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Downsampling by 3 when input buffer is not multiple of 3

 
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thabuteau



Joined: 11 Dec 2007
Posts: 34

PostPosted: Thu Mar 06, 2008 10:15 am    Post subject: Downsampling by 3 when input buffer is not multiple of 3 Reply with quote

Hello everyone.

I am trying to build a downsampler with a downsampling ratio of 3.
In the case of an input buffer size that is not a multiple of 3, things gets really nasty.

For example :

input (128) -> (128) downsample_by_3 (42) -> (42)processing(42) -> (42) upsample_by_3 (128)

In this case, we have many options :
- Build an Asynchronous Sample Rate Converter (that fully resample the signal) very time consuming but fully compliant with NuTech.

- Make the up/downsampler accumulate datas during one cycle and do the processing during two cycles.

- Make the amout of data handled by the up/downsampler change between cycles.

-> How to make NuTech and all the NUTS handle these kind of synchronisation ?
(1 cycle of nothing, 2 cycles of work or buffer length changing at each cycle)

Could the NuTech Team tell me if there is a plan do allow this kind of behaviour ?
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thabuteau



Joined: 11 Dec 2007
Posts: 34

PostPosted: Thu Mar 06, 2008 11:01 am    Post subject: Reply with quote

Back to my code, I am realizing that PinType contains two parameters :
DataLen and MaxDataLen.

Is the DataLen parameter synchronised between NUTS at each cycle ?
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admin
Site Admin


Joined: 28 Jun 2005
Posts: 72

PostPosted: Thu Mar 06, 2008 3:45 pm    Post subject: VARLEN DataType Reply with quote

In the SDK you can find documented the VARLEN datatype which should fit your needs (Pag. 14).

Please notice that it is not yet fully supported by NU-Tech and you can experience some mulfunctioning.

Should you need some code snippet please ask.
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thabuteau



Joined: 11 Dec 2007
Posts: 34

PostPosted: Tue Mar 11, 2008 11:00 am    Post subject: Reply with quote

Thank you for this tip, I didn't tried that data type yet.

I am currently making an effort to bring a dozen of NUTS to support the VARLEN data type. Could you give me a short list of known malfunctioning ?

I need to build a downsampler that set the datalen at each processing cycle and then to have each NUTS to obtain a size depending on the first one.
This downsampler will probably accept PLAYBUFFER or VECTOR datatype at the input and provide VECTOR or VARLEN datatype at the output in function of the chosen frame size.

Thank you again.
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admin
Site Admin


Joined: 28 Jun 2005
Posts: 72

PostPosted: Tue Mar 11, 2008 12:12 pm    Post subject: Reply with quote

thabuteau wrote:
Could you give me a short list of known malfunctioning ?


Actually there's no list. VARLEN data type has not yet been debugged enough with NU-Tech 2.0 version.
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