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Finding clicks
I've recently been experimenting with using Audacity to deal with clicks in
digital recordings made from old LPs. I suspect I'm not the first to do this or encounter the following! Hence I'd be interested in feedback on what follows... LPs in very good condition only have a few clicks, and these can be easy enough to find and fix. Particulary if they are loud 'rifle shots' that stick out clearly on something like Audacity's waveform plots! However other LPs can have many many clicks per LP side. This can make finding and fixing most of them fairly time-consuming. In particular when a small 'tick' is hiding as a small alternation to a larger and complex audio waveform. It becomes a bit like looking for a sapling in a forest! For some old classical LPs there may be lots of these which are audible as the music can have long low-level sections, meaning that clicks it would be impossible to hear with loud Jazz, say, show up against quiet classical. Because of this I've been experimenting with ways to scan a wave file looking for clicks. Using tricks like looking at the first or second derivative of the waveforms which appear rise and fall quckly to emphasise short sharp clicks out of the steady music background. However I'm wondering about two things. 1) Anyone know of decent free software that already does something like this well and can list a good set of 'click candidate' times in a wave file. i.e. low levels of 'misses' and 'false alarms' even with classical music. 2) To what extent this is simply a waste of effort beyond finding the most obvious clicks. i.e. That there isn't a simple and reliable algorithm for this and it ends up being quicker and better to use ears and eyes and Audacity. So far I have the impression that (2) comes into force pretty quickly as the clicks vanish into the waveforms. But I thought I'd ask as I suspect others have explored this already. :-) BTW At present simply using ear/eye/Audacity I seem to find that the 'hard cases' where I'm searching for many tiny 'ticks' can mean about 0.1 rate working. i.e. About 200 - 300 mins of work per LP side for classical if I really want to clear even the faintest ticks I hear. Fortunately, LPs that tend to spend most of the time at higher levels are much quicker as the music drowns out the smaller ticks. BTW2 Having experimented I haven't found the declicking 'effect' of Audacity to be much use. I've just been using the 'repair' instead. But maybe I'm missing something here... Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
Finding clicks
On Sun, 07 Sep 2014 14:29:07 +0100, Jim Lesurf
wrote: I've recently been experimenting with using Audacity to deal with clicks in digital recordings made from old LPs. I suspect I'm not the first to do this or encounter the following! Hence I'd be interested in feedback on what follows... LPs in very good condition only have a few clicks, and these can be easy enough to find and fix. Particulary if they are loud 'rifle shots' that stick out clearly on something like Audacity's waveform plots! However other LPs can have many many clicks per LP side. This can make finding and fixing most of them fairly time-consuming. In particular when a small 'tick' is hiding as a small alternation to a larger and complex audio waveform. It becomes a bit like looking for a sapling in a forest! For some old classical LPs there may be lots of these which are audible as the music can have long low-level sections, meaning that clicks it would be impossible to hear with loud Jazz, say, show up against quiet classical. Because of this I've been experimenting with ways to scan a wave file looking for clicks. Using tricks like looking at the first or second derivative of the waveforms which appear rise and fall quckly to emphasise short sharp clicks out of the steady music background. However I'm wondering about two things. 1) Anyone know of decent free software that already does something like this well and can list a good set of 'click candidate' times in a wave file. i.e. low levels of 'misses' and 'false alarms' even with classical music. 2) To what extent this is simply a waste of effort beyond finding the most obvious clicks. i.e. That there isn't a simple and reliable algorithm for this and it ends up being quicker and better to use ears and eyes and Audacity. So far I have the impression that (2) comes into force pretty quickly as the clicks vanish into the waveforms. But I thought I'd ask as I suspect others have explored this already. :-) BTW At present simply using ear/eye/Audacity I seem to find that the 'hard cases' where I'm searching for many tiny 'ticks' can mean about 0.1 rate working. i.e. About 200 - 300 mins of work per LP side for classical if I really want to clear even the faintest ticks I hear. Fortunately, LPs that tend to spend most of the time at higher levels are much quicker as the music drowns out the smaller ticks. BTW2 Having experimented I haven't found the declicking 'effect' of Audacity to be much use. I've just been using the 'repair' instead. But maybe I'm missing something here... Jim The click fixer in CoolEdit (many incarnations, and there is a shareware version among them) has a good reputation, and I've used it successfully. The product was subsequently bought by Adobe and has morphed into Audition - and become bloatware while abandoning the best features. You will need to adopt the dreaded windows to use it, I'm afraid. d |
Finding clicks
On Sun, 07 Sep 2014 14:29:07 +0100
Jim Lesurf wrote: I've recently been experimenting with using Audacity to deal with clicks in digital recordings made from old LPs. I suspect I'm not the first to do this or encounter the following! Hence I'd be interested in feedback on what follows... LPs in very good condition only have a few clicks, and these can be easy enough to find and fix. Particulary if they are loud 'rifle shots' that stick out clearly on something like Audacity's waveform plots! However other LPs can have many many clicks per LP side. This can make finding and fixing most of them fairly time-consuming. In particular when a small 'tick' is hiding as a small alternation to a larger and complex audio waveform. It becomes a bit like looking for a sapling in a forest! For some old classical LPs there may be lots of these which are audible as the music can have long low-level sections, meaning that clicks it would be impossible to hear with loud Jazz, say, show up against quiet classical. Because of this I've been experimenting with ways to scan a wave file looking for clicks. Using tricks like looking at the first or second derivative of the waveforms which appear rise and fall quckly to emphasise short sharp clicks out of the steady music background. However I'm wondering about two things. 1) Anyone know of decent free software that already does something like this well and can list a good set of 'click candidate' times in a wave file. i.e. low levels of 'misses' and 'false alarms' even with classical music. 2) To what extent this is simply a waste of effort beyond finding the most obvious clicks. i.e. That there isn't a simple and reliable algorithm for this and it ends up being quicker and better to use ears and eyes and Audacity. So far I have the impression that (2) comes into force pretty quickly as the clicks vanish into the waveforms. But I thought I'd ask as I suspect others have explored this already. :-) BTW At present simply using ear/eye/Audacity I seem to find that the 'hard cases' where I'm searching for many tiny 'ticks' can mean about 0.1 rate working. i.e. About 200 - 300 mins of work per LP side for classical if I really want to clear even the faintest ticks I hear. Fortunately, LPs that tend to spend most of the time at higher levels are much quicker as the music drowns out the smaller ticks. BTW2 Having experimented I haven't found the declicking 'effect' of Audacity to be much use. I've just been using the 'repair' instead. But maybe I'm missing something here... Jim Many years ago the BBC (I think) developed a system that worked by playing a track *backwards*. The clicks still presented themselves as sharp edged pulses, while the music was a slowly rising signal. -- W J G |
Finding clicks
In article , Don Pearce
wrote: On Sun, 07 Sep 2014 14:29:07 +0100, Jim Lesurf wrote: [snip] The click fixer in CoolEdit (many incarnations, and there is a shareware version among them) has a good reputation, and I've used it successfully. The product was subsequently bought by Adobe and has morphed into Audition - and become bloatware while abandoning the best features. Does it *find* the clicks automatically? Fixing them is easy. You will need to adopt the dreaded windows to use it, I'm afraid. It would be easier to experiment with making use of the approach for auto-finding clicks if the above has one, and use my own software. Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
Finding clicks
On Sun, 07 Sep 2014 14:29:07 +0100, Jim Lesurf wrote:
BTW2 Having experimented I haven't found the declicking 'effect' of Audacity to be much use. I've just been using the 'repair' instead. But maybe I'm missing something here... Agreed. I've never found it worthwhile. However, on the few records I've digitised with Audacity and found click removal necessary, the clicks have all had enough amplitude to spot by eye once playback provided the approximate location. Maybe I've been lucky, but so far that have all been a single high amplitude wave cycle and have been simple to remove after zooming in far enough. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
Finding clicks
In article 20140907144744.351a420b@debian,
Folderol wrote: On Sun, 07 Sep 2014 14:29:07 +0100 Jim Lesurf wrote: [snip] Many years ago the BBC (I think) developed a system that worked by playing a track *backwards*. The clicks still presented themselves as sharp edged pulses, while the music was a slowly rising signal. In effect, that's what I'm experimenting with at present. My first experiments scan though looking at the level. Then finding places where the peak levels drop a great deal in a short time. Thus picking up events with a sharply falling trailing edge. I've tried combining this with the peak level and crest factors. It works for the most obvious clicks. But not for the small ones whose size is *not* much bigger than the musical waveforms. So it shows clicks that are also clear to see with Audacity, but misses the smaller hard-to-see examples. So it is useful, but limited in value. Hence I'm thinking of trying the same approach as above, but to the first or second differential of the waveforms to change the relative scaling of quick events (with a lot of HF) to the surrounding music. BTW I also recall the old Hi Fi News cover showing some LP replay systems at their pressing factory. These looked strange because they were playing the LPs 'backward'. They were being used to look for faults (clicks) so went backwards for the same reason as above. Anyone buying EMI classical LPs at the time may not have been astonished that 2 out of 3 of the decks shown had a big red 'fault detected' light lit up. 8-] That seemed about right to me at the time. About 2/3rds of the EMI classical LPs I bought then had to be returned due to the added rifle shots! Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
Finding clicks
In article ,
Don Pearce wrote: You will need to adopt the dreaded windows to use it, I'm afraid. Or grab a glass of WINE! I still run CoolEdit Pro 2.1 under WINE on Slackware, the last version from before Adobe stuck their bib in. -- --------------------------------------+------------------------------------ Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk --- news://freenews.netfront.net/ - complaints: --- |
Finding clicks
On Sun, 07 Sep 2014 15:03:37 +0100, Jim Lesurf
wrote: In article , Don Pearce wrote: On Sun, 07 Sep 2014 14:29:07 +0100, Jim Lesurf wrote: [snip] The click fixer in CoolEdit (many incarnations, and there is a shareware version among them) has a good reputation, and I've used it successfully. The product was subsequently bought by Adobe and has morphed into Audition - and become bloatware while abandoning the best features. Does it *find* the clicks automatically? Fixing them is easy. You will need to adopt the dreaded windows to use it, I'm afraid. It would be easier to experiment with making use of the approach for auto-finding clicks if the above has one, and use my own software. Jim It has several modes. There's full auto where you just let it loose, a directed one where you can set thresholds and a manual one where you find the clicks, surround them with a pair of cursors, and some algorithm - spline or whatever - connects the two ends together. d |
Finding clicks
I can illustrate the real challenge here with an example.
http://jcgl.orpheusweb.co.uk/temp/ZoomCircled.png This shows the start of side 2 of an LP of Brahms 1st Piano Concerto (Barbirolli, Barenboim on EMI 1967) Its a lovely LP but has various various 'ticks' that are clearly audible in the quiet passages. The tick shown here at about 6.42 sec from the start is audible with the piano. Note the low modulation levels. The music is below about -25dB as recorded (0dBFS was about +17dBRIAA) and the tick is smaller in amplitude than the music. This one is relatively easy to find by ear-eye *but* you have to zoom the time and amplitude scales to be able to see it. If you don't the ripple at the bottom of the previous cycle looks like the cause because it sticks out of the displayed waveform, but it isn't. Other ticks are harder to find. But even this one seems a challenge to find by an 'automated' locator. Doing an automatic locator for loud bangs is easy. But then so is seeing them with Audacity! Question is if this kind of example can be detected by something of the kind I've mentioned. Ideally a program that generates a list of 'click candidates' that would find this but not be swamped with false positives. I suspect its almost impossible, but wonder what people think. Took me hours to do side 1! 8-] Its only something I'd do for 'special cases' where I really want to clean up as much as possible particularly enjoyable examples. ... and this is a 2 LP set. 8-] Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
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