New Portsdown 4 Software Release 202101090

[G8GKQ]

I have just issued a new software release for the Portsdown 4 which adds a number of minor features, cures a few bugs and paves the way for possible future DVB-T support.

New Features

• You can now configure IP TS streaming and TS File playout from the "TS IP Config" Menu accessible from menu 3. TS files need to be put in the ~/rpidatv/video folder and can currently only be retransmitted by a LimeSDR.
• The no-signal timeout in the LongMynd receiver can be adjusted from the Receiver Config menu. The default is 5 seconds, but it needs to be set to 10 seconds to enable the reception of 66 kS signals.

Maintenance and Big Fixes

• RTL SDR drivers are now installed in new builds allowing the use of the RTL-FM receiver and curing a USB bug (causing Lime or Pluto to be inaccessible) that occurs if an RTL-SDR is connected. It is also possible to overcome this bug by installing the Langstone software (even if you do not plan to use the Langstone).
• New builds should now use the latest version of Raspios 2020-12-02.
• Reference to UGLY mode and other non-supported output modes has been removed from the software and, in new builds, from the Presets.

Future DVB-T Support

• Experimental support for DVB-T reception using the Knucker DVB-T tuner has been included. Note that DVB-T reception is not possible without this specialised hardware which we hope to be able to make available from the BATC Shop within a few months.
• Some touchscreen buttons and menus have been added to allow experimentation with DVB-T transmission using extra software and hardware that is still under development.

Please report new bugs associated with this release here.

Dave, G8GKQ

[vk3vcl]

Hello folks

Portsdown 2020 - Firmware v.202101290
Rpi 4 8 Gb
C920 Camera

So, I have had this system running for some time on the previous iteration of the firmware - v.202101240 - and it was quite remarkable. All features, at least those I utilised were fine.

Following the recent change to High Definition on VK3RTV here in Melbourne, I made the switch to v.202101290 as is has extra features and wish to test these against the new system here.

The software worked, vision was good, actually amazing is a better description - not due to anything I had done but because of the change up stream however there is a problem with on board USB audio via the C920 camera.

The audio transmitted is reported as broken and stutters despite the setting, constellation, rate what have you. Tried everything. Camera tested independently and is fine.

Any thoughts appreciated.

[G8GKQ]

Hi

I take it that you are in fact using Portsdown 4, not Portsdown 2020. The first software version that you mention (202101240) is only a development version released yesterday, that does not necessarily work; the most recent production (supported) version is 202101090. The other software version you mention (202101290) does not exist.

However, there has been no change in the C920 video/audio encoding since last August or September. What is significant is that the repeater receiver has changed.

The Portsdown is not perfect; the signal it generates has some minor video and audio encoding errors and some receivers/video players are more tolerant of these errors than others. The default Windows video players are very strict and do not tolerate the errors well. However, if you configure MiniTioune to send the video to VLC and then view that, the video and audio playback is generally smooth. So please could you try that and see if VLC plays the video/audio OK?

You do not say what SR, FEC, image format, transmission mode or output SDR you are using. It's a bit difficult to provide advice when I don't know what I'm advising on.

Dave, G8GKQ

[vk3vcl]

Hi Dave
The 202101290 was a typo, my apologies.

I am using the current supported version of the software and have also experimented with the new development version, 202101240, in fact, it is running now out of curiosity - your right, it doesn't work but looks promising. And yes, Portsdown V4.

However you have answered my question. The USB audio handling on the C920 has not changed which is exactly what I wanted to know.

With regard to the repeater changes, that's irrelevant as I began this testing phase after the installation of the new receivers however had used it for some months before the change. I found the old and new receivers handled the audio fine, in fact I received many comments about the quality of audio reproduction from a simple webcam on this system.

The audio worked before the change then also after, but before I tried the new software release. The variable here is the latest software release, hence the question.

At the time I was using the previous version of the software, sadly I cannot remember which one that was but I will look at setting up a new card next time I sit down and see if I can start again on that specific version which had stable audio. 202101090 sadly does not work well with the camera sound.

Specs as requested:
Lime mini as transmitter: Band: 23cm, Freq 1278 MHz. Distance to VK3RTV - 27 Kms just LOS@~8 watts via Gridpack @23dB.
Proven reliable path.

H264 - 4000 K/sym - 3/4 FEC - Format - 4:3 (and others where specified)

DVB-S QPSK H264 - 4:3 only (worked once with Audio)
DVB-S2 QPSK H264 - 4:3 - and all other supported formats. (Video only, audio broken)
DVB-S2 8 PSK - H264 - 4:3 and all other supported formats. (Video only, audio broken)
DVB-S2 16 APSK H264 - 4:3 to 16:9 but struggled with 1080p. No Audio
DVB-S2 32 APSK H264 - See note 1.

Note:
1. All video formats as noted above work flawlessly on the HD repeater with the exception of DVB-S2 32 APSK. It almost locks but looks like the Pi struggles. It has sufficient input power but just boggs down.
2. After a restart, I had one instance of good video and stable sound on the system (Meaning through the repeater) this was in DVB-S QPSK however when I tried to repeat the test, the audio went back to stuttering.
3. I can test locally with a mini-touner and other equipment, but these results are via the device it needs to operate on.

Thanks for any insight you may have or suggestions on rolling back. Happy to test further.

[G8GKQ]

I'll give this some more thought when I have had time to test at high symbol rates (we rarely use anything over 1MS in the Southern UK).

The one thing that is different is that the primary audio system used by Raspios has changed in the operating system. This change would have been loaded when you did a software update (as the latest operating system updates are loaded as part of the update). It did not seem to affect the audio at low SRs (I tested it at the time), but may have affected it at high SRs.

Rollback is almost impossible, because the Portsdown software works (should work) with the latest current version of the operating system. You'd need to roll back the operating system as well.

Dave

[vk3vcl]

Thanks Dave
Overnight I used the trusted technical technique of ignoring to problem and sleeping on it.

Your comments about the Raspios updates make perfect sense. As I have not tried this OS with any other application I have no reference but I might look into that further.

Today, I looked at some simpler aspects, none of which really relate to the OS and Portsdown software, but as they are relevant to my issue I will record them here:

I changed the common supply voltage to the Amplifier and Pre-Amplifier (a PHA-1) to 12VDC from 13.8VDC in order to to level the playing field.
The voltage to the Raspberry Pi System was not changed however I gave it access to a little more current to draw upon. Supply is via the header not the USB C.
I then tested the system on the same path into RTV2. I will only record the best result rather than a long list.

Portsdown power level 60 gave a solid picture into the Repeater with excellent Video and clear, uninterrupted audio.
- 2W out into the coax and Gridpack
-16APSK - H264 - 720p - C920 camera audio and video.

I was pretty amazed after yesterdays problems. 1W gave some breakdown so I did not push the matter and left it at that.

Environmental conditions today are significantly different as well. Today is 18 deg and overcast, yesterday was 40 deg and humid.

Thank you for you help so far, as I find out more regarding the potential changes to the OS and how they affect my situation I will report back.
Regards
Wayne

[G8GKQ]

Hi Wayne

I have been doing some Portsdown testing today at high SRs. 4 MS is towards the upper limit of what the RPi 4 and LimeSDR is capable of. Certainly 32APSK at 4MS is pushing it too hard. At 16APSK the main process to drive the LimeSDR is running at 90%, so has little headroom.

The other thing that I realised today is that you may have one of the newer C920s without the in-built H264 encoder. If so, your results will not be as good as mine. Logitech sneakily changed the internal specification of the C920 about 18 months ago to make it cheaper to build, but it is a much less capable device. I hope to put a C920 model identification facility in the Portsdown soon to highlight this issue.

My last thought is that you would do far better to reduce the receive SR of your repeaters when the time allows. There are multiple QO-100 users transmitting full HD using 500 kS or less in Europe. That would give you 9 dB more margin. The BATC Ryde Receiver is designed for repeater use and can scan through multiple SRs. Some here are set up on 1MS, 333kS and 125 kS. Last night I saw acceptable pictures from a transmission at 25 kS; progress is fast!

Dave, G8GKQ

[vk3vcl]

Thanks Dave
I appreciate you taking the time to test and post those results.

In answer to your question about the camera, I managed to source an older C920. I did have one here prior to the project, identical in every respect yet one works (the older) and one does not. Unbelievable move by Logitech. An advisory or modification would be of great assistance to many.

I had been watching the SR issue with regard to resources here and agree its a beast at that level but I generally operate it at lower levels.

FYI, I tested some configuration changes last night during an amp run in. I got the following results:
23cm - SR4000k/s - FEC 3/4 - Res 720p. Path 27Km LOS (Kinda)

Portsdown power level / Output in mW
46 200
45 170
44 150
43 100
42 80
41 65
40 50
39 40
38 35 Would not stay locked

All except the last produced an excellent picture and sound. Whatever the issue with audio was, it definitely has resolved itself. I would suggest just by messing with things enough to annoy it.

As far as the SR goes, that along with the settings in use here are designed to cater for a majority and many operators have several platforms, either experimental or in production, so to speak. The Administrator and designer of VK3RTV, Peter Coussins, VK3BFG has spent many years developing the system and still surprises us with innovative and clever features. Its a great resource and we are lucky to have it.

Thank you all for the feedback and help, I hope this is of assistance to others in the future.

Wayne

[G8GKQ]

Thanks for the feedback Wayne.

The next version of Portsdown 4 will have the ability to show (on the info screen) what model of C920 is connected.

The Portsdown video encoder already uses different code for the 2 models in some modes, but not all. The problem is that I only have an old C920 for development and testing, and the new ones are nearly £100 over here at the moment, so I am not rushing to buy one.

Dave