A question for dZeus...

[magician]

Hi!

I'm trying to help to DirectFB community on testing and development of driver for G400DH.

I remember once (long ago) you had posted something about Maven chip on G400DHs working natively in "6_something_something"x576, instead of 768x576 (square pixels) or 720 (CCIR.601). Though I've read that post couple of years ago, I never actually botherd to ask you where did you get that information from? Can you tell me more about it?

Search engine on this forum seams to be broken... so I have to ask you this way. I think that the thread was about fullscreen video in cloned desktop vs DVDMAX. As I understood that issue, it's better to pass an overlay content to Maven for video signal generation then scaling a video up (internally) and down again (in Maven) before D/A conversion itself. Though, I've read once on AVS forum that G400 has poorly implemented scaling algorithm/engine, so that could be another reason for superior picture of "untouched" video passed to Maven for D/A conversion and PAL/NTSC timings generation. Can you please comment on that?

Another thing... some people start to encounter some rather familiar problems with DVDMAX like feature under linux... it's a purple-green picture while playing videos. I remember seeing that strange behaviour more then once under Windows, and I'm quite sure I've seen it discussed here, so... Can somebody tell me more about this problem's origin?

Thank you in advance.

[magician]

I've managed to find that thread in which dZeus was referring to Maven's internal resolution (prior to D/A conversion).

He stated it was 688x480 for NTSC and 688x576 for PAL. I find it very interesting and I'm wondering where he get that information from, namely how reliable it is? I assume that it has nothing to do with Maven's input feed, which still has to be in accordance with CCIR.656 (YCbCr, YV12, 720xXXX).

dZeus, can you give me some info on this matter? Also... can somebody please tell me where can I obtain a copy of G400 developers documentation, which is not available through Matrox any more. Any help would be appreciated.

[Jon P. Inghram]

You might do better to send dZeus a PM if you didn't already.

[dZeus]

Hi!

I'm trying to help to DirectFB community on testing and development of driver for G400DH.

I remember once (long ago) you had posted something about Maven chip on G400DHs working natively in "6_something_something"x576, instead of 768x576 (square pixels) or 720 (CCIR.601). Though I've read that post couple of years ago, I never actually botherd to ask you where did you get that information from? Can you tell me more about it?

I once heard that the horizontal sampling in the DA step on the G400 tv-out is done at 688 pixels. I've never tried to verify the claim but you probably can find out by sending a signal with for example 720 alternating black and white vertical lines through tv-out and capture using a high quality capture card which has an effective horizontal resolution of at least 720 lines.

Search engine on this forum seams to be broken... so I have to ask you this way. I think that the thread was about fullscreen video in cloned desktop vs DVDMAX. As I understood that issue, it's better to pass an overlay content to Maven for video signal generation then scaling a video up (internally) and down again (in Maven) before D/A conversion itself. Though, I've read once on AVS forum that G400 has poorly implemented scaling algorithm/engine, so that could be another reason for superior picture of "untouched" video passed to Maven for D/A conversion and PAL/NTSC timings generation. Can you please comment on that?

scaling is bad whenever it's not needed. It'll make the picture look softer/blurrier than when the picture is only scaled when absolutely necessary (and it will mess up interlaced source often). For example consider the following 2 (simplified) scenarios in windows:

1. PAL DVD with interlaced video content is played back in dualhead clone mode to PAL tv-out
2. PAL DVD with interlaced video content is played back with DVDMAX to PAL tv-out

what actually happens is this:
1. the video is deinterlaced by the dvd playback software, scaled to the resolution of the desktop by the g400 video engine and then back to 576 lines by the maven chip.

2. video is not scaled and passed without deinterlacing in correct field order to tv-out

as this shows, 1 is very bad as it introduces 2 unnecessary scaling steps, as well as needing a deinterlacing step which will further reduce the image quality on tv. With 2, DVDMAX bypasses the scaling done in the maven chip because any scaling necessary is scaled by the overlay scaler in the G400 video engine (afaik).

Another thing... some people start to encounter some rather familiar problems with DVDMAX like feature under linux... it's a purple-green picture while playing videos. I remember seeing that strange behaviour more then once under Windows, and I'm quite sure I've seen it discussed here, so... Can somebody tell me more about this problem's origin?

Thank you in advance.

in Windows I often get this in YV12 colour space. When I use YUY2 colourspace this never happens. YUY2 will require a different upscaling routine for interlaced and progressive sources (at least, if you want the best possible colour upscaling with progressive sources). The Dscaler5 mpeg2 directshow filter takes care of this.

You should ask Ville Syrjälä about the G400 documentation. He has done a lot of work on the DirectFB stuff for the Matrox G400.