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I confirm that the V0.30 version continues to work with datvexpress, but I could not always operate the SR4000 It's limited, Time Clock on Minitioun is not locked. I have tested on 437Mhz and 1265Mghz.
For the SR2000, it is absolute perfect, Minitioun lock instantly.
I think it must be machine dependent as on my HP Pavilion I can get reliable 4.5 MS/s on the new firmware
but I can't achieve that with the old firmware.
The DATV-Express hardware will work up to 10 MS/s, at that point the anti-alias filters are starting to affect the performance.
The filters on the Express hardware were designed for a +/- 5 MHz bandwidth.
Updated mine just before our local net this evening; 4Ms/s was more stable with the new firmware.
During the net I used 2Ms/s but changed to 333Ks/s for a quick test; the result was a huge drop in power output from 15W down to 3W just on a symbol rate change.
We were chatting so I looked no further and switched back up to 2Ms/s, I'll check again tomorrow.
Anyone else found a problem?
There is an issue with very low symbol rates due to the x8 interpolater in the Pluto's PL fabric which does not
have unity gain, I have to raise a bug report with Analog Devices apparently to get that fixed.
The Pluto works out what clock rate and oversampling are required itself. The interpolaters in the transceiver
chip are simple halfband filters so should have fixed hardware gains.
I am wondering whether the old firmware had the same problem or whether that is something new?
The h.264 encoder seems to overshoot in bitrate, since when there's a lot of new content in the picture the TX queue goes up. But that's not the main problem since audio stutter also occurs with a black screen transmitted. Fiddling with the "Video bitrate twiddle" (tried settings from 0.7 to 0.1) didn't seem to help much with the stutter but, displayed video bitrate got down to the expected 10th of the TX bitrate. TX queue was happily bouncing between 19% and 20% but the stutter continued. TX Hardware seems not to be the problem, tried Pluto and LimeSDr mini on different USB ports.
Tried the older version 25p11 but had the same problem.
Any idea what that could be?
This morning I reverted to the earlier firmware and made a comparison with v0.30, results are similar. Yesterday was the first time I had used the Pluto for transmit at low symbol rates; in fact it only came of the box in the last week.
Thanks for the information; I don’t really need it for lower symbol rates at present, it’s a stand in for the shack DTX1 which has developed a fault.
It will of course be great if Analog Devices can make improvements.
H.264 doesn't seem to have a CBR mode (constant bitrate mode) so what I do is set the max and min bitrates to the same value
to try and force it to do CBR.
I suspect the stuttering maybe due to a non compliant MPEG2 bitstream. This is a known problem with the Express software
and something I have been unable to fix (and I have tried very hard to fix it). It does not affect all receivers only those that
enforce full compliance to the standard.
You may like to try the Portsdown software and see if the problem persists with that.
Has anyone else noticed this?
Its powered separately and has a short USB lead into a front USB3 on my desktop.