Found this in another area
Upconversion vs. scaling
dbacksfan11-09-06, 12:38 PM
I need to better understand these two terms and how they relate to receivers. First of all, what is the difference between these two terms?
Second, If I buy a receiver with HDMI inputs/outputs, and it converts component and s-video signals to HDMI, does it also take the 480p signal from my standard DVD player and upconvert it to 720p or 1080i, thus eliminating the need for an upconverting DVD player? Or is the receiver merely converting the component/s-video signals to HDMI so only a single cable needs to run to the TV?
Thanks to anyone for helping to clarify this for me.
Bob Pariseau11-09-06, 04:55 PM
Technically the two terms refer to different things although the marketing guys are doing their darndest to confuse the difference.
Upconversion technically refers to taking one style of video signal (e.g S-video at 480i) and converting it to a "better" or "more convenient" style of video signal (e.g., Component video at 480i) AT THE SAME RESOLUTION. If the conversion involves making an analog video signal (e.g., Component video) into a digital video signal (e.g., HDMI video) then the upconversion also involves the important process of "digitizing" the analog signal -- or vice versa.
Scaling technically refers to taking one resolution of video signal (e.g., Component video at 480p) and converting it to a differerent resolution (e.g., Component video at 720p) -- possibly while also doing "stretch/zoom" distortion to the image or while generating "letter/pillar box bars" to pad one shape of image to fill out a different shape of screen. Scalers often are called upon to work both ways. For example a 720p plasma TV fed a 1080i HDTV signal needs to "down scale" that signal.
There is a third important piece of this which is "de-interlacing" -- e.g., taking a Component video at 480i and converting it to Component video at 480p. Quality de-interlacing is important for lots of reasons, but one big one is that it is too tough to "scale" an interlaced signal well, so any scaling solution needs to include a de-interlacing solution as well.
Due to industry hangups about copying of content, there's another important piece to this puzzle which is copy protection. Copy protection restrictions may force your receiver to NOT always do what it is capable of doing.
For example, if the source content is protected content from an HDMI device, then the receiver is *NOT SUPPOSED TO* have any video output on it's Component outputs. Only HDMI output is supposed to be live, and even that will be true only if the TV (and any intervening devices) are compliant with HDMI's copy protection protocol, known as HDCP. Thus even though the receiver is capable of converting HDMI input to Component output it may be prevented from doing so due to copy protection of some content (e.g., DVDs).
Now you already know about upscaling DVD players. They are standard def DVD players with built in de-interlacers and scalers. They can take a standard DVD (which is inherently 480i) and spit out a 720p or 1080i signal by kind of averaging real pixels to invent the extra ones in between.
What you may not be aware of is that HD TV sets already include THEIR OWN internal scalers (and de-interlacers). That is, if you fed that 480i DVD signal to the TV, then the TV would do the de-interlacing and scaling ALL BY ITSELF.
And now you may be purchasing a receiver with YET ANOTHER de-interlacing and scaling solution.
Why? Well first of all it makes the industry very happy if you spend money to buy the same thing yet again, and we all want the industry to be happy.
But perhaps a better reason is that the new scaler you buy today *MIGHT BE BETTER* than the old scaler you already own in some other device. It might, just might, do a better job!
So people buy upconverting and scaling receivers as part of the quest to improve overall image quality and convenience (i.e., ease of cabling).
If your TV, or new receiver, has a really great de-interlacing and scaling solution, then you *DON'T NEED* an upscaling, standard def DVD player -- and even if you have one you really want to set it to output unchanged the 480i imagery coming off the DVD so as to let your better, downstream scaler do the work. However since the data on the DVD is inherently digital, you might still want to find a DVD player with the ability to output a 480i digital video signal -- which means certain HDMI DVD players -- so that you don't have that extra step of converting the digital DVD data to analog video. One less step where things can go wrong. But the industry has cleverly bundled upscaling with HDMI output in many players so that you may be forced to pay for upscaling in the player -- EVEN IF YOU AINT GONNA USE IT -- just to get HDMI!
Also understand that just because something says "scaler" on the box, it may not be a very good scaler. And so you might buy it and then end up turning it off so that the better scaler somewhere else in the video chain (perhaps in your upscaling DVD player or in your TV) does the work.
For example the scaler in many set top boxes (HD cable and satellite boxes) is really bad. So when viewing SDTV content (old, standard TV), you really REALLY want those boxes to send out a 480i signal (which is what SDTV is) and let some OTHER piece of your electronics take it from there -- perhaps the TV itself or perhaps your new upscaling receiver.
Lastly you have to know what your TV will accept as input. For example, fixed pixel displays such as LCD or plasma TVs need to have the video signal scaled to match their physical pixel count. However not all such TVs will actually accept that exact resolution as input! And that means that the scaler in the TV will have to do at least some work no matter what signal you feed the TV.
For example, a typical plasma flat panel TV these days might accept a standard 720p HDTV signal, but then scale it to 768p to match it's real, physical pixel matrix. However, if you get a fancy external scaler that knows how to generate a 768P signal, you may very well find that the plasma WON'T accept that resolution as input. So you can't completely bypass the plasma's own, internal scaler and the math will have to be done one more time than you'd like.
You will find many receivers out there which neither up-convert nor scale. You can select between S-video sources for example, but the output will only be S-video. Similarly Component inputs will only generate Component output -- and at the same resolution. This is sometimes called pass-through switching. As simple as it sounds it is still possible for the receiver to screw up the signal in the process of passing it along from input to output. You will need to run multiple styles of cable to your TV if you have multiple styles of input cable coming in to the receiver.
You will find other receivers that up-convert but don't scale. You can take a variety of sources with different cabling and have all those signals go out one style of cable (usually Component video). The input resolutions are just passed along unchanged. You only have to run the Component cable to your TV. The quality of the conversion may be important. Also look for gotchas and limitations -- the receiver may only up-convert certain styles of signal to other certain styles.
Finally you will find receivers that scale -- and usually also up-convert. There will likely be many more of these out next year. They are all over the map in terms of quality. [I'm currently using an Anthem D2 pre/pro to do this sort of thing. It's a good one.]
Be aware that there is yet another gotcha here which is that the receiver's own user interface may or may not be visible on all styles of output cabling at all resolutions. You may end up having to run another style of cable to your TV just to view the receiver's "on screen" displays. Video overlay processing of the receiver's own user interface is yet another way that better receivers differentiate themselves from cheaper receivers.