23-05-2019, 07:21 PM
Just to explain where Hedghog fits into the various ways TR memory can be done, that Jeffrey has outlined.
Hedghog uses a FIFO for TR memory. A FIFO was chosen simply because it was easy to implement using the Quartus tools.
It is 8 bits X 4096 words. (Hedghog II will use 9 bits X 4096 words)
Just the active part of each line is stored. When aspect ratio conversion is done the line is cropped before being wrote to the TR memory. It is cropped over sized to allow for tweaking to be done on the 405 side to centre it. The unused portion of the over sized lines lies in the H blanking period so wont be seen.
The SAV(Start of Active Video) signal in the embedded syncs is used to reset the counter that determines the length of each stored line.
There are no H sync markers stored, hence the need for only to read or write full lines.
Frank.
Hedghog uses a FIFO for TR memory. A FIFO was chosen simply because it was easy to implement using the Quartus tools.
It is 8 bits X 4096 words. (Hedghog II will use 9 bits X 4096 words)
Just the active part of each line is stored. When aspect ratio conversion is done the line is cropped before being wrote to the TR memory. It is cropped over sized to allow for tweaking to be done on the 405 side to centre it. The unused portion of the over sized lines lies in the H blanking period so wont be seen.
The SAV(Start of Active Video) signal in the embedded syncs is used to reset the counter that determines the length of each stored line.
There are no H sync markers stored, hence the need for only to read or write full lines.
Frank.
