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#1
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Tape speed correction on wav files
Hi all,
I'm new here so please just point me at a faq or whatever if this has been done to death before. I'm transferring old audio tapes to wav playing back on a Revox A77 but some were recorded on an older machine where the speed wasn't very accurate but could be reasonably consistent. I'm looking for a utility that will let me process the wav files to change the speed by an arbitrary percentage, presumably by simple interpolation. I'm not looking for great quality as the originals were poor quality and quite noisy anyway. Some may even have been at 1 7/8 ips but they have sentimental value. I'd rather use some shareware solution than write my own so does anyone have any suggestions. Thanks George |
#2
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On Fri, 17 Sep 2004 18:44:37 +0100, "George Dishman"
wrote: Hi all, I'm new here so please just point me at a faq or whatever if this has been done to death before. I'm transferring old audio tapes to wav playing back on a Revox A77 but some were recorded on an older machine where the speed wasn't very accurate but could be reasonably consistent. I'm looking for a utility that will let me process the wav files to change the speed by an arbitrary percentage, presumably by simple interpolation. The program you need should change the sample rate. Most audio editors can do that. The function to look for is "change time/pitch". I use Adobe Audition for that and it offeres three functions: "change time (and preserve pitch)" and "change pitch (and preserve time)" require a hefty interpolation that may leave some artifacts. Changing both time and pitch are done by change of sample rate (which is done without artifacts). Norbert |
#3
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"George Dishman" wrote in message ... I'm transferring old audio tapes to wav playing back on a Revox A77 but some were recorded on an older machine where the speed wasn't very accurate but could be reasonably consistent. I'm looking for a utility that will let me process the wav files to change the speed by an arbitrary percentage, presumably by simple interpolation. I'm not looking for great quality as the originals were poor quality and quite noisy anyway. Some may even have been at 1 7/8 ips but they have sentimental value. I'd rather use some shareware solution than write my own so does anyone have any suggestions. The best freeware I know of for changing sample rate, is Voxengo R8Brain. You can resample at a higher or lower rate, but set the output file headers for the original sample rate. This has the same effect as increasing or decreasing tape speed. Resample quality is excellent. The other problem for 1 7/8 ips recordings, assuming your A77 doesn't have 1 7/8 ips playback, is that the EQ will be wrong. You can change that in software too. TonyP. |
#4
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"TonyP" wrote in message u... ... The best freeware I know of for changing sample rate, is Voxengo R8Brain. You can resample at a higher or lower rate, but set the output file headers for the original sample rate. This has the same effect as increasing or decreasing tape speed. Resample quality is excellent. My thanks to you and Norbert, this is exactly what I was looking for. The other problem for 1 7/8 ips recordings, assuming your A77 doesn't have 1 7/8 ips playback, is that the EQ will be wrong. You can change that in software too. Good point, I hadn't thought of that. I doubt the original quality is good enough for it to show up as most was recorded from AM radio thirty years ago but now I know where to look. thanks again George |
#5
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On Sat, 18 Sep 2004 15:58:29 +1000, "TonyP"
wrote: The best freeware I know of for changing sample rate, is Voxengo R8Brain. You can resample at a higher or lower rate, but set the output file headers for the original sample rate. This has the same effect as increasing or decreasing tape speed. Resample quality is excellent. In deed, it's a great program. I did some checks: I used a recording with 44.1 kHz original sample rate and tried to speed up to 102%. So I patched 45 kHz into the file and started r8brain. Output sample rate was then selected as 44.1 kHz. No problems. The file got converted and it sounded ok. To verify that is was converted at all I played back both files at the same time - the difference is clearly audible. Another fine program, Shibatch Sample Rate Converter (ssrc.exe), tells me that the ratio 44100/45000 is not in its tables. It does a good job on converting well known sample rates though. Norbert |
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