How to switch HDMI?

Discussion in 'AV Receivers' started by Jeremy:::, Feb 28, 2005.

  1. Jeremy:::

    Jeremy::: Auditioning

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    I have on order an Onkyo TX-SR702 receiver and a Denon DVD-2910 DVD Player. The receiver won't accept the HDMI input from the DVD player, so should I run the DVD's HDMI directy into the TV? What am I sacrificing if I do this?

    This seems like a tricky time to buy a receiver.

    Thanks,

    Jeremy
     
  2. ChrisWiggles

    ChrisWiggles Producer

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    Running video directly to the display is always preferred. Running it through any kind of switcher is a compromise for convenience, all you are losing is convenience. In most cases, using a switcher won't cause any visible harm to the picture, but it will never do any good, and as such it's best to run straight to the display unless convenience issues come into play.
     
  3. JeremyErwin

    JeremyErwin Producer

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    The HDMI output can carry multiple channels of digital audio-- so if you had a receiver that supported hdmi, you might be able to avoid a digital to analogue conversion. But the Denon can not send SACD or even CPPM protected DVD-Audio through HDMI. (see manual for details). Isn't copy protection fun?

    So, you won't be missing much (except perhaps switching) if you run a hdmi cable directly between your player and the tv.
     
  4. ChrisWiggles

    ChrisWiggles Producer

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    you make a good point, I always think video stuff first, I kinda forgot that HDMI can do audio first, in which case that could be a benefit, but he'd still need to get a whole new receiver, and there wouldn't be any sonic benefit over SPDIF.
     
  5. Jeremy:::

    Jeremy::: Auditioning

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    It seems like a pain in the butt to have to get up and jack around with cables in order to switch between dvd and dish. I may just have to upgrade my receiver in a couple of years when reasonably priced models have 2-3 HDMI inputs.

    Jeremy
     
  6. Pat Frank

    Pat Frank Stunt Coordinator

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    If HDMI is digital, why would it be degraded by switching? Bits are bits....
     
  7. JeremyErwin

    JeremyErwin Producer

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    After reading the manuals of various high-end dvd players, I've come to the conclusion that if you wanted a high resolution digital output for SACD/DVD-Audio, your only option is IEEE 1394/iLink/Firewire. And even then, you'd have to be especially careful to select compatible dvd players and receivers/prepros.

    HDMI does, in theory, support high resolution audio (up to eight 192 KHz streams, iirc). I don't know if it supports Direct Stream Digital. But, at present, dts, ac3, and 48Khz stereo are pretty much the only audio formats carried by hdmi.
     
  8. ChrisWiggles

    ChrisWiggles Producer

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    It's also a lot of bits, and if they are all getting there, then you're good to go. When it comes to video, there are definitely limits on length and quality for DVI/HDMI that are visible as reported by quite a few pros. As long as all the bits are getting there you are right, but unfortunately this isn't always the case. In any case, there will never be an *improvement* in quality by using a switcher. The best you can hope for is the equivalent quality, and this is hard to achieve in the analog world. With digital, yes it's easier, but again, if there is any effects that will happen by using a switcher, they will be negative.
     
  9. JeremyErwin

    JeremyErwin Producer

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    Does anyone know if HDCP DVI-D and HDMI use the same key exchange algorithm?
     
  10. ChrisWiggles

    ChrisWiggles Producer

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    I believe they do, they are really kinda the same thing, except HDMI has more capability for YCbCr in addition to RGB, and audio.
     
  11. JeremyErwin

    JeremyErwin Producer

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    It has been claimed, in reputable academic journals, that the master key for hdcp can be recovered, assuming one has access to on the order of 40 hdcp displays and some computational power. This is because the key exchange protocol used in hdcp is fundamentally flawed. The master keys themselves have not been published, yet. (iirc)

    HDMI might introduce enough complications to make the cryptoanalyst's task more difficult, while retaining some backwards compatibility with DVI. The added feature (high definition digital audio) might just be a marketing promise, designed to sell yet another connector.
     
  12. AaronMan

    AaronMan Second Unit

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    What happened to IEEE 1394 firewire? I thought everything was heading that direction. I guess its used mostly with computers.
     
  13. Pat Frank

    Pat Frank Stunt Coordinator

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    But most data transmission in the digital world is handled on a lossless basis via the use of a simple process of packet acknowledgement and retransmission.

    Is this not the case with HDMI?

    Thanks to digital technology, I can transmit data without loss of information clear around the world using the Internet. Why should there be data loss in a digital transmission between my DVD player and my HDTV, just because a switch has been introduced? No, that's analog thinking. If a switch causes picture degradation in HDMI transmission, surely there has to be another factor involved.
     
  14. ChrisWiggles

    ChrisWiggles Producer

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    The video guys I trust are very clear that some cheapie longer length DVI or HDMI cables introduce gilmmery artifacts to the picture, so that's my take on it.
     
  15. David_Rivshin

    David_Rivshin Second Unit

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    I would be quite surprised if HDMI had any form retry mechanism for video or audio data transfer. With real-time data there is rarely any point to retransmitting, because by the time you've retransmitted you're already past the point in time where you needed the data. With video and audio it's generally accepted that a small amount of data loss is acceptable from a users point of view, as they will rarely notice it. Another example would be most action oriented multiplayer games, were if player position data is not received in time (or at all) it is interpolated by the client until such time as a new value is received. This is why (non-guaranteed) UDP is often used in preference to (guaranteed) TCP. Of course if your data loss rate is too high you get very bad results.

    The "shimmering" often noted is probably the result of losing some (alot of) video data, and the display having to make up some value to fill in the hole. If you lose one pixel every few seconds you'd probably never notice at a high enough resolution. Lose a few hundred pixels per frame and now it's unwatchable. In any event, it's not a very gradual loss of quality as with analog. If your cabling or switching is hurting you, you should know it almost immediately.

    Disclaimer: I have no engineering knowledge of HDMI, so take my comments with a grain of salt. It's just educated guessing on my part at this point.

    -- Dave
     
  16. John Garcia

    John Garcia Executive Producer

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    Do you have a fixed pixel display? If using a CRT display, you may not see a considerable improvement via HDMI. In either case, I'd say leave the HD box on HDMI and use component for the 2910.
     
  17. Jeremy:::

    Jeremy::: Auditioning

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    I don't have an HD Box. I was thinking of running the DVD-2910's HDMI output to the RPTV and running component from Dish Network (SD) to the RPTV.
     
  18. John Garcia

    John Garcia Executive Producer

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    If you don't have an HD box, then that's definitely what I would do.
     

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