Login at Kodi Home

smallclone · 2013-09-11, 11:20

As I know nothing about processors and graphics, can someone please answer me the following:

I am using a Raspberry Pi with RASPBMC. It is ok but I'm convinced the picture quality is slightly inferior to when I play the same files through my Boxee. (h264 720p 5.1 mkv running from HDD).

Is this just my imagination?

Also, how will the picture quality compare on a Celeron 847 and a Little Black Box?

Thanks

glypto · 2013-09-11, 11:58

It's not your imagination, in case your RPI's output is set to 1080p, then it's the RPI who does upscaling 720p > 1080p. The same stands for Boxee. So whichever of them has better upscaling will produce better picture .
Cannot comment on Celeron/LBB as I do not have any of them.

smallclone · 2013-09-11, 12:06

(2013-09-11, 11:58)glypto Wrote: It's not your imagination, in case your RPI's output is set to 1080p, then it's the RPI who does upscaling 720p > 1080p. The same stands for Boxee. So whichever of them has better upscaling will produce better picture .
Cannot comment on Celeron/LBB as I do not have any of them.

Thanks, interesting.

Is there a way in the specs of these things that I can see which unit has better upscaling before I purchase them?

glypto · 2013-09-11, 13:20

I do not think they put any objective measure of video processing quality to specs for these devices. You can look for comparison of GPUs used in those devices assuming device with better GPU will provide better video processing. Then, it also depends on driver available for that device/GPU...
Only safe way is to see them side by side - by you or any fellow member of this forum Wink

smallclone · 2013-09-11, 13:25

(2013-09-11, 13:20)glypto Wrote: You can look for comparison of GPUs used in those devices assuming device with better GPU will provide better video processing.

So presumably, the quality of the GPU in the following devices is thus:

Celeron 847 > The Little Black Box > R Pi

?

(apologies, my knowledge is limited)

**popcornmix** · 2013-09-11, 15:25

To determine if the upscaling is the issue, set the resolution to 720p in settings/system/video, and then play the file.
The TV should be in a 720p mode, and it will do the upscaling.

Does the picture look better?

The upscaling done by the Pi, is decent ("Sinc over the range +-3*PI with Hamming window applied", rather than something basic like bilinear),
so I'd be surprised if other players are significantly better. I'm sure a $2K TV/AVR can do a better job.

smallclone · 2013-09-11, 15:31

Thanks I will do. Doesn't really make sense to me that 1080p upscaling is worse than 720p but there you go.

**popcornmix** · 2013-09-11, 15:42

(2013-09-11, 15:31)smallclone Wrote: Thanks I will do. Doesn't really make sense to me that 1080p upscaling is worse than 720p but there you go.

If the video is 720p and the TV is set to 1080p (and we'll assume 1080p is its native resolution), then the media player has to upscale and the TV does no scaling.
If the video is 720p and the TV is set to 720p, then the media player does no scaling and the TV will upscale to 1080p.

The TV is probably more expensive than the media player and will have better quality upscaling.

In the 720p->720p (or the 1080p->1080p) case, assuming the YUV->RGB coefficients are correct (they are on Pi), then everything is digital and bit exact, hence the output is perfect.
You won't get a more accurate picture on any other media player under the same conditions.

There are a few other issues that may effect perceived quality, like frame rate sync (i.e. true 24p output), but the Pi is very good at that (make sure "adjust display refresh rate to video" is enabled).
There can be post processing applied (e.g. sharpening), but they are only likely to have a benefit when the source is low resolution, and this is something better done at the TV/AVR end.