Post processing of NBTV

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Postby kareno » Sun Oct 17, 2010 8:34 pm

A periodic discontinuity might reveal a scene edge but that won't always work, as you say.
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Postby Viewmaster » Tue Sep 18, 2012 6:39 pm

gary wrote:I am posting a hacked up utility I have been using to test my algorithms for additional NBTV formats and would appreciate any feedback but especially from anyone who can test the video on mechanical monitors of the appropriate format.

The utility supports:

NBTVA (standard 32 line)
Baird (30 line with outermost 3 lines widened)
TeKaDe/Telehor (30 lines landscape)
Visionette (24 lines, 30 frames/sec, landscape)

The utility allows video to be created from bitmaps either provided internally or user provided.


This is regarding this utility posted by Gary 4 years ago. It was OmniNBTV.zip

I have used this utility OK many times but recently on trying to use it, it doesn't ever save the created file. I have tried everything (change of format/ number of lines/save to different folders etc) but it never saves at all.
Rebooting the computer and re installing from the zip file makes no difference, it still will not save.
If I try to save it and then try again under the same name I get the standard note of " This file already exists, do you still wish to save it."
But the file doesn't exist at it wasn't saved the first time !!

Does anyone with more PC knowledge that me (which is near zero!) have any ideas please, bearing in mind that I have twice reinstalled it from Gary's old thread, but it still doesn't save?
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Postby Harry Dalek » Tue Sep 18, 2012 7:16 pm

Hi Albert i have just been playing with video2NBTV that program sounds like this .

Might be just best to download it ...Gary will more than likely see this and put you on the right track .

I was playing with the other one that does colour but i really like this video2 that does all the other formats .
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Postby gary » Tue Sep 18, 2012 7:26 pm

Hi Albert,

If the application is saying the item already exists then it does exist. Can you describe exactly how you are saving - i.e. what directory, file name etc. It is possible to "fool" the system with certain kinds of file names - if you haven't already done so the first test should be to save the item to your desktop (so it is easily found and is visible) with a "safe" name like temp1, temp2 etc.

If that doesn't show the problem we can install a process monitor to have a look to see how and where it is writing the file.
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Postby gary » Tue Sep 18, 2012 7:44 pm

BTW Harry is right in that most of the formats (if not all) supported by OmniNBTV are available in the alpha version of Video2NBTV.

Also note that BEFORE you save the item it exists in your systems "temp" folder as something like:
NBTC7E1.tmp

Depending on your system the temp folder is usually something like

C:\Users\<your>\AppData\Local\Temp\

The ACTUAL save is really just a move and rename.
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Postby Viewmaster » Wed Sep 19, 2012 1:47 am

gary wrote:BTW Harry is right in that most of the formats (if not all) supported by OmniNBTV are available in the alpha version of Video2NBTV.
.


Thanks for all replies, but Gary's alpha version of Video2NBTV does not allow one to choose, to include or not, frame and line pulses. (or am I missing something?)

The old multi format OmniNBTV does allow line/frame pulse omission/inclusion.
This is the version I was trying to use again, to save NBTV with only the line sync pulses. Worked OK until now.

gary wrote:Also note that BEFORE you save the item it exists in your systems "temp" folder as something like:
NBTC7E1.tmp

Depending on your system the temp folder is usually something like

C:\Users\<your>\AppData\Local\Temp\


Gary, the temp file is not saved in the temp file folder, nor is it placed on the desktop nor in the desktop folder if I save to the desktop.

I have tried saving with many names and to many folders but it is never saved and is never in the temp folder at
C:\Documents and Settings\<your>\Local\Temp
Will spend some more time frigging and digging about.
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Postby gary » Wed Sep 19, 2012 9:19 am

Albert, when you create the file can you play it? That's after it is created do you then get a dialog box saying:
"Video created
Press 'Viewer' button to preview
Press 'Save As..' to save to a file"

and then if you press the "viewer" button and press start does it play?
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Postby Viewmaster » Wed Sep 19, 2012 6:30 pm

gary wrote:Albert, when you create the file can you play it? That's after it is created do you then get a dialog box saying:
"Video created
Press 'Viewer' button to preview
Press 'Save As..' to save to a file"

and then if you press the "viewer" button and press start does it play?


Yes Gary, it sure does. Everthing works OK on all formats, except the save.


BTW I also looked in the other temp files at 'all users/temp' and also at 'default user/temp just in case, but nothing there.

As a test I have just saved an Audacity .wav file to the desktop and it can be seen there OK.

I have recently upgraded my firewall and I do wonder if that is the problem....when I install your applications I do get warnings which I have to overide in order to instal...

......maybe Zonealrm Pro doesn't like Gary ! :lol:

But once installed OK I don't see how a firewall would effect the saving, but these PC's are so cantankerous at times you never know.
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Postby gary » Wed Sep 19, 2012 6:55 pm

Viewmaster wrote:Yes Gary, it sure does. Everthing works OK on all formats, except the save.


Well there you go Albert - the play can't work if the file doesn't exist - it has to get the data from somewhere - so at least the temporary file must exist.

The easiest way to solve this Albert is to install procmon from here:

http://technet.microsoft.com/en-us/sysi ... 96645.aspx

with that you can add a filter to show all of the disk activity for OmniNBTV.

Attached is an image the type of thing you will see.

Let me know if you want to try this.
Attachments
procmon.jpg
procmon.jpg (83.58 KiB) Viewed 7178 times
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Postby Viewmaster » Wed Sep 19, 2012 11:15 pm

OK Gary, thanks for that link which I have made a note of.

However I have found a work around to the problem.
Instead of reinstalling by hitting the download in your original letter
(the 3rd letter in this thread) I tried "saving target" to a new folder.
When I unzip the file in the new folder it all works OK and saves too !

So thanks for your help in all this, Gary, but I do have another question just out of interest.....
How accurate is the freq of the 400 Hz lines on all your applications which generate NBTV and how is it generated ? I am puzzled as to how it is controlled and I daresay many others who maybe reading this and, like me, are not very
PC "with it", would also like to know this.
I daresay the answer is hidden in the depths of the C (?) language you use to write the applications and which I do not know.
Thanks again.
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Postby gary » Thu Sep 20, 2012 12:03 am

Well Albert, unlike analogue systems, when you create a frequency in the digital domain it is PERFECTLY accurate. It has nothing at all to do with the programming language used, it is just simple digital signal processing - in fact as simple as it gets if the frequency is an integer multiple of the sample rate (as the NBTV line rate is for a 48 kHz - i.e. 1 line is EXACTLY 120 samples long), however it gets a little trickier when it is a non integer multiple (as the NBTV line rate is for that pesky CD sample rate of 44.1kHz - i.e. 1 line EXACTLY 110.25 samples long). In the case of non-integer multiples it is necessary create the signal in a higher integral sample rate and then low pass filter and down sample to the non-integer sample rate - for instance for 44.1kHz the signal is first created as four times 44.1kHz and then down sampled to 44.1kHz. None-the-less despite all of this extra complexity the line frequency is still exactly 400 Hz because it is in the digital domain - of course, as soon as you shift it back to the analogue domain through, say, your PC's sound card, it may no longer be at exactly 400 Hz. This is particularly so when playing out 44.1 kHz through a sound card whose native clock rate is 48kHz (or multiple thereof for more modern cards). In this case the sound card resamples, somewhat inaccurately, the 44.1 to the native clock rate and, as it is a non-integral sample rate conversion it "cheats" a little and there is some drift in the final clock rate. This is why I always recommend that NBTV signals always be created as an integral multiple of your sound card's native clock rate if you are going to use it as your primary destination - if you are burning to CD then 44.1kHz is the logical choice. Generally speaking, if the sample rate of the NBTV file is an integral multiple of the native clock rate of the sound card (or other digital to analogue converter) then the frequency in the analogue will be exactly the same as that in the digital domain (i.e. exact).

It should be noted that when NBTV is converted into digital audio of sample rates higher than 19.2kHz then the resolution in the line scan direction is higher than that of the 48 pixels as specified. For the 44.1kHz versions of my software that resolution is lost due to the use of a 9.6kHz anti-alias low pass filter but for the 48kHz (or higher) I leave that extra resolution in and it is quite noticeable on an analogue monitor such as a Nipkow disk.

Edit: Whoops, the more astute reader would have noticed I wrote 9.6kHz sampling rate where I meant 9.6kHz bandwidth - I have modified it to 19.2kHz sampling rate to keep the terms used the same. (9.6kHz is, of course, the maximum frequency present in the NBTVA 32 line specification).

Also for those that query the use of a 9.6kHz low pass filter for 44.1kHz audio when it could be almost (theoretically) 22.05kHz the main reason is to reduce the order of the filter.
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Postby Viewmaster » Thu Sep 20, 2012 5:26 pm

Well thanks for that reply, Gary. I shall have to ponder upon all that and then re read it. :)
Thanks once again for all your suggestions re OmniNBTV.
I created a 2 minute file from it in its new folder, with only line sync (no missing frame), and it saved all OK.
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Postby gary » Thu Sep 20, 2012 7:23 pm

Viewmaster wrote:Well thanks for that reply, Gary. I shall have to ponder upon all that and then re read it. :)
Thanks once again for all your suggestions re OmniNBTV.
I created a 2 minute file from it in its new folder, with only line sync (no missing frame), and it saved all OK.


I just realised I may or may not have answered your question - if not don't hesitate to ask again.

Re the file saving - it's a shame really I would have like to have discovered the root cause of that.
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Postby Viewmaster » Thu Sep 20, 2012 9:47 pm

gary wrote:
Viewmaster wrote:Well thanks for that reply, Gary. I shall have to ponder upon all that and then re read it. :)
Thanks once again for all your suggestions re OmniNBTV.
I created a 2 minute file from it in its new folder, with only line sync (no missing frame), and it saved all OK.


I just realised I may or may not have answered your question - if not don't hesitate to ask again..


I'm sure that you have Gary....the problem is at this end not yours :lol:

But I now assume, rightly or wrongly, (probably wrongly!) that as a digital file can be accessed at any speed, then it is the accuracy of the PC or CD player on playback that controls what the exact freq of 400 Hz NBTV lines run at.

gary wrote:Re the file saving - it's a shame really I would have like to have discovered the root cause of that.

The original problem file has now been deleted so I'm sorry, but cannot help now to discover what it was.
I shall not tempt providence by saying ,"Another time maybe" :shock:

The OmniNBTV application is very useful for me in generating constant line sync pulses without any frame sync, to lock a 3000RPM 180W DC motor exactly to 3000 RPM. I did wonder why you haven't put OmniNBTV on your website, but only a download link at the beginning of this thread,
even though it is for use on a static NBTV frame only.
All your very useful applications should be made sticky on this forum too.
Last edited by Viewmaster on Thu Sep 20, 2012 10:03 pm, edited 2 times in total.
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Postby gary » Thu Sep 20, 2012 9:55 pm

Viewmaster wrote:But I now assume, rightly or wrongly, (probably wrongly!) that as a digital file can be accessed at any speed, then it is the accuracy of the PC or CD player on playback that controls what the exact freq of 400 Hz NBTV lines run at.


Correct, once the signal is needed (if it is!) in the analogue (or time) domain then physics raises it's ugly head and there are limitations, however, any reasonable DAC will to a perfectly reasonable job for all intents and purposes - it is just that one caveat I mentioned (namely non-integer sample conversion) when the lowly PC sound card *may* present a significant problem for NBTV video.
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