Propellerhead Reason - 1.0.1 Manual de Operações descarregar pdf (Página 196)

ABOUT AUDIO ON COMPUTERS

194

General Information

Audio Quality

The general audio quality in a computer based synthesizer system depends

on two things:

➜ The quality of the software calculating the audio.

In our case, this is the Reason DSP (Digital Signal Processing) code.

• Reason uses 32-bit floating point arithmetic for all internal audio op-

erations which ensures the highest possible resolution throughout

the signal chain.

• The program supports 16, 20, and 24 bit audio output.

• The program supports sampling frequencies from 22kHz to 96kHz.

• A number of digital audio techniques are implemented that reduce

the risk of “aliasing”, background noise, unwanted distortion and

“zipper noise”.

There is no technical reason why this program should not sound as good as

or better than dedicated, professional hardware.

➜ The quality of the hardware playing back the sound.

In a PC this is the sound card. In the Mac it is the built in audio circuitry or any

audio card you have installed. Don’t be fooled by the “16 bit, 44.1kHz, CD

quality” tags. How good some audio hardware actually sounds depends on a

number of things, its frequency range and frequency response curve, the sig-

nal to noise ratio, the distortion under various circumstances, etc. Further-

more, some designs are more prone to disturbance from the other

electronics in the computer, than other. Such disturbance might add hum or

high pitched noise to the signal.

As you probably understand by now, this is a big subject and there’s no way

we can help you find the right solution in this manual. There are a number of

text books and magazines covering this subject and any music dealer spe-

cializing in computers will happily help you out. The only advice we can give

is that if you are serious about sound, choose your audio hardware carefully!

About Latency

On any personal computer system, there is a delay between the moment you

“ask” the hardware to play a sound and when it actually does it. This delay is

referred to as the “latency” of the design. This imposes a problem for any

system where you want real time user input to affect the sound.

! See the Getting Started book for basic information on adjusting

Output Latency!

Why is there latency?

Any audio application creates its audio in chunks. These chunks are then

passed on to the audio card where they are temporarily stored before being

converted into regular audio signals.

The storage place for these chunks are called “buffers” (an analogy would be

a bucket brigade, where a number of people each have a bucket, and water

is poured from one bucket to another to reach its final destination).

The smaller the buffers and the fewer they are, the more responsive the sys-

tem will be (lower latency) However, this will also raise the demands on the

computer and its software. If the system can’t cope up with moving the data

to and from the buffers fast enough, there will be problems that manifest

themselves as glitches in audio playback.

To make things worse, audio playback always competes with other activities

on your computer. For example, under Windows, an Output Latency setting

that works perfect under normal circumstances might be far too low when

you try to open files during playback, switch over to another program while

Reason is playing or simply play back a very demanding song.

What is acceptable?

Normally, hardware synthesizers provide you with a latency of 3 to 7 ms (mil-

liseconds – thousands of a second), at least if the instrument is targeted to-

wards a “professional” audience.

On a regular PC or Mac, the latency can vary from anything from 2ms to

750ms! This wide range of values is an effect of the fact that computers and

their operating systems were created for many purposes, not just playing

back audio. For multimedia and games, a latency of a 100ms or more is per-

fectly acceptable, but for playing a musical instrument it is not!

• The internal audio under MacOS provides an output latency of

11ms. This is deemed acceptable by most users.

• A regular PC “SoundBlaster” type audio card with an MME driver

(see later in this chapter) might at best give you a latency of around

160ms.

• The same card with a DirectX driver provides at best around 40ms.

• The best possible situation is a card specifically designed for low

latency, with an ASIO driver, which can give you figures as low as 3

ms under both MacOS and Windows. This is just as good as any

dedicated hardware synthesizer!

Reason’s built in sequencer is not affected by latency!

When Reason’s sequencer is playing back a song, the timing between notes

is perfect! Once playback of a Reason pattern or song is up and running, la-

tency isn’t a consideration at all. The computer clocks the audio between the

steps and does this with perfect quartz accuracy! The timing is immaculate!

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