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What DSPs and in which order for reduce Tape Hiss?
servimo
post Oct 18 2009, 22:41
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I have a lot of FLACs recorded from cassete tapes and want to know if there is a away by using DSPs and in which order to reduce the Hiss during playback? And If there is a good Equalizer preset that do the trick? Noise Sharpening or Dolby Headphones could be for this thing? I know that I could try out, but I want to try some others experiments with this from others. I mean exchange experience (Google translation)

This post has been edited by servimo: Oct 18 2009, 23:06
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servimo
post Oct 19 2009, 01:30
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QUOTE (servimo @ Oct 18 2009, 18:41) *
I have a lot of FLACs recorded from cassete tapes and want to know if there is a away by using DSPs and in which order to reduce the Hiss during playback? And If there is a good Equalizer preset that do the trick? Noise Sharpening or Dolby Headphones could be for this thing? I know that I could try out, but I want to try some others experiments with this from others. I mean exchange experience (Google translation)


Maybe the right question on this is: How to reduce Tape Hiss when playing tracks using foobar2000?
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odyssey
post Oct 19 2009, 01:55
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I don't think you can (easily). You can probably find some nice VST's that does this and use the VST wrapper, but it will be applied to all the tracks you listen to, then.

Hiss reduction is not easily to get rid of. It is not tied to a certain frequency, but rather a large spectrum of frequencies (much like white noise)

You need an advanced filter to sort out random noise and while it may have somewhat good effects on your tape-recordings, it will probably destroy parts of music with weird alien-like artifacts. If you find a good VST with configurable settings, you might be better off converting the needed tracks with VST plugin applied to different files, however the best approach might be to edit them in an audio editor.


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servimo
post Oct 19 2009, 02:13
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I didn't think about a VST wrapper, I will try this. Thanks for replying.

It looks like VST will make hard use of the CPU, at least for the ones I tried. I am not want to totally exterminate the Noise just want to reduce it a little while playing. I was thinking in slowing the highs using Equalization and maybe somebody know of some DSP plugins that will do this. I found this dsp plugin for Winamp "Tape Restore Live" to use with winamp DSP bridge, but still lots of CPU usage.

This post has been edited by servimo: Oct 19 2009, 02:46
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shakey_snake
post Oct 19 2009, 02:26
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QUOTE (odyssey @ Oct 18 2009, 20:55) *
I don't think you can (easily). You can probably find some nice VST's that does this and use the VST wrapper, but it will be applied to all the tracks you listen to, then.

You can use the converter with an appropriate VTS plugin+wrapper to avoid this, although the files would then be permanently altered.

This post has been edited by shakey_snake: Oct 19 2009, 02:27


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servimo
post Oct 19 2009, 02:48
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QUOTE (shakey_snake @ Oct 18 2009, 22:26) *
QUOTE (odyssey @ Oct 18 2009, 20:55) *
I don't think you can (easily). You can probably find some nice VST's that does this and use the VST wrapper, but it will be applied to all the tracks you listen to, then.

You can use the converter with an appropriate VTS plugin+wrapper to avoid this, although the files would then be permanently altered.


Is not a good idea, I don't want to modify the sound source.
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shakey_snake
post Oct 19 2009, 02:58
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Well the tape hiss could be considered a modification in itself. smile.gif


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odyssey
post Oct 19 2009, 09:12
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QUOTE (servimo @ Oct 19 2009, 03:13) *
It looks like VST will make hard use of the CPU, at least for the ones I tried. I am not want to totally exterminate the Noise just want to reduce it a little while playing. I was thinking in slowing the highs using Equalization and maybe somebody know of some DSP plugins that will do this. I found this dsp plugin for Winamp "Tape Restore Live" to use with winamp DSP bridge, but still lots of CPU usage.

As I said, it's an advanced process and not something you would normally fix using a DSP. It doesn't matter how "hard" you want to apply the reduction - The process itself is very CPU intensive. That's why I recommend you to modify your files instead.

There is currently no DSP that does this in foobar2000 natively, so your best option is to use a VST or maybe the Winamp DSP wrapper.

QUOTE (shakey_snake @ Oct 19 2009, 03:26) *
QUOTE (odyssey @ Oct 18 2009, 20:55) *
I don't think you can (easily). You can probably find some nice VST's that does this and use the VST wrapper, but it will be applied to all the tracks you listen to, then.

You can use the converter with an appropriate VTS plugin+wrapper to avoid this, although the files would then be permanently altered.

...i already wrote that in my initial post


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Dynamic
post Oct 20 2009, 23:22
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QUOTE (servimo @ Oct 19 2009, 02:48) *
Is not a good idea, I don't want to modify the sound source.


I can't see the problem. Don't over-write the original, just create a new file, perhaps in a separate folder, which is a dehissed version, and possibly then prevent the original from being part of the fb2k library/album list (i.e. exclude C:\Music\OriginalHissyTapeTransfers\*.flac or whatever) so you only have the best-sounding copy in your playlists. The de-hissed version doesn't even need to be a large lossless file so keeping the original + dehissed versions needn't double your disk storage requirements. (Any "transparent" lossy format for the dehissed music should be great to listen to, be it something like lossyWAV|FLAC, WVlossy, LAME -V2, AoTuV Ogg Vorbis -q6, neroAACenc -q0.5 or whatever your preferred players can use).

If your tape captures didn't utilise Dolby NR but it was utilised on the recording (you can generally be pretty sure they did not if you're hearing bright high-frequencies and lengthened cymbal and hi-hat decays in the hi-frequency part of the spectrum compared to CD or vinyl versions as well as fairly substantial amounts of hi-freq hiss), I'd suggest that Tape Restore Live outputting to a new file with Winamp's Disk Output feature would be an excellent first step. Then you can use fb2k or whatever you prefer to compress the PCM WAV that results to your desired format and then to copy the tags from your original file onto the resulting dehissed file. You may then delete the intermediate PCM WAV and keep just the original tape capture (with hiss) and the dehissed file. If a better dehissing method becomes available, you can always reprocess the original tape capture and create a new dehissed file.

Having tried a few audio editors' free/bundled digital noise reduction routines on tapes that I'd captured with Dolby-B NR turned on, I'm of the conclusion that:
The hiss remaining after you have applied Dolby NR is usually masked from audibility by moderate-to-loud music, so digital noise reduction processing is likely to cause more damage than good (e.g. warbling 1960's sci-fi computer sounds/underwater burbling and mucking up the transients in the original).
It's only during fade-in, fade-out, possibly track gaps and quiet tracks or movements that it's seriously worth considering, and then applying to the minimum degree you can get away with to minimize those nasty side-effects that you might not immediately notice, but can become permanently annoying once you recognise them.
There's probably a scope for a psychoacoustically aware digital noise reduction algorithm to be made which automatically determines the masking level and thus would only attempt to de-noise where the noise (measured from the noise-only sample) is predicted to be audible, and would take care to detect transients and avoid smearing them or mistaking them for noise.
I haven't ruled out that other (e.g. professional DAW-grade denoisers or more recent algorithms) are far more transparent, though I suspect that tape noise remaining after Dolby NR on studio master tapes is considerably less perceptible than on consumer cassettes anyway.

I did also try an experiment some years ago in arithmetically adding a sample of captured tape-hiss in silence (captured with Dolby B NR turned on) to a sample of ripped CD audio so that I could ABX or ABC/HR the original clean CD version against the dehissed version. The methods I tried weren't very successful at recovering the clean audio from the noise, having robbed it of some of the transients in particular. Given that the noise was moderate, the noise+hiss version (after Dolby B NR, of course) was better than the result of any of the Digital Noise Reductions I tried.

For that experiment my recorded tape hiss was perceived to be about 48 dB quieter than the album itself (based on Track Gain and Album Gain measurements, album gain being -0.89 dB).

In that experiment the quietest track had an especially quiet intro, with Track Gain of +10.46 dB, meaning 78.54 dB SPL perceived loudness (just measured on the intro, not the whole track, using the Replay Gain formula). The perceived hiss loudness was thus about 37 dB below the perceived intro loudness and was much more objectionable at this time than for the rest of the album (except inter-track gaps and fades), particularly because of relative silences between notes and phrases in the music as much as the perceived overall loudness.


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servimo
post Oct 21 2009, 07:15
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What a repply, don't know if I should say thanks, need to read it more carefully tomorrow by the morning.
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servimo
post Oct 21 2009, 21:00
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Yes, I should say thanks, looks like a resume of what is found when you try to reduce the tape hiss. Better keep it and try to listen to the music without paying attention to the hiss. The more you give attention to the hiss the more you hear it. I save your answers to my post in my HD for future reference. I don't want to put anything more in my HD, it is full. That's the reason why I didn't want to make experiments with sounds. What I need is another HD or delete more files.

This post has been edited by servimo: Oct 21 2009, 21:05
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