Re: [linux-audio-user] Re: Digital Fidelity

Quoting Maluvia <terakuma@email-addr-hidden>:

> >copying from one .wav to another .wav on a hard drive will never, ever
> >produce any difference of any kind, and if you claim otherwise, you are
> >either completely ignorant of how digital audio works or being
> >deliberately ridiculous.
>
> Your opinion - not fact.
> I am describing exactly what I hear, and you are free to interpret that
> in
> any fashion you choose.

This is what happens: the data is read from the file via the filesystem. The
IDE/SCSI/Firewire/USB controller will do error detection & correction when
data is passed from the disk to the controller. Through DMA, this data will
be stored in memory. This buffer is the buffer which your soundcard uses as
a memory mapped output buffer. (There might be DSP phases between reading
the signal and storing it in the output buffers, but let's forget about that
for now).

Now, this output buffer is the same place in memory where your DA unit reads
data to convert into an analog signal. The source of the data inside the
memory has no impact on where the data is. The jitter of the data source has
no impact on how the data is stored in the buffer. This is pure digital
copying, all done with error correction.

I can write a piece of software which will read a signal from file(s) to
this buffer, and compare them to eachother. If the files are copies of the
same data, the signal in the output buffer will not differ. At all.

After this phase, the DA unit will convert the data to an audible signal.

What the DA unit does with the data is totally independent of how the data
in the output buffer has been gathered. At this point, jitter or other
differences between data sources have no effect on how the DA consumes the
signal.

The hard drives do _not_ produce any reading or writing errors, because
otherwise your system would be totally unusable, as the programs you are
running to read this email would be broken and incapable of performing their
duties.

The whole of computerland depends on one thing: predictability. Without
this, no computer system would work at all. The same error detection &
correction which makes your software work, will keep the audio data (copies
or not) correctly on disk.

Let go of your anxieties. You can make perfect digital copies of your
sessions, and that will not make any difference in how they sound. Why do
you think the RIAA is after us all? :)

  Sampo
Received on Tue Feb 28 12:15:14 2006