Lost MPG thumbnails

[terrypin]

This may be a little OT for this forum, but it is video related so maybe it will ring a bell with someone here please?

I've lost most of my MPG thumbnails. IOW, in a Windows folder in Thumbnail View, I just get standard icons, not a picture taken from a frame in the video.

After much googling I tried various fixes, including:
Run: regsvr32 shimgvw.dll but that didn't get them back
Run: REGSVR32 SHMEDIA.DLL, which has worked for me in the past, but no change this time.

Also checked the 'PersistentHandler' registry entries descrtibed as a solution in this thread, but mine are already OK
http://tinyurl.com/yaw2klq

The aspect that seems different this time is that some thumbnails are still OK. In the past I recall it was probably all or nothing.

Can anyone help me isolate and fix this please?

--
Terry, East Grinstead, UK

[terrypin]

Anyone with any thoughts at all on this vexing problem please? In addition to trying the potential fixes above I've done successive System Restores. And removed the MPG association from File Types and re-installed it. All so far in vain.

I strongly suspect it's some sort of codec issue.

For all of the files with .MPG extension that use MPEG2, I DO NOT get thumbnails. For all other .MPG (and other movie and graphics) files I DO get thumbnails. I'm hoping that therein lies the key to identifying the cause.

Maybe a selection of the files' video properties as reported by MediaInfo will help the experts here to spot something? (I've included all of the data under the 'Video' subheading, as I'm not sure what might/might not be relevant):

NO THUMBNAILS:

Format: MPEG Video
Format version: Version 2
Format profile: Main@Main
Format settings, Matrix: Standard
Duration: 21s 640ms
Bit rate mode: Constant
Bit rate: 5479 Kbps
Nominal bit rate: 9500 Kbps
Width: 720 pixels
Height: 576 pixels
Display aspect ratio: 16/9
Frame rate: 25.000 fps
Standard: PAL
Colorimetry: 4:2:0
Scan type: Progressive
Bits/(PixeI*Frame): 0.916

Format: MPEG Video
Format version: Version 2
Format profile: Main@Main
Format settings, Matrix: Standard
Duration: 34s 560ms
Bit rate mode: Constant
Bit rate: 5714 Kbps
Nominal bit rate: 9500 Kbps
Width: 720 pixels
Height: 576 pixels
Display aspect ratio: 16/9
Frame rate: 25.000 fps
Standard: PAL
Colorimetry: 4:2:0
Scan type: Interlaced
Scan order: Bottom Field First
Bits/(PixeI*Frame): 0.916

THUMBNAILS DISPLAYED
I have a few files with Cinepack and S-Mpeg 4 v3 that do display thumbnails OK, but the bulk are MPEG1 types with properties like these:

Format: MPEG Video
Format version: Version 1
Format settings, Matrix: Standard
Duration: 17s 533ms
Bit rate mode: Constant
Bit rate: 920 Kbps
Nominal bit rate: 1152 Kbps
Width: 320 pixels
Height: 240 pixels
Display aspect ratio: 4/3
Frame rate: 30.000 fps
Scan type: Progressive
Bits/(PixeI*Frame): 0.500

My next step will be to go back to the source of some of the no-thumbnail files, where possible, and try re-making the MPG files in various alternative programs.

Any suggestions would be much appreciated please.

--
Terry, East Grinstead, UK

[Safesurfer]

Have you changed the default DirectShow MPEG2 decoder, perhaps inadvertently by installing some new video software? If so, that's where I'd look first.

Might also try reregistering the quartz.dll file in case something got broken - Start>Run>regsvr32 quartz.dll

[titigrom]

Have you installed Mastroska Splitter ? there's an option you can enable-disable : "show thumbnails" or something like that in the Splitter properties.

I thought it was usefull but this option made my system be slower. The fault of some MPEG-2 files stored in directories. So I had to disable thumbnails...

As Safesurfer suggested : your default DirectShow MPEG2 decoder may have been changed...

[terrypin]

Thanks both. I'm sure you're onto something here about DirectShow and I'm impatient to try it. But I'm technically way out of my depth on most of this codec stuff. ffdshow in particular. That is what you mean, yes? Can you step me through how I (safely!) check it out please?

To get started, here's what I hope is a relevant screenshot, but happy to provide anything else you need.




Edited an hour or two later:

Success!



But can we please keep talking as
a) I'm sure that I'll now need to make further changes to that configuration, which is now mostly showing 'Disabled'
b) I'm flying blind on all this and would dearly love to learn a little more!

--
Terry, East Grinstead, UK

[titigrom]

I think you have solved your problem !

Ffdshow is a DirectShow decoding filter for decompressing most of video files (AVI, MPEGs, etc). If you have installed XviD codec for playing back XviD files, DivX for DivX files... you can try ffdshow filter by ticking the option "disabled" for each codec to "libavcodec" for example. You can evaluate the quality of that filter. And ffdshow combines some handy image postprocessing options. Of course, you can revert the changes by going "disabled" back !

In my case, I use this filter since a long time because of its large options and decoding codecs. Usually for MPEG-2, I chose "libmpeg2" in conjonction with the "Output" section in "Overlay" and tick "Set interlace flag in output media type" like showed down :

[terrypin]

Thanks titigrom. I've now changed my setting to match yours, apart from mine already having one extra box checked. Is that significant? (I have no idea what 'Packed YUV' or 'NV12' means!)



Is it possible to explain in non-technical terms what the effect of your change is please? Where will I notice any difference?

Re all those types that I now have set by default as Disabled, would my safest approach (given my basic lack of understanding) simply be to 'wait and see'? IOW, wait until something doesn't work properly and then try changing it in ffdshow?

I suspect that the reason these were previously set as I showed in my earlier screenshot was that at some stage I must have used the option 'Set all stable formats to libavcodec', while in experiment mode, and forgotten all about it. Do you use that option and what are its advantages/disadvantages?

Finally (shouldn't say that - I expect I'll be back with more questions!), do you use the option under DirectShow Control >
Don't use ffdshow in: ?

Sorry to throw so many questions into the thread. Any replies from any of the experts would be greatly appreciated. After much searching in the past and again recently I've still not found any documentation or tutorial that teaches a novice like me how to use ffdshow in detail.

--
Terry, East Grinstead, UK

[terrypin]

My comment about NV12 was obviously rubbish - yours is also checked. Don't know what I was looking at!

--
Terry, East Grinstead, UK