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Old 02-15-09, 09:14 AM   #1
davelaser
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Default Vdpau video scaling quality?

Question to the nvidia devs (I don't believe this information is in the documentation):

What scaling algorithm does vdpau use for video? Is it the same standard bilinear that Xvideo uses, or is it better quality?

Sam
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Old 02-15-09, 04:12 PM   #2
Stephen Warren
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Default Re: Vdpau video scaling quality?

Off the top of my head, I don't know. Is there a problem, or are you just curious?
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Old 02-15-09, 04:19 PM   #3
davelaser
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Default Re: Vdpau video scaling quality?

No problem, just curious. On windows you can get higher quality scaling algorithms than the standard bilinear like bicubic or even gaussian, which makes standard and low definition movies look less pixellated when they're scaled up to the screen resolution.

I'm fairly certain nvidia's implementation of xvideo uses bilinear scaling (I seem to vaguely remember asking before) and I was just wondering if vdpau allowed for higher quality upscaled movies.

Sam

PS. I have to say, nice job on vdpau, I'm using a 8400GS and all I had to do was put some options in smplayer and flawless video acceleration ensued.

PPS. Oh yeah I had to disable the composite extension as well, presumably composited vdpau is something that's still being worked on?
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Old 02-16-09, 05:42 AM   #4
drdaz
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Default Re: Vdpau video scaling quality?

Looking at the vdpau's output in mythtv, it looks to me as though it's bilinear - I've been using Mark Kendall's openglbicubic filter otherwise, and the scaling in vdpau is less impressive. It would be good if other scaling algorithms were available.

/me requests Lanczos.

Good work on vdpau all around though. When it's complete, a lot of people will get a lot of value from it.
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Old 02-16-09, 06:55 AM   #5
piotro
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Default Re: Vdpau video scaling quality?

@drdaz

Are You using vdpau as decoder and opengl as scaling filter in mythtv ?
If so - may You hint me about myth config for opengl scaling filter ?
br
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Old 02-16-09, 07:14 AM   #6
drdaz
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Default Re: Vdpau video scaling quality?

@piotro

No, as far as I know that's not possible. I'm not completely certain how vdpau works, but as I understand it, once the video is given to vdpau, we don't have the ability to post-process (devs / techs, feel free to correct me on this). I was just testing vdpau in mythtv; it's currently unstable for me (crashes X hard), so I've reverted to ffmpeg / opengl.

There is a noticeable difference in upscaling quality though; opengl bicubic is currently far superior.
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Old 02-16-09, 02:00 PM   #7
zbiggy
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Default Re: Vdpau video scaling quality?

AFAIR Opensource Nouveau Geforce driver supports bicubic but you have to downgrade to Geforce 4Ti.

Matrox Parhelia about year 2003 offered bicubic scaling. However their Linux driver is the worst I ever seen. It is sad that in year 2009 GPU leader has no bicubic interpolation not mentioning more powerful algorithms. I watch many low bitrate video clips and they are really ugly on Nvidia. When Geforce6 offered high quality scaling I bought it to only see this was marketing BS. Then was Geforce7900GS without picture quality difference and now Geforce8200 with impressive VDPAU. Bitstream decoding is masterpiece with 0% CPU usage. But postprocessing sucks with poor bilineral quality, no deinterlacing (I see feathering on some DVD movies), no deringing, no deblocking.

Nvidia made very big and impressive progress in 2D acceleration. XRender (except non-accelerated gradients) have professional look now. VDPAU decoding perfect.

I believe Nvidia will do something with VDPAU postprocessing so in the future there will be no feathering on interlaced DVDs and low quality clips from youtube will look great.

ATI has deblocking (they advertised it as fullstream, maybe only on Windows). S3 Chrome also has deblocking in "Chromotion Programmable Video Engine". Nvidia was always quiet about this feature. VDPAU has postprocessing block, currently without features. Maybe Nvidia devs will fill it with features like deblocking/deringing/lanczos filtering.
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Old 02-17-09, 05:09 AM   #8
piotro
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Default Re: Vdpau video scaling quality?

Well,
Thats why I asked this question.
Technically, in VDPAU environment, implementation of any postprocessing filter is non-trivial (in resources sense), as data flow will be quite complicated.
Namely: app will push frame to GPU for decoding, next external postprocessing filter code should pull frame again to memory for postprocessing, and finally frame will be again pushed to GPU for sending to RAMDAC. So it will require 3 mem transfers instead of 1 (when we are using GPU postprocessing).

AFAIK Nvidia's VP3 has quite advanced filtering capabilities - I don't remember why all of them are not used myth (in case of mplayer support simply isn't implemented yet)

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Old 02-17-09, 08:44 AM   #9
davelaser
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Default Re: Vdpau video scaling quality?

Are the VP3 filtering capabilities exposed in the vdpau api? Do they include better quality video scaling?

Oh and by the way, does vdpau implement deblocking as standard for h264? It is part of the h264 spec, but some implementations leave it out for performance reasons.

Sam

Last edited by davelaser; 02-18-09 at 05:31 PM.
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Old 06-12-09, 06:42 AM   #10
jusst
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Default Re: Vdpau video scaling quality?

I'd like to get this topic up again.
Stephen, are there any plans to add a higher quality scaling to VDPAU sometime? - IMHO this is a point where VDPAU could gain a big quality improvement and make it finally the reference in picture quality on Linux systems.
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Old 06-12-09, 11:03 AM   #11
DeeZiD
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Default Re: Vdpau video scaling quality?

Well, I've tried Vdpau (185.18.14, Geforce 9600GT) today with DVB-T (me-tv + xine-vdpau svn).
Quality is amazing compared to xv!

- No tearing - even if composite is active (kwin4)
- Black is Black and White is White (0-255 luma!)
- Same deinterlacing algorithm as in Windows Vista or 7 (spatial/temporal - don't know, but with bobbing
- Scaling is very sharp (seems to be bicubic)

- 1080p/24p works fluent as aspected

regards Dennis
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Old 06-12-09, 01:32 PM   #12
Stephen Warren
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Default Re: Vdpau video scaling quality?

I did some research on this. Under Windows, NVIDIA offers improved SD to HD scaling on some high-end GPUs. There are some implementation difficulties that make it unlikely that we'd support this in VDPAU for currently shipping GPUs.

Where did you get your information regarding bicubic/Gaussian options on Windows? Are you sure they are video scaling options, and not OpenGL or DirectX features?
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