01-04-2019, 03:03 PM
The problem in the Hedghog (and Aurora) isn't the output. This is a simple R-2R ladder DAC preceded by an oversampler to minimise the need for output filtering. If you programmed a frequency sweep test into the FPGA it would show the characteristics of the DAC and filter. I'm sure it would be good enough for Sytem E.
At present the pixel clock rates are 13.5MHz for the 625 side and about 8.7MHz for the 405 side. I'm not sure what clock rate would be used for an 819 output but I would estimate about 17MHz. This gives a theroretical BW of 8.5MHz. The limitation would be the 625 line input. 5MHz on a 625 signal corresponds to about 6.6MHz on 819.
The 1280 active pixels of a modern 720p system would be enough to give full BW 819. Not quite enough lines but by a very small margin. Remember that 819 is total number of lines, 720 is active lines. System E had about 770 active lines. Obviously any 1080 HD standard would be amply good enough.
At present the pixel clock rates are 13.5MHz for the 625 side and about 8.7MHz for the 405 side. I'm not sure what clock rate would be used for an 819 output but I would estimate about 17MHz. This gives a theroretical BW of 8.5MHz. The limitation would be the 625 line input. 5MHz on a 625 signal corresponds to about 6.6MHz on 819.
The 1280 active pixels of a modern 720p system would be enough to give full BW 819. Not quite enough lines but by a very small margin. Remember that 819 is total number of lines, 720 is active lines. System E had about 770 active lines. Obviously any 1080 HD standard would be amply good enough.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
