Excerpt from "Broadcasting & Cable" 7/6/09
Perhaps the best example of the current HD squeeze is Live Well HD, a new high-definition, lifestyle-focused subchannel launched by the 10 ABC owned-and-operated stations in late April. ABC O&Os like WABC New York had already been transmitting two 480i standard-def subchannels—generally a local news channel and an AccuWeather channel—alongside their primary 720p HD stream, with no major impact to HD picture quality. But when ABC stations replaced the news channel with Live Well HD and began transmitting it as a second 720p HD program stream at the same time they were broadcasting National Basketball Association playoff games, the primary HD picture suffered significantly.
Viewer complaints flooded into stations as well as enthusiast Websites such as the AV Science Forum, where HD experts accused ABC of destroying its HD picture quality and derided both HD streams as looking no better than widescreen SD.
Since then, ABC engineers have tweaked the compression parameters on their Harris NetVX encoders, devoting more bits to the primary HD channel and reducing the bits that Live Well HD gets. From watching WABC, these changes appear to have eliminated major problems on the primary ABC program stream. But Live Well HD is still subject to frequent compression artifacts. Moreover, many HD purists say ABC's HD primary service is now significantly “softer” than the HD fare from CBS, NBC and Fox.
According to Dave Converse, VP of engineering for the ABC station group, the way the NetVX encoders are now set across the group gives the primary ABC channel an average of 11 Mbps, peaking as high as 14, while Live Well HD averages around 6.5 Mbps. The Local AccuWeather Channel is delivered at an average bitrate of 1.5 Mbps; it is hard-coded at a constant bitrate at some stations and statistically multiplexed with the two HDs at others. Converse believes that setup delivers good picture quality for the primary feed and still gives enough bits to Live Well, whose “talking head”-type material isn't as demanding.