Interlace

[rs38]

anyone from RL developers can explain in detail, why there is still no option to avoid the interlace video?
Of course the bullet cams are providing interlaced PAL, but internal Deinterlacing in den VVBox would improve visual quality so much, even the efficiency of the mpeg enconding will benefit.

thx in advance.

[Mike Broadbent]

VVB video processing is done in hardware designed for TV input and output, and no stage of the pipeline has a hardware deinterlace filter.

The MPEG-4 encoder works in interlaced mode so the encoding efficiency is not affected by interlacing artifacts.

Deinterlacing always reduces quality (loses information) so can be undesirable. If wanted it can be done at least as effectively at playback time, with more control over the final output and powerful software deinterlacing filters available.

Check your player's options; VLC can do this, and YouTube runs a deinterlacing filter as part of its normal upload processing.

Playing the video back on a system that handles interlacing (e.g. a TV) will show the full quality and temporal component of the original video which would be lost with deinterlacing.

[Steve]

More information about the VLC players deinterlacing can be found here.

[rs38]

Deinterlacing always reduces quality (loses information) so can be undesirable

But deinterlacing IS mandatory if you don't view the video on an old CRT TV. Do you still have one?

So if you don't want to postprocess the videos (as advertised) you need to live with the ugly combs or rely on what youtube is doing (they do not deinterlace or do it very badly, look at your own RLVboxvideo channel) or it depends on the player software or your Flat-TV who also try to deinterlace on their own.

If the MPEG encoder handles Interlace enconding correctly or even at all, depends from implementation to implemantation (e.g. h.264 vs. x264).
Progressive enconding efficiency is always superior to interlaced. This was one important reasons (Bandwidth) why the ITU recommended 720p/50 instead of 1080i resolution for HDTV.

But ok, let us (or me) be more pragmatic. If the interlacing cannot be changed or improved we need to live with it and there is a little advantage with the 50Hz to make it look smoother.
But it should always be in your mind when developing to get rid of it.
it would be a big step towards true HD 720p50 Quality.

[Steve]

The short technical answer is that deinterlacing on the box is likely not possible with the hardware we have, and determining if it is possible without a major redesign would be a lot of work possibly for nothing, so it's not something we have plans to do - especially as deinterlacing at playback time is quite simple. We appreciate it would be nice to have as an option and if it were as simple as flipping a switch, it would have been put in.

[Mike Broadbent]

Just for the purposes of discussion and information (as this is a handy thread to point other people to - it's not aimed at you RS38, I am aware that you know all this already )

Most of if not all HDTV’s have built in deinterlacing engines that are specifically optimised for that particular display. The engine can upscale, rescale, reduce/remove artifacts, apply colour and noise correction, remove/smooth jagged edges as a result of the rescaling of the image. This is something most if not all newer HDTV’s can do as we still use and watch PAL/NTSC television broadcasts.

As PAL is interlaced, every two fields are summed to make a complete picture frame. Most TV channels that are available through digital satellite and digital cable are older standard-definition signals.

All standard-definition content is captured and broadcast in a method called interlace. Because of PAL and NTSC, TV manufacturers will still be producing engines to deal with interlaced broadcasting so this is not a problem for older or new TVs.

This is far better than a generic pre processed deinterlace conversion as you could potentially lose picture quality. Even to this day digital broadcasting is interlaced and until that changes the TV manufacturers will still be producing HDTV’s with deinterlacing engines.

When you play an interlaced video on a computer monitor the "combing" effect will be noticeable because there is no engine to convert the video, but there are many Windows and Mac applications out there that will do a decent conversion (such as VLC).

Wikipedia article on Interlacing in video: http://en.wikipedia.org/wiki/Interlaced_video

[Steve]

^ Couldn't have put that better myself

[Steve Taylor]

^ Couldn't have put that better myself

Is that 'couldn't' meaning 'incapable'?

[Steve]

Go back to your cave Steve

[Steve Taylor]

I think I got a bite on the end of my line there...

[Steve]

Yeah you just landed a keyboard warrior...

[rs38]

When you play an interlaced video on a computer monitor the "combing" effect will be noticeable because there is no engine to convert the video, but there are many Windows and Mac applications out there that will do a decent conversion (such as VLC).

I think from the ~400 different VVBOX Videos I already watched, nearly 90% were played directly through youtube.
So it depends solely an the way Youtube receive, encode, store and how the flashplayer plays it finally in the browser.
It may be indeed that youtube does some sort of de-interlacing but for sure not one of the better techniques.

Further 5% I watched throught circuit tools which do not de-interlace.

may be the last 5% I watched through TV which changes from time to time.

So we need to place a "better deinterlacer" petition at google/youtube?!

[dwz8]

I'm trying to work around the interlace issue right now.

I understand that the PAL cams produce interlaced video. So far, so bad, as discussed above. That can be cured by players or software.
However, it looks like the scene graphics are placed on top of the interlaced graphics without being interlaced themselves. That seems to lead to an effect that deinterlacing algorithms work on the perfect scene graphics as well as on the interlaced video underneath.
So, no matter what you do, you get a jaggy image, either on the scene graphics or on the video.

Is there any way to synch this to avoid this effect? Or am I wrong with my assumption?

[Jon P]

I'm trying to work around the interlace issue right now.

Hi dwz8.
The graphics are part of the interlaced video, so they are interlaced. They only change once per frame rather than once per field though, so in the temporal sense they are not completely smoothly interlaced.

What I expect you are seeing though is not related to that, but is due to deinterlacing algorithms trying to deal with the graphics overlaid on video that has horizontal motion - I suspect you are seeing this even with graphics that are not changing, such as gauge faces and static images.

I assume this is because the deinterlacing algorithm is trying to be smart and move parts of fields around to compensate for motion between fields. Unfortunately that would also shift parts of the (non-moving) graphics and cause shear artifacts on graphics while improving the camera video.

Unless you can tell your deinterlacing filter to ignore the graphics areas, I don't see an easy way to fix that.

This is based on my guesses about what you are seeing, not having any screenshots to look at.

[dwz8]

Hi dwz8.
The graphics are part of the interlaced video, so they are interlaced. They only change once per frame rather than once per field though, so in the temporal sense they are not completely smoothly interlaced.

What I expect you are seeing though is not related to that, but is due to deinterlacing algorithms trying to deal with the graphics overlaid on video that has horizontal motion - I suspect you are seeing this even with graphics that are not changing, such as gauge faces and static images.

I assume this is because the deinterlacing algorithm is trying to be smart and move parts of fields around to compensate for motion between fields. Unfortunately that would also shift parts of the (non-moving) graphics and cause shear artifacts on graphics while improving the camera video.

Unless you can tell your deinterlacing filter to ignore the graphics areas, I don't see an easy way to fix that.

This is based on my guesses about what you are seeing, not having any screenshots to look at.

Jon, you are exactly right. Static images suffer from these operations, especially if the algorithm drops one set of lines (even or uneven) and tries to interpolate the rest.

One more challenge I'm fighting with is the scaling of static images. If I use a 100 x 100 pixel image as a static image it will be scaled in the VBOX output.

For example, this is the original:


here is the output of the VBOX (screenshot):
http://www.dwz8.de/fun/output.jpg

direct comparison:


So is there always some sort of scaling (potentially uneven in x and y direction) happening? I can't get things like dials to look crisp and clear because there is always some kind of distortion and dithering in the way.
What am I doing wrong?

Thanks for your help!