[linux-audio-user] External DAC for mastering use?

Mark Knecht mknecht at controlnet.com
Thu Mar 18 13:36:15 EST 2004

Steve Harris wrote:
> On Thu, Mar 18, 2004 at 08:12:40AM -0800, Mark Knecht wrote:
>>Steve Harris wrote:
>>>Yeah, my initial feeling is that JAMin should offer to dither, so you can
>>>control it centrally before JACK gets it hands on it, and be sure the
>>>recording will be an accurate reflection of what you hear.
>>I agree. I've never thought the dither option in Jack made sense to me. 
>>Jack should be a patch bay, not a processor. Too many options for mistakes.
> JACK has to be able to dither - its receiving float data and outputting
> ints - you cant reasonably ask every app to add dither to its outputs for
> the case when thier going to ALSA, or for the user to attach a dithering
> client to the output of every app that goes to ALSA.

OK, good points one and all. I hadn't considered it in quite that way 
before. To me (and I could be wrong) what you talk about above sounds 
more like format conversion. I'm not a programmer so I could have this 
messed up from a programmer's POV, but converting from a 24-bit ADC on 
receive data to some internal float format and then later back to a 
24-bit DAC on transmit is not what I think of as 'dithering'. I grant 
you that there might be some form of dithering, in the sense of removing 
low-order bits, taking place. Some ADC's insert noise in their 
conversion at record time. However, I wouldn't have thought that either 
apps or Jack is inserting noise into the process at all those steps are 

My POV in the previous statement was more about the form of dithering we 
use when outputting specifically to a CD, for instance. The lost bits at 
the bottom problem and the fact that people can hear below the noise 
floor of 16-bit audio. I don't think people can hear below the noise 
floor of 24-bit audio, or at least my ears certainly can't.

>>You *might* consider having 2 outputs from Jamin - dithered and 
>>undithered - so that possibly you could A/B the two. Please time align 
>>the two if you ever do add an option like this.
> I was imagining you would be able to switch the dither on the fly in the
> UI.

Great! If that can be done in a smooth way, without clicks and pops, it 
would be really useful for blind testing of dithering agorhythms.

Take care,

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