Flickering frames in full frame capture

[mits]

I have followed Dr. Mordrid's instructions about overclocking the RRS and my successful settings are :
MjpegQuality : 60 for 704*576/25fps
70 for 352*576/25fps

the only problem is that when i output to tv
(or tape) there is more flickering in 704*576 than in 352*576. The strange thing is that the flickering occurs only in some frames of the clip.
Camcorder is a Panasonic S-VHS using S-Video connection and the flickering may occur irrespectively the type of the tape (VHS or SVHS).
I use media studio pro 5.2 and all the settings are correct (field order A,best preview etc)

Thanks

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mits

[Dr Mordrid]

If it occurs only after the O/C then reduce the frame size and see if it stops. I'm using NTSC so I don't know how PAL will react to this hack.

Dr. Mordrid

[This_Idiot]

One thing you need to bear in mind is that high levels of contrast (or brightness) can screw the codec up. Also fast pans and zooms can have a similar effect.

These can happen at standard capture resolutions with both RR-S and RR-G, but will be exaggerated on playback if you hike the frame rate.

[Nick Piercey]

Does this "flickering" occur at exactly the same place on playback?

If it does it could be the dreaded "evil frames" which plague the RRS.

Just overlay a blank title over the dodgy part of the timeline which will force that part of the clip to be rerendered.

If it isn't this, then there is no one better than Chris and The Doc to help you sort out the problem.

Kind regards,


Nick.

[mits]

Originally posted by Dr Mordrid:
If it occurs only after the O/C then reduce the frame size and see if it stops. I'm using NTSC so I don't know how PAL will react to this hack.

Dr. Mordrid

Doc, thank you for your reply,
I tested it with and without overclocking the RRS and flickering is still noticable in 704*576. The problem is that i can't reduce the frame size since i always output the edited clips to a tape. According to Chris (This_idiot) -Thanks Chris-, this might be a problem inherent to RRS/RRG.
One more question (and sorry for bothering you), which frame size/compression is preferable for outputing to VHS tape ?
352*576 2.5:1 (Mjpegquality :70) or
704*576 5.5:1 (Mjpegquality :60)

I know that you suggest the half frame size in the o/c instructions, but why?. With some tests that i've performed, my humble opinion is that with full frame size the picture is a little sharper.
Thanks again.

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mits

[This_Idiot]

Hi Mits

Well to be honest, it isn't just the Matrox capture cards that can react like this. The problem is that certain frames or frame sequences can overrun the selected capture datarate, basically overloading the MJPEG compressor. The circumstances that I described are the most likely to produce the effect.

BTW, using an RR-S I couldn't distinguish the difference between 704*576 and 352*288 projects output to VHS when played back from the VCR to a TV. I even ran a "blind test" with my family, asking them to watch the same clip output at different resolutions. Their choice was the 352*288 !