Dear all,
I would like to share some more findings here regarding the implementation of an 819/576/405 signal generation system on a Linux PC in the hope some of you might find this useful. My first experiments were with two laptop computers an HP 8440p and an even older Dell Latitude 6400
Both employ the Intel integrated GMA graphics solution which seems to be limited when it comes to clock rates below 20Mc. While this is not a limitation for higher resolution output formats it will limit possibilities for outputting low res formats like PAL (576i) or 405i. Sine the french 819i format requires a clock close to 30Mc this format could be generated with ease on both laptop PCs. I was unable, however, to get a PAL or 405 output to work on those PCs.
Since I was aiming for a solution that could be switched to 405i, 576i and 819i I decided to conduct some more experiments. A few considerations had to be made for the whole system to work well with all desired formats:
1) The output of the TV signal should be over a VGA connector and this should be a second head on the PC. This meant a graphics card with both DVI/HDMI and ananlog VGA outputs needed to be found.
2) The main or primary monitor should have a decent resolution e.g. 1280x1024 or higher, so all OS menus, VLC player etc. could be run in a normal fashion
3) It should be easy to switch resolutions for the secondary monitor without a reboot and without interrupting playback of a video. This is to be able to demonstrate the different formats while playing the same video file.
4) The PC should be powerful enough to play HD content since only HD content could be down scaled to 819i while SD content would be up scaled thus not using the full potential of the 819i format. For a 405i only system a much less powerful PC would suffice as only SD content would need to be playable.
The problem, or so I thought, was to find a suitable graphics adapter that could be configured to output all desired formats while at the same time having an interface that was compatible with a modern PC motherboard. As I had read here that old GeForce 4 graphics cards were a suitable choice I tried an old GeForce 6600 with AGP interface. I still had this as well as the quite dated PC with a Pentium 4 processor. The results with the GeForce 6600 were disappointing. It worked with 405i but on 819i it produced a second vertical sync pulse halfway across the picture. Since the old Pentium 4 PC was not an ideal choice for playing HD content anyway I decided to investigate a more modern PC architecture.
I also had an old small PC that I had built a few years ago with an
Asus N4L-VM Motherboard and an Intel core2duo this has a PCI-Express 16 interface which makes the choice of graphics card much easier. Also not the most recent technology but just powerful enough to play HD content as long as a good graphics adapter was used.
Originally this had an ATi Radeon 4000 (EAH4350) in it which worked well under Windows 8 as an HTPC. When I installed Linux Mint XFCE 32 Bit on this machine it also worked well for the OS and I could get modelines to work for 405i. It would not work with 819i, however, in this case the sync of every second field was inverted and no matter which setting I chose in the modeline this issue remained. Back to the drawing board...
As a next test I extracted an Nvidia N210 card made by MSI from another machine I had and put it into the one I was testing. This was the answer! All modes were supported immediately and I could switch between formats even while playing a video in full screen on the second "monitor" i.e. VGA output to my modulator. All this worked until I decided as suggested by the Linux OS driver manager to install the proprietary Nvidia drivers. After doing so the modelines no longer worked, so be warned only use the integrated Xorg drivers...
As a third choice I had ordered or more recent Nvidia N710 card made by Zotac. This costs around €35 and is very sleek and does not need a noisy fan. This card also works perfectly with all modes. Here is an image of the card which can still be bought online:
So as a conclusion from this non representative test it seems that Nvidia cards even of newer design work with all modes we need for generating 405i, 576i and 819i. Summary:
Intel integrated graphics: good for 819i not good for 405i (576i was not tested)
ATi Radeon EAH4350 (Radeon 4000 series): good for 405i, not Good for 819i (576i was not tested)
Nvidia N210 made by MSI: good for all modes 405i, 576i and 819i
Nvidia N710 made by Zotac: good for all modes 405i, 576i and 819i
Here are a few images of the settings:
for a 405i output
for a 819i output
A few hints for setting up VLC:
- I used the detached video interface setting, so the window containing the play list will remain on the PC screen while only the full screen video can be moved to the secondary monitor. This will allow adding new clips to the play list while playback is ongoing
- It is a good idea to select a fixed video output renderer instead of "auto" in the VLC video settings. If this is not done the VLC interface will initialize every time it starts playing a clip and this will move the full screen video back to the PC screen.
Finally an image of the PC in its case:
I hope this information will be useful to others here while experimenting with modeline signal generation.
Cheers
Semir