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  #1  
Old 08-22-2007, 05:31 PM
pat_smith1969 pat_smith1969 is offline
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short explanation...

I am pretty sure how all of this stuff goes, but I thought I would check to see if my understanding is correct.

Is there a link that has this information perhaps?

Can someone write up a brief explanation on what the following are and specifically how they are used within sagetv? Which ones work the best in SageTv

1. video decoder (i.e. NVidia)
2. VMR9 vs Overlay (is this the renderer?)
3. How the decoder and the renderer work together (or don't they?)
4. What is FFDShow used for?
5. What is DirectShow (or DShow)?
6. what is purevideo?

I am not asking for a hute encylopedia of all this stuff, but rather an brief explanation of what they do and how they work in sageTV.
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  #2  
Old 08-22-2007, 06:32 PM
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GKusnick GKusnick is offline
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Quote:
1. video decoder (i.e. NVidia)
A video decoder takes a compressed video file (MPEG or other format) and decompresses it to produce a sequence of images that can be displayed on screen.

Quote:
2. VMR9 vs Overlay (is this the renderer?)
Yes, these are video renderers, which means they take the sequence of images produced by the decoder and actually display them on screen. The Overlay renderer uses a special hardware video buffer to display the images. VMR9 uses DirectX to paint video on the screen the same way it would for any other sort of text or graphics.

Quote:
3. How the decoder and the renderer work together (or don't they?)
The decoder decompresses the file; the renderer draws the decompressed images on the screen.

Quote:
4. What is FFDShow used for?
It's a filter that can be inserted between the decoder and the renderer to handle various kinds of effects such as deinterlacing. With good decoders you don't really need it.

Quote:
5. What is DirectShow (or DShow)?
DirectShow is the name of the overall software architecture that includes decoders, filters, and renderers and connects them together for playback (like plugging together AV components).

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6. what is purevideo?
PureVideo is Nvidia's name for its video decoder product.
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Last edited by GKusnick; 08-22-2007 at 06:34 PM.
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Old 08-23-2007, 08:44 AM
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lobosrul lobosrul is offline
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I'd like to add:

If you have a powerful computer FFdshow might be all that you need (and it costs $0) for decoding virtually anything*. I'd still recommend purevideo if you have an nvidia vid card though.

Directshow decoders work in sort of a chain. One decoder will split (or "demux") the container. Then other decoders will decode the video another the audio and there may be other intermediate decoders. For instance I have ffdshow setup to decode AAC audio, and AC3 filter setup to process any raw decoded audio to adjust audio levels and always send a 5.1 signal.

*Powerful as in a mid-level AMD x2 or any Intel dual core.

Last edited by lobosrul; 08-23-2007 at 08:48 AM.
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Old 08-23-2007, 12:36 PM
wheelrandolph wheelrandolph is offline
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Thanks to both of you for good explanations--I also was not sure how it all works.

Randy
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  #5  
Old 08-23-2007, 01:09 PM
pat_smith1969 pat_smith1969 is offline
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Thank you both for taking the time to respond. I was kinda half expecting a "do some research NOOB !!" type response. I think this post might help other NOOBs too.

Another question...
If I encode all my videos in AC3 and use the NVidia decoders can I force my sound to always be 5.1 using the AC3 Filter thingie I had to install? I looked and didn't see anything saying "always make sound 5.1" in the AC3 filter config app.
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Old 08-23-2007, 03:01 PM
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lobosrul lobosrul is offline
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Quote:
Originally Posted by pat_smith1969 View Post
Thank you both for taking the time to respond. I was kinda half expecting a "do some research NOOB !!" type response. I think this post might help other NOOBs too.

Another question...
If I encode all my videos in AC3 and use the NVidia decoders can I force my sound to always be 5.1 using the AC3 Filter thingie I had to install? I looked and didn't see anything saying "always make sound 5.1" in the AC3 filter config app.
AC3 filter is just a decoder, its not going to effect how you encode a saved recording. But if you leave the AC3 files intact then you can decode it how you like. Of course not all shows are in surround sound.



In the dropdown box at the top left, select 3/2+SW (i think thats what its called im at work and cant check). I also like to use DRC, that will dynamically adjust the volume levels depending on how quiet or loud the audio level is. I set it at about 8, and set the master volume down to about -3.




On the next page, I like to turn OFF matrix normalization (if you leave this on, don't adjust the master gain down), and adjust the voice control up some.

Some of this only applies if you have a 5.1 audio setup! The great thing about AC3 filter is it can be customized to any reasonable speaker setup. You could for instance have just 4.1 audio or only 1 rear speaker.

Last edited by lobosrul; 08-23-2007 at 03:10 PM.
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  #7  
Old 08-23-2007, 03:27 PM
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GKusnick GKusnick is offline
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If you're asking how to make 2-channel sound play through all 5 speakers instead of just 2, that's what the "Expand stereo" checkbox in the above screenshot is for.
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