Picture looks slightly grainy using 720p outupt? (Panasonic AX100 front projector)

Discussion in 'DirecTV TiVo Powered PVRs & Receivers' started by Leila, Dec 7, 2006.

  1. Dec 7, 2006 #1 of 12
    Leila

    Leila New Member

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    Apr 28, 2006

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    I recently bought the new Panasonic AX100 front projector. It's a 720p
    native projector. I was playing/experimenting with all the different settings.
    Boy, I've never had a projector this bright. (save the xenon projector headlights
    on my RV)

    When I switch my HR10's output from 1080i to 720p, I noticed that the
    picture looks slightly more grainy in 720p mode. If I switch back to 1080i,
    the picture becomes normal again. On my previous front projector, with
    the same HR10 unit, I cannot notice any difference between 720p and 1080i.

    Is it possible that my AX100 projector is having trouble accepting 720p
    output from the HR10? Or is this just normal?
     
  2. PrimusSucks

    PrimusSucks It's a band...

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    Mar 10, 2004
    Seems backwards... if your projector is native 720, shouldn't that look better? Or does this have to do with the HDLITE comments - 720 not really 720, 1080 not really 1080? But maybe the 1080 DHLITE is closer to true 720 - if you get my drift?

    Is this graininess true for all front projector users?

    I see complaints of quality - is it really bad, say if watching on an 8ft screen witht he projector set to 720?

    Been threatening to get an HD unit... but would like to use on the front projector - thus the questions.



     
  3. tnedator

    tnedator New Member

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    Dec 3, 2003
    I'm not HD expert, but it is my understanding that DirecTV signals are 1440x1080i or 1280x1080i.

    So, if that is true, then it probably comes down to which unit HR10 or Panny projector. If you have the HR10 output set to 720, then it is having to de-interlace and scale to 720p.

    I know in researching projectors, there are several different methods of converting 1080i to 720p. In one method, they essentially convert the 1080 signal to 540p and then upconvert, then at the other end of the extreme they line double the signal to 1080p and downconvert to 720p, and then there are several other weave methods.

    Bottom line, the best picture is often gained when you let the device (source or display) with the best scaling deal with the conversion. In your case, it appears the Panny is doing a better job then the HR10, so you should go with your eyes and let it output 1080i and have your Panny downconvert it to 720p.
     
  4. tnedator

    tnedator New Member

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    Dec 3, 2003
    What you see on the projector is source dependent. Since it is bigger, you do tend to see more artifacts that might exist. The flip side is that most modern rear projection units have anti-glare coatings that create a shimmer or film like appearance that results in a picture that is brighter, but often not as good as a projector.

    The 1080 lite shouldn't be closer to 720 in that as I understandit (and I am not an expert by any means), the horizontal resolution is a true 1080i, but where they cheat is by squeezing the pixel so that instead of 19xxX1080i, they go they squeeze the width of the pixel down to 1440x1080 (the resolution of much source material, since many early HD cameras used this res) or 1280x1080.
     
  5. Mar 1, 2007 #5 of 12
    norneslo

    norneslo New Member

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    May 25, 2004
    Alpharetta, GA

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    Just a quick thought, make sure you try a native 720p channel, like ABC HD or Fox HD. Then you could see if a 720p source direct to the projector looked good or not. ESPN HD's are also 720p channels.

    Ron
     
  6. Mar 1, 2007 #6 of 12
    tnedator

    tnedator New Member

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    Dec 3, 2003
    But, does anyone know if DirecTV is broadcasting them as 720p, verusus upconverting them to 1280x1080i?

    The resolutions I keep seeing stated that DirecTV uses are 1440x1080i and 1280x1080i.
     
  7. Mar 2, 2007 #7 of 12
    TyroneShoes

    TyroneShoes HD evangelist

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    Sep 6, 2004
    I'm pretty sure they don't rescale 720p, as there would be no advantage for them. In fact, it would create more motion artifacts for an identical bit rate, so keeping 720 as 720 is the most efficient way to uplink 720p channels, and results in less pq degradation.
     
  8. norneslo

    norneslo New Member

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    May 25, 2004
    Alpharetta, GA
    Leila and other future AX100 owners,

    I find it funny that I replied to this thread back on 3/1, and now I find myself as a new owner of a PT-AX100 myself, and I see the same graininess that Leila described in the first post.

    To begin with, it was probably a miracle of miracles that the HDMI port on my tivo even worked, as its an old one (3 years now?), and many recall that there was a horrible failure rate on these HDMI cards. I never needed HDMI with my TV which was component only. Anyhow, the HDMI does work, I ran a 35ft cable to the projector and it worked fine.

    Anyhow, I've got to say, my initial thought with the projector was to set the output to 720p on the HR10 and forget it. (720p to 720p projector makes sense right?) When messing about one night, I watched my local OTA CBS station and switched to 1080i and noticed quite a difference. Since then I've paid attention to it. This is all subjective, but to me, local 720's (ABC and FOX) look fine at 720p setting on the tivo, but local 1080i's look better letting the scaler in the projector do the work. For the sat channels, well, it's a crapshoot. The 720p ESPN's are better at 720, but also look fine at 1080. HDnet's, UHD, TNT, Disc,are better at 1080. For the sat channels, they all pale compared to OTA, so it doesn't matter as much.

    I finally understand why there were people calling for native output support in the hr10 a couple years ago. At the time I didn't understand the request, as my tv only supported 1080i, it was moot to me.

    Perhaps the HR20 will work better.

    RonO



    For sat channels, they all look very grainy to me in 720p, and look better in 1080i. The ESPN's are a toss up 720 vs. 1080. It's slightly shaper but grainy in 720, smoother and less grainy in 1080i.
     
  9. TyroneShoes

    TyroneShoes HD evangelist

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    Sep 6, 2004
    One would also have to wonder about whether this is an interlacing issue. 720 output usually provides a better result over 1080 output when there is poor de-interlacing in the display. Most displays are progressive (other than CRTs) and those made prior to 2005 don't typically have great de-interlacing. Since 720 already is progressive, that doesn't apply there, but when de-interlacing from 1080i output, jaggies can appear on diagonal lines or curved lines.

    That said, is the projector natively progressive? if not it could be having the opposite problem of re-interlacing 720 (which would not apply to 1080).
     
  10. jeff125va

    jeff125va New Member

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    Mar 15, 2001
    Ashburn, VA USA
    I have the same projector, but I have my HR20 connected to it, not my HR10. I've had it set to 720p from the get-go, and I don't notice any graininess at all, but this makes me want to do a comparison. Might try it tonight if I get a chance.
     
  11. PrimusSucks

    PrimusSucks It's a band...

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    Mar 10, 2004
    Size of your screen?


    How'd your evening test go?


     
  12. Ein

    Ein New Member

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    Jul 7, 2004
    For some odd reason 1080i signal do look better on a Panasonic than 720P. My old Panasonic 720p RPTV always look better with 1080i. The new Pannies converts everything to 1080P first. I don't know how old the AX100 is. Maybe it doesn't pass through 720p natively but converts to 1080i/p first then to screen resolution.
     

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