SSTV / NBTV Player

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SSTV / NBTV Player

Postby acl » Tue Feb 08, 2022 3:20 am

Subject to future article in NBTVA Newsletter
Last edited by acl on Sun Feb 20, 2022 11:01 pm, edited 1 time in total.
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SSTV / NBTV Player

Postby acl » Wed Feb 09, 2022 1:31 am

Regards Chris Lewis G6ACL
Last edited by acl on Sun Feb 20, 2022 11:01 pm, edited 1 time in total.
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Re: SSTV / NBTV Player

Postby Steve Anderson » Wed Feb 09, 2022 5:20 pm

One would have hoped that some of the more reputable distributors would insist that suppliers to them produced a product which actually does what it's supposed to. e.g. RS or Farnell in the UK, perhaps Digikey in the US. - maybe they do. I've not checked if any of these suppliers do in fact carry similar products, and sure, they're gonna cost more than the usual 'net-based suppliers (generally significantly). But they're gonna work! I'd rather have one that performed as expected than six that were substandard or complete duds.

The old adage, "You get what you pay for."...

OK, I'll get off my soap-box now...

Steve A.

I recently saw an ad, "100 x 2N3055 transistors, US$15.00 including shipping," What do you think you're gonna get? Something suitable for your land-fill, not theirs.
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NBTV video Jukebox

Postby acl » Sun Mar 13, 2022 11:13 pm

Following on from the last newsletter I have added a small micro controller to sequence tracks and provide a simple display. The NBTV files are stored on a micro-SD card and the controlling software is written in BASIC and downloaded to a little development board. I am using a PICAXE processor which is a normal PIC with BASIC interpreter. Anybody interested just PM me and I will send you more details.
IMG_3749.JPG
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NBTV video Jukebox

Postby acl » Sun Mar 13, 2022 11:18 pm

Production unit
IMG_3748.JPG

IMG_3750.JPG
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NBTV Jukebox Finished unit

Postby acl » Thu Mar 17, 2022 1:45 am

IMG_3761.JPG
Front of unit


IMG_3753.JPG
inside unit
Attachments
IMG_3760.JPG
Rear of unit
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SSTV / NBTV Player

Postby acl » Wed Apr 20, 2022 7:03 am

278712530_7634041229969611_4473075276553453001_n.jpg
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Re: SSTV / NBTV Player

Postby Steve Anderson » Wed Apr 20, 2022 7:53 pm

Unless my two brand-new Eizo monitors are colour-blind I didn't see any 220 Ohm resistors at all. At the price they are (US$2200 each) I doubt they're wrong. More likely a bad camera and/or colour banding. The presets are a possibility, but they're almost illegible too.

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Re: SSTV / NBTV Player

Postby Harry Dalek » Thu Apr 21, 2022 6:15 pm

Under some artificial lighting reds and browns fool my eyes good to always double check with the multi meter .
I also have trouble with greens and blues orange and reds working under artificial lights :roll: either that or my eyes are going down hill fast !
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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SSTV / NBTV Player

Postby acl » Thu Apr 21, 2022 6:28 pm

278384818_4859327544189647_482203235557432280_n (1).jpg
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Re: SSTV / NBTV Player

Postby Steve Anderson » Thu Apr 21, 2022 6:42 pm

Nope. none of them look like 220R here...or maybe they do in the second version, perhaps...

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Re: SSTV / NBTV Player

Postby Dave Moll » Fri Apr 22, 2022 7:22 pm

The second image clearly shows red/red/brown/gold resistors in the ticked boxes, though these colours are not visible in the first image. Maybe only visible to a robot. :roll:
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Re: SSTV / NBTV Player

Postby Steve Anderson » Fri Apr 22, 2022 10:41 pm

Yes, I think someone has 'shopped' (i.e. Photoshopped) those images.
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Re: SSTV / NBTV Player

Postby FlyMario » Sun May 22, 2022 8:15 am

Just out of curiosity, what bit rate are you storing the MP3s at? It occurs to me that if the bitrate were high enough we could hold more lines.

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Re: SSTV / NBTV Player

Postby Steve Anderson » Wed May 25, 2022 5:18 pm

MP3 sampling rate...two things to think about here...MP3 is a compressed format designed for audio, i.e. speech and music. NBTV is most certainly neither of those. So the compression algorithm will 'throw away' information that we will not hear being missing in true audio but may be essential in NBTV video. Record NBTV in (say) WAV format and then MP3 and compare the difference both visually on a screen and on a 'scope.

The other thing is crosstalk between the channels. For stereo audio (speech, music) MP3 and the like 'blends' the lower frequencies into effectively a mono channel as in most listening arrangements it's hard to determine the source (left or right) of the lower frequencies, that's a natural human thing. Determining sound directionality is based on the speed of sound (around 305m/s) and the distance between our ears, then the brain can get a measurement of phase difference and determines the direction of the source. It does get quite a bit more interesting determining whether it's behind us or in front.

For NBTV that's a problem. MP3 may work well in certain circumstances and with suitable source material, but these days file size really isn't a problem, at least within the NBTV context. So really is there a reason to use MP3 or similar?

Klaas Robers covered this many years ago in a newsletter...

An alternative is FLAC, a compressed audio format. It doesn't achieve the same amount of compression, granted, but there's no crosstalk. It is also lossless, akin to Winzip...which is a viable alternative if you really need to shrink file sizes these days....

https://en.wikipedia.org/wiki/FLAC

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