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 Post subject: Dropped Frame Problem
PostPosted: Fri May 12, 2006 6:53 pm 
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Joined: Sun Dec 12, 2004 6:45 am
Posts: 139
Dear All,

Could someone please advise on how to overcome dropped frames when capturing astro. videos ? I've recently started imaging with a NexImage webcam and processing the images with Registax. My laptop has a 700 Mhz 'brain' with 512 Mb of RAM and 40 Gb hard drive.

The problem is, when capturing videos of the Moon and planets, the system is dropping many more frames than it's capturing, so a lot of information is lost :( . Having gone through the optimization process typically leaves only about 60 or 70 images for stacking, rather than hundreds. My first guess is to disable the security software so that the system has less to do and can concentrate more on the video capture ?

By the way, on some occasions when selecting an .avi file to process in Registax, an error message comes up which says the .avi can't be accessed. Anyone know why this is ?

Thanks and Best Wishes,

Non Computer-Literate Geoff :?


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PostPosted: Fri May 12, 2006 9:52 pm 
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Location: Wellingborough
Dear Geoff,

You certainly can't live with that rate of dropped frames. I normally get one dropped frame per avi - at the start, can't seem to stop that!

It's probably all down to the bandwidth you have available to transfer frames from the camera to your hard disk. So there's the USB link, RAM, processor speed and write speed of the HD to consider. USB1 should be up to passing 5fps at 640x480 pixels uncompressed frames (although I believe that USB1 webcams work more "reliably" on a USB2 computer). You have plenty of RAM (more than my 384MB anyway) and that 700MHz processor should be able to cope.

If the writing to HD is slow, that can be a bottleneck, although a 40GB disk sounds quite modern and quite fast. 5400 and 7200rpm disks should be OK. Do you have DMA access set for the HD? Is the HD defragmented? That will help, I think.

My experience is that (as you suggest) handling the downloading to HD is a major task for the system, and so I run only the imaging software while I'm imaging. I disable the wireless link and anything else that's unecessary to lighten the load. Even dropping out of imaging to look at Skymap for example, then closing Skymap and returning to imaging has caused me dropped frame (and other) problems, so I tend not to fiddle and image at the same time. That's with 1.8GHz celeron , 384MB RAM, and 32MB graphics card.

One way to ease the download bottleneck is to use smaller frame sizes in video. For lunar work it's useful to set 640x480 pixel frame size , but for the planets I use the Toucam's 352x288 "cropped" framesize. That just means the redundant black sky surrounding the target isn't recorded, the frames are smaller and more frames per second can be downloaded. I'm not sure just what is possible for the Nextimager, but it's essentially a Toucam under the skin.

The Registax problem isn't one I've encountered. There are some codec issues with Registax, but that can't be the cause if your avis are accepted sometimes and not others. There is sometimes a 2 (or 4) GB limit on avi size, but some say that's a Microsoft issue, not Registax. I'm wondering if the dropped frames are the root of that problem - if the avi possibly starts with a dropped frame , could that trigger a problem? I think the question is "can other software read the avi?" If it's "no" then the problem is unlikely to be with Registax, more likely with the avi itself.

OOPs - that went on a bit :)

HTH,

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Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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 Post subject:
PostPosted: Sat May 13, 2006 5:43 am 
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Joined: Sun Dec 12, 2004 6:45 am
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Hello Brian,

Thank you for the detailed reply; I'll take a look at the DMA access, 'defrag' and frame size options to begin with and also try to cut right down on any other programmes which might be running whilst capturing videos. I've already disabled the security software but haven't had a chance to use the webcam since then. Something tells me that the laptop might not have a graphics card, presumably that would make a difference as well ?

BTW, I bought the webcam equipment last weekend, so if's been overcast since then now you know why..... :wink: .

Best Wishes,

Geoff :)


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 Post subject:
PostPosted: Sat May 13, 2006 7:49 pm 
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Joined: Fri Dec 03, 2004 9:58 pm
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Location: Wellingborough
Geoff Burt wrote:
Hello Brian,

Something tells me that the laptop might not have a graphics card, presumably that would make a difference as well ?

:)


Dear Geoff,

I bought a cheapo "minimal" desktop PC for imaging. It came with on-board graphics which shared system RAM (Intel Extreme Graphics?) . After a couple of years the on-board graphics "ceased to be" and I installed a cheapo 32MB Radeon graphics card. Since then it seems to me that I have less dropped frames and many less computer freeze-ups, so Yes, you are probably right.

Good Luck with the imaging,

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Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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 Post subject:
PostPosted: Sun May 14, 2006 6:24 am 
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Hello Brian,

Last night I was thwarted by the clouds having just set up (we've all been there many times...... :wink: ) to image Jupiter following a few 'tweaks' to the laptop settings.

Instead, I tried a bit of trial and error with the Registax and noticed there was an avi. which just happened to be set at the cropped frame rate you mentioned. Interestingly, this ran well with far less dropped frames and produced a satisfying image of the Alpine Valley region.

Moreover, the frame rate is defaulted to 30 f/s, so thinking about something you've recently said in a similar thread over in the Gallery, I'll reduce to 15 f/s and perhaps this'll cure the problem completely.

Thanks and Best Wishes,

Geoff :)


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 Post subject:
PostPosted: Mon May 15, 2006 4:25 pm 
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Joined: Wed May 10, 2006 3:24 pm
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Location: Kent, UK
Geoff.

Set the frame rate to 5 fps.

Usb 1.1 cannot handle anything more than 5fps without compression at 640x480. Even though your laptop may have usb2, the camera is usb1.1 and is the limiting factor.

The camera will be automatically compress the images above this framerate so you will be loosing detail anyway. You don't need more than 5 fps to image successfully.

Cheers,

Drew.

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 Post subject:
PostPosted: Mon May 15, 2006 5:59 pm 
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Hello Drew,

Much appreciated. I'll try 5 f/s as soon as the weather co-operates, the sky here is a solid mass of grey sponges at the moment.

Any idea where I can get a cloud filter... :wink: ?

Best wishes,

Geoff :)


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 Post subject:
PostPosted: Sat May 20, 2006 12:36 am 
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Hi geoff

I am having the exact same 2 problems you are experiencing. I bought the new Philips SPC900 and was/am suffering HUGE frame loss my laptop is around 6 years old with a slow processor etc so thats prob why :)
And i am haveing the same Registax problem, found out there are 2 types of .AVI file.... "old" and "new". (This was news to me) so after a bit of Googling i found a program that can convert from new to old (so Registax can recognise them) The weird thing is I do four or five different sets of .AVIs in a night and Registax likes some of them and not others...anyway the program is at the following link and its free 8)

http://www.virtualdub.org/

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 Post subject:
PostPosted: Sat May 20, 2006 6:36 pm 
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Hello Milkywaheey,

Thank you for the links; I didn't realise there were different types of .avi file ! Beginning to think I should have stayed with the sketch pad...... :wink:

Best Wishes,

Geoff :)


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 Post subject: Dropped Frames
PostPosted: Tue May 23, 2006 3:11 pm 
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Joined: Tue Apr 12, 2005 5:15 pm
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Location: Feltwell, UK
I had the exact same problem. The fix I found was not using a USB mouse while imaging. I use a PS2 mouse, my laptop has the port. This cured the problem for me. I am guessing the mouse and webcam were over taxing the usb port.

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Feltwell, UK
http://www.dabsonastronomy.com


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 Post subject:
PostPosted: Thu Jun 01, 2006 10:12 pm 
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Joined: Tue May 02, 2006 7:00 pm
Posts: 30
Location: Nr Towcester, Northants
To back-up Dan's comments..

Many PCs only have a single USB 1.1 controller, and this works in an 'isochronous' manner (under the hood, each device you plug in requests a certain % of total bandwidth, and doesn't relinquish that until it's removed).

This means that if you plug in a game controller (or similar) in before your camera, then your webcam may not be granted its desired bandwidth, and you're going to have problems. It actually depends on the order that your USB devices are detected!

I'm a video-game developer by profession, and I've encountered similar issues with game controllers and other peripherals. I won't waffle on, but feel free to PM me if you have any specific questions about this sort of thing.


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 Post subject:
PostPosted: Sat Jun 03, 2006 4:02 pm 
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Dear All,

Many thanks for your advice 8) . Using the smaller default picture size running at 15 fps, no frames are dropped :D . Going up to 20 fps at the same resolution results in a lot of dropped frames again, so somewhere inbetween is the processing limit for the laptop's 700 Mhz brain.

Thanks and Best wishes,

Geoff :)


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