[LAD] FULL audio-signal path

Arnold Krille arnold at arnoldarts.de
Sat Jul 21 11:58:04 UTC 2007


Hi,

Am Samstag, 21. Juli 2007 schrieb Andrew Gaydenko:
> The questions are:
> - what is full strict list of "audio-entities" steps in such
> roughly-presented chain? - which formats (float/integer, bitdepth) are used
> on each step?
> 1. analogue source (say, mic-amp),

This one doesn't use either double nor float :-) But you want to keep this 
part of the chain as high-quality or at least as short as possible.

> 2. sound card's line input (let sound card be rme hdsp9632),

Even if the drivers would expose it as doubles, it is still quantified which 
is best represented as integers. Most (all?) drivers present the soundcard io 
as integers.

> 3. JackRack (or some other JACKified LADSPA host) with the only LADSPA
> plugin, let last one be a simple aplifier,

With jack the internal processing is done in floating point numbers. This 
leaves some quantification-steps but these are _much_ smaller than any 
soundcard can reproduce and only affect you when you do some very serious 
amplification or something like that...

> 4.1. sound card SPDIF output.
> 4.2. sound card analogue output,

This is integer again with fixed bit-depth. Again you will want to keep the 
path from your soundcard to the speakers as short and high-quality as 
possible.

> - which format convertions between steps may be treated as lossless and
> whcih as "lossness"?

The AD/DA-steps are lossy. Depending on the quality of the converters and the 
used samplingrate and bitdepth it is sometimes more lossy and sometimes less. 
And there is always the question of improvements being better than the human 
ear can hear (see the ongoing discussions about 48/96/192).

> And more generally: are there common rules for keeping sound quality
> intact?

Use integer calculations as few as possible (unless you know exactly what you 
are doing).

Arnold
-- 
visit http://www.arnoldarts.de/
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