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Discussion Starter · #1 ·
If one compares the signal path of a Blu Ray STB modded with SDI-HD into a scaler like a vp50 pro to the path of a HTPC internal BR player to a video card across the PCI E bus.

How do they match up in terms of cleanest signal path least amount of processing before any upscaling or output ? Lets assume the output is the same RGBHV

Thanks

David
 

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Discussion Starter · #3 ·
Here is the question:

Blu Ray standalone via SDI vs Internal BR drive into card

See my attachment

Thanks
 

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The decoder/player in your HTPC will pass the decoded 1080p/24 frames to your graphics card which will in turn output it in the resolution you have selected over the output interface you are using to the TV.

I would certainly suspect that the hardware decoding chip in a standalone player provides better better picutre quality and scaling if any is required then that in a PC graphics chip or in a software bvased decoding program since PC components are designed to support many different graphic and applications.

Certainly if the decoding and scaling chips in a standalone unit are several years old from a design stanpoint then the latest generation graphic chips in PC may do a better job.

Regretfully, there are few if any reviews that compare these products between graphic cards much less between PC cards and stanalone units.
 

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Quote:
Originally Posted by walford /forum/post/15434006


The decoder/player in your HTPC will pass the decoded 1080p/24 frames to your graphics card which will in turn output it in the resolution you have selected over the output interface you are using to the TV.

I would certainly suspect that the hardware decoding chip in a standalone player provides better better picutre quality and scaling if any is required then that in a PC graphics chip or in a software bvased decoding program since PC components are designed to support many different graphic and applications.

Certainly if the decoding and scaling chips in a standalone unit are several years old from a design stanpoint then the latest generation graphic chips in PC may do a better job.

Regretfully, there are few if any reviews that compare these products between graphic cards much less between PC cards and stanalone units.

With any modern graphics card the unaltered bitstream is passed to the video card for all processing ie decoding, scaling etc.
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by abr27440 /forum/post/15434400


With any modern graphics card the unaltered bitstream is passed to the video card for all processing ie decoding, scaling etc.

Is this same as the SDI out of a modified stand alone player?
 

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No, the SDI modded player outputs raw uncompressed video. Well it depends on what you mean by "Blu-ray player". In an HD SDI modded standalone, the mod is connected to the output of the video decoder, before it's sent to the DAC or TDMS transmitter (for HDMI).


In a PC, there really isn't such a clean line. There's the BD-ROM drive which pulls the raw data off the disc, and then that's passed to software, which does at least some demuxing of audio/video, and at most full decoding of the video. At which point the remains (either raw compressed video bitstream or uncompressed video) is passed to the video card where the video is rendered to the Windows desktop which is in turn rendered to the the video output.


Theoretically if you draw a line after the video decoder (be it software or hardware) in the PC, it should be essentially the same as the decoded video from a standalone. The issue is that line in the PC is mostly theoretical.


The other issue is standalones are often/usually based on a single SOC chip which does all the UI and video decoding, so I'm not sure how an SDI mod on a BD player works.


Of course the simple answer to your question is that if you want the least "manipulated" image, a standalone is the way to go. PCs are handicapped by having an always-running, full-time user interface that is the primary "rendered object" and video is crammed into that, where as a standalone is primarily rendering video and cramming UI into that.
 

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Discussion Starter · #9 ·
Thanks for the excellent explanation. That was just what I was looking for. Seems like the software doing the decoding is a really key piece to the HTPC version. The rendering of the image as in the Theater Tek world, forgot about that. How good a job does TMT do at the decoding?

Thanks again
 

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Quote:
Originally Posted by David1 /forum/post/15436211


Thanks for the excellent explanation. That was just what I was looking for. Seems like the software doing the decoding is a really key piece to the HTPC version.

Except it's not that simple because I'd say most of the time, especially for Blu-ray, the decoding isn't done in software, it's done in dedicated hardware on the video card.
 

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Quote:
Originally Posted by abr27440 /forum/post/15434400


With any modern graphics card the unaltered bitstream is passed to the video card for all processing ie decoding, scaling etc.

AFAIK the decoding assistance is only provided by the graphics card if Hardware Acceleration is enabled in the decoder and then the decoder will infact call the display card drivers for the decoding assistance.

With Nvidia PureVideoHD capable chips h.264 decoding is only provided if the decoder specifially calls the card drivers with separate a API from the standared HA call.
 

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At least on my ATI based HTPC, when playing BR, hardware decoding cannot be turned off. Oh, you can uncheck the box, but as soon as you start a BR, it's back on.


Having just done a side by side comparison of an HTPC vs a new PS3, I can say that the HTPC did a better job of playback on BD, and it was noticeable to all who viewed it. This is however with a brand new, nice (read, high end) htpc. Not a bargain basement version.


Stanger89, would you not agree that most of the data path during it's trip through the PC is on a bus where data loss is not a concern? For the purpose of a "Clean" signal, much of the path in the PC is irrelavant since it makes no change from input to output?
 

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Discussion Starter · #13 ·
Ok , so for you guys who really get it, you must know where I am going with this. I have a Sony CRT 9" 1080p which either needs a card, scaller or HTPC get HDMI or a RGBHV.

So the choices are really three:

HTPC output rgbHV

HDMI/DVI Card

Scaller

The costs diff can be significant,

the scaller is the most expensive $2k, plus player.

the card $450 plus the player

The HTPC $700

Now the first two are plug and play, the last being a little more finicky.

So what then is the quality befits of each, not including frame rates.
 

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I would not dare compare htpc to any standalone.

Even the simplest things like refresh rate (timings) are impossible to get right on an htpc.

Htpcs cannot send 30/36/48bit color. They render in rgb progressive. If you want YCbCr you must convert to rgb & back again, same with an interlaced signal, must convert to progressive & back again.

Nothing is pure about the htpc and lets not get started about the software side. This is even not taking into account the components that go into an htpc. These components are not build for audio/video quality they are build for computers which are multitasking beasts they do a million things as opposed to be optimized for one thing.

You can pick up the cheapest possible dvd player & I guarantee you you'll have to spend 50 times the money and 5000 times the time to get your htpc to the level of what this "simple" machine can muster.

Sure some will disagree, they will say I can pop in a dvd disk in my htpc and watch the movie, if that's your view of a dvd player then you wouldn't be asking this question.

I've thrown all the money ($$$$) & time (over a year now) I had into my htpc and a humble ps3 can show it a clean pair of heels in five minutes setup time, as I've personally witnessed on my system when I borrowed one from a friend. Video/Audio/Usability where 5 times better easily.

Then you ask, why bother with htpc. Well I love my htpc, I love tinkering and I love all computer stuff, I didn't buy it for video/audio quality I bought it as a toy.

HTPC = stuff to do

SA = quality


Windows doesn't care how your bd looks/sounds as long as it works. If you wanted an mp3 player would you buy a phone that plays mp3? How about a camera? Or a gps device? It's the same with all things. You want to listen to cds buy a cd player. Don't buy a mini stereo that plays dvds/mp3s/divx/etc. to listen to music.

If you want to view bd movies buy a blu-ray player not an htpc. If you want things done properly you have to have the proper tools for the job, simple is best.
 
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