DATV-Express Project - May update report

[KenW6HHC]

The good news is that the Express_DVB-S_Transmitter software (long discussed on the Forums) for using the hardware board in a Windows environment is now available for download in a BETA-release. The BETA-version v1.10 can now be downloaded from the DATV-Express web site at http://www.DATV-Express.com on the DOWNLOADS page. Also available on DOWNLOADS page is a NOTES.TXT file (aka README) for v1.10. No User Guide is yet available for this BETA release. One of the real advantages of this software for windows is that it uses the FFmpeg library of software CODECs (H.262, H.264, and H.265) for encoding the video (no Hauppauge boards needed). Figure 1 below shows the MAIN user interface screen when running the Express_DVB-S_Transmitter software


Fig 1- The MAIN users screen running Express_DVB-S_Transmitter. The PTT button has been toggled to the TRANSMIT mode.


Fig 2- Typical set-up for Express_DVB-S_Transmitter software for Windows that was tested on Win7 and Win10.

W6HHC testing used both the LogiTech C615 and C920 webcams for MPEG-2 (aka H.262). WA8RMC testing included an NTSC video camera with a EasyCap USB-dongle. G4GUO testing favors using the free vMix video-editing software with Decklink mini recorder or the Magewell USB3 dongles.

One of the impressive features (to me) of this software implementation that Charles G4GUO has achieved is that the video latency is less than 0.5 seconds for MPEG-2 encoding…much smaller than even my old trusty SR-Systems Minimod hardware transmitter could achieve.

The next step is to complete a draft version of a Users Guide for this Windows software (already started).

73…de Ken W6HHC (project speed set to slow…)

[ON7KGK]

Hello Ken,
I successfully used this awesome software for transmitting DVB-S signals.
I know Charles is on another time consuming project but is there a chance this software can also transmit DVB-T signals ?
Thank you.
Best 73's from Michaël ON7KGK

[G4GUO]

Hi Michaël,

Currently I don't have any plans to add DVB-T to the Windows program.

The main problem is that the FPGA on the Express board is not big enough
to do the DVB-T encoding so it would need to be done on the PC. That means a
more powerful PC will be required. The idea of Windows Express was to be
able to run it on portable devices.

There is also an issue with the Linux DVB-T code for Express in that it is dropping
samples now and then. It does it at all channel bandwidths so I don't think it is
a performance issue. I believe it is an underflow in PC software. I will try and
address that when I next get time to look at it.

- Charles

[KenW6HHC]

Just a quick follow up note that I finally received a good H.264 transmission picture in 16:9 format (aspect ratio?) using v1.10 Express_DVB-S_Transmitter beta software by using the trusty PCI-based TuTioune analyzer software on my old WinXP lab computer as the receiver. The SR=5.0 MSymb/sec and FEC=7/8 video was still somewhat jerky…so I probably need to increase SR to 6.0 MS/sec? Also note that the Express_DVB-S_Transmitter software allows you to send audio at either 64 Kbps stream or the normal DVB-S spec of 192 Kbps. The reduced 64 Kbps audio is a big asset for obtaining better video on 2M RBDATV efforts.

My multi-protocol AMIKO “mini-combo” set-top-box received and displayed the H.264 OK…EXCEPT it never would show the entire picture….it always truncated the ends off….maybe even some top and bottom, too?


The Express_DVB-S_Transmitter is sending H.264 video as payload inside the DVB-S protocol on 1.2 GHz. Received 16:9 aspect ratio video using PCI-based TuTioune from F6DZP.

The next step is to still complete a draft version of Users Guide for this Windows software (already started).

73…de Ken W6HHC

[KenW6HHC]

Just put an updated beta-release of the Express_DVB-S_Transmitter software (for Windows) v1.11 up on the DATV-Express web site.
The new update can be downloaded from the DATV-Express web site at http://www.DATV-Express.com on the DOWNLOADS page. Also available on DOWNLOADS page is a NOTES.TXT file (aka README) for v1.11. User Guide is still NOT yet available for this BETA release (in progress - 50% completed).

The main fix is that the correct the v1.10 FPGA code that was inadvertently commented-out and thereby disabled the PTT line out to connector J4 - pin 2.

73...de Ken W6HHC

[F1CJN_alain]

Hi Ken
I am using the 1.11 version.
It is ok with Vmix but I have an issue using the C920 camera.
The camera is present in the Capture video settings as "Logitech HD pro Webcam C920" but the device formats menu stays blank with this camera.

Best 73's
Alain
F1CJN

[G0EID]

I have been playing with the port selection and sequencing of the PTT and C/O Relay lines in V1.11.

I found that the timing of the PTT signals on J4 - pin 2 and on J6 - pin 3 are not the same.
When going into Transmit mode the PTT line, on J4 - pin 2, rises at the same time as J6 - pin 4, C/O Relay line.
Then when returning to Standby, the PTT line, on J4 - pin 2, falls at the same time as the PTT line on J6 - pin 3.
Not sure if that is a bad thing or not, it might be a useful feature in the future?
Just be aware that the timing of PTT on J4 - pin 2 and J6 - pin 3 are not the same.

There is a warning in the release notes.
"These pins are connected directly to the FPGA with no protection you have been warned."

I found, on OSHPark, a PCB designed by W3DRK to interface to the Altera FPGA DevKits used in the Hermes-Lite project.
It has eight opto-isolated lines and an inverted PTT output line for systems that need it.
On the bench the outputs from the opto-isolator board control an HMC252AQS24 six way RF switch.

20160612_DATV-Express_Output_Buffering.jpg (673.49 KiB) Viewed 8042 times

Thanks Charles, please can we have an "Apply" button, on the Modulator settings window, in the next release?
Opening and closing the Modulator settings window gets old after awhile when testing.

73
Dave - G0EID

[G4GUO]

Hi Dave,

Yes J4_2 is the old PTT line. I left it as it was before for backward compatibility.

I still have to tweak things so that the RF output is sequenced as well, at the moment it is not
and could cause an issue. A better solution would probably be to do the sequencing in external logic.
That is what I currently do myself (using a cheap FPGA board, the one I wrote an article about
a few years ago in CQ-TV) but a PIC or plain logic would be just as good. I know a number of
people have developed sequencing boards mainly for use on microwaves and on moonbounce.

Interested in the HMC252AQS24 six way RF switch, where did you get the PCB from?
I picked up some latching selector switches recently good to 26 GHz but they are a bit
overkill for this application.

Yes I can add an apply button for the power level and RF frequency.
I noticed some other funnies during the contest that I will have to fix as well.

- Charles

[G4GUO]

Alain,

I have the same camera and don't see the problem you are seeing.

Did you use the Logitech install program when you installed your camera?
If not try doing that.

I have noticed before that Windows default drivers and manufacturers own drivers
support different formats. The Express application only supports a limited number of
formats, those formats it does not support are not displayed. That may explain why vMix can see
the camera and Express not.

- Charles

[f1faq]

Hello Alain,

I have tried release 1.11 (and 1.10) with my C920 Cam and I have all
formats available (Windows 7 SP1). Whas it working before by you ?
I have installed the Logitech software package at first
My first try sometimes ago was with a french Windows version and
I had the same problem. Changing to an english version resolved the case...

BTW : I have tried the DATV-Express version 2.03 with ubuntu release 15.10
and now 16.04LTS and it is working on both

73
Christian - F1FAQ