 for 62%).
- Pitch each part manually to 50%, 51%, 52% until the end.

The result was really satisfactory. To be honest, only a musician would eventually hear a very small pitch change somewhere, and it's not that noticeable. These are voice recordings on the small machine with the microphone put on a table and two persons speaking at a certain distance.

I'm still much interested in finding the software that would do all that for me in the fine way...

paulsherwin · 29th Jul 2010, 09:43 AM

Post #22 suggests Audacity can do this over the whole recording by using the envelope tool. I've never done this so can't give specific instructions. This will have the same effect that you've achieved manually, but without the discrete stepping and with much less work.

ajs_derby · 29th Jul 2010, 10:50 AM

How good a programmer are you?

You just need to convert the .wav file to raw PCM data, insert extra samples into the stream to slow it down, reconvert back to .wav and apply some low-pass filtering to remove the distortion caused by adding the extra samples. (You could do proper interpolation and resampling in the first place, of course, but that'd be more effort.)

Easy enough with sox and your favourite scripting language!

cheerfulcharlie · 29th Jul 2010, 11:11 AM

Quote:

Originally Posted by Paulus.d

For a few years I have been using Cool Edit Pro 2.1 by Syntrillium Software. It can do this feature as part of it's gliding pitch sweep - I presume it's for pretty nifty speeding up and slowing down effects in sound production. It's sweep can be set using an initial start point and can pitch shift to another point over a given time.

This, I presume is what you need? an initial key to start at and then gradully get slower as time increases?

This program was found on-line and downloaded, problem is that was 5-10 years ago.

Please send me a PM.............

Regards Paulus.d

Second that Paulus the gliding pitch shift is brilliant once you know what your doing. Cool Edit was bought by Adobe who slapped an extra 100 quid on it and called it Audition.

most of those pitch increases on old tapes are just caused by worn batteries
slowing the tape down.

dseymo1 · 29th Jul 2010, 03:26 PM

In case anyone decides to use Audacity or this, I should have mentioned (because it's far from obvious) that if you click on the triangle next to the 'Time Track' legend, there's an option to select the upper and lower range of adjustment, which effectively adjusts the 'sensitivity' of the time-domain envelope.

Top Cap · 29th Jul 2010, 08:41 PM

I had an archive Brian Clough tape that changed pitch as it played, can't believe the BBC used a faulty machine. Anyway what I did was as post #28 using Sony Sound Forge. In this you have the option of time stretching (or shortening) either the entire length or marking up segments and time shift on these. I used the latter technique over many segments (lots of patience required) to get a more even pitch throughout the tape length. I do not have Audacity but wonder if you have the option to time correct on marked up segments as well the whole? Since then I have acquired a machine with variable speed control so I probably would use this in preference, noting the speed control position at beginning and end, then using a stop watch adjust the speed in time segments as the tape played. The problem as I see it with your recordings however is the large amount of speed differential so the software version might prove the best way to go as the speed control on tape decks have a limited range.

Lodgesound · 29th Jul 2010, 08:41 PM

A method I would propose is as follows:

Take a 3 motor tape machine.

Remove the pinch roller

Disconnect the power to the take up spool motor

Now the tricky bit - set up some kind of belt drive to right right hand spool table from the capstan - the speed at this point does not matter - just the ability to provide a constant speed drive to the right hand spool table. The back-tension may need reducing on the feed spool depending on the stability of your drive arrangement.

I think most folk on here can see where this is going now.

Load tape and transfer at constant linear speed into software such as Wavelab or Adobe Audition.

Once transferred isolate the hum component if available in the original audio and adjust the pitch in software as required - a contant pitch change will be all that is needed since your transfer would have been done at constant angular velocity as per the original recording (ie. constant speed take up and increasing pack diameter causing an ever increasing linear tape speed).

Lodgesound · 29th Jul 2010, 08:54 PM

The alternative to all this is to find someone with a Nagra T or a machine such as a Studer A820 - these machines have the ability to operate in a very high stability constant speed take-up shuttle mode at more or less any speed.

This removes capstan control and allows for CAV drive of the take-up reel - equivalent to rim drive.

Then use the software as before.

dseymo1 · 29th Jul 2010, 09:01 PM

Quote:

I do not have Audacity but wonder if you have the option to time correct on marked up segments as well the whole?

You do indeed.
The time track is in effect locked to the audio tracks, but can be stretched or compressed as desired, either as a whole, or in segments On playback, this track is read in a liner manner, but as 1 cm of time track can represent, say, 1 second, 10 seconds or 100ms once it's been manipulated, the audio playback speed varies accordingly.
I hope that makes some kind of sense!

woodchips · 2nd Aug 2010, 09:20 PM

Hello, did this 25 years ago with a Racal Store 4. Had to look up my notes to remember how though. Sample the speech at 8kHz or so, we used standard telephone CODECs. Low pass filter to about 1kHz, autocorrelate the result which is the vocal cords opening and closing. With a circular buffer used for input and output samples, when the output catches up with the input, speech to fast, then just move the output pointer back the number of samples generated from the autocorrelation. Do a three sample blend to stop and clicks and that is it. We had the advantage of a capstan speed signal from the TAC4, but in this case the 50Hz (100Hz?) hum can be used as a reference signal.

We used a TI TMS32010 and that would cope with a rate change from half to twice, with no pitch change, worked a treat.

Bob

david winter · 2nd Aug 2010, 09:31 PM

I finally got it done perfectly with CoolEdit. It was only a matter of finding the initial and final pitches pertentages (which I did using Goldwave as I'm really used to this program), and then use the pitch bend through the progressive bpm variation, using the values found, and with a base of 100bpm so that the percentages correspond to the bpm. Worked perfectly with all files. So thanks again to Paul for his precious help, and to all others who gave interesting suggestions.

28th Jul 2010, 01:05 PM	#21
jamesperrett Pentode Join Date: May 2007 Location: Mid Hampshire, UK Posts: 212	Re: What software can correct constant pitch increase (CLV recording) ? Cool Edit Pro is now Adobe Audition and isn't free - although they have a limited time free demo. Reaper has a play rate function that can be automated. If the play rate change is linear you can adjust it so that it is right at the start and then again at the end and the play rate will gradually change between the start and the end. It even comes with a basic spectrum analyser that can show you the frequency of your mains hum. The latest version can be found at http://www.reaper.fm Cheers James.

28th Jul 2010, 05:43 PM	#23
david winter Pentode Join Date: May 2008 Location: Paris, France Posts: 111	Re: What software can correct constant pitch increase (CLV recording) ? This is not exactly what I want. Changing both speed and pitch will never generate a file at accurate speed. I need to change the speed only, not the pitch. But we're getting closer !

28th Jul 2010, 05:52 PM	#24
Dave Moll Moderator Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 2,070	Re: What software can correct constant pitch increase (CLV recording) ? Surely, changing the speed without changing the pitch would fail to compensate for the physical change of speed - where the pitch would have changed in proportion to the speed. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

28th Jul 2010, 07:58 PM	#25
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 2,474	Re: What software can correct constant pitch increase (CLV recording) ? It would normally yes, but in this case the speed and pitch would have changed when you playback on the revox. Adjusted the speed in audacity will automatically change the pitch. If I was doing it, I'd use a varispeed machine and try and get the analogue output as close to the original as possible. Perhaps if David could lay his hands on a Revox B77 Mk2 that has got varispeed and may prove the best solution to his problem.

28th Jul 2010, 08:09 PM	#26
david winter Pentode Join Date: May 2008 Location: Paris, France Posts: 111	Re: What software can correct constant pitch increase (CLV recording) ? I also have a B77MK2 machine, it's the 2-track in 19/38 speeds. The 2-track head would not have been a problem, quite in the contrary. But playing 10 tapes at 19cm/s when they're originally recorded at +/- 4.75cm/s would not have been very practical (insufficient sampling rate of my ADS InstantMusic Line-to-USB box which won't do over 96KHz) and much larger files taking longer to process any modification. Quite honestly, it's not that a problem to work on those files manually. But I have to send them tomorrow, or at least a few, so if there's a software option to fix the speed automatically that would be much preferred.

28th Jul 2010, 04:17 PM	#22
dseymo1 Heptode Join Date: Dec 2007 Location: Shropshire Posts: 737	Re: What software can correct constant pitch increase (CLV recording) ? You can achieve the desired effect in Audacity by adding a new time track, then using the envelope tool to adjust this track. Doing so will affect both the pitch and speed of the audio tracks, which is, of course, what's neded.

29th Jul 2010, 12:34 AM	#27
TIMTAPE Hexode Join Date: Jul 2006 Location: Perth, Western Australia Posts: 370	Re: What software can correct constant pitch increase (CLV recording) ? David, I know you are in a hurry to get these tapes done but you mentioned you have a B77. At least in the MkII model there is an optional variable speed control unit which connects via a DIN plug to the back. I seem to remember it gives a much wider range of variable speeds than does the inbuilt front panel pot. This would be handy to accomodate the range of speeds encountered from beginning to end of a small rim drive tape. The circuit is quite simple, using one IC and a few other cheap components. Next time I'm given a rim drive tape, I'll definitely be constructing such a unit. Will make life a lot easier. The circuit details are in the B77 service manual. I suppose one might also be lucky and pick up such a unit second hand. Cheers Tim

29th Jul 2010, 08:55 AM	#28
david winter Pentode Join Date: May 2008 Location: Paris, France Posts: 111	Re: What software can correct constant pitch increase (CLV recording) ? Tim: I have the original B77 service manual but got used to manually pitch the files section by section. I found that the tapes had a slightly different length of +/- 1 minute. What I did for 4 of them so far is simple: - Playing at the begining and at the end to find the accurate percentages of pitch. They all start at 50%, and all finish at 60% to 62%. - Dividing the recording in 11 to 13 sections depending on the pitch determined at the end (11 for 60%, 13 for 62%). - Pitch each part manually to 50%, 51%, 52% until the end. The result was really satisfactory. To be honest, only a musician would eventually hear a very small pitch change somewhere, and it's not that noticeable. These are voice recordings on the small machine with the microphone put on a table and two persons speaking at a certain distance. I'm still much interested in finding the software that would do all that for me in the fine way...

29th Jul 2010, 09:43 AM	#29
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 7,038	Re: What software can correct constant pitch increase (CLV recording) ? Post #22 suggests Audacity can do this over the whole recording by using the envelope tool. I've never done this so can't give specific instructions. This will have the same effect that you've achieved manually, but without the discrete stepping and with much less work.

29th Jul 2010, 10:50 AM	#30
ajs_derby Octode Join Date: May 2008 Location: Derby Posts: 1,073	Re: What software can correct constant pitch increase (CLV recording) ? How good a programmer are you? You just need to convert the .wav file to raw PCM data, insert extra samples into the stream to slow it down, reconvert back to .wav and apply some low-pass filtering to remove the distortion caused by adding the extra samples. (You could do proper interpolation and resampling in the first place, of course, but that'd be more effort.) Easy enough with sox and your favourite scripting language! __________________ -- AJS

29th Jul 2010, 03:26 PM	#32
dseymo1 Heptode Join Date: Dec 2007 Location: Shropshire Posts: 737	Re: What software can correct constant pitch increase (CLV recording) ? In case anyone decides to use Audacity or this, I should have mentioned (because it's far from obvious) that if you click on the triangle next to the 'Time Track' legend, there's an option to select the upper and lower range of adjustment, which effectively adjusts the 'sensitivity' of the time-domain envelope.

29th Jul 2010, 08:41 PM	#33
Top Cap Heptode Join Date: Mar 2006 Location: Watford, Herts Posts: 668	Re: What software can correct constant pitch increase (CLV recording) ? I had an archive Brian Clough tape that changed pitch as it played, can't believe the BBC used a faulty machine. Anyway what I did was as post #28 using Sony Sound Forge. In this you have the option of time stretching (or shortening) either the entire length or marking up segments and time shift on these. I used the latter technique over many segments (lots of patience required) to get a more even pitch throughout the tape length. I do not have Audacity but wonder if you have the option to time correct on marked up segments as well the whole? Since then I have acquired a machine with variable speed control so I probably would use this in preference, noting the speed control position at beginning and end, then using a stop watch adjust the speed in time segments as the tape played. The problem as I see it with your recordings however is the large amount of speed differential so the software version might prove the best way to go as the speed control on tape decks have a limited range. __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way!

29th Jul 2010, 08:41 PM	#34
Lodgesound Triode Join Date: Jun 2009 Location: Surrey Posts: 23	Re: What software can correct constant pitch increase (CLV recording) ? A method I would propose is as follows: Take a 3 motor tape machine. Remove the pinch roller Disconnect the power to the take up spool motor Now the tricky bit - set up some kind of belt drive to right right hand spool table from the capstan - the speed at this point does not matter - just the ability to provide a constant speed drive to the right hand spool table. The back-tension may need reducing on the feed spool depending on the stability of your drive arrangement. I think most folk on here can see where this is going now. Load tape and transfer at constant linear speed into software such as Wavelab or Adobe Audition. Once transferred isolate the hum component if available in the original audio and adjust the pitch in software as required - a contant pitch change will be all that is needed since your transfer would have been done at constant angular velocity as per the original recording (ie. constant speed take up and increasing pack diameter causing an ever increasing linear tape speed).

29th Jul 2010, 08:54 PM	#35
Lodgesound Triode Join Date: Jun 2009 Location: Surrey Posts: 23	Re: What software can correct constant pitch increase (CLV recording) ? The alternative to all this is to find someone with a Nagra T or a machine such as a Studer A820 - these machines have the ability to operate in a very high stability constant speed take-up shuttle mode at more or less any speed. This removes capstan control and allows for CAV drive of the take-up reel - equivalent to rim drive. Then use the software as before.

2nd Aug 2010, 09:20 PM	#37
woodchips Tetrode Join Date: May 2010 Location: Grantham Posts: 72	Re: What software can correct constant pitch increase (CLV recording) ? Hello, did this 25 years ago with a Racal Store 4. Had to look up my notes to remember how though. Sample the speech at 8kHz or so, we used standard telephone CODECs. Low pass filter to about 1kHz, autocorrelate the result which is the vocal cords opening and closing. With a circular buffer used for input and output samples, when the output catches up with the input, speech to fast, then just move the output pointer back the number of samples generated from the autocorrelation. Do a three sample blend to stop and clicks and that is it. We had the advantage of a capstan speed signal from the TAC4, but in this case the 50Hz (100Hz?) hum can be used as a reference signal. We used a TI TMS32010 and that would cope with a rate change from half to twice, with no pitch change, worked a treat. Bob

2nd Aug 2010, 09:31 PM	#38
david winter Pentode Join Date: May 2008 Location: Paris, France Posts: 111	Re: What software can correct constant pitch increase (CLV recording) ? I finally got it done perfectly with CoolEdit. It was only a matter of finding the initial and final pitches pertentages (which I did using Goldwave as I'm really used to this program), and then use the pitch bend through the progressive bpm variation, using the values found, and with a base of 100bpm so that the percentages correspond to the bpm. Worked perfectly with all files. So thanks again to Paul for his precious help, and to all others who gave interesting suggestions.