[Gamester17]

note! this is a continuation on this other (link) bug-topic thread as that ended up being about the poor quality in video renderer instead!

this new topic thread thread will discuss mplayer's post-processing filters (and only the mplayer postprocessing/postproc filter!;
(for referense: the official bug-report for this can be found in our sourceforge.net bug-tracker here (link), feedback is welcomed):

basic problem description:
mplayer post-processing filter has always been broken in xbmc, first it was thought that this was a bug in the original mplayer (for linux/unix/windows) and not just our xbox port of mplayer for the xbmc video/audio-core but it does now apper that the bug must be in xbmc's mplayer port.

symptoms/replication:
enabling the video post-processing filters under xbmc settings cause the video quality to be worse than with post-processing disabled (when should be vice versa).

more information:
xbmp('old' player) does not show this issue, both it's post processing filter work fine and improve the quality.

developer(s) assigned/working on this issue:
none?, since bug was before though to be in mplayer.

ps! @end-users of xbmc; linked video-samples and screenshots (bmp) are welcomed if can be hosted by yourselves (the bug reporters), thanks in advance.
...just make sure that the source video is progressive (not interlaced), (and that you first have disabled the deinterlace filter in xbmc settings) for now.

pps! @developers, xbmc uses a port of mplayer 1.0-pre6, mplayer's cvs been updated many times since then so though unlikely the fix may still be in there.

[Dolfhin]

what exactly does it do (deblock? dering?) that way it would be easier for someone to create a nice low bitrate test file where the difference is very visible :d

what i know the post-procesing does is :

- automaticly adjusts brightness/contrast (to what ''optimal'' valua's?)
- deblock (remove the ''green blocks'' on mpeg4 codecs)
- dering? (something with the edges of objects, i have no clue)

i suggest to use cartoons (futurama or the simpsons would be great those cartoons contain quite a bit of detail but it might be more visible with southpark) and a extremly low bit-rate for the test video. i'll give things a try myself but unless i can get a decent video in 1/2 try's don't count on it, considering that my rig just isn't suited to encode videos

[GhostDog__]

i almost completely forgot that post-procesing was still broken in xbmc. the video quality has improved so such much this year that it's hard to imagine it getting any better. it would be great to see the results if this bug is eventually fixed. i'm confident the devs will get to the bottom of it.

[Caldor]

@Dolfhin heres some details from divx : its geared towards the divx codec but for our purposes it explains the issues.

***********

because of the way divx compresses images at very low bitrates, phenomena known as "blocking" and "ringing" can sometimes be seen in the picture during playback.
where blocking becomes visible you may begin to recognize that the picture is actually composed of a lot of small squares that move around as the video plays.

de-blocking is a post-processing technique applied by the decoder on the fly to reduce the blocking effect, helping to blend adjacent blocks together smoothly.

ringing is typically most visible around highly contrasting edges in the picture. where ringing occurs it is possible to see subtle bands of color around the contours of these edges.

de-ringing is a post-processing technique applied by the decoder on the fly to remove these faintly colored bands, helping to improve the playback quality.

of the two post-processing filters, de-ringing is the most costly in terms of cpu power for the least improvement in quality.

[Dolfhin]

i did some testing and i found that the difference was visible on the tv very clearly however nothing was really related to post-procesing... turned out my tv reset itself to the default settings because i left it withouth power for 14 days

the default settings include sharpness enabled and dnr (digital noise reduction) and that f*cked everything up so make sure you disable any postprocesing stuff on your tv before doing anytest's

btw : for some good low quality video's try searching for the simpsons on p2p networks and download the ones around 30 mb ofcourse you can only do this if you own the simpsons on dvd, their is no excuse not to have the simpsons on dvd so i assume you do. their's also a torrent site dedicated to southpark that has some very nice real media player version, ofcourse i can't give a link but google can :d

[Dolfhin]

http://divxtest.surdvd.com/article.php3?id_article=58

no idea if this helps but worth the try!

[Caldor]

i discussed this with gamestar17 and i agree with him that at this stage we dont need standard sample media to serve as reference.

to me atleast the important considerations are:

1. is the post processing universally bad across all video container / codec types or is it different?

2. what effect horizontal / vertical deblocking has on display in isolation

3. what effect deringing has on display on isolation

4. what the cumulative effects are of both.

5. what effects the upsampling of resolution or video filters may be having (if any) on post processing.

[jizmo]

you guys probably know this, but htpc users have archieved some amazing results combining ffdshow and high-definition displays (tvs and projectors):

http://htpcnews.com/main.php?id=ffdshowdvd_5

xbmc does a terrific job upscaling the video to 720p, which is really heaps better than 480p, so thanks for that. but, would there be any possibilities to add some sort of light shapen filter that would try to bring out more details from the source material?

i know xbox's cpu doesn't stretch for anything near ffdshow is doing (scaling to 1780x resolutions with multiple filters applied), but some sort of subtle shapen might just cut it - as you might know there are some very speedy algorithms available on net with sources included.

thx for your effords and keep up the good work.

[Gamester17]

@jizmo, ffdshow got most of its postprocessing- filters from mplayer and ffmpeg and xbmc uses both however the function is currently 'broken', moving to existing bug report.

you can help the troubleshooting process by following the intructions given within this topic thread.

[jizmo]

@jizmo, ffdshow got most of its postprocessing- filters from mplayer and ffmpeg and xbmc uses both however the function is currently 'broken', moving to existing bug report.

as it was stated in this thread, the video sources used these days are of such a good quality, that postprocessing filters like dering or deblocking are needed seldomly. while it does mediocre job in hiding the packing artifacts introduced by low bitrate, deblocking generally softens the image, making it even less enjoyable to watch on hd displays.

i'm not too familiar with the post-processing filters mplayer has, but if there's some kind of sharpen filter, please do enable it if you get fixing the bug with xbmc ignoring the filters, as i'm pretty confident it'll bring out some additional detail from dvd in 720p.

now that you mentioned it, i've been wondering before that enabling the filters don't do jack, even with the clips with very visible blocking. this explains a lot.

[Caldor]

just re-enode some media at a low bitrate.

[sssasss]

hello all

i really really hate the image quality issues with xbmc and i am still hoping that the quality will one day be as good as the old xbmp. whenever i want to watch a movie i always see if it works with xbmp 2.4 if it doesn't (some relativly new xvid encodes) i just use the tv-out from the laptop.

question:
is there a way to improve the compatibility of the xbmp.

thanks

[Gamester17]

whenever i want to watch a movie i always see if it works with xbmp 2.4 if it doesn't (some relativly new xvid encodes)

firstly do not double-post! secondly please understand that's your problem is not related to this topic thread, read this (there's a bug in ffmpeg libavcodec qpel decoding)
...xbmp doesn't suffer from that issue with qpel encodes because it doesn't use ffmpeg libavcodec to decode xvid, instead it uses a native xvid decoder (which xbmc don't use)

ps! since this is off-topic for this topic thread please do not continue this discussion here instead post in the existing xvid topic thread.
(by the way, i believe you can deactivate/disable qpel usage in avi video-files without reencoding, try searching on forum.doom9.org)

[sssasss]

sorry for the duble post. and please bear with me

i am not sure i understood you correctly and why this is not related to this topic

but i am having a problem with xbmp not being able to handle some xvid movies i have. they work just fine on xbmc. i don't want to use xbmc because it has worse image quality compared to the old xbmp or my laptop.

i want to update the dlls of the xbmp so it can decode the newly encoded videos (some are xvid1.1 and some are x264 movies).

i am having doubts that the image quality issue with xbmc will ever be fixed

[elupus]

first of.. you are in the xbmc forum.. no support for xbmp here at all.. secondly xbmp never supported dll at all, so forget about that one..