Picture quality from HTPCs in general

[bolders]

Hi

Ive suffered from stuttering playback with my HTPCs for years and have considered on many occasions giving up on using a HTPC for video playback however in the last month or 2 I seem to have managed to get my TV playback running perfectly.

I am also using the gigabyte 780g MB but I have a 4450 chip (2.3GHz) its using the F3 bios which is what it came with and I have catalyst 8.5 drivers installed. I use the Nvidia pure video decoder with the MPA audio decoder, hardware acceleration is on and the system is totaly stable (TV runs quite happily through the night and on into the nest day).

Im running XP SP2 and use a Nova T 500 and PVR150. The picture quality from my Nova T is excellent (especially BBC channels which seem to provide a very good quality transmission) and its easily as good, if not better than, my NTL box connected directly to my TV - I really cant tell the difference anymore. If im watching channels from my NTL box passed through my PVR 150 then picture quality is not quite as good and it never will be as there is another stage of conversion going on. Having to use composite instead of RGB (scart) doesnt help either but playback is still smooth. When i bring up FPS i get 25FPS constantly (although sometimes it reads 50FPS - havent figured out why tho).

I also use 1280x720 @50Hz and have vsync set to always on. I know this info doesnt really help much but i just wanted to make you aware that smooth playback is definately possible although im quite happy to go through all my settings with you to see if there are any differences between our system configs. Before I got the TV running smooth I always questioned if it was possible with a PC (especially after reading the text file supplied with reclock - has some very good info). I always wondered if people who said there playback was smooth were just not critical enough, however I am now satisfied that it really is possible.

Again im sorry I cant provide any real help but i will add that im sure all my problems were to do with syncing issues between video frame rate and tv refresh rate. I think any modern PC has more than enough power to decode an mpeg 2 stream. Especially considering my rig plays back a 720p rip of starwars (which has a frame rate of 25FPS) perfectly using coreAVC which uses software acceleration.

bolders

[KevL]

Many thnks Bolder, your observations give me hope - especially as my hardware is almost the same as yours.

I've not tried the Nvidia codec recently. I will try to get hold of a copy.

I have to say I'm being very critical in my judgement of picture quality. My TV has bucket loads of settings and only after I spent many days setting up input from my set top boxes did the difference become noticable. Most of the TV setting improvements involved switching off all manner of filtering and picture "improvement" settings in the TV. I now get very good pictures from all sources.

HTPC is very watchable but it does lack smoothness.

You might be able to get your PVR150 to give a better picture by using ChrisTweaks. This allows you to change the operation of the BT chip and tweak up the video settings. It gives access similar to the settings which used to be avaliable on DScaler on analogue cards.

When you say that you get 25fps continuously do you mean that when you do the shift1 (!) thing on MP video it says 25.00 fps continuously? (as I posted mine says 24.xx to 25.xx with about 3 values.)

I have not tried ! on HD material yet but I too use the CoreAVC codec.
Let me play some more with my settings (at the pc end) and see how I get on. Maybe when I have done some more experimenting I will start a thread on optimum settings for the GA78GM Mainboard. I suspect this will be useful as the MB is very popular and I bet I'm not alone in having judder issues.

@Paranoid Delusion

Did my Shift1 results suggest any particular problem? Is jitter the issue here? Is jitter a measurement number a measure of when the video frame is sent to the TV or when the renderer recieved the from from the mpeg decoder codec?


Kev

[KevL]

Hi Bolder.

Tried The NVidia Pure Video decoder.

I think overall the picture is now smoother. Less judder. Picure has a tad more video noise but I probably need to tweak the decoder settings.

Hitting shift! gives same results as with cyberlink decoders. Text on Bloomberg ticker is better but still not a patch on my set top boxes.


Many thanks.

Kev

[Bascombe]

Nice to see the xcard mentioned in a thread about picture quality. I'm still using one, and its a great piece of hardware. Despite the fact that it seems to have become the unloved, ugly step child of the htpc development community, threads like this underline the fact that in many ways it remains relevant - particularly when you consider that there's still a sector of the AV community who consider crt pictures better than those of LCDs/plasmas. TVedia 4.2 (now 2 years old) was its last great hurrah, just very unfortunate that it didnt include pvr functionality. I still live in hope that some inspired soul will make a plugin that integrates it fully into mediaportal - either that or develop a tvedia plugin that integrates the mediaportal tv engine!

[bigj]

Check exlcusive dx mode is enabled.
Check that you haven't disabled vsync via a gfx driver tweak.
Try powerstrip to set custom timings that are closer to true 50hz

I run 50hz interlaced on PAL CRT via VGA->SCART - occasional stutters due to system load, but otherwise good jitter free picture as good as STB.

re: purevideo codec -- it generates 50fps when deinterlacing (e.g news/sports channels.) IIRC.

[myriad]

It sounds like your problem could be an interlace issue (i). Are you watching an interlaced format (1080i)?

[KevL]

Hi

Picture quality issues may well be something to do with interlacing.

Im watching PAL SD DVB transmissions mainly.

I do also have a couple of PAL HD channels to watch.

I have the ATI catalyst driver 8.4 set to output 1280x720p @ 50Hz via HDMI to a pioneer plasma. This reports 1280x720 @50Hz.

I'm now using the Nvidia Pure Video decoder for Mpeg2 decode (following Bolders kind recommendation) and CoreAVC for HD decode.


MP is configured as follows.

VMR9 ON
Use for playback of webstreams = ON
Use Exclusive mode = ON
Use Nons square mixing for scaling = ON
Filtering Mode = None

NVidea PureVvideo
Use Hardwarte Acceleration = ON
De-Interlace Control = Automatic
De-Interlace Mode = VMR Default
Colour Scheme = Default
Adio Decoder External Reciever = SPDIF Mode


ATI driver is configured as follows.

Display Manager Select display on HD3200 = Pioneer_PDP (single)
Display Manager Desktop Area = 1280x720
Display Manager Colour Quality = 32bit
Display Manager Refresh Rate = 50Hz
Wait for vertical Refresh = always ON.
3d Refresh rate override = 50Hz
AVIVO Video Basic Quality = use automatic deinterlacing

I have also applied the ATI Tweak registry settings from here http://exdeus.home.comcast.net/~exde...weaks_0.14.vbs. These clean up picture quality and set video levels to 0-256 for SD and HD output to get black blacks from all sources.


So, lots of Auto settings for deinterlacing. To be honest find the whole dinterlacing thing confusing for video playback. I understand exactly what deinterlacing is but am not sure of the implications of settings various bits in the playback chain to do it or not to do it etc. Presumably if the ATI card does the deinterlacing then it will be best since it will use its hardware engine to do the job. But since the purevideo decoder uses HA then maybe this doesnt matter???? But then I've read that VMR9 thing also does deinterlacing?????? Maybe my picture is being over deinterlaced

HTPCs are Bloody complicated .

Kev

[gxtracker]

Have you tried setting any of the interlace settings from auto to forced or something similar?

When I built a HTPC for my parents, image quality was one of the largest factors I considered. I knew that my father would complain if the picture didnt look just as good as it did on his stand alone DVD player since he's a bit of an A/V-phile.

I used FFDshow tryouts with an ATI 9550 card in their system - no CCC, no purevideo decoder, just the driver and ATI tray tools for configuration of VSYNC and other miscellaneous settings.

Interlaced content was the only hurdle I encountered to resolve picture quality issues. Sporting events, news programs, and some live TV shows are all shot and trasmitted interlaced, so recordings we being played back with a low and stuttering framerate.

I tried various interlacing settings in the driver, in the VMR filter, but the best setting I used was hardware de-interlacing in FFDshow. This made the picture identical to anything that was coming out of the STB.

So resolving picture quality issues can be difficult, but they really can be overcome.

[robyf]

Originally Posted by gxtracker

I tried various interlacing settings in the driver, in the VMR filter, but the best setting I used was hardware de-interlacing in FFDshow. This made the picture identical to anything that was coming out of the STB.

So resolving picture quality issues can be difficult, but they really can be overcome.

Didn't know ffdshow was capable of hardware deinterlacing. So did you set ffdshow as mpeg2 renderer or did you use some other codec and ffdshow deinterlacing as post-processing filter?

[KevL]

I'm confused by all sthis stuff also.

I have used FFDShow as a post processor in the past. I used it to do some picture enhancement (denoise and sharpen). I know it can also be used as a scaler and deinterlacer and an MPeg decoder. I didn't realise it could be made to use the graphics card as a hardware accelerator. I thought it was a software filter.

All of my source material is interlaced. I think I'm right in saying that almost all video formats are interlaced.

All PAL SD formats (DVB broadcasts and DVDs) are 576i @25Hz, I think that BBC HD is 1080i@25Hz. So deinterlcacing is needed somewhere (if I want to send my video to my TV as a 720p format at 50Hz).

My problem is that I'm not sure which bit in the chain should be set to do the deinterlacing and how to set the other bits up so that they dont do it. And how VRM9 fits into all this is another mystery.


Kev