#1  
Old 08-08-2008, 07:36 AM
Kal's Avatar
Kal (Andrew)
1¼" ñì®våñá

Kal is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 1,845
Toucam experiment, results, conclusions?

Last night I did the firmware hack on my 840K Toucam to effectively make it a 900nc. The hardware is exactly the same, but the 900nc has the option to use the lower compression YUY2 codec. The hack went without a hitch, so I decided to do an experiment to see exactly how much less compression there was on my video captures. The following 4 captures were each for exactly 60 seconds:

5fps IYUV codec - 133MB
5fps YUY2 codec - 180MB

10fps IYUV codec - 270MB
10fps YUY2 codec - 234MB (dropped ~200 of the 600 frames, about 34%)

Based on this data it, you can clearly see how much less compression there is between the YUY2 codec compared to the IYUV codec. However, it appears to me as though there is no difference in compression rate when moving from 5fps to 10fps. When reading Mikes planetary imaging guide I was under the impression that there was higher compression when moving from 5fps to 10fps, but this data doesn't seem to show that. Am I missing something here?

Based on this data, I would say my best option would be to capture at 10fps YUY2 codec in good seeing, accepting the frame loss as I still capture 33% more frames when compared to 5fps. In poor seeing I should capture at 10fps IYUV codec for no frame dropping, to capture more frames with higher compression.

Thoughts? Comments?

Last edited by Kal; 08-08-2008 at 08:24 AM.
Reply With Quote
  #2  
Old 08-08-2008, 08:09 AM
matt's Avatar
matt
6000 post club member

matt is offline
 
Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
I've never used that particular codec with my (hacked) 840k ToUcam...and I don't think Mike used that codec either when he he was using his ToUcam
Reply With Quote
  #3  
Old 08-08-2008, 08:23 AM
Kal's Avatar
Kal (Andrew)
1¼" ñì®våñá

Kal is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 1,845
My error, it is the YUY2 codec, not the YUV2 codec, I'll edit my orignal post.
Reply With Quote
  #4  
Old 08-08-2008, 08:46 AM
Kal's Avatar
Kal (Andrew)
1¼" ñì®våñá

Kal is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 1,845
I found this Microsoft support page which describes the differences between I420/IYUV and YUY2
Reply With Quote
  #5  
Old 08-08-2008, 09:57 AM
Kal's Avatar
Kal (Andrew)
1¼" ñì®våñá

Kal is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 1,845
Maybe I am mississing the point here somewhere. Is the render size of the file on the HDD independant of the transfer of data from the camera to the pc with regards to compression? In other words, the file size on the HDD will be the same even if the data transfer is of a higher compression?
Reply With Quote
  #6  
Old 08-08-2008, 04:03 PM
Kal's Avatar
Kal (Andrew)
1¼" ñì®våñá

Kal is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 1,845
Thinking about it more, the USB 1.1 specification only allows a maximum data transmission of 1.5MB/s which is well below the 4.5MB/s that I seem to be capped at with my AVI files, so there must be some underlying compression that I am not taking into account.
Reply With Quote
  #7  
Old 13-08-2008, 11:16 PM
AlexN's Avatar
AlexN
Tunnel Vision

AlexN is offline
 
Join Date: Mar 2008
Location: Caboolture, Australia
Posts: 6,801
push it to 15fps and see the compression kick in, then again on 20 ~ 30 fps.

widen parameters to get broader results.

I found when using the default phillips software with my 900nc, @ 25fps, a 2 min video would be around 30mb. using K3CCDTools, @ 10 fps a 2 min video would be closer to 1gb.

Thats some compression issues for your a$$
Reply With Quote
  #8  
Old 15-08-2008, 12:27 PM
Kal's Avatar
Kal (Andrew)
1¼" ñì®våñá

Kal is offline
 
Join Date: Nov 2006
Location: Sydney
Posts: 1,845
I did some more testing and couldn't repeat the 'dropped frames' I was having last time. The size on HDD went up proportional to the fps captured at. At 25fps I could visually see the differences compared to 5 or 10fps though, so compression was definately effecting the quality, but not the filesize.

The comparison between YUY2 and IYUV still stands though, since for the same fps rate the filesize was always bigger.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 01:35 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement