View Full Version : Video quality (de-interlacing, upsampling) on ISOs
gfairbanks
2008-08-08, 23:24
I'm glad that ISO images are playing, and have been for some time now on the linux port. The quality of the video image seems to be worse than for other types of video, including the same disc if I convert it to (say) h264 using HandBrake. Specifically, (1) while I can select various de-interlacing algorithms, none seem to work great, and (2) I'm no expert but it's not clear that the image is being upsampled -- my display is 720p.
I've been running the a2 build, but I also tested this from a fresh SVN pull yesterday.
If this is a known issue then that's ok -- I just want to know if anyone else is seeing this and/or if it's future work.
1) In Settings - Videos - Player; set your resolution to match the display, 1280x720 or 720p
2) in the same window try enabling high quality upscaling, using the bicubic or lanczos modes.
3) As for de-interlacing I'm not sure what the best mode is XBMC linux, but in XBMC-xbox it's bob or bob inverted to my knowledge.
it's my belief that our deinterlacers are broken in linuxbranch.
I have no other explanation for the endresult after eg, BOB deinterlace (bob is supposed to work for both for interlaced and progressive outputs)
There is an option under Settings/Video/Players to enable HQ Software Upscaling or something similar, this too is broken I think ?
Wouldn't it be simpler to hook into the FFDshow deinterlacers rather than custom written ones on the linux port? Same as the HQ upscaling? why re-invent the wheel right?
ffmpeg deinterlacers should be used when you select deinterlace from interlace handling.
so is that the best quality mode? I think its not recommended on xbox because of performance issues but given the excess horsepower on most htpcs maybe that should be default for interlaced content.
Deinterlace: Deinterlace crashes on Intel GM965 though
ah, infernal intel chipsets lol, the foil of many a good idea.
gfairbanks
2008-08-09, 00:24
1) In Settings - Videos - Player; set your resolution to match the display, 1280x720 or 720p
2) in the same window try enabling high quality upscaling, using the bicubic or lanczos modes.
3) As for de-interlacing I'm not sure what the best mode is XBMC linux, but in XBMC-xbox it's bob or bob inverted to my knowledge.
Tried this and my results are much better. The resulting discussion has been very informative. In my testing, using the "no deinterlace" with the above 1-3 worked best, certainly much better than before, but perhaps not quite as good as ripping using HandBrake.
can we do some definitive testing to find out if de-interlacing is broken or not? I'm unsure how to go about such a test. Presumably if it is someone should open a bug on trac for it.
in my opinion its a fairly big deal, dvd playback is a big part of htpc for me, aswell as a great deal of OTA content (think mythTV) is mpeg2 with various interlacing schemes.
I'm not sure either. Here's an interlaced NTSC vob uncompressed from DVD
First is None (no de-interlacing), Second is BOB
http://img255.imageshack.us/img255/5553/deinterlacetestnonebobjp4.png
Difference is not big at the org res (which this is. no scaling).
It's even less difference when you output it onto a BLURRY old crt tv. Which I don't since I recently went HD
Now here are similar positions in video stream, zoomed to fill screen in 1080p. no HQ SW Upscale. I had to resize shots to 1280x720 due to PNG size.
First shot has BOB de-interlace applied, it can be seen that the image is quite blurry, but it STILL has visible interlace artifacts:
http://img523.imageshack.us/img523/2204/screenshot359uu8.png
2nd shot has no de-interlacing applied. And I guess you have to be blind to miss the Interlacing in video:
http://img376.imageshack.us/img376/1994/screenshot360sf8.png
Might it be a good idea to invite someone like Lyris ( Lyris-Lite (http://www.lyris-lite.net/reviews.html) ) who reviews de-interlacing DVD players all the time to comment on the performance of XBMC?
oh, also I think your first link there is broken Pike, won't load for me.
Silverbolt
2008-08-26, 03:21
I'm a really big fan of XBMC, and I've used it on Xbox for a long time. I want to build an HTPC to play HD video files, so I love the idea of using the same software, but the only things really stopping me are a couple of deinterlacing problems.
The first problem is with the bob deinterlacer in the Linux port. It doesn't double the frame rate. The Xbox version properly deinterlaces to 60 FPS, but the Linux version deinterlaces to only 30 FPS. I watch a lot of pure interlaced video like sports and concerts, so the difference is really noticeable. This could also be the cause of the issue pike is seeing. All non-adaptive deinterlacers create jaggies like those seen in pike's screenshots, but they're invisible when the deinterlacer properly outputs both fields, which doubles the frame rate.
The second deinterlacing problem is with field order in DVDPlayer. The Xbox version is the only one with a fully working bob deinterlacer, so I can only see this problem on that platform, but it may also affect the Linux version. DVDPlayer doesn't detect the field order of MPEG-4 ASP (DivX, XviD) videos. It works fine with MPEG-2, but for MPEG-4, it always assumes bottom field first. Unfortunately, every interlaced video I have is top field first, so I always get stuttery video when I use Bob in DVDPlayer. Switching to Bob (Inverted) is a workaround, but I set the default to Auto Select, which always uses Bob when it detects interlaced video and results in stuttery video. I think even just changing DVDPlayer to assume top field first for MPEG-4 videos would be good because most interlaced videos are top field first. I think DV cameras are the only common devices that use bottom field first.
Really, it's just the first problem that's stopping me from leaving the Xbox and going with an HTPC. The second issue has an easy workaround. I've tried other HTPC media center software, and none are as good as XBMC. No installing tons of DirectShow filters. No going through dozens of configuration pages. It just works.
Gamester17
2008-08-26, 18:01
if they are bugs or feature requests then submit new tickets (after searching) to our tracking system http://xbmc.org/trac