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Old 03-06-2006, 07:38 PM   #1
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linux interlace / video playback - any experts ? - what works??

The short version:

I want to play interlace video e.g. MPEG2 streams or MPEG4 streams back via my PC using an interlace modeline (in my case 720x576@50Hz PAL interlaced or 720x480@60Hz NTSC interlaced - for the few NTSC discs I have).


My main goal is to fit as much DVD quality video on a PC and be able to play it back with as little loss of quality as possible. i.e. a video server with all my DVDs available (complete Xfiles, voyager, tng, futurama, most of SG1, some Simpsons, dilbert, red dwarf, father ted, wonderfalls... and about 150 odd movies etc etc). As I already own the originals and intend to buy more I'm trying to make a practical project out of this (well by my standards :P) as I can always just use the originals, this could in future (if I could just get this damn bit working) include multi room access and I would fully expect all my music CDs too, and eventually the PVR function. I would expect at least 1 500g drive maybe 2, and I would not expect to be able to fit everything in MPEG2 format in this space and would also assume to buy more DVDs etc. I believe my project is more about the video jukebox interface and good quality playback than pure quantity (although it is a factor).

What worked and why I dont like it!

I've been experimenting for several years with different technology (hardware/software) with varying results. This includes the ubiquitous Windows platform (including MCE), Gentoo Linux, mainly XvID encoding, MythTV, KiSS DVD player and a wide variety of deinterlacing techniques etc etc.

Initially I had some good results with GordianKnot and the KiSS DVD player. I found that some stuff deinterlaces better than others and that I'm alot more aware of deinterlacing flicker/ judder than block noise caused by compression when comparing to the original VOB using the KiSS player. I also found that all this experimentation seems to take a long long time when all I want to do is sit and watch the DVDs anyway. I'm also really not keen on the white on black simplistic menu system on the KiSS... it doesnt even have a nice font!! I recently solved the interlacing issue by generating an interlaced mpeg4 avi and replaying it on the KiSS which does give very similar results to the original + a small bit of block noise which I really dont notice at my normal seating position (where as the problems introduced by deinterlacing were quite noticeable). Curiously enough the software deinterlaced mpeg4 avis looked very similar on the LCD monitor (progressive) as it did played back on the KiSS via my Plasma (Panasonic th-42pwd4 via RGB - interlaced). I have tried a multitude of software deinterlacers, including the ones in DScaler, virtual dub, transcode these include the motion adaptive types that are said to do a good job. The only one that seemed to come close was one from alparysoft which although it did a better job on the harder scenes it failed on the most basic one of all!! which all the other software deinterlaces seemed to pass ok. Curiously the MSE figures displayed on Aparysofts web page do seem to tally with my own guestimate of how well the other software deinterlaces do their job. Anyway if I have to spend hours (of my time) encoding ever single DVD/episode really what is the point. The bottom line is the original interlaced material can be encoded and then played back without problem via a hardware player so it should be possible via a standard PC too - with all the nice extra things that a standard PC can do. Although I'm told a negative of interlaced encoding is the requirement for more bitrate (as is not bothering to crop). However encoding speed is very good which is definitely a plus point and I can tolerate wasting a little hard drive space I was getting about 3 times reduction in space when doing a full 720x576 interlaced XvID avi with AC3 - (I didnt experiment much with this as I just wanted to see if I could get it to work) and if I could dump the KiSS player and use better encoding techniques I'm sure I could achieve better.

Now I'm Stuck!!

After experimenting with windows / powerstrip on my ATI radeon 9800 && (p4 3GHz) I did get the relevant interlace modes up. Playback of interlaced material was variable using the interlaced resolution also windows seemed to crash a lot (although probably no more than normal . The worst thing about playback of video in this mode was that it was blurry both temporarly and spaceshally. There was very significant ghosting which I couldnt remove, I did try some other players etc and the settings in the Catalyst driver but it appeared to be a waste of time so I gave up. Most software players seem to have a hard time understanding that an mpeg4 wrapped avi is interlaced as none of the software deinterlacers seem to work properly (not as well as with the original mpeg2 stream if at all). DScaler does try but there are some noticeable horizontal banding artifacts that are not present with the original mpeg2 stream, also other artifacts are present when deinterlacing both streams as mentioned before (flicker and judder mainly).

Eventually after much swearing and cursing I got the interlaced mode lines working under linux (I understand radeon support is limited). This is using the same HW as the above window setup. I run gentoo linux it's a very recent kernel as I only installed a month or so a go (apologies for not know which one - i will look it up later if important - using different box now), i use KDE3.4 and I've mostly gone with what it marked as stable by the gentoo maintainers. However video playback did not seem to work properly when playing an interlaced avi / vob back via these interlaced modes. In fact results seems to be better using a progressive mode ??
XV output was very blurry and the sync seemed to drift in and out when playing back under the interlaced modes - sometimes it worked sometimes not. X11 was sharper but again did not sync up properly (sync is not available under X11?). I know that displaying the fields in the correct order can be a problem for interlace video particularly with the method I'm using which I believe most people refer to as Scart on VGA or something similar. The only time I got it to work was with Xine and setting the deinterlace option on. This seemed to cure the juddering and give what seemed to be a correct output (but only using the original vob and not the interlaced mpeg4 avi). Anyway I dont think the results were as good as my regular DVD player (panasonic) so it seemed like another waste of time. I believe that when playing back interlace mpeg2 streams on via EPIA boards via the TVout & XVMC it is still necessary to use deinterlace to get it to work properly. I tried a whole range of Mplayer filters and got no workable results even with the original vob. I dont know a great deal about linux but the Mplayer manual seems to imply that what I want to do is possible just not exactly how to do it. I havent got OpenGL working properly yet as I couldnt get the interlaced modes working under the ati drivers. I believe there is an open source driver for R300 chips but that it is not complete yet - I havent tried this yet, as a result Mplayer did work but was very slow under OpenGL - couldnt see interlacing artifacts but video was so slow it was unusable - as is OpenGL screen saver. Couldnt get vidix working at all dont know why or whether it would help? (believe that it requires more drivers that I dont have). If someone knows whether OpenGL output would work that would help as I've kind of run out of energy, I didnt dream that something that sounds so easy could be such a pain, afterall I'm just trying to do exactly what a regular DVD player does i.e. output interlaced video correctly synced up.

So in summary the hardware deinterlacer in the Panny is still better than any software deinterlacer I've seen to date (although I'm not sure its anything special in relative terms), software deinterlacers seem to mess up the original fields meaning that the progressive frames do not interlace in the same way as the original interlaced fields and the hardware deinterlacer is no longer able to properly do its job - this is in part caused by shifting from 50fields per second down to 25 frames per second - presumably one of the fields is changed in order to generate the new frame. Anyway surely someone somewhere has managed to get interlaced video playing back correctly via interlaced RGB output from a VGA socket to a regular TV / Plasma display? I know that it may be dependant on hardware support etc but I'm willing to consider something different if it does the job e.g. Nvidia GFX card? I looked at alternate solutions such as DVD changers (standalone and PC based) but it's not really what I want although I do believe that Sony may release there's but it will probably be more expensive than a bunch of HDs of equivalent storage! Besides its really part of a MCE solution and I really don't want to give M$ any more money so as they can tell me how I can use what I've just purchased and prevent me from doing all the obvious things I might want to do with it.

Sorry for the length of my post and if it sounds like i'm being unecesarily fussy hopefully someone knows how to get this working )


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