Video capturing problem.

MCMLXXXVIII · **Posted:** Tue Jun 17, 2008 8:51 pm **Post subject:** Video capturing problem.

I've ripped a movie and used VirtualDub to make screenshots, but it plays and makes captures with a weird 'stepping' effect round the edges of intense colours (especially red) as seen here:

However, when I play it using MPC or VLC the effect isn't there, but it is when I make a capture.

Can anyone see the effect (means it is a fault of the rip) or not (a fault in my graphics card or VDub?)

spudthedestroyer

That will be 4:2:0 chroma subsampling done by your graphics card:
http://en.wikipedia.org/wiki/Chroma_subsampling
Its related to your colour space which is the way its storing colour information; when you get to the extremes of what it can store you get that lego mess.

That is why you have to be really careful with operations that involve changing colour space when ripping and filtering, you loose information and get that effect that almost looks like an interlacing problem on colour edges.

elchupacabra

Hmmm... I can't see any red steppding effect on the screenshot.

spudthedestroyer

elchupacabra wrote:

Hmmm... I can't see any red steppding effect on the screenshot.

Your monitor sucks balls, there's chroma problems all around the red :lol:

Just to follow on, the reason why a 'crap' colour space is used is to save bandwidth, as it says on the wiki link the human eye isn't entirely perceptive of the entire colour space which is why it uses it... results in a smoother capture.

I did some googling but don't know any filters (there's a man who will though, everyone knows who he is :lol:

)... pages like this:
http://www.adamwilt.com/SteppyEdges.html
Suggest turning off chroma blur / playing with the capture settings.

If you are capturing as DV avi, another dv codec maybe better... if its as MPEG2, they have chroma problems of their own but i think the problem is the graphics card. Try google for the card itself, people will have the same problem and hopefully there's some fix for it

elchupacabra

Ahhh now I see. I was actually looking at the edges of the screen and not the red cape. :lol:

Sorry folks. :oops:

MCMLXXXVIII

So the problem is with the method I'm using to make screenshots rather than the rip itself then?

I've just made a cap of another movie and it is there too.

I can provide an avi snippet of the above scene if anyone wants to check it on their PC.

If it's just the way screengrabs are created on my PC, then I can live with that for now I suppose as long as the rip is okay.

Maybe a drive update for the video card will help. :roll:

DxaKrator

What vid card is it?Is this a capture card or something that is built into your video card?I used to capture with the input in on my old video card but I would get substandard results..watchable...but not great like I wanted it..so I went out and got a capture card and life is a dream :mrgreen:

..so it very well may be your card itself in which case possibly a driver update might work(but probably not)..or trying a different capture codec..which one are you using now?Does the maker of the card have a forum or anything to see what other people say about it?

MCMLXXXVIII

No, I'm not referring to recording from an external source, I'm meaning making screengrabs from DVD rips.

Not sure if that's what spud thought I meant now.

spudthedestroyer

I'm actually suggesting the flaw is with the ripping method.

It could easily be the screenshot if you performed a colour scheme transform when saving the picture, however, read the section on 4:2:0 chroma on the wiki link i posted...

MCMLXXXVIII

I haven't tried updating the graphics driver yet, hopefully it is that. This is certainly something new (I would have spotted this earlier if it wasn't).

If anyone wants to view the above scene from the rip and confirm or deny the chroma artifacts, it's here:

http://www.evilshare.com/08f4cbc6-8f74- ... 0b6aa2a5f8

elchupacabra

It's not your driver. For me it looks the same as on the screenshot.

MCMLXXXVIII

elchupacabra wrote:

It's not your driver. For me it looks the same as on the screenshot.

Really? For me it's fine.

Confused now.

elchupacabra

What exactly did you change?

MCMLXXXVIII

elchupacabra wrote:

What exactly did you change?

I haven't changed anything (I think).

I've updated the graphics card driver and there seems to be no change.

elchupacabra

I don't understand. Does the red jacket still look bad on the edges or not?

For me it does, which should mean that the rip is bad.

spudthedestroyer

you need to post the source, not the end rip... the problem can be any filtering you are doing, for example ConvertToYUV(), ConvertToRGB() would probably mess things up too.

MCMLXXXVIII

spudthedestroyer wrote:

you need to post the source, not the end rip... the problem can be any filtering you are doing, for example ConvertToYUV(), ConvertToRGB() would probably mess things up too.

I'm only using the Lanczos resize filter that comes with gknot as standard, nothing else as far as I know. Same as any of my rips.

Code:

[ About file ]

Name: guitar.avi
Date: 17/06/2008 01:10:40
Size: 780,949,504 bytes (744.771 MB)

[ Generic infos ]

Play duration: 01:18:35 (4715 s)
Container type: AVI OpenDML
Number of streams: 2
Type of stream nr. 0: video
Type of stream nr. 1: audio
Audio streams: 1
ISFT: VirtualDubMod 1.5.10.2 (build 2540/release)
JUNK: VirtualDubMod build 2540/release

[ Relevant data ]

Resolution: 576 x 320
Width: multiple of 32
Height: multiple of 32
Average DRF: 4.778973
Standard deviation: 1.129003
Std. dev. weighted mean: 0.764832

[ Video track ]

FourCC: xvid/XVID
Resolution: 576 x 320
Frame aspect ratio: 9:5 = 1.8
Pixel aspect ratio: 1:1 = 1
Display aspect ratio: 9:5 = 1.8
Framerate: 25 fps
Number of frames: 117875
Stream size: 549,712,538 bytes
Bitrate: 932.704200 kbps
Qf: 0.202409
Key frames: 1487 (0; 167; 467; 744; 856; ... 117709)
Null frames: 0
Min key int: 1
Max key int: 300
Avg key int: 79.270342
Delay: 0 ms

[ Audio track ]

Audio tag: 0x2000 (AC3)
Bitrate (container): 384 kbps CBR
Channels (container): 6
Sample rate (container): 48000 Hz
Chunks: 117447
Stream size: 225,518,592 bytes
Preload: 480 ms
Max A/V diff: 496 ms
AC-3 frames: 146822
Play duration: 01:18:18 (4698.304 s)
Chunk-aligned: No
Mode: 3 front, 2 rear, 1 LFE
Delay: 0 ms

[ About MPEG4 encoding ]

User data: XviD0046
Packed bitstream: No
QPel: No
GMC: No
Interlaced: No
Aspect ratio: Square pixels
Quant type: MPEG custom (*)
Custom intra quant matrix: 
      8  16  20  23  27  30  32  34
     16  16  23  24  29  31  34  38
     20  23  27  28  30  35  38  40
     23  24  28  29  35  39  40  44
     27  29  30  35  39  42  45  50
     30  31  35  39  42  46  54  59
     32  34  38  40  45  54  62  72
     34  38  40  44  50  59  72  84
Custom inter quant matrix: 
     17  19  21  23  25  27  29  31
     19  21  23  25  27  28  29  33
     21  23  25  27  29  30  32  37
     23  25  27  30  31  34  40  45
     25  27  29  31  38  46  54  60
     27  28  30  34  46  58  72  74
     29  29  32  40  54  72  90 100
     31  33  37  45  60  74 100 124
Number of frames: 117875
Drop/delay frames: 0
Corrupted frames: 0

I-VOPs:  1487 (  1.262 %)                          
P-VOPs: 46810 ( 39.712 %) ##########               
B-VOPs: 69576 ( 59.025 %) ###############          
S-VOPs:     0 (  0.000 %)                          
N-VOPs:     2 (  0.002 %)                          

Max consecutive B-VOPs: 2
    1 consec: 18618 ( 42.221 %) ###########              
    2 consec: 25479 ( 57.779 %) ##############           

[ DRF analysis ]

Average DRF: 4.778973
Standard deviation: 1.129003
Max DRF: 8

DRF<2:     0 (  0.000 %)                          
DRF=2:   938 (  0.796 %)                          
DRF=3: 10847 (  9.202 %) ##                       
DRF=4: 47306 ( 40.133 %) ##########               
DRF=5: 18159 ( 15.406 %) ####                     
DRF=6: 35901 ( 30.457 %) ########                 
DRF=7:  4306 (  3.653 %) #                        
DRF=8:   416 (  0.353 %)                          
DRF>8:     0 (  0.000 %)                          

I-VOPs average DRF: 3.486213
I-VOPs std. deviation: 0.541155
I-VOPs max DRF: 4

P-VOPs average DRF: 3.823029
P-VOPs std. deviation: 0.523940
P-VOPs max DRF: 5

B-VOPs average DRF: 5.449752
B-VOPs std. deviation: 0.931683
B-VOPs max DRF: 8

[ Profile compliancy ]

Profile to check: MTK PAL 6000
Resolution: Ok
Framerate: Ok
Min buffer fill: 81%

This report was created by AVInaptic (18-11-2007) on 21 giu 2008, h 20:59:31

VOB sample here: http://www.evilshare.com/c116d060-9126- ... 0b6aa2a5f8

elchupacabra

The VOB sample looks better for me:

MCMLXXXVIII

The rip plays exactly the same as that VOB for me, it is just when I play the rip in VDub or make a screenshot that I get the effect in the first post.

Are you sure the AVI sample has the effect and the VOB doesn't? If that is so then I'm stumped.

elchupacabra

Ok, I think we found the problem here. It seems to be Virtual Dub and how it displays the video.

I downloaded the AVI sample again just to make sure, because I'm on a different PC with a different monitor now.

Both samples (AVI and VOB) look good when played with Video LAN.

The AVI sample looks like the first picture you posted in VirtualDub. I can't open the VOB with Virtual Dub, because it tells me it is no valid MPEG-2 stream.

Video capturing problem.

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