AVISynth Picture Quality Problem

[sue denim]

Hi guys!

When I use an AVISynth script to load an MPEG2 file into CCE or TMPGenc, the video looks terrible.
In fact it looks like a really heavily compressed JPEG.

(BTW - I use MPEG2DEC.dll to access a DVD2AVI .d2v file)

However, when I load the script into VDub it looks cool 8)

I've got a feeling that something's gotta be going on in the YUV/RGB area, but I haven't a clue what!

Any ideas?

I've tried running no AVISynth filters, just the file load, and still the same.
Also tried RGB colorspace in DVD2AVI - no change.

Any help would be much appreciated.

Cheers,

Sue xxx

[KoalaBear]

Details, Sue. The devil is in the details.

When I use an AVISynth script to load an MPEG2 file into CCE or TMPGenc, the video looks terrible. In fact it looks like a really heavily compressed JPEG... However, when I load the script into VDub it looks cool.

Assuming you're using VirtualDub purely as a frame server (i.e., "Direct stream copy"), what you see when you load an AVS file is exactly what you're passing to the encoder for compression.

If you're not pleased with the encoder's rendition of that picture, that's the result of the encoder and settings used and not a failure on behalf of AviSynth.

[sue denim]

Thanks Koala, but I think you've misunderstood me ........

I'll try again (with as many details as I can muster!) --

When I use the AVISynth --to--> VDub --to--> CCE/TMPGenc method
the picture is great.
I used this as an example so you could understand that it's the only way I can use AVISynth before I encode.

If I use an AVISynth script straight into CCE2.50 or TMPGenc, the preview and final MPEG look terrible (the 'compressed JPEG' I mentioned before).

Any thoughts?

Thanks,

Sue xxx

[KoalaBear]

Alrighty. Let's see if I'm understanding you now:

When you frameserve AVS -> VDUB -> (CCE|TMPGenc) you get a good picture; when you skip VirtualDub and load the AVS directly into (CCE|TMPGenc) you don't.

Right?

You've suggested this might be a colorspace conversion issue. I don't think so, but it's easy to rule out -- just add the line

ConvertToYUY2 (to force AviSynth to perform the conversion), or
ConvertToRGB (to force the encoder to perform the conversion).

If you get the same result, colorspace isn't the problem -- VirtualDub is doing something else to the picture that should be handled by the AVS file instead. Let's use the process of elimination to find out.

[sue denim]

Hi Koala .......

Now I think you understand!!
Sorry if I was a bit misleading before .......

I tried the AVISynth command lines you suggested and it's fixed!
The ConvertToRGB line seems to be what VDub was contributing to the process chain.

The only trouble is, the whole reason for using AVISynth direct into an encoder is so as to remain in the YUY2 colorspace and not have to do multiple conversions between YUY2 and RGB !!!!

I was under the impression that AVISynth handled YUY2 and that encoders such as CCE and TMPGenc could accept video in that format ........am I wrong here??

Cheers,

Sue xxx

[KoalaBear]

Actually the purpose of loading an AVS file directly into an encoder is to avoid having to create a temporary working copy of the file you're trying to encode. Without it, you'd have to convert your VOBs to a series of AVIs and process them as a batch.

If you can reduce the number of colorspace transformations that's good, but it's not a high-priority objective in itself. Nevertheless, I'm glad we can cross this one off the problem list. :)

[Kdiddy]

Yes AVIsynth handles YUV just find...the keys are

Set DVD2AVI to YUV scale & TV scale.

And if you working in Win2K or XP, you might need to install a YUV codec such as Huffy.

If that doesnt correct the problem, then as Koala said, there is something wrong in your settings of your encoder.

[$$$]

Have you tried to open your AVI using avisynth's OpenDML handler by using the OpenDMLSource filter instead of AVISource? Maybe this solves your problem.

$

[sue denim]

Nevertheless, I'm glad we can cross this one off the problem list.

You and me both Koala !!
We're slowly, but surely getting there ....... with your help

I'll check my DVD2AVI settings and try again Kdiddy - cheers!

$$$ - I'm not using an AVI source .... it's an 'mpeg2source' loaded via the MPEG2DEC.dll plugin.

I'll be back when I have something to tell ya ........

Laters,

Sue xxx