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Sample Rate Conversion



 
 
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  #1  
Old January 5th 19, 05:16 PM posted to rec.audio.pro
mcp6453[_2_]
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Default Sample Rate Conversion

For whatever reason, I have some spoken word cassettes that were
recorded at 15/16 IPS that I want to transfer to digital. What's the
best way to digitally correct the tempo and pitch? Using Audition, I
recorded a segment at 88.2 and converted the playback sample rate to
44.1. Tempo and pitch are correct. Is that procedure the best way? Doing
them in software, at least using Audition, is not the way to go.
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  #2  
Old January 5th 19, 06:10 PM posted to rec.audio.pro
Ralph Barone[_3_]
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Default Sample Rate Conversion

mcp6453 > wrote:
> For whatever reason, I have some spoken word cassettes that were
> recorded at 15/16 IPS that I want to transfer to digital. What's the
> best way to digitally correct the tempo and pitch? Using Audition, I
> recorded a segment at 88.2 and converted the playback sample rate to
> 44.1. Tempo and pitch are correct. Is that procedure the best way? Doing
> them in software, at least using Audition, is not the way to go.
>


This sounds like a robust and easy way to do it. There are two downsides:

1) Your cassette deck may not be capable of playing back the doubled
frequency components on the tape, so your highest octave is theoretically
lost. For spoken word, that shouldn't be an issue.

2) The playback eq will be wrong because the frequencies that were boosted
on record aren't being played back at the same frequency they were recorded
at. I forget what the corner frequencies for cassette tape are, but you
should be able to apply eq after the fact to compensate for the difference
between what should have been applied and what was actually applied. If the
model in my head is correct, it would be a 6 dB shelving bass boost,
applied over one octave.

PS: Somebody who actually knows this stuff properly will hopefully chime in
and clarify.

  #3  
Old January 5th 19, 07:43 PM posted to rec.audio.pro
Scott Dorsey
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Default Sample Rate Conversion

mcp6453 > wrote:
>For whatever reason, I have some spoken word cassettes that were
>recorded at 15/16 IPS that I want to transfer to digital. What's the
>best way to digitally correct the tempo and pitch? Using Audition, I
>recorded a segment at 88.2 and converted the playback sample rate to
>44.1. Tempo and pitch are correct. Is that procedure the best way? Doing
>them in software, at least using Audition, is not the way to go.


That's probably the easiest solution. Realize of course that the equalization
is going to be all screwy since you have just doubled all the eq constants in
the process of playing it back faster. And of course all of the analogue
electronics that roll off at 20kc are now rolling off at 10kc. But for
spoken word that might not be any worry.

I know that the cassette machines that folks used to use for surveillance
applications often had super narrow track heads in them in order to get
better intelligibility at very low speeds. It might be nice to have such
a thing. But if you don't, and it sounds okay, you should be fine.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #4  
Old January 5th 19, 08:57 PM posted to rec.audio.pro
PStamler
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Default Sample Rate Conversion

On Saturday, January 5, 2019 at 10:17:01 AM UTC-6, mcp6453 wrote:
> For whatever reason, I have some spoken word cassettes that were
> recorded at 15/16 IPS that I want to transfer to digital. What's the
> best way to digitally correct the tempo and pitch? Using Audition, I
> recorded a segment at 88.2 and converted the playback sample rate to
> 44.1. Tempo and pitch are correct. Is that procedure the best way? Doing
> them in software, at least using Audition, is not the way to go.


I think doing the conversion in software *is* the way to go, not by futzing with sample rates, but by using Audition's resampling speed-conversion function, which avoids the EQ hassles. It's not perfect, but it's damned good, and I think that's what you should do.

Peace,
Paul Stamler
  #5  
Old January 5th 19, 09:44 PM posted to rec.audio.pro
John Williamson
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Posts: 1,590
Default Sample Rate Conversion

On 05/01/2019 19:57, PStamler wrote:
> On Saturday, January 5, 2019 at 10:17:01 AM UTC-6, mcp6453 wrote:
>> For whatever reason, I have some spoken word cassettes that were
>> recorded at 15/16 IPS that I want to transfer to digital. What's the
>> best way to digitally correct the tempo and pitch? Using Audition, I
>> recorded a segment at 88.2 and converted the playback sample rate to
>> 44.1. Tempo and pitch are correct. Is that procedure the best way? Doing
>> them in software, at least using Audition, is not the way to go.

>
> I think doing the conversion in software *is* the way to go, not by futzing with sample rates, but by using Audition's resampling speed-conversion function, which avoids the EQ hassles. It's not perfect, but it's damned good, and I think that's what you should do.
>


The EQ problems are with the analogue part of the system. Both 15/16 and
1 7/8 ips cassettes have very similar record equalisation profiles, and
playing a 15/16 ips cassette back at 1 7/8 ips will move the HF peak
response by an octave. It is, however, easy to compensate for this by
applying the appropriate eq to the resampled or sample rate altered file.

It may also be worth applying a noise reduction filter in the DAW software.

--
Tciao for Now!

John.
  #6  
Old January 7th 19, 05:24 AM posted to rec.audio.pro
geoff
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Posts: 1,375
Default Sample Rate Conversion

On 6/01/2019 5:16 AM, mcp6453 wrote:
> For whatever reason, I have some spoken word cassettes that were
> recorded at 15/16 IPS that I want to transfer to digital. What's the
> best way to digitally correct the tempo and pitch? Using Audition, I
> recorded a segment at 88.2 and converted the playback sample rate to
> 44.1. Tempo and pitch are correct. Is that procedure the best way? Doing
> them in software, at least using Audition, is not the way to go.


I assume that you cannot play back at 15/16 ips.

Sample-rate conversion should not affect the pitch or the speed of the
audio at all. Changing the header info will though, by fooling the
playback dev ice..

But you would be better to edit the playback speed in your editing
software, ignoring sample-rate as an issue entirely.

geoff
 




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