USB audio transmission isn’t bit true

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This is why I use garlic nearby my USB cables for keeping away errors and witches.

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6 hours ago, mansr said:

That's for USB 3. The USB 2.0 spec doesn't mention any particular number. Of course, given the much lower data rate, achieving the same level there should not be a problem.

USB 2.0 do have Jitter and Eye aperture specifications. Therefore this translates into BER even if probably not specified ( I need to check)

A certified USB cable will be more than sufficient at audio rates.

 

 

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4 hours ago, beerandmusic said:

try injecting all the different kinds of noise at different points

If you need to "inject" more noise than the one you are creating I will direct you to places like the following picture.

 

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@beerandmusic

 

If you want try by yourself the effects of one errored bit or more take an audio track and then modify one or more bits in a single or more sample. Then play the modified version and compare.

When an audio packet (max 1024 bytes) is detected faulty it is not discarded just played as it is.

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1 hour ago, mansr said:

That's not true.

That was my understanding when dealing with asynchronous audio transfer. It can be DAC choice to discard the packet or not..

Do you mind elaborating, thanks.

 

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4 hours ago, Sonicularity said:

I wonder what the special mechanism might be and how the RME device goes about correcting a drop-out.   Maybe they are repeating the last known bit?  I suppose with a large enough buffer that other options would be available.

 

 

http://www.rme-audio.de/download/adi2dac_e.pdf

 

Most probably it must be some kind of interpolation.

Otherwise in digital transmission you do have error correction mechanisms such as Vitterbi or/and Reed Solomon. But those supposed you send extra bits for error correction at receive side.

Such is not implemented in USB audio as far as I know.

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6 hours ago, sandyk said:

 

Most recent DACs use an asynchronous sink coupled with an adaptive source (the host computer) ?

 

Recent DACs use an Asynchronous Transfer Mode.

It means that the DAC takes the data from its buffer using a first in, first out (FIFO) logic, and controls the timing using its own clock. The timing of the signal is, therefore, completely independent of the computer/DAP hence the asynchronous term.

USB is isochronous ( single clock/timing) inside computer. When dealing with USB data transfer you have different possible modes.

In asynchronous transfer mode DAC controls its buffer size by requesting host a variable packet size in order to avoid buffer Ful/empty states. Hence host is an adaptive source.