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Quick Question on Buffers - Samples or Megabytes

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Quick Question on Buffers - Samples or Megabytes

Postby RKS » Mon Feb 24, 2014 7:29 pm

Hi all,

Has anyone ever come across adjustable buffers for recording audio which are based on megabytes rather than samples?

I am having a text based chat with someone about it and they seem to be mixing up terms. They insist that with their Presonus interface on Windows that there was terrible trouble being had with having to constantly adjust a buffer size in megabytes.

Never come across this in all my years. It seems to me that there is a mix up of terms between buffers in samples and megabytes.

Thanks!
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Re: Quick Question on Buffers - Samples or Megabytes

Postby robinv » Mon Feb 24, 2014 8:07 pm

Buffers will be described in either samples or milliseconds - so 256 samples would probably be around 10-20ms. There's maths you can use to work out the relationship but there's certainly no megabytes involved.
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Re: Quick Question on Buffers - Samples or Megabytes

Postby RKS » Mon Feb 24, 2014 8:16 pm

That was what I was thinking, I think I am getting drawn in by a troll to be honest
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Re: Quick Question on Buffers - Samples or Megabytes

Postby dmills » Tue Feb 25, 2014 7:32 pm

Maybe, maybe not..

Disk buffers as used for example when streaming samples are often sized in megabytes, and while it is seldom an issue these days, there was a time when trying to stream multiple samples from disk took some careful tuning.

Regards, Dan.
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Re: Quick Question on Buffers - Samples or Megabytes

Postby RKS » Tue Feb 25, 2014 9:25 pm

Aye, that makes sense. Though we were speaking specifically about recording and playback of audio rather than sample based stuff.

Thanks!
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Re: Quick Question on Buffers - Samples or Megabytes

Postby Johnsy » Wed Feb 26, 2014 3:22 am

You could describe audio i/o buffers in terms of megabytes, but it wouldn't be very practical.

A 256-sample buffer, for example, contains (obviously) 256 samples. Let's assume those samples each consist of twenty-four bits. Let's also assume that each of those 24-bit samples are contained in a 32-bit frame (as they will be unless you're using a 'packed' format). That's a total of [256 x 32] 8192 bits, or 1024 bytes. Depending on which interpretation of the term 'megabyte' you're using, that's either 0.001024MB or 0.001MB per buffer (properly and unambiguously, 0.001MiB.)

A one MB (MiB) buffer would thus contain 256,000 samples, and introduce around 5.8 seconds of latency at 44.1kHz.
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