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dundurs  
#1 Posted : Tuesday, June 26, 2012 3:17:38 PM(UTC)
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Hello,
We are creating video content for TV channel, which means 50i standard is best suited since it will produce better quality on TV screen compared to 25p. The question is how can I make sure that vMix uses 50i through the whole workflow:
1. Inputting live video from camcorder,
2. Recording to a local file,
3. Outputting to external output - vMix virtual capture?

We have camcorders configured to output 720x576 50i and at this point Im worried that vMix downgrades 50i to 25p in case of live input and therefore has a negative effect on natural video motion. When we add input via “Capture” tab using USB Capture device, we get 25fps in vMix compared to 50fps when inputting a recorded video copied from the same camcorders flash drive (media player classic displays that the video from camcorder’s flash drive is actually 25fps interlaced).

Any suggestions how to deal with this will be much appreciated,,
Dundurs

P.S. As a suggestion, Martin, would introducing “50i” and “25p” as separate options solve the problem?
admin  
#2 Posted : Tuesday, June 26, 2012 10:57:28 PM(UTC)
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Interlaced is generally not recommended for a variety of reasons but it is possible.
Keep in mind the following limitations:

1. True interlaced video will show up as 25fps with alternating fields making up the 50i footage.
If you have a source that is playing back at 50fps it means it has already been deinterlaced.

2. The resolution of all interlaced sources must match the output resolution. (I.E 720x576 in, 720x576 out)
If resolutions do not match even by one pixel the interlacing will not be preserved.

3. vMix Virtual Capture and the recording will preserve the interlacing as long as point 2 above is followed.

4. Untick the deinterlace box when adding the camera.

5. Most video formats will be deinterlaced automatically by the decoder so usually only live camera sources will retain the full motion.

dundurs  
#3 Posted : Wednesday, June 27, 2012 6:37:10 AM(UTC)
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1. Im playing video, that has been coppied from camcorders flash drive. Camcorder is set to save videos at 720x576 50i, which is PAL SD standard. When I copy the video to computer's hard drive and open in media player classic, it displays "25fps" and "interlaced" on property pages. When I open the same video in vMix, it displays 50fps in the left bottom corner. You can check out that video here: http://failiem.lv/u/mwlrlet

2. I have set all settings in vMix to 720x576 50i or 25p, except input and preview size, also Im using widescreen everywhere.

3. I tried to record live video (with deinterlace off for specific capture input) using HDMI input (timeleak 80HD) and composite input (usb hauppauge live 2). In both cases after opening the recording in media player classic, in property pages it displays "progressive", not "interlaced". I made sure that camcorder is using 576i for HDMI output, composite output should be using 567i since its PAL standard, but I was not able to check that for sure.

6. To make sure which mode is being used currently, what about adding an "interlaced" or "progressive" indicator on the bottom left corner of vMix?

7. Assuming, I have interlaced live sources working, what happens in recording/external output if I mix in, for example, picture or a progressive video? Does recording/output switches to progressive or it adapts during time? Would be cool to force one mode, in my case 50i.

Regards,
Dundurs
mh166  
#4 Posted : Wednesday, June 27, 2012 6:09:00 PM(UTC)
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Regarding your video: could you use MediaInfo to get the correct parameters for this video? I'm honest: I don't trust Media Player in this. ;) So I guess it could be useful for Martin to have the output of MediaInfo for your video. :)

HTH.

Regards, mh166
dundurs  
#5 Posted : Thursday, June 28, 2012 2:41:22 AM(UTC)
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Thanks mh166, I've been looking for a long time for such a piece of software.

Yes, I can confirm that Mediainfo displays the same information as media player clasic for videos described above.
admin  
#6 Posted : Thursday, June 28, 2012 5:19:22 AM(UTC)
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Hi Dundurs,

Unfortunately there isn't always an easy way to specify that a video is interlaced at the time of recording.
If the recording is to an AVI you can open it up in most video editing programs and specify that the video clip is interlaced manually.

Fortunately with interlaced video any progressive videos or sources you add will work fine alongside interlaced sources the only difference being
less visible motion in fast moving scenes.

As for the video playing back at 50fps, many video cards upconvert 50i to 50p automatically making it next to impossible to convert that back down to
50i again. In this instance I would suggest having a look at the nVidia/ATI control panel and disabling any deinterlacing options.
You can also try switching between the VMR9/EVR renderer in the vMix settings to see if they handle interlaced content differently.

Regards,

Martin
vMix
dundurs  
#7 Posted : Saturday, June 30, 2012 8:37:18 AM(UTC)
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Hello, Martin,

I changed the renderer from EVR to WMR and disabled the deinterlace option in nvidia panel, and indeed the problem with video recording playing at 50fps disappeared and video is now being played at 25fps.

But this did not change that the MPEG2 recorded video in vMix is always "progressive" either when recording from a video file or a video capture source.
At this point we cannot be shure if the problem occurs at video capture source or video MPEG2 recording level. Perhaps introducing p/i status on vMix status bar would be a good next step to solve this mystery.

Dundurs
dundurs  
#8 Posted : Monday, July 2, 2012 5:44:54 AM(UTC)
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The reason Im digging deep in 50i workflow is that we have always experienced some motion issues with vMix. They are visible when the camcorder is being quickly zoomed in, out and moved around as it is necessary when capturing sports events.

I know that because I compare the 50i video recording coppied from camcorders flash drive and 25p MPEG2 recording created by vMix and there is quite the difference in motion, and I wonder if thats because 50i somehow gets lost along the way. Also when playing 50i recording from camcorders flash drive in vMix using EVR (vMix displays 50fps) and recording at 50p MPEG2, the result in terms of motion is much, much better.
admin  
#9 Posted : Monday, July 2, 2012 5:59:41 AM(UTC)
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I could look at adding an alternative deinterlacing option that converts the cameras 50i input to 50p.
That could then be recorded to 50p to retain full motion.

Would that be a suitable compromise?

It won't be in v4 but most likely the release after that.
dundurs  
#10 Posted : Monday, July 2, 2012 6:07:48 AM(UTC)
dundurs

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admin wrote:
I could look at adding an alternative deinterlacing option that converts the cameras 50i input to 50p.
That could then be recorded to 50p to retain full motion.

Would that be a suitable compromise?

It won't be in v4 but most likely the release after that.


Thanks for suggestion. I will do some more tests and get back to you.
Dundurs
admin  
#11 Posted : Tuesday, July 3, 2012 2:37:43 AM(UTC)
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I've managed to implement the new deinterlacing method in v4.
There will be two options available:

Blend: This is the current 50i to 25p conversion.
Bob: This converts 50i to 50p to retain full motion. Needs to be recorded to 50p.

dundurs  
#12 Posted : Thursday, September 27, 2012 12:34:32 PM(UTC)
dundurs

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admin wrote:
2. The resolution of all interlaced sources must match the output resolution. (I.E 720x576 in, 720x576 out)
If resolutions do not match even by one pixel the interlacing will not be preserved.


Any chance I could use 1024x576 external output with 720x576 capture inputs? If we resize at FMLE level, the cpu usage skyrockets because of FMLE (but FMLE preserves interlacing information). If we did this at vMix level, we would save 20-30% of i7-2760QM, which makes a huge difference and leaves cpu resources for video delays, etc.

Dundurs

P.S. We use 1024x576 (16:9) specifically to deliver to TV and for efficient stream transcoding later.
admin  
#13 Posted : Thursday, September 27, 2012 12:38:27 PM(UTC)
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Yes, you can safely export 1024x576 while preserving interlacing information.
I should have clarified point 2 by saying only the height needs to match across all inputs, the Width can be changed as requried.
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