10-08-2019, 05:17 PM
Success of sorts.
I have used a PLL to double the video clock frequency. This is used as the oversampler clock in the output of the converter.
It works but not consistently. I may have to power cycle a few times to get it to lock. When it don't lock the oversampler clock is clearly at the wrong frequency most likely due to the PLL not locking properly to the jittery video clock.
When it does lock it works very well. No jitter and the decoder does a very good job of decoding the 405 video. I cant see any degrading of the decoded video when compared against the original.
I am using the odd/even from the LM1881 in conjunction with the SAV signal from the embedded syncs to produce the frame sync which gives a solid lock with no jitter.
The odd/even from the LM1881 on it's own probably wouldn't work so well as it would be a async reset and probably cause some jitter.
Photo below of the 405 output.
More to try.
Frank
I have used a PLL to double the video clock frequency. This is used as the oversampler clock in the output of the converter.
It works but not consistently. I may have to power cycle a few times to get it to lock. When it don't lock the oversampler clock is clearly at the wrong frequency most likely due to the PLL not locking properly to the jittery video clock.
When it does lock it works very well. No jitter and the decoder does a very good job of decoding the 405 video. I cant see any degrading of the decoded video when compared against the original.
I am using the odd/even from the LM1881 in conjunction with the SAV signal from the embedded syncs to produce the frame sync which gives a solid lock with no jitter.
The odd/even from the LM1881 on it's own probably wouldn't work so well as it would be a async reset and probably cause some jitter.
Photo below of the 405 output.
More to try.
Frank
