NBTV Camera Question

Forum for discussion of narrow-bandwidth mechanical television

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Postby Steve Anderson » Sun Jun 24, 2012 9:47 pm

gary wrote:....real engineers use desktop computers - go to your dump shop and grab a P4 for $5-$10 - it will do a much better job than ANY laptop for what we want to do. Rant, rave, and general mutterings of discontent.... ;-)


I concur. My almost eight year old laptop went to that great skip in the sky a couple weeks ago. When new I used it on a job in the middle east for a couple of months then it became my internet machine. I used it for browsing here at home and nothing else. Nothing.

The only reason I bought it in the first place was the client insisted I brought one with me.

It did a great job of browsing I have to admit, but that's I used it for. With the issues with Windoze security in those days I ran it on Linux until its demise. Its replacement (this machine I'm using right now) is also an old-ish P4 desktop I cobbled together from a pile of junk, it also runs Linux.

Unless you need to do Power-Point presentations to a bunch of corporate goons...never buy a laptop. They get stolen, dropped, and are simply a headache unless you truly need that portability.

Steve A.
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Postby gary » Sun Jun 24, 2012 10:02 pm

Thanks for the support Steve, sometimes when I get on my high horse I wonder if I have overstepped the mark a little, but in this case I think I have a good one (case that is ;-)).

I know that Harry is a little short of work space and so that is probably his rational for using them. (Of course he may also have happily come into possession of them at bargain rates ;-)).

However, I think a smallish case and an LCD monitor represent a foot print not that much larger than a decent sized laptop. With a desktop you can modify them and you have a chance of fixing them when they break, two really important factors for me at least.
gary
 

Postby Harry Dalek » Sun Jun 24, 2012 10:18 pm

Yep, but just for the record - in 98% of cases (that's a guess, but an educated one) it is best to record at 48k - this is because the sound card can ONLY record at that rate and every other sample rate is provided by very poor sample rate conversion. Now 24k is ok because it is an integer multiple of 48k so the sample rate conversion is relatively easy - but 44.1 or other non-integer multiples are a no no because the sound card samples rate conversion is not temporally precise and you end up with a time base error. It is generally best (at least this is what I always do) to record at 48k - then if you want to post it use your audio editor to resample to whatever rate you want - it will generally do a very good job of that.


Ok Gary 48k it will be ....this time its 24k mono if its not i am not sure whats up .

The first one is the crystal clock 10sec recording the other out of the sync video mixer the motor speed from start up to what to me looks like its control speed..



Well that will prove whether the ghost images are being introduced by the laptop or not.


They looked like they recorded ok .

BTW - I do not own a laptop - I hate them - they are for facebook loonies - real engineers use desktop computers - go to your dump shop and grab a P4 for $5-$10 - it will do a much better job than ANY laptop for what we want to do. Rant, rave, and general mutterings of discontent.... ;-)
[/quote]

Gary i am sort of stuck with these and doing projects small due to time kids.... room ...and such other wise i wouldn't be able to do this stuff ..i used to like desk tops these let me do the hobby ..
OH face book is all iphones in this house they think laptops are old hat ,i think desk tops and lap tops we bite the dust soon and these HD less slabs will take over ..who wants a slab :roll:
Attachments
crystalclock.wav
(1.62 MiB) Downloaded 532 times
pllmotorspeed.wav
(11.57 MiB) Downloaded 537 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby gary » Sun Jun 24, 2012 10:24 pm

Definitely 44.1KHz again Harry... perhaps you need another recorder application.
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Postby Steve Anderson » Sun Jun 24, 2012 10:27 pm

I know this has gone OT as is my style...but you can't put anything else inside a laptop. I'll probably be proven wrong here, but a second or third hard-drive for automatic backups? External drives are useful, but the human has to remember to plug it in and start the backup manually.

Or say four serial ports (or more)? Still used a lot in industrial applications. OK, you can get USB-serial adapters by using a VCP. (FTDI stuff is quite good for that)

I did have to take that laptop apart one time to re-seat what turned out to be a loose connector. It wasn't an enjoyable experience and took hours...and I had download the full manual from Compaq (as they were).

Anyway, let's get back to Harry's camera...

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Postby Harry Dalek » Sun Jun 24, 2012 10:30 pm

I think i can see the other pulses around the sync from this recording does not look good ...i will see if its the reflective sensor...start where it starts i say .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby Harry Dalek » Sun Jun 24, 2012 10:38 pm

looking at the 400hz ......i hope on garys Big screen and scope there looks to be a slight amount of drifting .

So am i right in saying its a touch off 400/?

I was also expecting a full screen white ...the pulse width is large is this the reason for a half screen...

Interesting as i have never tried this before.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby gary » Sun Jun 24, 2012 10:44 pm

Yes Harry there is drift - and no, in NBTV (unlike normal TV) the sync pulse forms part of the actual picture so however wide the pulse is in comparison to the line length is what you'll see. In other words you are not seeing half a picture you are seeing the whole picture half of which is taken up by the sync pulse.

Now back to the drift... I am not convinced this yet that this is due to your clock, it may be but because you recorded it at 44.1kHz - try again to record it at 48kHz - we will *probably* get a different result.
gary
 

Postby Harry Dalek » Sun Jun 24, 2012 10:46 pm

gary wrote:Definitely 44.1KHz again Harry... perhaps you need another recorder application.


Bugger !

OK i will try some others in case it is this one ...before doing the big stuff again .

Is there a way i can check it program wise that it is that or any rate i change it to ...i know i set this one right ..i hope its just changing a program.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby gary » Sun Jun 24, 2012 10:53 pm

harry dalek wrote:Is there a way i can check it program wise that it is that or any rate i change it to ...i know i set this one right ..i hope its just changing a program.


Yes, if you load it back up into Power Sound Editor it will tell you the sample rate in the title bar.
gary
 

Postby Harry Dalek » Sun Jun 24, 2012 11:05 pm

gary wrote:
harry dalek wrote:Is there a way i can check it program wise that it is that or any rate i change it to ...i know i set this one right ..i hope its just changing a program.


Yes, if you load it back up into Power Sound Editor it will tell you the sample rate in the title bar.


I just swapped to free audio editor is very much a like the last one but when saving it i can also choose 8 to 32 bit

This one is 48 16 it says as you have said when reloading it thats good so i don't waste time ..thanks for that .

looks a little better i think on your scope drift wise
Attachments
crystal400.wav
(862.72 KiB) Downloaded 546 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby Harry Dalek » Sun Jun 24, 2012 11:22 pm

Heres the pll motor speed sync only wav ...I adjusted the reflective sensor it looks better i don't see ghost pulses perhaps it was just pot bad luck i had the sensor pointed just right to double reflect off the cd ...perhaps
Attachments
pllmotorspeed2.wav
(600.15 KiB) Downloaded 506 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby gary » Sun Jun 24, 2012 11:26 pm

Just a small amount of drift now Harry, 1 sample in 90.

This may be unavoidable, but can I confirm with you that you actually set the recorder to RECORD at 48kHz, and not at some other rate and then converted to 48kHz when you saved it? because that is just as bad. I don't think that is what you did but I just want to be absolutely sure.
Attachments
crystal400.avi
(55.5 KiB) Downloaded 525 times
gary
 

Postby gary » Sun Jun 24, 2012 11:37 pm

That's getting pretty stable now Harry (see video).

I am now getting pretty convinced that the shape of the sync bar is due to irregularities in the encoder - can you record the pulses before they get to the comparator?

It is a pity that I haven't kept my wave files from my own camera otherwise I could do a comparison - it could be the encoder or it could be your printer - or even your cutting skills come to think of it!!!!?????
Attachments
pllmotorspeed2.avi
(160.5 KiB) Downloaded 594 times
gary
 

Postby Harry Dalek » Mon Jun 25, 2012 12:25 am

gary wrote:That's getting pretty stable now Harry (see video).

I am now getting pretty convinced that the shape of the sync bar is due to irregularities in the encoder - can you record the pulses before they get to the comparator?

It is a pity that I haven't kept my wave files from my own camera otherwise I could do a comparison - it could be the encoder or it could be your printer - or even your cutting skills come to think of it!!!!?????


I was thinking the slight difference cutting out of the encoder slots would cause the shape width of each pulse to be different ...that would be good to just be the encoder disk i can work on that now and know what i am doing .

i just put the camera away darn i did some video wav recordings soon as i switch on the light sensor i am getting some noise i would upload but is so bad this noise on the video so its either the light sensor circuit or the pc nothing else is on in the room ..i changed the battery ...i didn't try putting the lap top screen down it might be picking up the light from it come to think of it .And yes when i put it flat on the table the noise is gone mmm

I will record the reflective sensor pulses tomorrow no problems.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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