nVidia NTSC TV-Out interlaced field mix-up issue

[cybertheque]

Greetings:

I have struggled with the following issue for four years and the masochist that I am decided to give it another go -- I sincerely hope that readers of this forum with expertise will contribute to the discussion and hopefully a solution.

I cannot get proper NTSC interlaced video out of the S-Video or Composite ports on a variety of nVidia graphics hardware under various versions of MS-Windows. The symptom is that the last field from the previous frame of NTSC source material is combined with the first field from the next frame to produce an output frame. This is totally unacceptable for a variety of reasons not the least of which is that it produces visual artifacts, especially in motion sequences. To see how this looks, the following two clips may be inspected in virtualdub, using the bob-doubler filter, TFF, so that each field becomes a frame in the preview window. The first clip, the source material, shows a few frames properly composed of fields wherein the frame count increments correctly, with field 0 and 1 comprising 'frame 0', field 2 and 3 comprising 'frame 1', etc. The second clip, captured output from the S-video port of a 6150 graphics chipset, shows field 0 and a previous field comprising 'frame 0', field 1 and 2 comprising 'frame 1', etc. This is not an issue of field order (BFF vs TFF) -- it is a mixing of fields from separate frames, not the frames that they actually comprise.

source clip: http://waste.org/~msg/tmp/nvidia/inp-3frames.avi
output clip: http://waste.org/~msg/tmp/nvidia/tvout-3frames.avi

This issue has occurred on various nVidia cards running on Windows 2000, XP, and now Windows 7 64-bit. using drivers from 2002 to the present, in a variety of applications in 2D and 3D.

The platform of my current experiments and interest in repairing is this:

AMD X2 4400+ Nforce4 6150(le) nVidia chipset
Windows 7 64-bit SP1 (Aero mode for D3D support)
Dual display, primary HDMI digital, secondary NTSC TV full-screen 720x480 (with driver's overscan)
EVR Custom Presenter as renderer in test applications (including MCP-HC 64-bit), with vsynch forced on, various permutations of 3D settings in nVidia control panel.

Aero mode and EVR produce a tearing-free display on the TV but with the mixed-up fields problem.

The platform is an integrated device and it is not possible to replace the graphics controller; note that this device provided proper NTSC TV out when running on Linux 2.6 using a proprietary driver (not available to me).

Also at http://waste.org/~msg/tmp/nvidia are posted logs from 'dxdiag' and 'nvidia inspector' (nip xml file).

I also had this issue with certain ATI cards; there really is no room in the chassis for a decklink card (or matrox) so I _really_ need to resolve this issue and all help is appreciated.

Michael

[jagabo]

I think your problem is simple. The graphics card is putting out bottom field first NTSC video. Your capture device is capturing top field first. Neither is wrong in and of themselves. It's just that the combination that leads to the "problem" you're having. To "fix" it just change one or the other. Or recombine the fields in post (VirtualDub's Field Delay filter will work).

[cybertheque]

I wish it were just BFF <grin>; in any case, I can't fix in post because this is for a live switching application. Yet since the error is consistent, one could code a shim I suppose or come up with some amount of bounty $$$ to authors of the apps I intend to use to add some code to delay fields... I had hoped that there was some amount of tweaking I might try (out of the vast size of permutations) in driver settings (using Inspector) that may help...

[jagabo]

Encode your videos interlaced TFF instead of progressive. That should force the player to output TFF.

You might be able to use AviSynth in a realtime process. Just separate the fields, trim away the first, then weave them back together. Then play them as an interlaced video. You can open AviSynth scripts in some media players.