Audio Notes: Tim Carroll

Tim Carroll is a consultant based in New York City. In his copious spare time, he enjoys answering e-mail sent to him at: tjcarroll@ieee.org.

A Look at AC-3 Enhancements
This month, I'll take a look at an enhanced version of AC-3 (Dolby Digital), the coding standard developed primarily to support the new enhanced version of the ATSC digital television standard.

Achieving 5.1 Surround Sound
The one thing every network has in common is that they all must provide a Dolby Digital (AC-3) bitstream to consumers. Specifics aside, this bitstream is getting to consumers, and that is the only thing that matters.

Of Dolby, DVRs and Distant Signals
I am happy to report that in August, Dolby Laboratories was informed that the company had won a technical Emmy award for its LM100 Broadcast Loudness Meter. This is a definite sign that the rest of the world is noticing that there is a real problem here, and that the first step toward solving it is being able to measure it.

Learning About 5.1 From Grade No. 9
This fall season also brings with it the promise of 5.1-channel audio from all the major terrestrial television networks. This month, we will do a quick, high-level review of each network's capabilities thus far

Progress on Loudness And Sync Issues
The two major themes of broadcast these days, programming aside, seem to be either loudness or lip sync.

Transport Stream Distribution Models
As we prepare to enter into nice summer weather, I thought that it would be a perfect time to warm up to more details about transport stream distribution models.

Digital Audio: Getting From Here to There
This month we will describe how each of the major terrestrial networks has chosen to distribute multichannel audio to their affiliate stations.

Dolby, The Chipmunks And NAB2004
This time we will briefly wrap up our somewhat detailed look at audio compression by covering areas that some readers have submitted questions about.

Examining Audio Bitstreams
Welcome to the next installment of our investigation into how Dolby Digital (AC-3), AAC, MP3, PAC, WMA and other audio data compression schemes get all that audio into such a small package and keep it sounding good.

The Skinny on Audio Coding
To start the new year off on a solid foundation, we will begin a multi-part series of articles on audio data reduction, a.k.a. audio compression, a.k.a. audio coding.

Following Digital Audio To the Home
We will wrap up our look at how to monitor almost every type of audio signal in a DTV plant by briefly exploring how to deal with baseband audio and separate metadata.

Preparing Audio for Distribution
We return to the final stretch of our journey from post production to the consumer.

Audio Advances Rapidly Since 1983
From BTSC to Surround Sound, audio changed with the times

Giving Dynamic Range Control to Consumers
Last time we wrapped up our investigation of audio distribution. This time we are going to sidetrack just a little bit and take a look at a different approach to controlling dynamic range.

Alternatives to Dolby E
Last time we discussed the details of how Dolby E works. This time we will investigate some other techniques as well as give a brief overview of the SMPTE standards that help to organize all this data.

What Is Dolby E?
With the brief introduction to Dolby E last time, I figured it would be a good idea to leave an entire column to focus on the technology plus some of the difficulties in making it work in a typical plant, if such a thing as a typical plant exists.

Following Audio Through The Delivery Chain
Last time we started our trip following a program from origination all the way to the consumer. We got as far as getting the program on tape with audio metadata. This time we will deliver it to the front door of the network operation center and follow it to the start of distribution to the affiliate.

Keeping It All 'In Sync'
After tackling the "loud ad problem" last time, we are ready to jump into what I believe is the second most popular television audio complaint: audio and video synchronization, better known as "lip sync."

DTV and 'The Annoyingly Loud Commercial Problem'
Last time we investigated how audio metadata is created and distributed, and what happens if the values are wrong or missing. We also discovered that the Dolby Digital (AC-3) system can potentially be "tricked" into allowing overly loud program material to be delivered to consumers.

Exploring the AC-3 Audio Standard for ATSC
Last time we discussed the technical details of the BTSC system and some of the pitfalls that broadcasters need to be aware of when passing audio through the system. This time we will get into the technical details of the ATSC audio system, also known as AC-3.

BTSC Stereo Audio for Analog TV
In my last column, I introduced the BTSC sound standard for analog NTSC television and the AC-3 sound standard for digital ATSC television. This time, I'll look a little bit deeper into the BTSC system and explore some important consumer implementations and issues.