MPEG2 Encoding issue

Allanr wrote on 7/6/2002, 11:10 PM
Hi Everyone,

Since I have purchased VV3 I have had the following problem with MPEG2 Encoding which has made this part of the product not usable for me. I have captured DV footage and am saving/rednering the files as a MPEG2 file using the MainConcept codec. My settings are the standard SVCD template from the Main Concept dialog box. I have changed nothing else. The length of the video is approx. 10 mins. When I play back the file on both my PC and a DVD player I see what can best described as the following:

Every 1/2 second or so there is a 'pulsing' of pixalation and distortion on the screen which is fairly intense and very noticable but probably lasts for 100ms every 1/2 second. It is generally throughout the playback.

When I render smaller regions of my project for only say 30 seconds or so it doesn't seem to appear as noticable. However, I haven't been able to pin-point this to a length of file which does or doesn't create the 'pulsing pixalation'.

My machine is as follows:

1 Ghz Gateway with 80 GByte Hard drive, 512M Ram. I am using VV3c

This is very frustrating and I would appreciate any feedback if anyone else has had this problem of if anyone out there know's what this is and how to fix it.

Thanks

Allan

Comments

vonhosen wrote on 7/7/2002, 5:28 AM
Have you tried right clicking on the event & using the reduce interlace flicker switch ?
SonyDennis wrote on 7/7/2002, 8:39 AM
The pulsing / pixelating is probably everytime an I-frame comes along. If this is highly detailed video, the SVCD output might be spending too many "bits" on the high frequencies, at the cost of overall image fidelity. One thing you might try is a very light amount of Gaussian Blur on the final output (use the FX button on the Video Preview window). This will "roll off" the high-frequency images and let the MPEG encoder spend those bits elsewhere.
///d@
MCTech wrote on 7/7/2002, 9:47 PM
Hi,

Is there any way you could provide us with a sample file containing the pulsing? Downloading a big file is no problem for us.

Thanks,

MainConcept Tech Support
Chienworks wrote on 7/7/2002, 11:27 PM
I've noticed that when i do a montage of still images, about 1 second after the crossfade the picture will sort of blink to a very low-res version for a tiny fraction of a second, then it will be fine for the rest of the duration. These blinks only occur while the image is steady on the screen and never during a crossfade. Any chance that this is related to the same problem? It's more noticeable in WMV than in MPEG, but it does occur in both.
Frenchy wrote on 7/8/2002, 10:16 AM
I was running into this "pulsating" effect on my stills as well, as discussed on this thread:

http://www.sonicfoundry.com/forums/ShowMessage.asp?MessageID=103889&Replies=17&Page=4

My solution was to encode using the following settings:
Res=352x480 (the std. 480x480 works well also, but not DVD-compliant, for future conversion)
CBR=2,300
DC=10
"Write Sequence display extension"=checked

The biggest difference seemed to be going from VBR to CBR encoding - this eliminated the unwanted "pulsing" effect.

If you come up with other solutions, please post.

Frenchy
Cheesehole wrote on 7/8/2002, 9:43 PM
as mentioned, this sounds like an I-Frame issue and is usually only a problem with stills for me. you could play with the I-Frame distance setting in the encoder. for WMV I usually use 3 seconds. increasing the Iframe distance to 10 seconds or above could also help if it makes them fall in different places, like right on the transitions. for MPEG-2, I think a little blur is the most effective way to control the pulsing effect. I'll check out the CBR method to see if that helps too... thanks for the settings Frenchy.
MCTech wrote on 7/10/2002, 12:58 PM
What is the format of the still images you are using?
cvdhs wrote on 7/10/2002, 1:14 PM
My problem with MPEG2 is worst.

In both machines with Windows 2000 and XP the program crashes or stop responding. I even had one time a dialog box letting me know tha the MPEG2 wasn't generated due to an unknow problem.
Chienworks wrote on 7/10/2002, 2:58 PM
MCTech, i always use JPEG files, usually 800x600 pixels or so, and with a very low compression setting (10 on a scale of 1 to 100).
Frenchy wrote on 7/10/2002, 3:29 PM
MCTech - I'm using bmp's and jpg's and noticed the pulsing problem on each type. As a side issue, I wanted to render a vid as a .wmv, but didn't have the .veg file and the associated media at this location, but I did have the *good* .mpg, so I rendered it as a .wmv, and the pulsing showed up on many of the stills of the resulting .wmv file - I would guess this is a result of rendering the file twice.

Frenchy
MCTech wrote on 7/12/2002, 11:24 PM
I'm not surprised that JPEGs result in this, because JPEG and MPEG are both pretty intense compression methods (even at lower compression). I am surprised that you experience it with BMPs too (unless they are compressed). In theory, uncompressed BMPs shouldn't result in this.

Would either of you be willing to send me some of your still images for testing? If they're personal or proprietary I certainly understand if you don't want to, but I thought it might be good to try the actual images that are causing trouble instead of trying to reproduce the issue with other ones.

My e-mail: usa@mainconcept.com

MainConcept Tech Support
Frenchy wrote on 7/17/2002, 4:34 PM
MCTech:

I've emailed the BMP's and 15 second clips of the MPG's (one with the "pulsating" problem, and one with my workaround settings described above) to you.

Thanks

Frenchy
Allanr wrote on 7/17/2002, 9:22 PM
I have been out of town so thanks very much to those that responded. I did manage to fix my problem by using the following settings ( after reading various posts on this forum )

1. I changed to CBR rather than VBR
2. Changed the DC differential to 10 bit
3. Made sure the 'write sequence display extention' check box was enabled.

I'm not sure which made the most difference but I am very happy with the output.

Thanks for all the suggestions.

Allan