Main Concept MPEG2 Artefacts

Johannes_H wrote on 8/18/2002, 2:53 PM

Hi all!

I found a problem when rendering with Main Concept MPEG2 Encoder. I will try to describe it - pardon for my poor english.

I wanted to make a SVCD from a lot of pictures my wife has taken from her flowers in the garden. All pictures are in JPG format and same size.
So I put the pictures in the timeline, first simply one after the other - did a first render (always used MPEG2 SVCD PAL template) and had a look at the computer monitor - perfect. Also burned a CD-RW with this to test it on the external DVD-Player - perfect.
After this I did a little adjustment on the sound volume and inserted a 5 second generated media (solid color black) at the beginning. Rendered and burned again and had a look on the TV via the DVD-Player -> There I saw a strange flickering approximately 3 to 4 times a second, sometimes disappeared (fine picture) coming back again. So I took a very detailed look into the MPEG2-File on the PC and really, this flicker is there - so its not a fault of the DVD-Player.
In detail the flicker is a frame with a lot of "blocky" artefacts (especially in areas with a lot of details). This frame is side by side with frames that do not have this artefacts.

To make a long story short, I did a lot of testing to bring the thing down. First I did some comparison to other MPEG2 Encoders to find out, if the source is the problem - it is not. Canopus SoftMPEG and also the FreeTrial of MainConcept Converter encoded the same material fine.
Next I stripped down the VV project and after hours I found out:
If I only encode the picture (pictures) without the leading "Solid Black" in front, the result is OK. Even if using the leading "Solid Black" in front of the picture the result is OK if the "Black" is short. If the "Black" gets longer some frames the artefacts in the following pictures appear.
So, that means that the appearance of this artefacts is dependent on material which comes before?! I also found the same artefacts in an other MPEG2 rendered file with videos (instead of pictures) but in this case they are only on some places, not over the complete file.

Its hard to describe and I hope that someone can follow.
If there is an E-Mail address available, I can mail two very short MPEG2 files. One is with a short "Black" leader and no artefacts, the second has a "Black" leader which is 15 frames longer and the following picture shows the artefacts in some frames.

Thank you
Johannes

Comments

MCTech wrote on 8/18/2002, 6:55 PM

We'd like to see that sample. Please e-mail to usa@mainconcept.com.

One observation: A highly compressed format like JPEG doesn't always lend itself well to being rendered in MPEG (another highly compressed format). However, this doesn't explain why some encodes give you the problem and others don't.

If you could include a few of the pictures that would help too.

Best Regards,
MainConcept Tech Support

Johannes_H wrote on 8/19/2002, 12:02 AM

Its on the way.
Thank you
Johannes

Frenchy wrote on 8/19/2002, 10:43 AM

MCTech:

Is this the same/related to this older post? (and do you have any additional info regarding the "pulsating" effects previously described)?

http://www.sonicfoundry.com/forums/ShowMessage.asp?Forum=4&MessageID=111925

Frenchy

Johannes_H wrote on 8/19/2002, 11:01 AM

I had a look on this older post and the descriptions there look really like the same problem I have discovered now.

We will see?!
Johannes

Frenchy wrote on 8/19/2002, 11:13 AM

Johannes:
Did you try the SVCD encoding settings I described on the forementioned post (in PAL vs NTSC, of course), and was there any change/improvement? It seemed that a CBR instead fo VBR gave the cleanest/clearest results.

Frenchy

Johannes_H wrote on 8/20/2002, 1:20 AM

Not now - was very busy yesterday.
But I will do more testing in the next days and post the results here.

Johannes

MCTech wrote on 8/20/2002, 10:53 AM

Hi All,

We are still looking into the problem, and I hope that we will at least have some information this week.

MainConcept Tech Support

Johannes_H wrote on 8/22/2002, 5:06 AM

I did some testing on this issue and of course, switching to constant bitrate makes really a difference. The single frames with the artefacts I described in my first posting are not any more produced my the Encoder.
But the original question needs still an answer: Is this normal behaviour or is there some problem?

Johannes

phonelover wrote on 11/22/2002, 8:40 AM

Hi,
I have the same problem of Johannes. I created a SVCD PAL VBR video out of a series of jpeg images. For each of these images, I applied the pan/crop feature so that they are all zoomed and moved.
Rendering this video creates the same "flashing blocking artifacts" described by Johannes. I could send you three images: the wrong one with two adjacent well encoded one, so you can have a better look of what I am trying to describe here.
The "funny" thing is, the more I render the video and the more these artefacts appear: after one minute or so, the problems are really visible.
Each time I have still images, all these artifacts disappear.
Thanks for your help.

MCTech wrote on 11/23/2002, 3:10 PM

Hi,

First, which build of Vegas are you using?

It would help us to see samples of this effect. If they're small enough to e-mail, please send to markb@mainconcept.com. If they're too big, send a message without files and I can reply with FTP info.

Mark

SonyEPM wrote on 11/24/2002, 11:11 AM

If you would like to help us beta test some new encoder components that we believe fix the pulsing issue, please send an email to drdropout@sonicfoundry.com

phonelover wrote on 11/24/2002, 11:44 AM

Hi,
I can send you three images taken out from the MPEG file I have rendered. Then I could try to create a video file which only isolates the "pulsing video" so it should be short. I am using Vegas Video 3.0a.
I'll let you know about the second issue; I'll e-mail you soon the three frames.
Thanks for your kind help.

smeredith wrote on 11/28/2002, 8:48 PM

I have this very same issue. I get around it by using CBR.

It's very easy to reproduce: create a clip using a sequence of jpegs. Render to mpeg using the defaults for SVCD.

It still happens on version 3.0c.

Ritchie wrote on 1/15/2003, 8:37 AM

This seemed to attack me last night. Almost exactly as you describe, a pulsing effect every 1/2 to 1 second. I couldn't figure it out, every time I tried to render a section of my video to test my settings it looked fine. Then I would render the whole project and wham, it would kill me. Perhaps the black space at the beggining is culprit? I will try placing an empty black video at the begginning as a filler to see if this clears it up.

My project: I have a video file (nope, not stills this time) that was rendered previously at 23.976fps with 3:2 pulldown (so Vegas detects it as 29.97fps). Music starts several seconds before the video in the project, so there is some empty space with no video at the beginning. I have added one title overlay (generated media) early in the video. The entire clip is 3 minutes long. The original clip has already been rendered as MPEG2 so I expect degredation in this generation, but the flickering/pulsing seems out of place. I would expect a more global degredation, rather than this pulsing.

I haven't tried CBR as this just happened last night. I will try again tonight and see if that fixes it. As an alternative I rendered the project as an .avi using the Huffyuv codec, then encoded to SVCD using TMPGEnc instead with excellent results. Slightly softened look from it being a 2nd generation encode, but not bad overall. I would have prefered to keep it all in the same program so I will try CBR tonight.

I would be happy to email samples of it working and not working, both rendered with MainConcepts encoder. What is "too big" of a file?

Frenchy wrote on 1/15/2003, 9:34 AM

Ritchie:

Contact SonicEPM (a few posts above) - he supplied me with new MC encoder files that eliminated the "pulsing" issue I had. It sounds like you have the same issue. Also, I use teh default CBR (most of my vids so far have been under 30 mins in length, so fitting one movie on a CDR or CDRW is not an issue, and I like the consistency of results I've obtained), use the standard SVCD-NTSC template, and on the 'advanced video' tab, pick DC coefficient = 10 bit, and check Write Sequence Display Exension. I've also stopped using jpg's and instead use .png's or .bmp's for the reasons stated by MCTech, above. Have fun.

frenchy

Henry wrote on 1/15/2003, 9:56 PM

This is the recent mainconcept mpeg patch for UMSP 6.5

If you are having problems with visible pulsations and other quality issues using VBR, particularly with;

1. bitrates below ~6000 kbps
2. image file slideshows

please download the following *.zip and replace the following files in c:\program files\common files\Ulead Systems\MPEG\ with its contents;

MPGVOUT.000
MPGVOUT.001
MPGVOUT.002
MPGVOUT.003
MPGVOUT.004
MPGVOUT.DLL

http://digitalvideo.8m.net/mpgvout.zip

The ulead patch files ......also compatible with VV3 mpeg module
so, you can try replacement of the corresponding files in the sonic foundry subdirectory