Stange decoder problem... blue shadow on some things?

[Jeffster]

Greetings,

I'm new to XviD and have encountered a strange problem while playing back a test encode. It's hard for me to explain, but there are very light blue shadows appearing from time to time on the edge of faces, bodies or objects.

At first I thought it was an encoder problem (I am using Koepi's latest build 24062003), so loaded the defaults with the same result. Then I tried earlier builds from Koepi and umaniac's site, stil the same.

I wanted to take a screenshot to show what I am talking about, but I discovered when I load the encoded clip in VirtualDub (vfw) that the problem is not there anymore. I've come to the conclusion the encode is ok but the DS decoder is causing it.

The problem appears in WMP6.4, ZoomPlayer and MPC using ffdshow (latest build), the Xvid decoder from installed Koepi and umaniac builds and also Nic's standalone Xvid decoder.

Being curious, I changed the FourCC code of the encoded clip to Divx and played it in WMP using the DivX decoder. The DivX decoder displays it correctly, true to the original. Weird!

My graphics card is Asus v7100 GeForce 2, OS is Win2k and Celeron 1000 (tualatin) CPU.

I already searched the forum before deciding to post and was unable to find anything resembling this. If I have missed a post though, I apologize in advance for writing this.

As I was unable to make a screenshot of what I am describing, I did my best to emulate it in Photoshop. If anyone is interested, I've uploaded 2 examples you may look at, bearing in mind it not the actual screenshot but fairly close. I hope that is OK?

clip 1 (original) (http://homepages.ihug.co.nz/~jefx/doom9/clip1_original.jpg) (61 KB)
clip 1 (xvid) (http://homepages.ihug.co.nz/~jefx/doom9/clip1_xvid.jpg) (71 KB)
clip 2 (original) (http://homepages.ihug.co.nz/~jefx/doom9/clip2_original.jpg) (46 KB)
clip 2 (xvid) (http://homepages.ihug.co.nz/~jefx/doom9/clip2_xvid.jpg) (57 KB)

Also if anyone is interested, I have uploaded a short sample those shots are from, if you want to download it and see if you can see it too.

xvid_sample.avi (http://homepages.ihug.co.nz/~jefx/doom9/xvid_sample.avi) (3.7 MB)

Thank you for your time, and I hope I have covered everything I'm supposed to when posting.

Regards,
Jeff

[greycortex]

Using mplayer in Linux, I cannot reproduce these artefacts. Try checking "use xvid" in the codecs screen of ffdshow.

[Jeffster]

Thanks for your reply and taking the time to look at it.

With ffdshow I have tried it with both libavcodec and xvid enabled, and have the same problem. In fact the only decoder that plays it correctly on my PC is the DivX one.

Something else I have discovered... if I pause the movie and minimize it, when I restore the window the artifacts are gone. Now if I continue to play the file, all will be ok until the next scene change, then it is back again.

Regards
Jeff

[greycortex]

Is ffdshow the only filter that you have installed? Do you have anything else like ffmpeg installed for example? What I want to know is: if you keep the FOURCC code correct (xvid), what does the filter graph look like if you fire up graphedit?

[OBcecado]

Hi, it's playable here, no blue shadows or anything like that, I got 23 may's ffdshow and koepi's 24062003 build, also i got XviD's IDTC enabled in ffdshow.


Greetz.

[Jeffster]

@ greycortex
Just ffdshow and the xvid decoder... and since you ask, the graph looks like below:
sample.avi > Avi Splitter > ffdshow MPEG-4 Video Decoder > Video Renderer

@ OBcecado
Thanks... I guess it must be a system related thing then. I have the same builds of ffdshow and XviD codec as you (with Xvid IDTC enabled in ffdshow). It still seems odd to me though.

As a final note, I read while searching that you can take a screenshot of WMP by setting hardware acceleration to None in WMP Options. When I set the hardware acceleration to None the blue shadow disappeared, thus spoiling my attempt to grab a screenshot of this, but perhaps it means something, I'm just not sure what?
:confused:

Regards
Jeff

[OBcecado]

Have you tried to use the grab function of ffdshow ?
It might be your graphics drivers that are outdated (if it's nvidia i've had some drivers that delivered bad output at some colorspaces).



Cheers.

[Shalcker]

Originally posted by Jeffster
As a final note, I read while searching that you can take a screenshot of WMP by setting hardware acceleration to None in WMP Options. When I set the hardware acceleration to None the blue shadow disappeared
Looks like overlay-related problem (perhaps with certain colorspace).
When you set hardware acceleration to None overlay is disabled as far as i know.

Check output colorspace in FFDSHOW for xvid and divx playback.
If they differ, try forcing another colorspace for xvid.

[Jeffster]

Thanks Shalcker! Well, I think I have this kinda figured out now.

ffdshow and presumably xvid defaults to YV12 output, whereas I think the divx decoder must default to YUY2 output. When I enable "yuv extended mode" in the divx filter (which enables YV12 output), then divx clips now show this same blue artifact.

It appears that my video card (Ge Force 2) does indeed have overlay problems in YV12 colorspace. It's a pretty common card too.

So now I have a couple of questions, and I thank you for your patience with me so far :)
I currently have all colorspaces enabled in ffdshow... do you have a preferred colorspace enabled for decoding, should I disable some of them, and is YV12 mode ok? (apart from my problem of course)

If you use the default YV12 output and don't have these artifacts, what graphics card do you have?

Thanks to you all

Regards
Jeff

@ OBcecado
I installed the latest nVidia drivers but it made no difference.

[Lobuz]

At last someone noticed it too. I posted about it a few times at that forum but apparently all those video gurus with GForce 2 cards are just simple blind. :devil:

I use just YUY2 and it's ok. With YV12 its even more CPU usage, propably cause nvidia buggy drivers conversion.

The same problem is with WM9 it's default to YV12. It can be solved by using ffdshow only for colour conversion.

It can be solved too be shifitng luma or chroma offset with ffdshow by 2 (at my card).

It could be really useful for XviD sake to set defaul color space to YUY2 cause less experienced users could think that's xvid related. :(

My raphics card is Winfast GForce2Pro64.

Regards
Lobuz

[Koepi]

Lobuz,

that's damn close to a rule 4.

If you'd read the FAQ and the posts before yours in this thread, you'd notice that some drivers for nvidia have that issue - and some not. (To make it worse, it seems to depend on chip revisions. I had a GF2 and didn't encounter that problem.)

try different driver versions.

Do not stick to your manufacturer's drivers but use the ones from the nvidia website.

Koepi

[Lobuz]

@Koepi

There's no need to be angry. I was just irritated that no one noticed it for a few months ( since defaulted yv12 ). I just use latest drivers from nvidia or guru3d site with thesame effect.

Anyway it's hard to notice with most clips but with some that's annoying. That's why I want to ask if You checked that posted clip with yv12 and yuy2 color space. The bug is visible at those prepared pics at the first post.

In that way we could proof that some cards are bugged but others not.
I really would like to find better solution that telling xvid users to "check your card and | or not change output color space".

Regards
Lobuz

[Koepi]

I watched the clip on my Gf4mx without any problems (well, some details are quantized away too heavily etc., but that's the clip itself ;) ).

Koepi

[Lobuz]

It's good to hear that GF4 is ok. ;)
But if someone have GF2 based card it could be useful to check it with that clip and see if there is that shifted blue line with YV12 instead of YUY2 output.

Regards
Lobuz

[ChronoReverse]

Confirmed that with a GF2mx, using the 44.03_win2kxp_international.exe drivers when decoding using ffdshow-20030422.exe with the yv12 checkbox checked, the blue shadow appears. Disappears when yv12 is unchecked. Unchecking and checking Use Xvid doesn't matter.

[emiisdev]

Hi there,

I know the last post was a while ago but I found this thread while trying to solve a problem with blue 'streaks'/'ghosts'/'artifcact' in my encoded xvid videos. I have the same exact problem as described above (in windows media player and media player classic) when i view the video in virtual dub there are no problems whatsoever.

I'm a little confused with what the solution was above? Have I encoded these videos wrong? Should I re-encode them in the YV12 colorspace? (I can't even find that option with Gordian Knot) Is there a setting in media player classic that i need to adjust or is it in the ffdshow options?

Can anyone help with a little guidance?

Thanks much

Emi

[foxyshadis]

In ffdshow config, under output, uncheck YV12, but leave the other modes. It should work then. Opening in vdub works because vdub sends it to the card in rgb.

[imcold]

Should I re-encode them in the YV12 colorspace?

XviD videos are in YV12... always. It's the colorspace of all MPEG4 (p2) codecs.