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Central Scrutinizer
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Discussion Starter · #1 ·
We toss around the term "rendering" around all over the place in this forum, yet I am ashamed to admit that I don't truly understand what it is and what it is doing. Would someone like to offer a brief (or even long) explanation of exactly what it is and what it is doing?


The reason I ask id because I am trying to understand when the various renderers (like overlay and VMR7 and 9) are in the signal path and when they are not. For example, I plan on using a PC to do some calibration work and I have sets of patterns that were constructed using video levels (black at 16,16,16 and white at 235,235,235), so if I load them into something like MS Paint and adjust my display, am I adjusting ANY renderer in the process?


How about if I load the same JPEGs into TheaterTek 2.1.1 and I have it set to render using VMR9. Are media picture files being "rendered" at all or is just MPEG encoded video "rendered"? This confusion on my part has come about due to the thorough lack of understanding as to exactly what "rendering" is and when it is "doing its thing".


Any volunteers for an explanation?
 

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To be more specific, read this
 

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Discussion Starter · #4 ·
Thanks, guys....The links help.


The link at inmatrix is written for us "normal" people and was thus very understandable, but the info at msdn was geared more for the programmer, so much of it just went over my head.


The problem is that neither of them helped me understand what happens when Media file (JPEG in this case) is opened into either TheaterTek or ZoomPLayer. I s a single JPEG rendered at all? How about when all apps are closed and you are viewing your desktop..Is the desktop "rendered"? Based on the articles, I would assume that if the desktop is rendered, then under XP it would be rendered by the VMR-7, the default renderer for XP. Is it possible to render the desktop using the VMR-9 instead? If so, how?


The explanation provided at inmatrix indicated that rendering is a method of displaying moving video on screen, but no mention of still pictures was ever made, as that wasn't the focus of the information, so the question of whether or not still pictures are rendered or not remains unanswered.
 

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Everything on a computer is rendered, the only question becomes what process is handling the rendering, DX9, VMR7/9 or the basic UI.


Rendering is the process of taking input data say the cooridinates for a window and processing it to create the pixels nessicary for display.


To phrase your question more susinctly, What renderer does Zoomplayer use when it's displaying a stationary JPEG.


To that I don't have the answer.
 

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Actually, strictly speaking, rendering should refer to how a 3D scene is displayed, or projected, onto a 2D screen or window. A bitmap is not therefore and I don't see why it should be - "rendered", but simply "displayed", as is.


I guess in movies - please correct me if I'm wrong - it's color - with all its atributes - that is rendered.
 

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Oh, rendering high quality images, the program first draws a wire frame or the starting sketch. Then the next rendering may be the colors, then shading, etc. At least from what I remember back in PC art class......
 

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Quote:
Originally Posted by Bob Sorel
We toss around the term "rendering" around all over the place in this forum, yet I am ashamed to admit that I don't truly understand what it is and what it is doing. Would someone like to offer a brief (or even long) explanation of exactly what it is and what it is doing?
A renderer in the directshow context is a filter whose job it is to turn a byte stream into pictures or sound. They are typically the end points of directshow graphs.

Quote:
Originally Posted by Bob Sorel
The reason I ask id because I am trying to understand when the various renderers (like overlay and VMR7 and 9) are in the signal path and when they are not.
Whenever you display video using a player that uses DirectShow (most do) then one of these filters will be being used, things are more complicated with VMR as the player can take on the displaying itself.

Quote:
Originally Posted by Bob Sorel
For example, I plan on using a PC to do some calibration work and I have sets of patterns that were constructed using video levels (black at 16,16,16 and white at 235,235,235), so if I load them into something like MS Paint and adjust my display, am I adjusting ANY renderer in the process?
No DirectShow renderer is being used in this case.

Quote:
Originally Posted by Bob Sorel
How about if I load the same JPEGs into TheaterTek 2.1.1 and I have it set to render using VMR9. Are media picture files being "rendered" at all or is just MPEG encoded video "rendered"? This confusion on my part has come about due to the thorough lack of understanding as to exactly what "rendering" is and when it is "doing its thing".
The answer here is possibly. I'd need to know more about how TT loads up the pictures if Directshow is envolved then yes, if it isn't them no.


John
 

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Discussion Starter · #9 ·
Thanks, John! I was hoping that someone like you, Blight, or Andrew might stumble onto my questions and lend a hand...:)


Between the links provided and the posts here (especially yours), I have a much better idea of what a renderer is and when it is most likely to be involved in the signal chain.

Quote:
The answer here is possibly. I'd need to know more about how TT loads up the pictures if Directshow is envolved then yes, if it isn't them no.
Then the quickest and easiest way to find out will be to simply ask Andrew directly. I'm sure he knows how he has TT configured to display picture files...:D


Thanks again!
 

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Bob, just a suggestion. You could create a short 24 or 30 frame mpeg movie with your single bmp/jpeg image. Then when you play it back in TT it certainly would use a decoder/filter and thus a renderer.


Hammer
 

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Discussion Starter · #11 ·
I talked to Andrew and he told me that picture files are indeed rendered, but they are rendered using the OS default renderer, which would be VMR7 for XP. He also mentioned that in the next release (2.2), that the pictures will now be rendered using the renderer selected, including VMR9 renderless.

Quote:
Bob, just a suggestion. You could create a short 24 or 30 frame mpeg movie with your single bmp/jpeg image. Then when you play it back in TT it certainly would use a decoder/filter and thus a renderer.
Great minds think alike...:D


I was considering a similar option...creating a short movie, but I would encode it with MPEG2 and create a structure that adheres to the DVD specification. This would not only insure that the renderer of choice would be used, but it would also make a handy, meat and potatoes calibration disc that I could use with any DVD player, software or hardware. I would loop each short "movie" infinitely, chapter it, and then create a menu to access the patterns randomly. I could also start at chapter 1, and just hit the "next" button to advance patterns and the "previous" button to back up. This would be a lot easier than navigating either DVE or Avia...:D
 

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Quote:
Originally Posted by Bob Sorel
I was considering a similar option...creating a short movie
I got the impression your pictures are meant for calibrating the display device. In that case I would stick to as simple a renderer as possible, especially as we know that DirectShow renderers like to interpret color levels differently. My gut feeling tells me not to trust these mpeg compressions and DirectShow stuff for bit-perfect output.. :)
 

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Discussion Starter · #13 ·
Quote:
I got the impression your pictures are meant for calibrating the display device. In that case I would stick to as simple a renderer as possible, especially as we know that DirectShow renderers like to interpret color levels differently. My gut feeling tells me not to trust these mpeg compressions and DirectShow stuff for bit-perfect output..
Yes, you are correct. If I use as simple a renderer as possible, that will be fine for calibrating the input of the display, BUT if I want to calibrate the entire chain from software player to display, then I will need a way of inserting the renderer of choice into the signal path. In my case I use TT (and VMR9) to play back both DVD and HD material, so I need a way to calibrate with VMR9 in the path, just to make sure that VMR9 and the TT color controls are not affecting the otherwise perfect patterns that I am using for calibration.


Also, the newer hardware DVD players can play back JPEGs, but older units are limited to MPEG2 sources, so it would be handy to have a MPEG2 encoded set of patterns (like those on DVE or Avia). I will just have to check very carefully that none of the levels are affected in the encoding process or the patterns will be worthless if they don't maintain reference video levels.
 

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@Tulli


I'm no expert, but I think you are confusing something. Rendering can mean a lot of things, not just in the sense of 3D rendering software. To my mind, rendering in the world of computers refers to the painting of pixels for display on a display device.


Cheers...

Duy-Khang Hoang
 

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Not to mention like cheese production and cooking and whatnot, right? Like mentioned above, I was always of the impressoin that the term came into being (in graphics terms, not cheese terms) in the 3D world, because it is composed generally of a pipeline of transformations that the data goes through to get turned into a 2D representation of a 3D image.


But, maybe the terminology has drifted a bit since then and become more generalized. And even in a 2D world there is still a set of transformations possible, in terms of scaling and viewport placement and units conversion, though they are trivial compared to 3D transformations.
 

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I think that the general idea is that rendering, like Dean Roddey says, should imply some sort of transformations from an original "space" (3D, for instance) to a "rendering" space (2D, for instance).


IMO color is rendered with DVD movies, just for the fact that it has to be transformed from an original space, say YUY, to RGB, or YV12. But then you could add more transformations to the pipeline through calibration.


Of course I'm not an expert either, but is it not PC games - with their need of 3D, video and sound rendering - that pushed the development of DirectX?
 

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Like some have suggested, it is my understanding that rendering is just a conceptual name for a subsystem that makes something visible on the screen. Developers need a name for everything and a subsystem for visualizing stuff is part of most apps. Hence, many different "renderers" out there. In Microsoft's developer documentation e.g, they use the term in the context of Internet Explorer, describing how it "renders" part of a web page before it has finished loading all the content.


I bet there's code in IE which they refer to as "Internet Explorer's renderer". This in turn gives instructions to another "renderer" - the GDI subsystem of the operating system. Which in turn gives instructions to a third "renderer" - the graphics driver DLL. Which in turn gives instructions to the chip on your graphics card (the renderer among your PC components). Which in turn has a subsystem that periodically generates signals on your VGA/DVI port based on what's in the front buffer. So a "renderer" is also like a russian nesting doll - a renderer has a renderer has a renderer...


The concept only implies that a renderer is the last visualizing subsystem from some point of view.
 
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