chapter 02 audio recording - part ii

Date: 22 November 2010

Chapter 02: Audio Recording - Part IIPrepared by: Nur Muizz Mohamed Salleh

Talk Layout

The Computer and Audio

The Digital Recording / Reproduction Process

Audio Recording System

Overview

In order to put that information to use, an overview of the gear used is needed.

The equipment, devices, software and setup that you use are what make up the entire digital audio rig.

The quality of this gear will make significant difference in the audio output and the overall sound design.

In the beginning, any gear will do, but techniques and more importantly, the ear start to “sharpen”, more advanced gear will be wanted.

Overview

the general setup for entire rig also important to understand.

there are specific locations for monitors, the chair and other gear that will help in the appreciation and analysis of project work.

A “5.1 surround sound” setup is also critical for surround mixing to take place.

Overview

the sound generated by your system is like an “aural fingerprint”.

your sound will leave an impression on the listener, eventually leading to a characteristic style.

weak physical links in the audio chain will become apparent when tested on proper gear.

Overview

eg: mixing through mediocre monitors might alter the overall mix and thus sound very poor through a commercial system - even worse in semiprofessional and professional sound rig.

the better the gear and software the cleaner the audio product will be.

The Computer & Audio

Hardware

The power and accuracy of your computer will determine the quality of your audio whether it is input or output.

The knowledge of how to construct a computer from the various available components is a valuable skill to have.

It can help to cut costs over the pre-made towers and allows you to pick and choose - the exact configuration.


Hardware- cont

Basically there are 9 devices in computer that should be understood:

The Central Processing Unit (CPU)

motherboard

Random Access Memory (RAM)

Hard Drive

Tower with power supply

modem / ethernet card.

graphic card

sound card

peripheral device connection - keyboard,mouse, mixer, monitor or other external


Power Plant (CPU)

The core of the entire machine.

A faster CPU allows more streams of audio to be recorded or played back at a time.


Motherboard

Is where all of the main processing occurs and where all of the data & power infrastructure for the computer are.

various attachable cards performing various functions all plug into similar sockets on a common motherboard.


Random Access Memory (RAM)

Allow data to be stored in a temporary location, which makes it easier and faster to access than the hard drive.

The more RAM the better.

Most machine have slots to increase RAM capacity.


Hard Drive

Need to be fast for audio needs.

The higher the resolution of your audio file, the more throughput you will need from your hard drive.

The general project size basically determines the amount of space needed, but the is more to it than that.


Graphic Card

Video games require high frame rates, which require a faster render times generated from the graphic card.

if your card can handle video games, it can easily handle audio.


Sound Card

the heart of an audio-configured computer is the sound card.

today PC or Mac can handle just about any audio needs.

the higher the end you go, the more complex and expensive things get and more power you will need.


Tower

the tower is where all of the components of your computer reside.

the main thing to keep in mind when purchasing a tower is whether the power supply built into the tower is strong enough to power your cards and devices.


Software

there are hundreds of software packages that you can use to create audio assets.

the industry is moving forward in making audio packages integrated with video packages.

most of applications now allow you to do just about everything in a video application as you can in a dedicated audio application.


Software - cont

Example of the application are:

Digidesign ProTools

Steinberg Nunendo

Sony Sound Forge

Apple’s Logic

Adobe Audition etc


Software - cont

The essential features that are required to successfully create and implement audio assets should be located in one or two applications on your rig.

Usually no need for 5 apps that all perform the same functions.

there are many other add-ons or plug-ins that can be applied to these, but these are circumstantial and many times costly.


Software - cont

Recording, editing and adding effects and processes to audio files are the most common tasks you will do with an audio software apps.

Each one is relatively easy to understand but, as with any creative enterprise, the trick is in knowing where and when to use them and how to apply them.


The following sections provide a basic overview of the various stages that are encountered within the process of encoding analog signals into equivalent digital data (Figure A)

and then converting this data back into its original analog form (Figure B).


Figure A: Digital Audio Chain: Recording


Figure B: Digital Audio Chain: Reproduction

The Digital Recording

The digital recording chain includes a low-pass filter, a sample-and-hold circuit, an analog-to-digital converter, and the circuitry for signal coding and error correction.

At the input of a digital sampling system, the analog signal must be band-limited with a low-pass filter so as not to allow frequencies that are greater than half the sample rate frequency to pass into the A/D conversion circuitry.

Filter generally makes use of a roll-off slope at its high-frequency cutoff point (as an immediate or ‘‘brickwall’’ slope would introduce severe signal distortion and phase shifts).


In order for the full bandwidth to be accurately encoded, the Nyquist theorem requires that a sampling rate be chosen that’s higher than twice the highest frequency to be recorded.

For example, a system with a bandwidth that reaches into the 20-kHz range is often sampled at a rate of at least 44.1K samples per second.


Following the low-pass filter, a sample-and-hold (S/H) circuit holds and measures the analog voltage level for the duration of a single sample period, which is determined by the sample rate (i.e., less than 1/44,100th of a second).

At this point, computations must be performed in order to translate the sampled level into an equivalent binary word.

This step in the A/D conversion is a critical component of the digitization process, as the sampled DC voltage level must be accurately quantized into an equivalent digital word (to the nearest step level) in a very short period of time.


Once the sampled signal has been converted into an equivalent digital form, the data must be conditioned for further data processing and storage.

This conditioning includes data coding, data modulation, and error correction.

In general, the binary digits of a digital bitstream aren’t directly stored onto a recording medium as raw data; rather, data coding is used to translate the data (along with synchronization and address information) into a form that allows the data to be most efficiently and accurately stored.

Reproduction Process

the digital reproduction chain works in a manner that is complementary to the digital encoding process.

Since most digital media encodes data onto media in the form of highly saturated magnetic transition states or optical reflections, the recorded data must first be reconditioned in a way that restores the digital bitstream back into its original, modulated binary state.

Once this is done, the data can then be de-interleaved (reassembled) back into its original form, where it can be converted back into PCM data.


Hard-Disk Recording:

Although the field of hard-disk recording has matured into a technology that’s become pervasive in all forms of media production, it’s still in a continual form of evolution as hardware, software, and personal working styles change.

As with all evolutionary revolutions, it’s always a good idea to keep abreast of these changes by reading the trade magazines, searching the Web, and keeping your eyes and ears open.

For the remainder of this chapter, we’ll be looking at the various types of hard disk systems that are currently available on the market


Advantages of Hard-Disk Recording:

The ability to handle long sample files—Hard-disk recording time is often limited only by the size of the disk itself.

Random-access editing—Once audio (or any type of data) is recorded onto a disk, any point within the program can be instantly accessed at any time, regardless of the order in which it was recorded.


Advantages of Hard-Disk Recording - cont:

Nondestructive editing—This process allows audio segments (often called regions) to be placed back in any context and/or order within a program without changing or affecting the originally recorded sound file in any way. Once edited, these edited tracks and/or segments can be reproduced to create a single, cohesive program.

DSP—Digital signal processing can be performed on a sound file and/or segment in either real time or non-real time (often in a nondestructive fashion).

THANK YOUQ & A Session

chapter 02 audio recording - part ii

Technology

computer audio tower

computer audio motherboard

audio packages

audioconfigured computer

computer audio sound

audio output

audio needs

audio assets