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Author Topic: HD on NBC... Sound Sync Problem? +OT Rants on all things bad with network TV Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 09-30-2007 07:22 PM                    I've been noticing this problem since I started watching HD over a year ago. Dish Network is my provider, but I've heard from Comcast cable folks that they have also noticed this problem. Can anyone else confirm this phenomenon across the fruited plains, or is this a local Philadelphia affiliate problem?  |  IP: Logged David Stambaugh Film God Posts: 4021 From: Eugene, Oregon Registered: Jan 2002 posted 09-30-2007 08:01 PM                        I bet it's the local affiliate. The networks send out a test feed that the affiliate is supposed to use to get the sound in sync with the video. I saw one that accidentally aired here a couple weeks ago. It was clearly labeled something like "FOR SOUND SYNC ONLY -- NOT FOR AIR". It was a closeup of a woman sitting in a studio reading a fake news story containing lots of words beginning with the letter "p". The local NBC station here has abysmally bad HD video quality, truly awful, so compressed it's blocky and unwatchable. Has been like that forever.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-30-2007 09:32 PM                     One of our local channel 7 PBS station had that problem way back when they started broadcasting digitally. I called and told the Chief Engineer about it and he didn't even know... Now this is back just before the SLC Winter Olympics when HD DTV was just getting started... I must have been the only person in town with an HDTV set. Now when I was in TV you were required to off-air monitor your transmitted picture and sound live so you knew if something was amuck. Anyway after a few days they apparently figured out how to make the adjustments which in KUED's case was a delay setting at the transmitter itself. Also noticed today some NBC audio that was out of sync.... I was just flipping through channels but don't remember what it was... hopefully some overpaid sports caster! Mark  |  IP: Logged David Stambaugh Film God Posts: 4021 From: Eugene, Oregon Registered: Jan 2002 posted 09-30-2007 09:43 PM                        Do stations outside the very largest markets (like L.A. and New York) even have "real" chief engineers any more? When the FOX station here first started HD, there was a huge imbalance in levels between their SD and HD material, so in the middle of an HD broadcast when they would insert local SD commercials, the audio was at what seemed like half the volume, almost inaudible. That went on for months. You'd think the advertisers would have been screaming.  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 09-30-2007 10:59 PM                        I bet the viewers were loving that. I always MUTE commercials as it is when I actually watch TV.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 09-30-2007 11:57 PM                     Stations do have real chief engineers, even in small markets. If you see a problem like this, call the station and ask for master control (apply social engineering skills). Often these problems affect only one of SD and HD, and they are generally not able to monitor the audio of both simultaneously. I've had my fair share of reporting these problems in real-time to master control in Boston. It's fun. (Then there was the time we reported a problem to the network guys in New York and said we were calling from "Boston" and they thought we were the Boston affiliate, but of course we were just some guys at MIT watching the Boston HDTV transmission... It was an honest mistake!) --jhawk  |  IP: Logged Mark Strube Master Film Handler Posts: 322 From: Milwaukee, WI, United States Registered: Feb 2007 posted 10-01-2007 01:10 AM                        The video is re-encoded from the network's feed at your local affiliate. (The only exception is FOX, their stream is passed through as its encoded from the source, save for a local logo inserted into the video stream.) The problem is, video encoders aren't instant, and add a delay... hence the digital audio stream must have delay added to it. This can be a bit tricky, as you must compensate for both people who are using DD decoders (slower), and people simply using a stereo downmix of the audio (faster). This delay can even change depending on what brand of receiver you have, and what year it was made. Generally, a happy medium is found, but in some cases it's a bit off (or a lot off). Awhile back I helped our local WB affiliate by loading the .TS video stream onto my PC and adjusting the audio delay in the AC3 track myself until it looked "right" to me... I then emailed their engineer with the ms of delay that had to be removed (he was adding too much).  |  IP: Logged James Westbrook Phenomenal Film Handler Posts: 1133 From: Lubbock, Texas, Usa Registered: Mar 2006 posted 10-01-2007 03:03 AM                     I used to notice numerous SD broadcasts on the local Cox cable franchise that the picture and sound was out-of-sync. The worst offender was The Weather Channel. The audio seemed to be one second ahead of the video. I thought even here, Digital is supposed to be "perfect".  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 10-01-2007 04:09 AM                        quote: Mark Strube save for a local logo inserted into the video stream. This would require recompression of the picture.  |  IP: Logged Mark Strube Master Film Handler Posts: 322 From: Milwaukee, WI, United States Registered: Feb 2007 posted 10-01-2007 07:39 AM                        quote: Joe Redifer This would require recompression of the picture. It does not. FOX provides a "splicer" to local affiliates that allows them to insert their local station bug into the video stream without re-encoding anything. The only positive to the other networks relying on the local station to choose their own bitrate, is then they can add as many sub-channels as they like... the downside obviously being quality loss. Central VBR encoding, like FOX does, is really the best way to retain quality, as the video is only being encoded once (and by very good encoders at that, not some old piece of hardware your local affiliate invested in when HD first appeared).  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-01-2007 07:55 AM                        Might as well get used to it....it's digital, therefore perfect. Theatres and TV stations have one thing in common: the low pay. Things just don't get done or inspected. One station here could not even get the assistant chief to accept the chief job since the pay raise was only 2k. ($27,000 total). A "paper" chief flew in one day a week for 4 years. Louis  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 10-01-2007 11:59 AM                        How can you insert a logo into an MPEG stream without encoding it?  |  IP: Logged Robert Minichino Master Film Handler Posts: 350 From: Haskell, NJ, USA Registered: Dec 2005 posted 10-01-2007 12:58 PM                        You only need to reencode the blocks you're modifying with the bug. You always need to decode the entire frame so you have the data to replace P frame macroblocks with motion vectors that reference an area under the bug.  |  IP: Logged Jesse Skeen Phenomenal Film Handler Posts: 1517 From: Sacramento, CA Registered: Aug 2000 posted 10-01-2007 01:18 PM                     I like how NBC not only puts a bug on their HD shows (therefore defeating the purpose of HD) but puts the letters "HD" right next to it so you always know you're watching HD! ABC does this too, and they put a nice black background around it. Too bad they didn't put "COLOR" in nice multicolored letters on color shows when they started. It's ironic that Fox, which brought this disgusting practice to the US, has no bug on their digital feeds but the local stations put their own bugs on it instead. If I can find a digital tuner that'll let me crop the picture down to 4x3, I'll finally be able to watch The Simpsons again though. I quit watching it when the whole bug thing started. Matt Groening is a sellout for allowing this to go on for so long.  |  IP: Logged Brad Allen Jedi Master Film Handler Posts: 688 From: Evansville, IN, USA Registered: May 2000 posted 10-01-2007 02:41 PM                     Heck our local stations can't even remember most of the time to switch back to HD after a SD commercial has ran. They may go through two commercial breaks before the "show" comes back to HD. Theatres apparently arn't the only place that "booth monkeys" exist. Why in the world in this day and age does the switch from SD to HD need to be done manually anyway?  |  IP: Logged

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