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Harry Dalek wrote:Good work Andrew just using the frame from locking was something i was wondering about in the past as well so interesting seeing it at work ....
Working but slowly was a problem that put me off a bit trying it but as you say work it does.
On the pulley side of things this is something i have tested a bit with and i found the tension is sort of critical so i put my little motor on an arm so i could adjust this and then lock it in place when it was correct.
Another idea i wonder if you could use the line and frame to lock the picture 33 holes the 33rd at some other position ...or perhaps half line 64 holes you would think the more you have the quicker more accurate the lock becomes so on ?
Klaas Robers wrote:Andrew, why do I see a sync-jump at the place where the scanning goes from line 31 to line 0? I would expect a sync bar that is straight, not a step of the height of the bar, which is now visible. It looks as if this is a problem in your video file, or a play-back problem.
Klaas Robers wrote:And then the jerkyness, also that could be a play-back problem in your time base corrector.
Klaas Robers wrote:Now that your time to get a stable synchronisation is this long, you should see that the disc is synchronised to an internal clock in the Arduino, and that the video files are also read / displayed locked to this internal clock. Then the time consuming synchronistion is needed only once: after switching on.
Klaas Robers wrote:A good stabilisation point for your PWM value is 128. Then there is equal "headroom" above as below.
Klaas Robers wrote:I doubt that the IR interrupt is the problem. That always occurs when the hole 31 is followed by the hole 0, so at a fixed moment in the rotation of the disc. I saw this jump in the sync bar moving horizontally, fixed to the 31-0 change in the video signal.
Any way, for me it looks a better idea to have a continuous interrupt in the Arduino each 80 msec (12.5 Hz), and synchronise the disc to that events as a separate process, and synchronise the video too to that events as a second separate process. Synchronising the video is much easier than synchronising the mass inert disc. Your Arduino has a crystal stable clock, so use that.
Klaas Robers wrote:Yes I understand you. But:
- what happens if the end of file is reached? Are the sync pulses then gone and is the disc running unsynchronised?
- what happens if a new file is started playing? Are the frame sync pulses then in a random phase and has the disc to be resynchronised? Then you mis at least the first seconds of the file.
When you create an internal crystal stable frame sync it should be rather easy to synchronise the output buffer of the video very fast to that internal frame sync. Then the disc IS already synchronised and you can enjoy the video from the second frame of the new scene. In this way all latency problems of the running disc are solved in an elegant way.
Klaas Robers wrote:When you create an internal crystal stable frame sync it should be rather easy to synchronise the output buffer of the video very fast to that internal frame sync. Then the disc IS already synchronised and you can enjoy the video from the second frame of the new scene. In this way all latency problems of the running disc are solved in an elegant way.
Andrew Davie wrote:Klaas Robers wrote:When you create an internal crystal stable frame sync it should be rather easy to synchronise the output buffer of the video very fast to that internal frame sync. Then the disc IS already synchronised and you can enjoy the video from the second frame of the new scene. In this way all latency problems of the running disc are solved in an elegant way.
The more I think about this, the more I agree with you. Spin up the disc based on a 12.5Hz signal, then the framing is automatic because the video playback is also synched to that signal (insofar as each new frame should start at the 12.5Hz pulse). Furthermore, fine adjustments can be made by simply adding an offset to the video playback pointer, so both vertical and horizontal adjustment of the framing should be possible too.
Klaas Robers wrote:Even simpler it will be to:
- bring the disc to speed. This is a separate routine that is only run when starting.
- When at speed switch to a "hold" routine just at the moment that the IR hole is sensed.
- This routine locks the disc IR hole to a cristal stable 12.5 Hz.
- Then play the files locked to the same cristal stable 12.5 Hz.
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