Picture quality issues - signal? hardware? scaling? codecs? (1 Viewer)

[MPM]

I've been a happy MP user for a while now and my TV watching was primarily about displaying standard analogue (cable) signal to a good old "fat" TV (CRT). And I was happy with picture quality...

Couple of weeks ago, my new adventure started as I performed a major hardware upgrade in my living room. I bought new LCD TV, installed new hardware in HTPC, installed new version of MP (using TV-server for the first time) and on top of it all hooked up dreambox to MP. Surprisingly enough, installation went smoothly and I got it all working in a day or so - but I'm now dissapointed with picture quality when watching TV through MP.

It's difficult to describe the issue, but basically the picture is very "fuzzy". With any movement there is a sort of "floating" happening on all lines. If there is a zoom shot of somebody talking, it looks like his facial lines are melting all the time - and if (s)he moves the head, all the lines are sort of dragging behind...

And the worst thing is that I have no clue where to start searching since this set-up is confusing me. I'm more or less surprised that it works at all...

To eliminate some of the variables, if I connect the dreambox (500C) directly to my TV (Samsung LE46B535) through either SCART or S-video, picture looks just fine. The dreambox is set to 16:9 screen type and TV to "auto wide" option and the picture looks good regardless of th input signal picture ratio (i.e. both 4:3 and 16:9).

- With MP (1.0.2), I connect dreambox to the TV-card (PVR-250) through S-video.
- The TV-server is configured to get signals through CVBS #1.
- I have a Gigabyte MA780G-UD3H board with on-board Radeon HD3200 and desktop resolution is 1920x1080
(and I'm very happy with quality of all other video (both HD and SD) except for TV)
- I'm using ffdshow for MPEG-2 and MPC - Video Decoder for H.264
(however, running GraphEdit during TV watching shows that MPC - MPEG-2 (Gabest) is used?!?)
- TV is set to "Screen Fit" (i.e. 1:1 pixel mapping)

Now, if I set MP zoom mode to "original", the picture looks just fine! Of course, watching a 720x576 video in original resolution on a 1920x1080 TV isn't that fun...

If I set the zoom mode to "stretch" or "zoom", I will experience all the issues I've described above.
Any thoughts?

(To add to my confusion, using "normal" zoom mode will always leave black stripes around the picture when watching TV - that's why I have to go with "stretch" or "zoom". But if I watch a DVD through MP, the picture will fill the screen in the "normal" mode although the resolution is same as TV picture, i.e. 720x576... Not sure if this is related to my problem or not...)

Apologies for this lengthy description, but if you've managed to read it I'll be thankful for any tips!
Thanks,
MPM

 

[velis]

I have the same problem as you.
I believe the culprit here is renderer scaling algorithm.
The scaling is done with the pathetic block method instead of a more sophisticated one like Lanczos or Spline.

I haven't yet started digging through code so I'm not sure how the scaling is actually implemented, but I'm pretty sure the algorithm is bad. One can see algorithm idiocracies on stationary feed with recognizable 2D elements like letters or lines. Instead of nice aliasing, they are blocky as hell!

The reason you interpret the picture as fuzzy is precisely because of this: A small change in source image (TV feed) causes a relatively large change in the rezised output (a block of multiple pixels). Since with somebody talking close-up, not much changes in the source, the remaining few changes make a huge impact in overall picture quality.

One of the reasons I'm attempting to pinpoint the reason for ffdshow ban in TsReader. I want ffdshow as the TV playback codec since it can do nice resizing. With a full HD picture to work with even this scaler does a much better job...

Said differently: if you set your resolution to 720x576 (even if it were possible), your TV will do the scaling and do it much better than MP. But you won't be able to enjoy the full HD content then...

 

[frenzy]

Set a different codec for mpeg playback (e.g.mpc) and ffdshow as a post-processing filter (enable RAW-all supported in ffdshow config).

 

[velis]

Tried that.
For some reason, playback gets jerky with that even if only 30% CPU is used (60% of one core).

 

[frenzy]

Untick all the filters you have turned on, turn on the OSD in ffdshow, watch the Decoder fps and make sure it's stable at 25 or 30fps (pal and ntsc respectively). Then start turning on filters one by one and see which one is causing most load (usually resize or sharpen will make the fps to drop at 23-28 occasionally). Also set NV12 as the output colorspace and tick the set interlaced flag. Works great here in numerous installations and many versions of ffdshow

 

[MPM]

After some more experimenting I pinpointed my issues to the S-video connection I used to get the signal from Dreambox. Have since my last post played with DVBLink and DVB-C cards and haven't experienced the same problem again. Although you state that you have the same problem, it doesn't sound to me like you are using S-video in, are you?

Your reasoning is still applicable as the picture looks fine in the original resolution even with S-video signal, so there is something weird going on when MP processes the signal. Fortunately, I don't have the same problem (which is also somewhat strange?) since I gave up on the S-video input...

 

[velis]

You're right. I wasn't reading your OP with attention and figured that S-video works and digital connection doesn't. :sorry:

Though I can't understand how your HD could be transmitted through S-video. Isn't that like the old SD protocol? Resolution on output should be at best PAL. At least I never could select a resolution higher than PAL for my SD outputs (used to do this with NV 6600GT --> PAL CRT TV).
If it's somehow HD, all my reasoning still applies since you get all the pixels. EVR just doesn't have good scaling algorithms.

 

[velis]

Untick all the filters you have turned on, turn on the OSD in ffdshow, watch the Decoder fps and make sure it's stable at 25 or 30fps (pal and ntsc respectively). Then start turning on filters one by one and see which one is causing most load (usually resize or sharpen will make the fps to drop at 23-28 occasionally). Also set NV12 as the output colorspace and tick the set interlaced flag. Works great here in numerous installations and many versions of ffdshow

Thanks. It seems to be working, though with quite high CPU usage. ffdshow takes about 70% CPU per frame with cropping, deinterlacer, postprocessing, sharpening and resizing. Resizing to full HD itself takes 40% time. I may need to revert my Athlon II to stock speed.
I'm having some issues though. Video playback isn't guaranteed. Sometimes it just won't play. Perhaps the culprit is too much experimentation (filters on/off, etc).

Dam, I seem to have hijacked the thread now.

 

[frenzy]

Thanks. It seems to be working, though with quite high CPU usage. ffdshow takes about 70% CPU per frame with cropping, deinterlacer, postprocessing, sharpening and resizing. Resizing to full HD itself takes 40% time. I may need to revert my Athlon II to stock speed.
I'm having some issues though. Video playback isn't guaranteed. Sometimes it just won't play. Perhaps the culprit is too much experimentation (filters on/off, etc).

Dam, I seem to have hijacked the thread now.

You don't need cropping you can set that in MP, turn off deinterlacing too-the instructions I gave you are for HW deinterlacing, don't resize when doing that, postprocessing OR sharpening better not use both or just use the resizer and set sharpening and blur values from there. Keep in mind that some filters don't work with each other and some need to be in a specific order. For example:
Postprocessing must be placed before other filters to avoid high cpu usage.
Blur and sharpen go after deinterlacing
Subs go after resizing.
etc.

You don't need to resize to full HD you'll see that 720p is fine. Personally I prefer HW deinterlacing than resizing, so I gave it up altogether.

 

[MPM]

>> Dam, I seem to have hijacked the thread now.

Yes, you did... But that's all good as my problem doesn't matter any more and it's good that you are getting help!

I never said I was getting HD through S-video. I was getting 720x576 and the entire issue was basically happening when MP was scaling that up to 1920x1080 to display on my HD TV...

Hmmm... Did you read my post at all or do you just randomly pick threads to hijack?