16-08-2019, 09:28 AM
(This post was last modified: 16-08-2019, 09:30 AM by ppppenguin.)
The LM1881 is fine for most purposes. When you need precision sync separation and something that will work with trisync (as used on HD analogue) you need something better. I look back over my older designs and see precision sync separators that I've designed from discretes. No point now when good chips are around.
Glad I managed to do my 405 to 625 conversion without extra hardware. The only hardware mod was removing the 24.576MHz xtal and adding a wire link. Not sure if this will be feasible with the TVP5150 decoder as used on Aurora and Hedghog. Lowering the clock frequency works but getting good H and V sysncs looks harder.
Now to resolve the remaining problems. Horizontal timing should be easy. Finding the flaw in the interpolator somewhat less so. I also need to consider whether the output should be genlocked to a colour black reference. This would be useful if a 405 source needs to be fed into a conventional vision mixer. May not be worth the effort. Can always use a framestore synchroniser if that's occasionally needed.
I did an audit of the various input and output modules I have around. Plenty of analogue input, plenty of SDI input and output. Just 2 analogue output. So I'll probably go with SDI output, on the grounds that SDI to analogue converters are cheap and readily available. In a professional environment SDI is standard anyway. Actually HD-SDI has been the norm for some time but converter boxes are not expensive. I use a Decimator MD-HX https://cvp.com/product/redbyte_design_dd-hx_md-hx which happily handles any SDI I care to throw at it.
Glad I managed to do my 405 to 625 conversion without extra hardware. The only hardware mod was removing the 24.576MHz xtal and adding a wire link. Not sure if this will be feasible with the TVP5150 decoder as used on Aurora and Hedghog. Lowering the clock frequency works but getting good H and V sysncs looks harder.
Now to resolve the remaining problems. Horizontal timing should be easy. Finding the flaw in the interpolator somewhat less so. I also need to consider whether the output should be genlocked to a colour black reference. This would be useful if a 405 source needs to be fed into a conventional vision mixer. May not be worth the effort. Can always use a framestore synchroniser if that's occasionally needed.
I did an audit of the various input and output modules I have around. Plenty of analogue input, plenty of SDI input and output. Just 2 analogue output. So I'll probably go with SDI output, on the grounds that SDI to analogue converters are cheap and readily available. In a professional environment SDI is standard anyway. Actually HD-SDI has been the norm for some time but converter boxes are not expensive. I use a Decimator MD-HX https://cvp.com/product/redbyte_design_dd-hx_md-hx which happily handles any SDI I care to throw at it.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
