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PQ: Toshiba XS32 - Panasonic E95 (Rasczak?)

Discussion in 'Blu-ray & DVD Players & Recorders' started by dknight, Oct 29, 2004.

  1. dknight

    dknight
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    Reading the forum, I have often found statements regarding the supposed better recording picture quality of Panasonic e85/95 compared to toshiba xs32.
    Having the toshiba a manual recording mode with video at 9.2 mbps, I found difficult to believe Panasonic at its highest setting can match PQ when Toshiba uses this mode (the only one I will use, picture quality is the priority for me).
    Can anyboy comment?
     
  2. Rasczak

    Rasczak
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    Obviously if your recording at the maximum allowed bitrate for DVD your not going to notice any substantial difference - the bitrate is just too high to suffer any noticeable artifacts. The difference in quality between the two MPEG encoders though becomes increasingly noticeable as you lower the bitrate: in my tests I detected clear differences at 7.8MBits/S when recording 'difficult' scenes, i.e. heavy rain, mist/fog, fire, running water or similar. The major issue though is that the Toshiba will drop the resolution 40mins prior to the Panasonic Ex5 series - that is quite some difference.

    From reading posts on this forum you could get the impression that the Toshiba MPEG encoder is bad - it isn't - it will make excellent recordings. I think a fair way to describe the difference is to say the Panasonic is more efficient at encoding as opposed to better.
     
  3. Oldjim

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    I am only just getting into DVD recorders but can you please explain the 40 mins reference.
     
  4. Rasczak

    Rasczak
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    It's all to do with resolution. To save space on the DVD disk - and thus allow more time for recording - all DVD recorders drop resolution from full (720/704 x 576) to reduced (352 x 576/288) at some stage. This means a visible drop in quality. The point where it occurs depends on the DVD recorder: Panasonic drop the resolution at 3 hours whereas Toshiba at 2hrs 20mins. Thus a 3hr recording onto a DVD-R on the Panasonic looks considerably better than a 3hr one done by the Toshiba.
     
  5. Oldjim

    Oldjim
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    Rasczak,
    Thank you for the very quick reply. I assume that recording onto a HDD and then dubbing onto DVD this would not be a factor.
     
  6. Rasczak

    Rasczak
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    Well it depends ;) It can be a factor when recording onto the HDD and it IS a factor when dubbing to DVD.

    With a HDD/DVDR combo you can do things one of two ways:
    1) Record in best quality mode onto the HDD, edit and then realtime dub to DVD-R
    2) Use an appropriate recording mode onto the HDD, edit and then high speed dub to DVD-R

    Lets look at method 1 first - the Panasonic has four recording modes:
    XP = Data rate of approx. 9.8MBits/S, Always Full Resolution = 1 hour per disk/4.7GB
    SP = Data rate of approx. 5MBits/S, Mostly Full Resolution = 2 hour per disk/4.7GB
    LP = Data rate of approx. 2.4MBits/S, Always Low Resolution = 4 hour per disk/4.7GB
    EP = Data rate of as low as 1.2MBits/S, Always Low Resolution = upto 8 hour per disk/4.7GB
    ...and so depending which you use will depend whether your recording is full or reduced resolution onto the HDD. For this method the normal solution is to record in XP and then re-encode using a 'fit to disk' option called Flexible Record. Thus if you record a 4hr programme onto the HDD in XP mode it will be full resolution but if you dub to DVD-R it will be reduced resolution.

    The Toshiba recording modes are slightly more complicated although it works on exactly the same basis. The Toshiba only has two 'fixed' recording modes:
    SP = Data rate of approx. 5MBits/S, Mostly Full Resolution = 2 hour per disk/4.7GB
    LP = Data rate of approx. 2.4MBits/S, Always Low Resolution = 4 hour per disk/4.7GB

    ...and the machine also has the equivalent of Flexible Record (called 'Auto' on the Toshiba) where it uses the remaining space on a disk. The only difference is the resolution drop occurs at a higher bitrate which translates at the 2 hour 20min mark. The Toshiba also has a 'Manual' mode which allows you to 'create' a fixed recording mode at your required data rate. Again resolution changes/bitrate change dependant on the settings.

    Now if you use method 2, i.e. use an appropriate recording mode onto the HDD, edit and then high speed dub to DVD-R, then the quality of your HDD recording will be dependant the length of the programme. If you have a 4hr programme then it will be low res on both the HDD and the DVD-R. However your ultimate DVD will be a first generation copy as opposed to a second generation created by the process above.

    Does that all make sense?
     
  7. Oldjim

    Oldjim
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    It does indeed make sense, thank you for your very clear explanation.
    The bit I had not realised before is the effect of real time dubbing which not only takes longer but creates, as you say, a 2nd generation copy.
    Normally I would expect to use method 2 both from a time point of view and the creation of a first level copy (I assume this very similar to a jpeg file where copying it gives an exact copy but opening and resaving gives a deteriorated picture because of the second encoding).
    Now all I need to do is wait until early next year when the first HDD plus DVD recorders come out with a built in digital decoder which from your reply to another post should be the Toshiba.
     
  8. Rasczak

    Rasczak
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    Yes - this is what most of us here do. Even if you don't know the exact length of the programme you will know the approximate length - and that will produce better results than a second generation copy that entirely fills the disk. Your JPEG comparison is along the right lines: making a high speed dub is a direct copy, whereas realtime re-encoding degrades the PQ.
     
  9. OARDVD

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    Rasczak, about a week ago or so, I remember you said that the JVC initially dropped to some intermediate resolution between D1 & 1/2 D1. You said that you were a bit too busy at the time to go into detail but when you returned you would provide more info. I was wondering what that resolution was and at what recording duration it dropped from D1. Presumably it's not compatible with DVD Video?
     
  10. Baj

    Baj
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    On a Panasonic E85. Record to HD in SP mode; edit; dub to DVD-R in real time in SP mode.

    Does re-encoding occur? I think not, but would someone please confirm.

    Thanks
     
  11. Rasczak

    Rasczak
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    Re-encoding does occur - however the quality difference between first and second generation is minimal - you'd be hard pressed to tell the difference even if examining the picture. Artifacts start to creep in when you encode at a different bitrate to the original.

    OARDVD - I have the info kicking around somewhere - I'll hunt for it and get back to you.
     
  12. jdarushall

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    When I had the DRM1 I did some tests and if you do a search for DVD Resolutions in this forum, you should get to the page (about half way down)


    Between 2.5 hrs and 4hrs it used a stange mode.
     

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