No more boring test signals.

If you wish to share NBTV-format media files, suitable for playback on a mechanical TV, please use this forum section to post them. Large files are OK.

Moderators: Steve Anderson, Dave Moll, Andrew Davie

No more boring test signals.

Postby Steve Anderson » Sun Dec 02, 2007 5:01 pm

Hi All,

OK, here's my first attempt at a real picture, it's just a 60-second still of the man without whom this forum might not exist. As before it's sampled at 48kHz, 8-bits and a mono track.

I have no way of displaying it where I am at the moment, so those of you that have the facilities please let me know if it's OK or not. It looks OK when analyzed in HEX, or a sound-editing program.

I tried to install 'The Big Picture' as well as DirectX 9.0, but with no success, I'll have a more determined go some other time.

It's created by a simple piece of schoolboy software that converts a TIFF file into a repeated NBTV frame with syncs and the missing version as well.

The original input file is also attached in JPG format as for some reason the TIFF version wouldn't upload., The black band at the top shows where the syncs would go with the exeption of line 32.

As it's a repetitive frame file it compressed very well.

Feedback as always is very welcome.

Steve A.

P.S. No more boring test-cards......well, for a while anyway...
Attachments
JLB1.zip
(20.73 KiB) Downloaded 179 times
JLB1.jpg
JLB1.jpg (26.74 KiB) Viewed 1865 times
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 3783
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: No more boring test signals.

Postby Viewmaster » Sun Dec 02, 2007 10:20 pm

Steve Anderson wrote:I tried to install 'The Big Picture' as well as DirectX 9.0, but with no success, I'll have a more determined go some other time.


Feedback as always is very welcome.

..


It plays OK here on 'The Big Picture' but with reduced "level" setting to get a good picture.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1273
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Re: No more boring test signals.

Postby Steve Anderson » Sun Dec 02, 2007 10:42 pm

Viewmaster wrote:[It plays OK here on 'The Big Picture' but with reduced "level" setting to get a good picture.
Albert.


OK, so I presume that at least the framing is correct. In converting the original file to NBTV I did use as much of the entire gamut available to encode the picture file. 00h (00 decimal) being sync tips, 4Ch (76 decimal) being black and FFh (255 decimal) being white. It might just be a little too over-contrasty compared to the more usual sources. I'll have a look at some of the other wav files that have been posted.

Thanks for the feedback Albert.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 3783
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Postby Steve Anderson » Sun Dec 02, 2007 11:57 pm

Hi All,

Albert, I can see why the wav file might have been somewhat over-contrasted to the usual files. It seems that the usual files are recorded at 44.1kHz (not that should make any real difference) and at 16-bit PCM for encoding onto an audio-CD.

In general the same signal encoded at either 8 or 16 bits should return the same signal amplitude on the same soundcard etc. The the 8-bit version will have lower amplitude resolution, but it's fine for NBTV. But in in effort to create 'standard' levels only a part of the full 16-bits have been used, around 20-25%. See attached picture.

Whereas I have used the entire 8-bit gamut from 00h to FFh thereby generating a far larger signal. If it's too large for your display method, use a resistive divider, a pot.

The other thing of note is the rather poor response and definition of the sync pulses in the CD version (bottom trace). No wonder many have problems extracting rock-solid syncs. Compare them to those above.

The top trace is part of the JLB1.wav file I posted earier, the bottom trace is taken from the club CD. It's centred around the end of frame, showing the missing sync.

Steve A.

P.S. The pictures are not the same, so ignore what seems to be a coincidence in the actual video signal.
Attachments
NBTVa1.jpg
NBTVa1.jpg (63 KiB) Viewed 1853 times
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 3783
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand


Return to Images and Sound

Who is online

Users browsing this forum: No registered users and 2 guests