02-11-2019, 01:19 PM
Hi Jeffrey
I would have to agree with you that it is a hard way to do it. Much easier to do it with a FPGA or for better results stored as a literal.
But in this case I already had the grunt work done in the PM5544 style test card generator it was just the matter of adding the software for programming the modulators to it. So not too big of a job.
It briefly crossed my mind to change the PIC crystal frequency to 16 MHz so that a 4 MHz clock for the modulators could be derived from it. But this would require a total rewrite of all the code and that simply wasn't going to happen.
At one stage I had thoughts of recording 405 lines video and audio to SD card. In the first version firmware for Hedghog all the 4:3 to 5:4 conversion was done in the 405 side so that a recorded video in 405 lines could be replayed in either 5:4 or 4:3. But this thread by Trevor put a stop to this and I mean that in a good way
.
These small cheep Freeview boxes that can play from a USB stick are incredible. They can play pictures, test cards, films etc. from the USB stick.
I use one now all the time and have all the test cards that I want on it. They are much more convenient to use than a DVD player as it is much easier to download to a stick than having to burn a DVD.
Hi Mike
If using a PIC to play video from a SD card I think the biggest pain would be keeping the timings right and keeping the syncs in the correct place. It might be easier to use 2 PIC's and to do timings and syncs the other to do the active line and read from the SD card. But if I were to attempt it I would go with a FPGA. They are cheap for what they are, not a lot more expensive than a higher end PIC18.
Frank
I would have to agree with you that it is a hard way to do it. Much easier to do it with a FPGA or for better results stored as a literal.
But in this case I already had the grunt work done in the PM5544 style test card generator it was just the matter of adding the software for programming the modulators to it. So not too big of a job.
It briefly crossed my mind to change the PIC crystal frequency to 16 MHz so that a 4 MHz clock for the modulators could be derived from it. But this would require a total rewrite of all the code and that simply wasn't going to happen.
At one stage I had thoughts of recording 405 lines video and audio to SD card. In the first version firmware for Hedghog all the 4:3 to 5:4 conversion was done in the 405 side so that a recorded video in 405 lines could be replayed in either 5:4 or 4:3. But this thread by Trevor put a stop to this and I mean that in a good way
.These small cheep Freeview boxes that can play from a USB stick are incredible. They can play pictures, test cards, films etc. from the USB stick.
I use one now all the time and have all the test cards that I want on it. They are much more convenient to use than a DVD player as it is much easier to download to a stick than having to burn a DVD.
Hi Mike
If using a PIC to play video from a SD card I think the biggest pain would be keeping the timings right and keeping the syncs in the correct place. It might be easier to use 2 PIC's and to do timings and syncs the other to do the active line and read from the SD card. But if I were to attempt it I would go with a FPGA. They are cheap for what they are, not a lot more expensive than a higher end PIC18.
Frank
