 |
Mobile DTV Reception - Advanced-Vestigial Side-Band (A-VSB) - Bandwidth Requirements | |
|
By Rodolfo La Maestra Senior Technical Director Posted on August 23, 2007 Category: Technology |
 Newsvine
 Del.icio.us
 Save
 Email
 Print |
|
Receive instant notification of new articles:
Register Now to receive notification of new HDTV Magazine Articles via email as soon as they are published. 
In the first article I covered the subject of how the architecture of the system works. In this article I address the subject of bandwidth requirements and how that plays a role with existing HDTV terrestrial bandwidth requirements for quality HD.
Bandwidth Requirements
At CES 2007, Mr. Godfrey addressed a subject that I have personally questioned at Samsung press conference regarding what A-VSB does to an HDTV channel in terms of quality when borrowing from its allocated bandwidth.
He started by initially saying "if the broadcaster is going to continue broadcasting his HD main program, there isn't enough bandwidth left to transmit an HD Turbo stream to mobile devices at the same time - so the Turbo stream must be SD or lower in resolution. The Turbo-Coded stream uses double- or quadruple-redundant coding to increase signal strength in high-speed applications."
If they adopt SRS, broadcasters who transmit a single HDTV program would encounter no tradeoff in the resolution of a signal sent to legacy and future DTV sets, Godfrey contended.
At its highest setting, he explained, the SRS signal would use only 2-3Mbps of the 19.4Mbps of bandwidth allocated to DTV stations, "and most HDTV broadcasters are not using the full 19.4Mbps for the main HD program", he contended. "MPEG-2 encoders used by broadcasters are so good now that even for rapidly changing images in sports broadcasts, 17Mbps is fine for a completely high-definition picture without trade-offs," he contended.
A few stations might run into trade-offs, however, if they broadcast one HD signal and two to three multicast standard-definition (SD) signals simultaneously.
The Turbo Coding option, which uses up much less bandwidth than SRS, is scalable up to 600kbps, which could suffice for improved reception on handheld devices with screens up to 5 inches, he added. For in-car TVs with 7-inch to 10-inch screens, a bit-stream with less than 4Mbps of bandwidth could be enough, he said.
If an HD station pushes Turbo Coding to 4Mbps for "big-screen" mobile applications, and sets aside the maximum 3Mbps for the SRS signal, only 12.4Mbps would be available for the station's main HD program. At that data rate, "it's still HD, but a bit of a challenge," Godfrey admitted.
As an alternative for smaller independent stations delivering only SD streams, Godfrey cited the potential for a subscription service that the station could offer to stream multiple channels of content to portable devices.
Stay tuned for further coverage of the subject in upcoming articles.
Posted by Rodolfo La Maestra, August 23, 2007 12:13 PM
More on Technology
More from Rodolfo La Maestra
About Rodolfo La MaestraRodolfo La Maestra is the Senior Technical Director at HDTV Magazine and participated in the HDTV vision since the late 1980's. In the late 1990's, he began tracking all HDTV consumer equipment, and since 2002 he authors the annual HDTV Technology Review report covering HDTVs, Hi-def DVD, content providers, broadcast, cable, satellite, government, standards, connectivity, content protection, H/DTV tuners and DVRs, etc. In addition Rodolfo has authored a variety of tutorials, books, and educative articles for HDTV Magazine, DVDetc, and HDTVetc Magazines, Veritas et Visus Newsletter, Display Search, and served as technical consultant/editor for the "Reference Guide" and the "HDTV Glossary of Terms" for HDTVetc and HDTV Magazines. In 2004, he began recording a weekly HDTV technology program for MD Cable television, which by 2006 reached the rating of second most viewed by the public, here is the opening episode.Rodolfo's background encompasses Electronic Engineering, Computer Science, and Audio and Video Electronics, over 4,700 hours of professional training, a BS in Computer and Information Systems, and over thirty professional and post-graduate certifications, some from American, George Washington, and MIT Universities. Rodolfo was also Computer Science professor for over 700 students in five institutions between 1966-1973 in Argentina, for IBM, Burroughs, and Honeywell mainframes. After 38 years of computer systems career, Rodolfo retired in 2003 as Chief of Systems Development from the Inter-American Development Bank where he directed 65 software-development computer professionals, supporting member countries in north/central/south America 24x7. In parallel, from 1998 he helped the public with his other career of audio/video electronics. Rodolfo started with hi-end audio in the early 60’s and merged with Home Theater video, multichannel audio, widescreen laser disc, anamorphic DVD, 16x9 NTSC displays, HDTV, Hi-def DVD, IPTV, HDMI, and 2.35:1 Cinemascope HD Home Theater over the past 40+ years. When HDTV started airing in November 1998, he was an early adopter of HDTV and realized that the technology as implemented would overwhelm regular consumers due to its complexity, and it certainly does even today. Rodolfo then launched his HDTV mission of educating and helping consumers understand the complexity, the challenge, and the beauty of the technology, so the public learns to appreciate HDTV not just as another television. |
Other Recent Discussion
Authors
Categories
|
See Forum Topic: 
Advertise
