[eskro]

hello all,
last night i downloaded a Bluray 720P MKV file
which was down-sampled from the retail Bluray 1080P disc...
File is about ~5.46GB....
Main movie only of course..

Now my question is,
Is it normal that in XBMC for Windows,
when watching this 720P movie,
during some dark colored scenes i can see some 'blocky artifacts'
just like i see usually see when watching a 700MB AVI movie..!?

But thing is, this is 720P movie!
im not sure why i see some blocky artifacts O.O
Not as much as on a 700MB AVI file but,
i thought i'd never see them again...

i got a FULL 1080P HDTV, so is this the reason?
it tries to upscale the 720P back to 1080P?

i mean i dont know....

would it be better for me to get DVD5 (4.37GB) movies
compressed from their Retail DVD9 discs?
Would i still see some blocky artifacts??

i thought 720P would be better then DVD5 quality...

someone has an answer? :/

thanks in advance!

[pcdude]

The blotchy artifacts has nothing to do with the resolution, but is a result of the compression scheme used to encode the video. Higher compression typically means more of these artifacts. The compression along with the resolution ultimately determines the bit rate of the video stream. Higher bit rate typically means higher quality.

Generally, the less compression used, the better. R5 rips typically (but not always) compress less than xvid rips, for example.

[eskro]

so basically, your saying its not XBMC,
and its not of course my FULL HDTV,
but its how the uploader compressed the movie?

Kinda like its fault?

im still amazed, a 700MB avi movie i undestand why i see blocky artifacts...

but i thought a 720P ~5.46GB movie had enough preserved quality to NOT see artifacts again....

:/

[mr.sparkle]

The blotchy artifacts has nothing to do with the resolution.

Not entirely true. My guess is upscaling from 720p to 1080p, combined with what I'll guess is an 8-bit (vs 10-bit or higher TV) is resulting in colour banding. Here's what I found at the AVS forum:

"The case where 10-bits for a consumer screen makes a big difference is in upscaling video from a lower resolution. Each color channel (red, green, blue), before scaling is multiplied by 4 to make it a 10-bit value to begin with. Then the image is scaled up by finding values inbetween "neighboring" pixels to jam in-between each pixel...The result is that the "sub-pixel-sampling" or the pixels in-between the encoded pixels are of a higher precision. The visible result, in special circumstances (generally you saw it more during the earlier jumps from 5 to 6 pixels per channel) is that color banding in the picture is much less."

http://www.avsforum.com/avs-vb/showthread.php?t=967859

[activoice]

Have you tried playing back the same video using a different player like KMPLayer

http://filehippo.com/download_kmplayer/

That will at least indicate whether the issue is with XBMC, or not..

[eskro]

hmmm,,, i think your on the right track mr.sparkle....

after reading here --> http://ow.ly/1toH8c

i'll have to check what that guy said but, indeed,
blocky artifacts may be caused by the number of reframes being to high for the profile used

profile flag [email protected] only allow up to 5 reframes for 720p

6 reframes = profile flag [email protected]

so basically he's saying movie is wrongly decoded because the profile flag is wrong

i'll verify if i have the correct reframes spec for the flag profile used..

if not, then, i'll try to change the profile flag to the correct one using tsmuxer...

tsmuxer will then demux the movie into 2 files --> .264 & .ac3

After that using i can use mkvmerge to re-create an MKV file from those 2 files....

[eskro]

Have you tried playing back the same video using a different player like KMPLayer

http://filehippo.com/download_kmplayer/

That will at least indicate whether the issue is with XBMC, or not..

i tried using MediaPLayerCLassic.... same issue....

[PatK]

An aside note on this subject: I grabbed a 720p file the other day...that was only 380 megs for 1:37 hr (I should have known better) and it opens most popular players up to a 1280x720 16:9 aspect screen, but the real resolution is terrible.... very blocky, fuzzy etc. Some players are not fooled and it's 320x200 resolution was clear. Many so-called Blu-Ray uploads are nothing more than DVD upscales at best.

There's really no definitive answers, blocky PQ and the lack of detail can come from the display, codecs, interpolation chips, graphic cards, and the software that decodes. Just because I have a 6 gig file doesn't guarantee me a quality file, if that was so.. there would be no need for 50 gig Blu-Ray disks. Even with a full Blu-Ray end to end system... the disk encoding can be bad.

[eskro]

very true... ok,,,

i'll then try DVD5 version of the movie just to see,,,,

Ive rip'ed some myself back in the days
and they have zero artifacts whatsoever...

well when burned to DVD using CloneDVD2

[>>X<<]

Your screen won't be up scaling anything if your outputting 1920x1080 from your HTPC

There's really no point trying to find out the cause I think you have just been unlucky with your choice sounds like it was encoded by an idiot, try something else if that's the same then maybe something else is going on

A bluray rip either 720p or 1080p should be perfect quality done right

[eskro]

ok, ill try another rip...

it'll take time tho.... im downloading off of filesharing sites...

not usenet....

thanx guys!!

[>>X<<]

I personally without a side by side comparison would find it hard to find a big difference between a perfect 720p, 1080p rip or bluray source others may not agree however