Rolling shutter and lightning footage

[Piotr Wozniacki]

Jack,

Did you call Prime Support? You can always say you're considering the V1E, and would like to learn about the rolling shutter issue. You could find a much more knowledgeable person there.

[Jack Zhang]

Originally Posted by Jack Kelly

I really like the 240-fields-per-second-for-3-seconds feature of the HC7. I love smooth slow-mo.

One warning for you, it is not in HD, it's processed in SD before being printed to tape so you're best off recording to the DV format when doing smooth slow rec.

Anyways, congrats on the purchase. and I seriously recommend that you also get a Blackmagic Intensity card to capture uncompressed or to a high quality compressed format such as NEOHD or DNxHD on the PC or ProRes 422 on the Mac for post work.

[Jack Kelly]

Originally Posted by Piotr Wozniacki

Jack,

Did you call Prime Support? You can always say you're considering the V1E, and would like to learn about the rolling shutter issue. You could find a much more knowledgeable person there.

Thanks for the reply. Hmmm... I'm not sure which part of Sony Support I called. It's too late now, unfortunately. I have to make the purchase now otherwise I wont have the camera in time for testing in time for a project I'm doing next week.

Originally Posted by Jack Zhang

One warning for you, it is not in HD, it's processed in SD before being printed to tape so you're best off recording to the DV format when doing smooth slow rec.

Oh, fair enough. Still - 240 fields per second (which hopefully I can convert to 240 frames per second using MVbob) is awesome, even if it is in SD. I imagine you need lots of light.

Originally Posted by Jack Zhang

Anyways, congrats on the purchase. and I seriously recommend that you also get a Blackmagic Intensity card to capture uncompressed or to a high quality compressed format such as NEOHD or DNxHD on the PC or ProRes 422 on the Mac for post work.

Yes, I've had my eye on NEO HD for a while now. I have a Blackmagic Decklink HD card (HD-SDI inputs, no HDMI). Unfortunately I've run out of PCI-E slots so I can't add an Inensity card... although I might look into HDMI-to-HDSDI converters.

If you're recording to HDV tape, is it still better to capture via the HDMI port rather than ingesting as .m2t and converting to NEO HD? Is the camera's HDV decompressor better than NEO HD's HDV codec? (sorry, this is getting a little off topic)

[Mikko Lopponen]

Originally Posted by Jack Kelly

I'm not sure I agree. Ghosting is an fairly inevitable side-effect of resolution-maintaining de-interlacing (even motion-compensated de-interlacers like MVbob produce some ghosting). Even using a top-of-the-line hardware de-interlacer will produce some ghosting.

Then something is wrong with your settings or the pulldown is going wrong.
Deinterlacing should never produce ghosting.

The HC1 actually has a warning in the manual about crooked pictures with the cmos sensor. Does the hc7 have the same warning?

[Jack Kelly]

Originally Posted by Mikko Lopponen

Then something is wrong with your settings or the pulldown is going wrong.

Pull-down isn't required for converting 60i to 30p or 50i to 25p (which is usually what you're doing when you make video for the web from interlaced footage). It's only required when doing things like 23.976 fps to 29.97 or when you're extracting 24p from 60i (which is what you'd want to do if you were editing 24p footage shot on an HV20). Luckily, I live in PAL land so I very rarely have to worry about pull-down because most of my projects are shot either 50i or 25p.

http://en.wikipedia.org/wiki/3:2_pul...ldown_patterns
http://www.zerocut.com/tech/pulldown.html

Originally Posted by Mikko Lopponen

Deinterlacing should never produce ghosting.

A very common form of de-interlacing is to blend the two fields to make a single frame. That will always produce ghosting on moving objects. More advanced forms of de-interlacing like motion-compensation attempt to interpolate the missing information but this often produces artefacts which looks a little like ghosting.

http://en.wikipedia.org/wiki/Deinterlacing

As far as I'm aware, the only way to de-interlace footage without producing any artefacts is to throw away one of the fields. But this, of course, cuts the amount of vertical detail by half. Which might not be a problem if you're shooting 1080i and distributing in SD. Maybe this is the sort of de-interlacing that you're using?

[Jack Zhang]

Originally Posted by Jack Kelly

If you're recording to HDV tape, is it still better to capture via the HDMI port rather than ingesting as .m2t and converting to NEO HD? Is the camera's digital-to-analogue converter better than NEO HD's HDV codec? (sorry, this is getting a little off topic)

If you record onto tape, the footage has already been compressed so outputing it to the HDMI port wouldn't make a difference between the quality of the .m2t capture and the quality of the HDMI from tape capture.

The only way to record uncompressed is to hook the HDMI directly to the card or adaptor and start rolling by starting a live capture on your PC.

[Jack Kelly]

Originally Posted by Jack Zhang

If you record onto tape, the footage has already been compressed so outputing it to the HDMI port wouldn't make a difference between the quality of the .m2t capture and the quality of the HDMI from tape capture.

Cool - that's what I would have hoped. Just out of interest - have you done a side-by-side test of footage decompressed by the camera and ingested uncompressed over HDMI versus footage ingested as m2t-over-firewire and decompressed by your computer's HDV codec?

I have heard that the HV20's HDV decompression algorithm is very good quality - so good that it's sometimes best to ingest material recorded on HDV tape as uncompressed over HDMI because the camera's HDV codec is better than many software HDV codecs... which would make sense.... not all MPEG2 codecs are made equal and it would make sense if you got an increase in quality by using the same codec for capture and decompression (i.e. the camera's)

[Jack Zhang]

Actually I use a laptop, but the image on my camera in play/edit and the image when playing a captured .m2t in VLC is identical.

I don't know about the decoding algorithms, The HC7 might have extra data from the x.v.color but I haven't played a tape in an HV20 to test out for myself.

[Stu Holmes]

Originally Posted by Jack Kelly

Oh, fair enough. Still - 240 fields per second (which hopefully I can convert to 240 frames per second using MVbob) is awesome, even if it is in SD. I imagine you need lots of light.

Hi Jack
You're in the UK so it's 200fields per second, not 240fields per second.

240fields/sec is the rate for SSR in NTSC-country models (120frames per sec) and 200fields/sec is the SSR rate for PAL-country models. (100frames per sec).

[Jack Kelly]

Originally Posted by Stu Holmes

Hi Jack
You're in the UK so it's 200fields per second, not 240fields per second.

240fields/sec is the rate for SSR in NTSC-country models (120frames per sec) and 200fields/sec is the SSR rate for PAL-country models. (100frames per sec).

OK - thanks for the heads up. 200fields-per-sec (converted to 200fps with MVbob) is still very useful. It's higher than an SR3-high-speed can get (120fps) so I'm happy.

I have to say that I'm well un-impressed with the published specs on Sony's website. Not only does is say factually incorrect statements like "Image Device: Progressive" but it doesn't make any mention of the framerate for SSR or the read-speed of the rolling shutter.

i'm very glad companies like Cineform and Red are taking a much more transparent approach to customer services.

[Jack Zhang]

Ok guys, the lightning footage is finally up:

http://stage6.divx.com/user/jackvanc...rnaby-(720p60)

[Jack Kelly]

Very good work - thank you.

Please may I ask what settings you used on the camera? Auto-exposure? 1080/60i? Shutter-speed?

I've taken a look at the video and progressed frame-by-frame through the lightening and - to my eyes - it looks like there are no rolling-shutter effects. But, then again, the lightening runs fairly horizontal so it doesn't really "test" the rolling shutter too much. Ho hum... I might get a chance to film some lightening with my new HC7... I should get the camera on Friday and the weather forecast is for lots of rain this weekend... and then I'm going up to Sheffield next week:

http://news.bbc.co.uk/1/hi/in_pictures/6240038.stm

[Jack Zhang]

The settings were 1/60th shutter, manual exposure, manual focus (infinity), outdoor white balance.

[John Mitchell]

Originally Posted by Jack Zhang

Anyways, congrats on the purchase. and I seriously recommend that you also get a Blackmagic Intensity card to capture uncompressed or to a high quality compressed format such as NEOHD or DNxHD on the PC or ProRes 422 on the Mac for post work.

Hi Jack - just interested in this statement. AFAIK the only way to capture DnxHD is with an Avid DnxHD board with exclusively HD-SDI input. Have you had success capturing with a Blackmagic Intensity card, because that would be interesting indeed?

[Mikko Lopponen]

Originally Posted by Jack Kelly

Pull-down isn't required for converting 60i to 30p or 50i to 25p (which is usually what you're doing when you make video for the web from interlaced footage). It's only required when doing things like 23.976 fps to 29.97 or when you're extracting 24p from 60i (which is what you'd want to do if you were editing 24p footage shot on an HV20).

That example video was ntsc and it was 24p and encoded badly. No pulldown. Ghosting on every second frame. It's apparent that it was shot in 24p mode with the hv20 and badly converted.

My point still stands. That video looked horrible. I can't understand why you're trying to counter it by saying ghosting is good. It's not. It's horrid.

A very common form of de-interlacing is to blend the two fields to make a single frame. That will always produce ghosting on moving objects. More advanced forms of de-interlacing like motion-compensation attempt to interpolate the missing information but this often produces artefacts which looks a little like ghosting.

I will never consider blending fields to be a proper way of deinterlacing video. It' s not. And if you get ghosting then you need to check all of your settings when using motion compensated filters. Smart deinterlacer for virtualdub works well as does Alparysofts filters.

As far as I'm aware, the only way to de-interlace footage without producing any artefacts is to throw away one of the fields. But this, of course, cuts the amount of vertical detail by half.

Interlaced material has 50% information in moving parts. The vertical detail rarely is that high anyway. Just do a simple deinterlace and be done with it. Ghosting looks way more horrible than the resolution loss.

That lightning video didn't prove anything. Just take the camera and way it around bravely. If there's no artifacts = no rolling shutter.