The recent very popular annual football game once again demonstrated some of the continuing issues with integrating legacy stereo content within 5.1-channel programming.
During some of the commercial breaks, the sound collapsed from the surround version with dialog in the center channel to an incorrect and audibly jarring version where all commercial audio was reproduced from the left front and right front speakers. This was due to either the metadata not properly signaling the Dolby Digital (AC-3) encoder to switch from 5.1-channel mode to two-channel mode, or metadata failing and the encoder sticking in 5.1 channel-mode all the time. In either case, the results made the perceived loudness and impact of the commercial drop noticeably.
While obviously this was a mistake of some sort, as this particular network normally does reliably send at least the correct audio channel configuration metadata, this situation is common elsewhere. In some cases, there is no path to get network metadata to the affiliate stations, so the situation does not have an easy answer. One possible solution would be for all commercials to be in 5.1; either delivered from the ad agencies this way, or upmixed by the network. It could certainly be in the best interest of the advertisers not to lose impact by failing to take advantage of all possible channels now available to them.
One bright side to all of this is that it happened in the "right direction." If the metadata had instead indicated two-channel mode and it in fact the audio was 5.1 channel, only the left front and right front channels of the surround mix would have been reproduced and the announcers would have been missing. Thankfully, this did not happen.
