PBS-HD audio sync

Discussion in 'Playback Devices' started by Randy Brist, Jul 15, 2003.

  1. Randy Brist

    Randy Brist Agent

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    My cable provider just added the PBS-HD channel to their HD lineup. PBS was playing a series of HD "eye-candy" videos over and over yesterday. Beautiful shots with music. Tonight I watched a program with actual "speaking" in it. Sound was definitely not in sync with the video. It was off just a bit but still was irritating as hell. This problem persisted into another program and then I quit watching. I tried powering the cable box off and on but that really had no effect.

    Has anyone else noticed this?

    RandyB
     
  2. Adam_Reiter

    Adam_Reiter Second Unit

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    Actually, my other HD channels do that too. CBS and ABC. Only breifly tho.

    And, ever more iritating is that my CBS HD channel, the damn color wigs out non stop. The only way I can explain it is if someone was sitting there mashing on the menue button on your tv that cycles through the colors from warm, neutral, and cold...... warm, neutral, cold, warm, neutral, cold, warm, neutral, cold, warm, neutral, cold, warm, neutral, cold,warm, neutral, cold,... non stop. CBS is the only channel with this problem for me.

    Very aggrivating since the mojority of my stuff I want to watch is on CBS. Also, CBS has noticible grain on the picture. Where as ABC is PERFECT HDTV, CBS looks like 720P w/grain and the annoying color problem.

    But yes, I do notice the sound to be out of sync sometimes on PBS. But its not all the time for me. I wonder if your cable provider is having some sort of uplinking problem? Maybe you should call them and ask if anyone else is complaining?
     
  3. MDHDGuy

    MDHDGuy Auditioning

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    Although I have had moderate audio-sync problems with various HD channels, it is only on PBS that it is severe. Also, on PBS (at least our local outlet, Maryland Public Television via Comcast cable) the video is ahead of the audio, which is strange because most audio/video sync problems occur because the various devices that may be decoding the signal (cable box, receiver if switching the video through there, or the TV itself if the digital signal is fed directly into it) take several milliseconds longer to process the video than the audio, resulting in the video being *later* than the audio. My receiver has the capability of delaying the audio, in adjustable amounts up to 2/10 of a second so that the video can keep up with it; but this is of no use when the video leads the audio, as it does on PBS. Not only that, the time between the video and the late-arriving audio seems to be on the order of a whole second; and as others in this thread have noted, it makes the programming very nearly unwatchable when it includes people speaking or making music.

    I've also noticed--and this could be a function of Maryland Public Television (MPT) and/or my cable company--that PBS HD suffers far worse pixelation than other HD channels when there's any kind of motion or scene change. This has been going on for months and is very upsetting. I don't know why PBS and/or their affiliates can't get HD right. I have tried contacting both my cable company and MPT, but neither of them seems even to comprehend the problem, much less offer any hope of fixing it.
     
  4. LanceJ

    LanceJ Producer

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    I don't own an HD monitor yet to give a personal opinion on this, but I've read several times that many PBS stations do multicasting i.e. broadcasting more than one digital channel at a time, so the bandwidth allocated for the HD channel is reduced. Since PBS' mission is to inform and educate, I'll bet they aren't quite as concerned about image quality as the profit-motivated commercial channels are.
     
  5. MDHDGuy

    MDHDGuy Auditioning

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    I would just point out that the relative quality of the various networks seems to depend a lot on the local cable provider unless of course one is receiving the signal over the air via antenna. I am fairly certain that it is ABC that broadcasts in 720p, while NBC and CBS broadcast in 1080i. There have been opportunities to make direct comparisons, such as in Presidential news conferences; and on my cable system at least, NBC and CBS are noticeably clearer. (Some tech writers have unfairly minimized the difference between 720p and 1080i, while others, in my opinion, have overstated the benefit of 1080p (as seen on Blu-ray discs) versus 1080i. In other words, while 1080p (and particularly Blu-ray, which eliminates the problem of pixelation one sees on compressed cable transmissions) looks a little better than 1080i, especially where motion is involved, the greater difference is between 720p and 1080i.) ABC's HD is not perfect as far as I'm concerned; but to see the difference between 720p and 1080i, one has to be viewing at a distance not much more than twice the diagonal size of the screen. By the time one gets 15 feet away from a 60" screen the difference is all but undetectable. As to your problems with CBS, Andy, assuming you are receiving it via cable, I'd definitely suggest complaining to the cable company; what you are describing is grossly unacceptable.

    Incidentally, where I am, halfway between Washington and Baltimore, some of the effects of how Comcast passes along the signals of our PBS affiliates are interesting: Comcast gives Maryland Public Broadcasting a higher-res signal than it does to WETA-HD, the Washington D.C. PBS affiliate (actually located in Arlington, Virginia). It isn't clear to me exactly what it is that causes Comcast to send out a degraded signal, and it may be that WETA's feed to Comcast is itself deficient. I also noted that during the Fourth of July program from the National Mall (again affording the opportunity for a direct comparison) the 5.1 audio that PBS announced at the beginning of the program was not available over either MPT or WETA-HD; but surely WETA, which originated the nationwide broadcast, must have broadcast in 5.1 but not provided it to Comcast. MPT, on the other hand, quirky as ever, provided a signal that my receiver interpreted as Dolby Digital left, right, and single surround--I'd call it Dolby 3.0.
     

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