|
|
| AdventurerGR |
 Posted: Jun 8 2008, 02:51 PM |
 |
|
Newbie
Group: Members
Posts: 3
Member No.: 23695
Joined: 8-June 08
|
Hi everyone.
I have been using VirtualDub to recompress my digital camera's mjpeg-videos to manageable sizes, and in the past year it's been very helpful. But lately I've began taking videos under very low-lighting and it seems that after the compression, the images become darkened -and thus distorted- much more than the original! And what's weirding me out is, it is INDEPENDANT on the codec used - it even happens without using any codec! In the meanwhile, all videos I edit in good/medium lighting have no such problems.
Below are three screencaps so you can understand the problem (click on the links below to see them).
Original video
Compressed without using any codec
Compressed using pretty much any codec
As you can see the image becomes so dark that details on the faces are lost, and the eyes look downright eerie. Can anyone tell me how to compress the video and have it look exactly as it appears in the original?
I am using full processing mode (tried the others but it didn't help) with no filters and all options on default. |
|
| stephanV |
| Posted: Jun 8 2008, 03:55 PM |
|
|
Spam killer ;)
Group: Moderators
Posts: 4348
Member No.: 8917
Joined: 18-February 04
|
Does it also happen if you use 'Fast Recompress'? It looks like a TV vs PC range issue at first glance, although when I save the JPG you uploaded as uncompressed video, the brightness remains the same.
What are your settings in video > color depth? Do you use any filters?
--------------------
useful links:
VirtualDub, Input plugins and filters, AviSynth, AVI-Mux GUI, AC3ACM by fcchandler, VirtualDub FAQ |
|
| AdventurerGR |
| Posted: Jun 8 2008, 06:42 PM |
|
|
Newbie
Group: Members
Posts: 3
Member No.: 23695
Joined: 8-June 08
|
Hi, thanks for your reply. All three of your questions are answered in the first post's last line ; I have already tried fast&normal decompress to no avail, am using no filters, and have the default options for color depth (Autoselect/24bit). Also it is not a TV/PC issue as all screenshots are viewed in my PC. |
|
| phaeron |
| Posted: Jun 8 2008, 07:00 PM |
|
|
Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
|
Actually, it probably is a luma range issue, although it's weird that the compressed/uncompressed images would vary so widely. Try switching input and output formats to YUY2 and see if it makes a difference in the uncompressed version; if so, you've got a luma range problem.
|
|
| AdventurerGR |
| Posted: Jun 9 2008, 12:10 PM |
|
|
Newbie
Group: Members
Posts: 3
Member No.: 23695
Joined: 8-June 08
|
Thanks a lot Phaeron. Although even YUY2 didn't work (screenshot here) you got me thinking on the color issue, and I put 16-bit as input color and it worked (screenshot here)! I don't know why that happened (maybe an issue with my Canon Powershot A710 camera?) but I got the solution now and hopefully if anyone has the same problem they'll find their way in this thread and also see it.
Thank you again! |
|
| phaeron |
| Posted: Jun 10 2008, 05:46 AM |
|
|
Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
|
What the heck is the video codec handling the decompression here (File > File Information)? Whatever it is, it's pretty badly broken.
|
|
| Synetech |
| Posted: Jun 13 2008, 05:54 PM |
|
|
Newbie
Group: Validating
Posts: 1
Member No.: 23718
Joined: 13-June 08
|
Hi,
I have the same problem. I asked around and got some information on the problem here.
Apparently it is because VDub uses an internal MJPG decoder which uses the PC.601 matrix (0-255) instead of the rec.601 matrix (16-235) that players and such use.
I worked around it by using AviDemux instead of VDub, but am trying to figure out a way to get it to work in VDub.
Is there a way to get VDub to use the default MJPG decoder (the one in Quartz.dll) instead of its own? I cannot find any information on disabling its internal decompressor.
Oh, and you just noticed this because you used a dark video. I can pretty much guarantee that it happens with the others as well, but you just didn’t notice because the difference was less.
--------------------
--
Synetech
|
|
| stephanV |
| Posted: Jun 13 2008, 10:36 PM |
|
|
Spam killer ;)
Group: Moderators
Posts: 4348
Member No.: 8917
Joined: 18-February 04
|
VirtualDub does not use PC.601 as far as I can tell.
Quartz.dll cannot be used as its directshow. ffdshow has a vfw mjpeg decoder.
--------------------
useful links:
VirtualDub, Input plugins and filters, AviSynth, AVI-Mux GUI, AC3ACM by fcchandler, VirtualDub FAQ |
|
| phaeron |
| Posted: Jun 14 2008, 04:55 AM |
|
|
Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
|
Hmm... it's been a long time, but it looks like I actually used the JFIF color space. That's probably not correct. I'll take a look at fixing this.
In the meantime, you can always install a third party MJPEG codec. FFVFW will probably work, too.
|
|
