Moderators: Dave Moll, Andrew Davie, Steve Anderson
AncientBrit wrote:A further thought.
If you really want to embed a digital sync pulse then peak white clip the signal at FEh.
Dedicate the value FFh to signify a frame sync flag.
The dynamic range is reduced by 1 in 255, not a great loss.
GL
AncientBrit wrote:Steve, re framing, that was the point I was making.
I "kick-off" with pixel 0, line 0 which is the start of a frame.
There is no other data preceeding this on the file.
2048 bytes later I assume a "frame flyback" and start painting again the pixels at 0,0.
I have no need to embed any framing info, it's implicit within the file format.
This of course will only work where the digital "channel" is not liable to interuption, or where the playback is fragmented.
BTW I can play back at any other frame by indexing a file pointer by n*2048 bytes and starting from the new reference.
Regards,
Graham
AncientBrit wrote:If you set aside a single level you lose only 1 in 255.
GL
Steve Anderson wrote:Now then Guys and Gals....
Attached is a conceptual hardware implimetation of the above. What I don't know is...
1) Can the PC keep up with the required data rate through the paralell port? This of course is dependant on the PC hardware.
2) Using Interrupts, how precise would the timing be? i.e. would the buffer/latch be needed? What is the latency within the interrupt routine?
3) Could this be expanded to four bytes at 48kHz? One for luminance, two for colour-difference channels, and one for 8-bit audio? This of course would require additional external harware.
Andrew, Gary, over to you, I'm no programmer...
As shown the gate produces sync only when the data is 00h, if changed from an OR gate to a NAND gate, then FFh would generate the syncs.
Steve A.
AncientBrit wrote:The problem now is that RS232 and parallel ports are legacy devices.
gary wrote:Steve, a PC is generally well able to keep up with this rate *providing* it is not running windows or a windows like OS, for instance DOS is fine.
gary wrote:Steve, a PC is generally well able to keep up with this rate *providing* it is not running windows or a windows like OS, for instance DOS is fine.
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