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Author Topic: Pitch shift idea  (Read 506 times)

Offline OgreVorbis

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Pitch shift idea
« on: July 06, 2018, 0020 UTC »
So I was thinking about the limitations of audio bandwidth for broadcasting. I was wondering what it would sound like if instead of filtering at something like 2-5khz (which is around the standard), you instead pitch shift down everything above that. I don't mean pitch shift everything, just what is above where the filter cuts off. What would this sound like? Clearly it would sound lower, but would it improve the quality of the music without using more bandwidth?

Also is this possible in any software (like audacity maybe)?

Offline OgreVorbis

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Re: Pitch shift idea
« Reply #1 on: July 06, 2018, 0205 UTC »
So, I just tested it in audacity. Audacity doesn't have the feature to pitch shift only a specific range, so:
I added the track twice.
Put a high pass filter on the first one.
Pitch shifted the first one.
Then put a 2.5Khz low pass on both tracks.
Played them together.

It sounds about the same as it would if you just used an EQ to the higher frequencies. Maybe it could be done better though. This was just me messing around. You could probably optimize the pitch shift to make it better. You might get distortion if the pitch shift isn't right.

Offline Stretchyman

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Re: Pitch shift idea
« Reply #2 on: July 06, 2018, 1033 UTC »
Just TX a wider B/W, I usually cutoff over 7KHz.

The pitch shifting kinda sounds like a very wierd idea bud!!???

Str.
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Offline TheRelayStation

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Re: Pitch shift idea
« Reply #3 on: July 06, 2018, 1717 UTC »
a better idea is to have a TX that has full audio range and use a professional sound processor to control, filter and tailor the audio to your specific desires.
obviously, loss of the audio amplitude level is greater at higher audio frequencies which is why (modified) pre-emphasis is used as an industry standard for AM broadcasting.
this is why many SWBC stations generally have their audio frequency set at 5Khz (10Khz total occupied bandwidth), audio density is greater with less bandwidth being used.
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Offline Josh

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Re: Pitch shift idea
« Reply #4 on: July 06, 2018, 1717 UTC »
What is really needed is called companding. The tx side has the compressor, the rx side has the expander. If one or the other lacks the means, the effort becomes pointless.

Offline OgreVorbis

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Re: Pitch shift idea
« Reply #5 on: July 07, 2018, 0033 UTC »
Just TX a wider B/W, I usually cutoff over 7KHz.

The pitch shifting kinda sounds like a very wierd idea bud!!???

Str.

Is the range compromised by that? It would be ideal, but does it have a significant impact on range or is it small enough that it doesn't really matter?

Offline OgreVorbis

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Re: Pitch shift idea
« Reply #6 on: July 07, 2018, 0038 UTC »
a better idea is to have a TX that has full audio range and use a professional sound processor to control, filter and tailor the audio to your specific desires.
obviously, loss of the audio amplitude level is greater at higher audio frequencies which is why (modified) pre-emphasis is used as an industry standard for AM broadcasting.
this is why many SWBC stations generally have their audio frequency set at 5Khz (10Khz total occupied bandwidth), audio density is greater with less bandwidth being used.

In terms of sound processing, I'm currently using an ADAU1701 DSP from analog devices. It works really well and I'd highly recommend. The DSP eval board is $200, but you can find Chinese clones of the board for cheaper on aliexpress.

It is controlled by a flow-chart type of software called SigmaStudio. It can be modified in real time to hear the changes to the audio. Cheaper and better than a pro-processor imo.

Offline TheRelayStation

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Re: Pitch shift idea
« Reply #7 on: July 08, 2018, 2102 UTC »
a better idea is to have a TX that has full audio range and use a professional sound processor to control, filter and tailor the audio to your specific desires.
obviously, loss of the audio amplitude level is greater at higher audio frequencies which is why (modified) pre-emphasis is used as an industry standard for AM broadcasting.
this is why many SWBC stations generally have their audio frequency set at 5Khz (10Khz total occupied bandwidth), audio density is greater with less bandwidth being used.

In terms of sound processing, I'm currently using an ADAU1701 DSP from analog devices. It works really well and I'd highly recommend. The DSP eval board is $200, but you can find Chinese clones of the board for cheaper on aliexpress.

It is controlled by a flow-chart type of software called SigmaStudio. It can be modified in real time to hear the changes to the audio. Cheaper and better than a pro-processor imo.
i use "stereotool", $35 USD it cost.
dont let the name fool you, this software is used on many commercial broadcasting radio stations.
6880 Khz AM 50W/500W - shortwavepirate@aol.com

Offline OgreVorbis

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Re: Pitch shift idea
« Reply #8 on: July 15, 2018, 0147 UTC »
a better idea is to have a TX that has full audio range and use a professional sound processor to control, filter and tailor the audio to your specific desires.
obviously, loss of the audio amplitude level is greater at higher audio frequencies which is why (modified) pre-emphasis is used as an industry standard for AM broadcasting.
this is why many SWBC stations generally have their audio frequency set at 5Khz (10Khz total occupied bandwidth), audio density is greater with less bandwidth being used.

In terms of sound processing, I'm currently using an ADAU1701 DSP from analog devices. It works really well and I'd highly recommend. The DSP eval board is $200, but you can find Chinese clones of the board for cheaper on aliexpress.

It is controlled by a flow-chart type of software called SigmaStudio. It can be modified in real time to hear the changes to the audio. Cheaper and better than a pro-processor imo.
i use "stereotool", $35 USD it cost.
dont let the name fool you, this software is used on many commercial broadcasting radio stations.

I've also used that and I like it, but it lags for me sometimes with the virtual cable. I just like the solidness of a DSP - knowing it's not going to lag or fail randomly.

Offline TheRelayStation

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Re: Pitch shift idea
« Reply #9 on: July 15, 2018, 1907 UTC »
Quote from: OgreVorbis
I've also used that and I like it, but it lags for me sometimes with the virtual cable. I just like the solidness of a DSP - knowing it's not going to lag or fail randomly.
what are you using for a virtual cable ?
if you have "stereo mix" in your audio control panel, that is preferred.
i use VAC (hi-fi version) as the default device for playback/recording (so it can be fed into ST) and have zero issues.
make sure all sample rates/bit depths match on all sound cards and on ST.
use WASPI for input/output on ST also.
6880 Khz AM 50W/500W - shortwavepirate@aol.com