achieve minimal latency when using pitch shifting

[alex dashevski]

Hi,

I have project with pitch shifting (resampling with wsola), It implements
on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.

Thanks,
Alex

['Don Turner' via android-ndk]

The fast path properties cannot be changed as they are set by the audio
hardware.

It sounds to me that you have to process 20ms of audio data at 8kHz (160
samples). If that's correct you probably need to do something like this:

1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer

Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It implements
on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

[Alex Dashevski]

Hi,
I don't understand your answer.

Why isn't it ?
1. Dowsampe to 8Khz and buffer size should be 240*6
2. To do proccessing on buffer 240*6 with 8Khz sample rate.
3. Upsample to 48khz with original buffer size.

Thanks,
Alex

‫בתאךיך יום ו׳, 5 באוק׳ 2018 ב-11:42 מאת ‪'Don Turner' via android-ndk‬‏ <‪

Post by 'Don Turner' via android-ndk
The fast path properties cannot be changed as they are set by the audio
hardware.
It sounds to me that you have to process 20ms of audio data at 8kHz (160
1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer
Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It implements
on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

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['Don Turner' via android-ndk]

"Dowsampe to 8Khz and buffer size should be 240*6"

When you downsample from 48kHz to 8kHz you have *less* samples (hence the
name - "downsampling") so if you start with a buffer of 240 samples at
48kHz and downsample to 8kHz you will end up with 240*(8/48)=40 samples.

That said, I don't know why your pitch shifting algorithm only works on
8kHz data - if your source audio data is at 48kHz then the algorithm should
just work on that.

Please explain more clearly your use case and what you're trying to
achieve.

Post by Alex Dashevski
Hi,
I don't understand your answer.
Why isn't it ?
1. Dowsampe to 8Khz and buffer size should be 240*6
2. To do proccessing on buffer 240*6 with 8Khz sample rate.
3. Upsample to 48khz with original buffer size.
Thanks,
Alex
‫בתאךיך יום ו׳, 5 באוק׳ 2018 ב-11:42 מאת ‪'Don Turner' via android-ndk‬‏ <‪

Post by 'Don Turner' via android-ndk
The fast path properties cannot be changed as they are set by the audio
hardware.
It sounds to me that you have to process 20ms of audio data at 8kHz (160
1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer
Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It
implements on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

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[Alex Dashevski]

Duration of pitch is ~20ms. Thus, duration of buffer samples should be
bigger than duration pitch.
Thanks,
Alex

‫בתאךיך יום ה׳, 11 באוק׳ 2018 ב-18:04 מאת ‪'Don Turner' via android-ndk‬‏ <‪

Post by 'Don Turner' via android-ndk
"Dowsampe to 8Khz and buffer size should be 240*6"
When you downsample from 48kHz to 8kHz you have *less* samples (hence the
name - "downsampling") so if you start with a buffer of 240 samples at
48kHz and downsample to 8kHz you will end up with 240*(8/48)=40 samples.
That said, I don't know why your pitch shifting algorithm only works on
8kHz data - if your source audio data is at 48kHz then the algorithm should
just work on that.
Please explain more clearly your use case and what you're trying to
achieve.

Post by Alex Dashevski
Hi,
I don't understand your answer.
Why isn't it ?
1. Dowsampe to 8Khz and buffer size should be 240*6
2. To do proccessing on buffer 240*6 with 8Khz sample rate.
3. Upsample to 48khz with original buffer size.
Thanks,
Alex
‫בתאךיך יום ו׳, 5 באוק׳ 2018 ב-11:42 מאת ‪'Don Turner' via android-ndk‬‏

Post by 'Don Turner' via android-ndk
The fast path properties cannot be changed as they are set by the audio
hardware.
It sounds to me that you have to process 20ms of audio data at 8kHz (160
1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer
Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It
implements on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

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['Don Turner' via android-ndk]

"Duration of pitch"

Pitch is a measure of frequency not time. Sorry if I'm missing something,
just trying to understand the problem you're facing.

Post by Alex Dashevski
Duration of pitch is ~20ms. Thus, duration of buffer samples should be
bigger than duration pitch.
Thanks,
Alex
‫בתאךיך יום ה׳, 11 באוק׳ 2018 ב-18:04 מאת ‪'Don Turner' via android-ndk‬‏

Post by 'Don Turner' via android-ndk
"Dowsampe to 8Khz and buffer size should be 240*6"
When you downsample from 48kHz to 8kHz you have *less* samples (hence the
name - "downsampling") so if you start with a buffer of 240 samples at
48kHz and downsample to 8kHz you will end up with 240*(8/48)=40 samples.
That said, I don't know why your pitch shifting algorithm only works on
8kHz data - if your source audio data is at 48kHz then the algorithm should
just work on that.
Please explain more clearly your use case and what you're trying to
achieve.

Post by Alex Dashevski
Hi,
I don't understand your answer.
Why isn't it ?
1. Dowsampe to 8Khz and buffer size should be 240*6
2. To do proccessing on buffer 240*6 with 8Khz sample rate.
3. Upsample to 48khz with original buffer size.
Thanks,
Alex
‫בתאךיך יום ו׳, 5 באוק׳ 2018 ב-11:42 מאת ‪'Don Turner' via android-ndk‬‏

Post by 'Don Turner' via android-ndk
The fast path properties cannot be changed as they are set by the audio
hardware.
It sounds to me that you have to process 20ms of audio data at 8kHz
(160 samples). If that's correct you probably need to do something like
1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer
Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It
implements on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

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[Alex Dashevski]

I don't understand your answer. [Hz] = [1/sec]. What problem of my sentence
?

‫בתאךיך יום ב׳, 15 באוק׳ 2018 ב-14:19 מאת ‪'Don Turner' via android-ndk‬‏ <‪

Post by 'Don Turner' via android-ndk
"Duration of pitch"
Pitch is a measure of frequency not time. Sorry if I'm missing something,
just trying to understand the problem you're facing.

Post by Alex Dashevski
Duration of pitch is ~20ms. Thus, duration of buffer samples should be
bigger than duration pitch.
Thanks,
Alex
‫בתאךיך יום ה׳, 11 באוק׳ 2018 ב-18:04 מאת ‪'Don Turner' via android-ndk‬‏

Post by 'Don Turner' via android-ndk
"Dowsampe to 8Khz and buffer size should be 240*6"
When you downsample from 48kHz to 8kHz you have *less* samples (hence
the name - "downsampling") so if you start with a buffer of 240 samples at
48kHz and downsample to 8kHz you will end up with 240*(8/48)=40 samples.
That said, I don't know why your pitch shifting algorithm only works on
8kHz data - if your source audio data is at 48kHz then the algorithm should
just work on that.
Please explain more clearly your use case and what you're trying to
achieve.

Post by Alex Dashevski
Hi,
I don't understand your answer.
Why isn't it ?
1. Dowsampe to 8Khz and buffer size should be 240*6
2. To do proccessing on buffer 240*6 with 8Khz sample rate.
3. Upsample to 48khz with original buffer size.
Thanks,
Alex
‫בתאךיך יום ו׳, 5 באוק׳ 2018 ב-11:42 מאת ‪'Don Turner' via

Post by 'Don Turner' via android-ndk
The fast path properties cannot be changed as they are set by the
audio hardware.
It sounds to me that you have to process 20ms of audio data at 8kHz
(160 samples). If that's correct you probably need to do something like
1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer
Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It
implements on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

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['Don Turner' via android-ndk]

Alex,

In order to solve your problem I (and other members of this community) need
to know *what the problem is*. At this point your questions are borderline
nonsense, and I can see you've been posting similar questions on the
music-dsp list.

This is not a forum for people who can't be bothered to do their own
research. Come back with a clear problem statement, a list of what you've
already tried and some evidence that you understand what your asking.

Post by Alex Dashevski
I don't understand your answer. [Hz] = [1/sec]. What problem of my
sentence ?
‫בתאךיך יום ב׳, 15 באוק׳ 2018 ב-14:19 מאת ‪'Don Turner' via android-ndk‬‏

Post by 'Don Turner' via android-ndk
"Duration of pitch"
Pitch is a measure of frequency not time. Sorry if I'm missing something,
just trying to understand the problem you're facing.

Post by Alex Dashevski
Duration of pitch is ~20ms. Thus, duration of buffer samples should be
bigger than duration pitch.
Thanks,
Alex
‫בתאךיך יום ה׳, 11 באוק׳ 2018 ב-18:04 מאת ‪'Don Turner' via

Post by 'Don Turner' via android-ndk
"Dowsampe to 8Khz and buffer size should be 240*6"
When you downsample from 48kHz to 8kHz you have *less* samples (hence
the name - "downsampling") so if you start with a buffer of 240 samples at
48kHz and downsample to 8kHz you will end up with 240*(8/48)=40 samples.
That said, I don't know why your pitch shifting algorithm only works on
8kHz data - if your source audio data is at 48kHz then the algorithm should
just work on that.
Please explain more clearly your use case and what you're trying to
achieve.

Post by Alex Dashevski
Hi,
I don't understand your answer.
Why isn't it ?
1. Dowsampe to 8Khz and buffer size should be 240*6
2. To do proccessing on buffer 240*6 with 8Khz sample rate.
3. Upsample to 48khz with original buffer size.
Thanks,
Alex
‫בתאךיך יום ו׳, 5 באוק׳ 2018 ב-11:42 מאת ‪'Don Turner' via

Post by 'Don Turner' via android-ndk
The fast path properties cannot be changed as they are set by the
audio hardware.
It sounds to me that you have to process 20ms of audio data at 8kHz
(160 samples). If that's correct you probably need to do something like
1) Perform your pitch shift processing on the source buffer (160 frames)
2) Upsample that to 48kHz (960 frames) and store in a buffer (the
"processed" buffer)
3) In your audio callback read 240 frames from the "processed" buffer
Does that make sense?

Post by alex dashevski
Hi,
I have project with pitch shifting (resampling with wsola), It
implements on android NDK.
Since duration of pitch is ~20ms, I can't use system recommended
parameters for the fast path. for example, for my device: SampleRate:48Khz
and buffer size 240 samples. That means, duration time is 5ms (< pitch
duration = 20ms).
Can I change the fast path ?
Can the resampling help ? I need to do processing in 8Khz.
My goal is to achieve minimal latency.
Thanks,
Alex

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