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Nebula v SAA7130 Comparison

Discussion in 'Desktop & Laptop Computers Forum' started by BBD, Jul 11, 2003.

  1. BBD

    BBD
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    I've just bought a Medion SAA7130 card from Aldi (£30) to replace my Bt848 card. The card is fed from a Grundig sky box (direct S-video feed) and I have setup D-Scaler 4.1.6 as per the excellent guide in the sticky. I also have a Nebula card in the same PC.
    I spent a few hours last night doing a back to back comparison between the 2 cards on a variety of programme sources. The difference between the 2 is not chalk and cheese but the SAA7130 card is definitely better. The picture quality is better with a cleaner picture, the colours are richer and the picture has more punch than the Nebula card. The biggest difference for me is the very smooth pans. I know this more of a problem for me than most but going back to the Nebula after watching the SAA7130 card makes the jerky pans of the Nebula card all the more obvious. I'll keep the Nebula card for recordings but I'll always be using the SAA7130 for live viewing.

    PS The VCR software supplied with the card crashes when I try to run it any ideas?
     
  2. MikeTV

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    Interesting post - since I purchased the Nebula recently! I am prepared to believe that decently deinterlaced analog sources may beat the Nebula under the right conditions - in the same way that vinyl beats CD.

    One question - what kind of display are you using? This is because with bigger/better displays, analogue vs digital becomes more of a factor.

    I agree that the jerkiness of the Nebula is it's achilles heel, although the effect can be reduced somewhat with tweaking.

    Have you tried it with composite video instead of s-video? Are there any noticeable differences?

    Sooner or later I will probably try the SAA7130 myself.
     
  3. BBD

    BBD
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    I'm using a Sony VPH-G70 CRT projector currently with a 7' wide screen. I agree that on a smaller screen the differences may be harder to spot.

    No not yet I'm in the process of changing the screen to a 8' 16:9. I'll try it when I'm up and running again and report back. If you have a Sky box as a feed the card only costs £30 from Aldi why not try it? It will give you the option of viewing one channel whilst recording another.
     
  4. nfordenfield

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    I'll have my nebula next week so can give a second opinion on sky via capture -v- digicard.

    Digicard "should be" better as no a/d involved, but this is not always a given.

    SDI modded sky + with a 120 gb HD is the answer but they are like rocking horse poo
     
  5. BBD

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    Sorted this problem. Removed Nebula software AND Hardware. Reinstalled VCR software then reinstalled Nebula Hardware and software. The capture software is surprisingly not bad. I'm using it to convert Videos to MPEGs for my youngest. He will be able to click on desktop icons to watch his films instead of messing around with tapes. The software includes an MPEG editing suite which is very easy to use.

    I look forward to hearing your opinion Nathan. I agree that in theory the Digicard should be better, that's why I bought it first.
     
  6. nfordenfield

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    Should be here Monday/Tuesday, so can comment on the new version 3 software aswell

    Has anyone got some comments on the Pinnicale PCI Sat card?
     
  7. Steve1138

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    with the difference between the Nebula and an analog feed from a Sky box... could it be down to the different MPEG decoder chips ion the Nebula card vs's those in the Sky box ?

    I had an original PACE digibox (early adopter...) and when I bought my Philips digital TV and became a bit more critical of absolute picture quality, was when I Started to REALLY notice all the digital PQ nasties (image crawl, smearing..)
    I bought a Panasonic digibox and it was better... but still very annoying artefacts.
    THEN after another 9 mths I got Sky+ and this was MUCH better.
    The effects are still ther slightly... but moreso when the TV switches back in the deadful Philips (un)Natural Motion mode. When you change back to 100Hz it's really not so bad and clearly MUCH better that the older digiboxes were.
    ONly thing now is some smearing on fast motion areas but this seems to be more down to the bitrate in the transmissions, occurring much less noticable (if at all) on some better PQ channels like BBC1 / 2.

    So - to summarise, the improved PQ I've experienced in 3 different Sky boxes, I imagine are partly down to better MPEG decoding... so sould be a facter with the Nebula.

    Also - I think that you'll see these effects more clearly on a digital projector vs.s a CRT device. I don't have a projector yet - BUT - from the video editing I've done on my PC, whereas I can see blockiness artefacts on some of my video files on the PC monitor, when the same thing is played back on the TV its much less noticable / intrusive...

    (Good old analogue... this coming from an avid vinyl user and LINN owner of > 21yrs)

    Steve
     
  8. Steve1138

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    following on from this...

    can one of you Nebula owners post the chip types on the card ?

    The PINNACLE PCTV Sat has: 2 Conexant chips:
    - QPSK DEMOD Cx 24110-11 E297710.1
    - FUSION 878A (25878-13) E315400.1
     
  9. Pootle

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    This is really interesting BBD, as my original DTV setup was nokia STB via RGB - S-video converter to s-video capture on a Radeon All-in-Wonder, and it was a no contest as regards still picture quality, once I installed a Nova-T card, with the Nova-T being very superior to the analogue route.

    On moving stuff of course the STB still wins hands down, as the interlacing problems with both Nova-T and Nebula are still pretty terrible.

    Can you post some screen shots of the 2 routes for comparison?

    BTW Steve, I understood that both Nebula and Nova-T do not use hardware decoders, they do it in software (with some help from the Video card)

    Here are some screen captures I did when I first got the Nova-T
     
  10. nfordenfield

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    Well i've had my new nebula card for a few days now and have been a/b with sky+ via svideo.

    The picture is alot sharper from digiTV than Sky.

    The Nebula seems to fall down on deinterlacing, there are visable jaggies, this maybe due to the fact that the source is cleaner and therefore is not masked by the additional a/d conversion from the Sky/capure card route and additional dscaler filters. Or could be it still needs some fiddling with.

    It is just a shame that Dscaler can not "see" the Nebula Card, this would be something to behold i'm sure.

    Nice that you can add or remove audio delay in DigiTV.

    Now big question, can you run TWO nebula cards in the same PC, then my sky + is totally redundant.

    Just need a crash course in Bluetooth, Girder and PDAwin and can let the wife loose on it.

    I would still like to see SDI Sky box, anyone got one?
     
  11. MikeTV

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    Nice captures. I intend to do the same for the nebula card, I just haven't found time. Watch this space. I will use BBC News 24 also.

    One thing - is there any chance of posting uncompressed images at 1024x576? This seems to be the native capture resolution of the Nebula, and would be useful for Nebula/Nova-T comparisons. Or at whatever native resolution the Nova-T uses (ie. raw, unstretched - if you see what I mean).

    Mike.
     
  12. GaryRees

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    I've just got rid of the Nova-t and replaced it with a Nebula. Whilst the picture quaity and software ( it works for one thing !) is better, the jerky picture is very annoying. I've tried enabling frame smoothing but this just makes it worse.

    Any suggestions?
     
  13. BBD

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    I tried to take some pictures last night but the pictures only show the poor quality of my digital camera rather than differences in picture quality. I have a CRT projector so light levels are relatively low. I had a look at your website (good stuff) and I think that the DigiTV may have the edge on static logo displays but static pictures of digitally generated images do look good on digital systems. I’ve noticed that Digital projector owners tend to post pictures of animation films for this reason.

    Interesting what system do you have? I assume you are using the S-Video feed from your Sky+ box. Its close run on clean transmissions like BBC news but what about ‘busier’ pictures or older recorded transmissions. A good example was an old episode of Frost the picture was a grainy, jerky mess on DigiTV far better on DScaler. Have you tweeked the DScaler setting to match the card as per the sticky?
     
  14. MikeTV

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    Here is my Nebula capture.
    The capture was scaled by the Nebula software to 1024x576 and is 792Kb. Sorry for the large file.

    It should be possible to use Dscaler to capture from an SAA7130 card, and then we could compare the three (Nebula, Nova, SAA7130).
     
  15. Pootle

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    These pics are at "as captured" resolution for X and the Nova-T picture is rescaled in Y to correct the Aspect ratio. I don't have the raw files anymore, bu the compression I used was relatively light, so they are close to original.

    BBD: Can't you get screenshots of the graphic image rather than a photo of the screen itself - as you say the result you got is more about the quality of the camera (and the projector you are using) , than of the image being displayed. Just use the frame capture facility in the nebula software??

    MikeTV: it would be really interesting to compare the quality of an SAA7130 with a digital card. I would expect the Nova and Nebula to be pretty identical on a still image at least, as they are both decoding the same digital bit stream, although it's quite possible there will be a difference!
     
  16. nfordenfield

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    Am using a Barco 1208 as the PJ via a MP-1 modded Radeon Card (this is a big improvement over standard vga output).

    Sky does look more solid, but alot softer, this IS more forgiving with panning sometimes.

    I'll have a chat with Nebula and see if I can find a res that is friendly and yes have used the guide best blah blah setting for the capture card ( BTxxxx 7 in there somewhere )

    I see neither as the idea situation. Dscaler is the Nuts at software decoding/filters, if nebula can progress this way, DigiTV will rock, until we all get bored of trying to make a low res behave like HD - an impossible task................................

    Maybe a PDI solution is needed to playback DigiTV recorded clips, this must be the best of both world if you watch pre recorded TV.

    Nighty Night
     
  17. BBD

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    What do you think?Screen Captures

    Sorry if I've made a mess of the website its the first time I've tried this and its late!
     
  18. MikeTV

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    Good stuff. Dscaler wins! At least when using sky digital fed to an SAA7130.

    Looking at the Nebula capture, I guess some of the artefacts may be digital artefacts in the stream itself, rather than the Nebula/DigiTV software. It may be that the sky stream has the greater bandwidth. This may also explain some of the punchiness of the sky solution - although that could be just calibration, and so it is difficult to say for sure.

    As you say yourself, I don't think it is night and day, and may vary depending on the channel choice or type of material. But there is certainly no dispute in the area of deinterlacing motion/pans - dscaler wins.

    It is suprising that the saa7130 can compete with an all digital solution like the nebula. Maybe someone will add Nebula support to Dscaler one day. And then there will be another shootout!
     
  19. Wilster

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    Has anyone tried to get Dscaler to work with the analogue input of a Nebula card? I ask as Im rather short of PCI slots on my mATX mobo and Id prefer not to have to squeeze in another card!
     
  20. Pootle

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    What is dscaler doing to the picture BBD? I know more recent versions of dscaler have a lot of tweakable settings and things you can turn on and off, although never having had a compatable card I have not used it myself.

    If you look around the collar and tie area of the two pics you can see some real strange things going on in the dscaler version - much more so than in the nebula version, which suggests that the 'punch' of the dscaler version may be due to edge enhancement / contrast exaggeration. There is clearly more ringing on the horizontal edges of the dscaler version - very obvious where the light band of wood meets the presenters elbow.

    MikeTV, I think the quality of the pic will also be dependant on the quality of the decode / output stages of the STB, so some STB's will probably look much better than others.

    Anyone know if there has been any serious comparisons of the output picture quality of the various STB's??
     
  21. nfordenfield

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    Pootle

    Must agree with your observations, also Nebula neeeds it's own internal settings tweeking as the picu=ture seems fairly 2d.

    Good question is do nebula and sky see the "same" amout of info, other not a "fair" test.

    Personally I now prefer the slightly Non smooth panning instead of the out of body experiwnce of dscaler via sky via svideo, anyone got a RGB H3DII comparison?
     
  22. BBD

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    I've added a zoom in on the shirt and tie area for comparison.
    Photos here

    I appreciate that the cal. of the Nebula isn't brilliant and I've used the sticky guide as a starting point for the DScaler cal. but all the tweaking in the world will not get get rid of the jaggies (around the collar) on the Nebula card. Also this is a static picture, motion on the DScaler set-up is far superior.

    I think it is fair to compare Sky STB to the Nebula solution. At the end of the day both solutions are for watching broadcast tv. It is highly unlikely that Nebula will ever have a Sky based card and therefore the Nebula solution has to live with the limitations of digital terrestial broadcasts.

    My STB is a not very new Grundig with S-Video output, I would be surprised if the latest Sky+ boxes don't have a superior S-Video output.
     
  23. Pootle

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    BBD, whatever you did to zoom in seems to have smoothed the umage as well. I've done a straight blow up with each original pixel duplicated over 4 pixels, which I think shows what is going on better. You can see them here

    Yes its also true that we need to know the same bandwidth is being used via both systems ideally. I don't know how we can check on this, but the STB may let you see the efective bit rate deep in the menu system somewhere. Its not so hard with the nebula, as a recorded file can be analysed quite easily.

    Remember that what nebula is passing to the display driver should be totally accurate (well accurate in that it is what the broadcaster intended!), as it a totally digital path. So setup should really be about getting the PC display unit to accurately display what the PC is outputing. Unless there is something strange going on, the nebula setup should be 'flat' , and the display adjusted to be correct. This setup should also work for DVD's, but since films are often 'darker' than TV programs, I find I need to up the brightness for some films. I suppose a rip of a DVD setup disc that can be played with the nebula player would be the best way to get it set up.

    The SAA capture card, since is coming from the analogue domain will need calibrating, but I would expect that both pictures should appear identically coloured if everything is set up correctly.

    Mind you the broadcasters get up to some very strange things , as I found when I compared the DVD of 5th element to a TV broadcast of the film - the colour balance was totally different, and varied as well. If you look at the last 2 shots on this page youwill see what I mean!
     
  24. BBD

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    I'm confused about this, the zoomed section only highlights the difference I can see on the unzoomed image?
     
  25. owain_thomas

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    Pootle, I'm not sure how you got those blocky images on your website, when I saved and then enlarged BBD's images they come out nice and smooth just like BBD's. This was just with straightforward magnification in a very simple paint package, how did you do yours?

    Owain
     
  26. Pootle

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    It depends how you enlarge the picture; if you resize the picture, it interpolates an 'invents' new pixels so what you get is not really what you started with.

    I used paint shop pro and looked at the image X 4 without scaling it up , and then just captured the image on the screen.
     
  27. MikeTV

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    I have posted another Nebula capture - only this time I used an ITN broadcast, and managed to capture the same Kelly Inquiry graphic as BBD (I haven't scaled it). I think it just reconfirms what has already been established, especially if you look at the lettering (the i's in "inquiry") - which show scaling/compression artefacts (shadows), and the digitization around the collar.

    Here is the link (scroll down)

    On the issue of colour in broadcasts (pootle's link), I am sure most of the problems are to do with the differences between colour gamma/temperature settings on material from across the pond, and the failure of broadcasters (on either side) to apply the appropriate correction in their media conversions. Colour management seems to be a bit of a black art, and the differences are not so great as to worry most people. Kind of like the 4% audio pitch issue, I guess.
     
  28. Pootle

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    MikeTV, I think the soft edge to the I is caused by a doubled vertical line, another interesting area is above that, between the K and the e, where there almost appears to be a dark line separating the edge of the characters from the character itself.

    The collar jaggies are also interesting - this effect has been obvious on all the nebula pictures. It looks almost like every 25th (approx) vertical line repeats - you can see an equivalent jag on the tie directly below one of the collar jags, I wonder if there is a problem with the nebula decoder? Have to try recording one of these, and see if it shows on playback with an alternative player tonite. The captures I did from Nova-T show no such effect.
     
  29. owain_thomas

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    sorry to be argumentative pootle, but that's exactly what I did (zoomed in and looked at the zoomed in picture) there's no way that what you've posted are simply zoomed images they are zoomed and then reduced in resolution.

    The paint package I used doesn't do any kind of resize/resampling, just a plain old zoom.

    owain
     
  30. Mr.D

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    Sorry there is no such thing as a simple zoom. Zooms characteristically employ subpixel filtering to interpolate information (similar to scaling).

    To get a 1:1 pixel representation on an image enlarged from a lower resolution you have to map the pixels to discreet whole pixel values ie 1 pixel maps to 4 pixels for a x2 emlargement.

    This is why things enlarged in this manner will look blocky. If the zoom has filtering options available then using a nearest filter will give you this non-interpolated result.

    Its a bit moot in this case as the interpolated images actually show the artifacts under discusion more obviously than the one to four pixel mapped version.

    Might I suggest that someone captures a frame from some film based material from the nubula/novatv and dscaler pipelines as this will disclose whether the shearing artifacts on the collar are caused by the deinterlacing or are actually native to the cards pipelins . (I'd expect both dscaler and the card solutions to use a simple weave type deinterlace for PAL film material) .
     

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