Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Video and Electronically Assisted Astronomy

Pages: 1
ccs_hello
Postmaster
*****

Reged: 07/03/04

It's a timed slide show, why don't we optimize new
      #6130127 - 10/10/13 11:09 PM

Recent donnie3 (Don) question on video recorder kind of raising the capture and storage (recording) topic to the surface.

In long exposure video imaging, a lot of time is used in displaying redundant information (repeated video frames with the identical information). It is necessary in NTSC analog video to satisfy the transmission and display of video.

In our case, it's more like a timed playback (at a fixed frequency) of still slides, as if it's a slide show.

Capture and store in such case can be simpler to save storage space and can afford to use better compression method designed for still image to preserve image quality, as oppose to use compression algorithms designed for video (continuous changing.)
Of course, the timed capture interval should be reasonably close to the actual long exposure time (e.g., every 8.5 seconds), and does not need to be perfectly in sync.

Using the 8.5 second (256 frames, 255 of them are repeated/redundant) long exposure as the example, a 85 second session will just yield 10 or 11 captured images.

For displaying, it does not need to be a delayed event (wait until the entire session to complete) but just to display immediately, refreshed with a new (the next) image every 8.5 sec.

What do you think?

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: It's a timed slide show, why don't we optimize new [Re: ccs_hello]
      #6130473 - 10/11/13 07:07 AM

Well once again your talking above my pay grade, but sounds good LOL, Kasey

Post Extras: Print Post   Remind Me!   Notify Moderator  
Puck Ja
professor emeritus
*****

Reged: 11/21/12

Loc: OK, USA
Re: It's a timed slide show, why don't we optimize new [Re: dragonslayer1]
      #6130859 - 10/11/13 11:36 AM

I share the similar feeling with ccs_hello. While he was addressing the optimized way to store results - instead recording "exactly the same" redundant analogue data, why don't you just store the still digitized image.

Similar principle applies for the viewing: instead of staring at the "same and repeated" frame with poor singnal-to-noise ratio, why don't you stack them and process them on-the-fly to improve the image quality.

Why don't we optimize the presentation of already collected data for even better viewing?


Post Extras: Print Post   Remind Me!   Notify Moderator  
GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: It's a timed slide show, why don't we optimize new [Re: Puck Ja]
      #6131572 - 10/11/13 04:57 PM

Indeed, why record/store video at 30 frames/sec if a unique image is updated at a much longer interval? If the integration time is, say, 8.5 seconds, an NTSC system sends out a redundant ~255 essentially identical frames which do nothing but eat up storage space.

Post Extras: Print Post   Remind Me!   Notify Moderator  
nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: It's a timed slide show, why don't we optimize new [Re: GlennLeDrew]
      #6133450 - 10/12/13 05:15 PM

Didn't expect cc-hello to seemingly suggest what I've been doing for over a decade eg saving individual CCD frames/images when the exposure of any duration is complete for display via PC/laptop for as long as needed - or am I missing something from video lore ? :-)

Post Extras: Print Post   Remind Me!   Notify Moderator  
ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: It's a timed slide show, why don't we optimize [Re: nytecam]
      #6133761 - 10/12/13 08:03 PM

"Streaming" is the key. You don't want the complete job done then come back to see result. You want to the current result being shown immediately.

I did an experiment by using AMcap (using USB video dongle to capture). I install a free software "AutoHotKey", focus on AMCap window, set the still capture folder name. Then run the test script I just created (Test1.ahk) The script looks like this

#SingleInstance FORCE
#space::
Loop 10
{
Send ^s
; then upload this file to Google Drive (your own code here)
Sleep 8500 ; Wait 8.5 seconds.
}
return


Every time I press the "Windows Logo" and "Space bar" keys simultaneously, it will capture 10 still images, sequentially 8.5 seconds apart.

Individual captured file will one by one showing up in my Google Drive (or ImageShack site, etc.)

Other viewers probably can run a script to see if a new file arrives in that "shared file repository site". The new one will be fetched, replacing old ones, and displayed onto the viewer's own computer.

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1


Extra information
7 registered and 11 anonymous users are browsing this forum.

Moderator:  csa/montana, JayinUT 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 397

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics