Somehow getting 60 unique frames in 1080 on GH2!

Welcome to the optical illusion known as interlaced. I have always considered interlaced a form of video compression sort of like compressing color down to 4:2:0. Yes you only have 540 unique vertical lines but because they are recorded every other line it sort of gives an optical illusion of 1080 lines because of how they are spaced out. Our eyes look at this single field and sort of the way our brains fill in the gaps between 24p frames our brains fill in the alternate lines. When you play this at 60 fields per second the optical illusion is even better.

This is all in theory of course. The reality is that this type of video doesn't compress as well and 4:2:0 color is putrid with interlaced video. For real world objects with lots of filtering interlaced still works very well but as soon as you have slight horizontal angles and thin lines this form of compression can fall apart. Sort of like 4:1:1 looking fine until you have a rich difference in colors.

So just think of interlaced as a sort of video compression where vertically you have a situation sort of like chroma subsampling that also affects the luma. Every other 1/60th of a second alternates vertically by 1 pixel. If both fields were the same then you really would have 1920x540 resolution with much more evident gaps in fine details.
 
Barry_Green said:
1080/60i @ 1/30 or 1/40 or 1/50 results in the same as 1080/30p.
Click to expand...

I can't find the thread now (possibly in the 1000+ post GH2 thread) ... but I think we decided that it's half-resolution 1080/30P, right? The folks clamoring for 25P for a while thought they could achieve that by shooting at less than 1/50 on their PAL cameras, but then it was determined that there was a resolution hit.
 
GrahamH said:
I can't find the thread now (possibly in the 1000+ post GH2 thread) ... but I think we decided that it's half-resolution 1080/30P, right? The folks clamoring for 25P for a while thought they could achieve that by shooting at less than 1/50 on their PAL cameras, but then it was determined that there was a resolution hit.
Click to expand...

The testing I have done with resolution charts indicates that it is true 1080p @ 30 FPS. I believe it gives you the same output as the 1080p 80% slow down mode if you speed that mode back up. You can only use it at 1/50 of a second shutter speed or slower though.
 
Thomas Smet said:
Welcome to the optical illusion known as interlaced. I have always considered interlaced a form of video compression sort of like compressing color down to 4:2:0. Yes you only have 540 unique vertical lines but because they are recorded every other line it sort of gives an optical illusion of 1080 lines because of how they are spaced out. Our eyes look at this single field and sort of the way our brains fill in the gaps between 24p frames our brains fill in the alternate lines. When you play this at 60 fields per second the optical illusion is even better.

This is all in theory of course. The reality is that this type of video doesn't compress as well and 4:2:0 color is putrid with interlaced video. For real world objects with lots of filtering interlaced still works very well but as soon as you have slight horizontal angles and thin lines this form of compression can fall apart. Sort of like 4:1:1 looking fine until you have a rich difference in colors.

So just think of interlaced as a sort of video compression where vertically you have a situation sort of like chroma subsampling that also affects the luma. Every other 1/60th of a second alternates vertically by 1 pixel. If both fields were the same then you really would have 1920x540 resolution with much more evident gaps in fine details.
Click to expand...

I understand this completely as I studied it when I was taking broadcasting but that was on tube CRTs where interlace works because as the laser scans the alternating lines the first line still has some fade glow time..... I can't see how this possibly works on a progressive display that does not have this laser fade glow time.. the modern LCD and LEDs don't do that they are progressive displays so... my brain is broken here as to how the handle this without really blocky looking jaggies....
 
Blackout said:
I understand this completely as I studied it when I was taking broadcasting but that was on tube CRTs where interlace works because as the laser scans the alternating lines the first line still has some fade glow time..... I can't see how this possibly works on a progressive display that does not have this laser fade glow time.. the modern LCD and LEDs don't do that they are progressive displays so... my brain is broken here as to how the handle this without really blocky looking jaggies....
Click to expand...

Your display bob deinterlaces the 60i signal. 60i=>60p

Simple sets just use bicubic resizing of fields (field 0 becomes frame 0, field 1 becomes frame 1, etc...) . You're right this leads to massive jaggies and aliasing.

But more expensive sets have better deinterlacing algorithms. They use antialiasing and line interpolation to fill in the "gaps"

Just like there are high quality deinterlacing algorithms in software, there are crappola deinterlacing quality algorithms as well.
 
I don't have any 1080p 60i material.. could someone shoot some and put up a native GH2 clip .mts file? I wan to DL it and see how my display handles it.

I have a ati HD 4870 x2 card that is a pretty awesome gfx beast... I just played some old DV video that was not the DVXs 24p but shot at standard NTSC video which is 60i correct.. even though they called it 29.97i it 720 by 240 at 59.94 in truth even though it is called 740 x 480 at 29.97... correct?

So on ONE computer.. it looks like crap and jaggy.. on my main ati 4870.. it actually looks fairly good and almost like it really is 480p & 60 frames per second.... but on fast ,ovement if I freeze frame I definitely see weirdness.
 
Blackout said:
I don't have any 1080p 60i material.. could someone shoot some and put up a native GH2 clip .mts file? I wan to DL it and see how my display handles it.

I have a ati HD 4870 x2 card that is a pretty awesome gfx beast... I just played some old DV video that was not the DVXs 24p but shot at standard NTSC video which is 60i correct.. even though they called it 29.97i it 720 by 240 at 59.94 in truth even though it is called 740 x 480 at 29.97... correct?

So on ONE computer.. it looks like crap and jaggy.. on my main ati 4870.. it actually looks fairly good and almost like it really is 480p & 60 frames per second.... but on fast ,ovement if I freeze frame I definitely see weirdness.
Click to expand...


Just turn on CBS or NBC or any other HDTV channel that broadcasts in 1080i. Any sports or news type video is going to be shot as 1080i. ABC and FOX are 720p broadcast channels. If you don't have cable then just grab a $5.00 antenna and pull in some free over the air HD channels.

The HDTV's pretty much handle it the way a computer would. By scaling each field to 1080 and only showing one field at a time. There is nothing really fancy going on there. Some HDTV's do try a fancier method of de-interlacing but thats about it. I think because it happens 60 times a second we just don't notice it as much. But yes I do notice jaggies every now and then from 1080i material on progressive displays. This is why I really prefer watching 720p. I would rather have a tiny bit softer video then deal with all the issues from cramming interlaced into a progressive world. For me at least softer trumps artifacts.
 
Blackout said:
I don't have any 1080p 60i material.. could someone shoot some and put up a native GH2 clip .mts file? I wan to DL it and see how my display handles it.

I have a ati HD 4870 x2 card that is a pretty awesome gfx beast... I just played some old DV video that was not the DVXs 24p but shot at standard NTSC video which is 60i correct.. even though they called it 29.97i it 720 by 240 at 59.94 in truth even though it is called 740 x 480 at 29.97... correct?

So on ONE computer.. it looks like crap and jaggy.. on my main ati 4870.. it actually looks fairly good and almost like it really is 480p & 60 frames per second.... but on fast ,ovement if I freeze frame I definitely see weirdness.
Click to expand...


Here are three high detail samples. Straight out of the camera. Gotta love the EYE-FI cards. I uploaded these videos straight from the camera to my computer as I shot them! You can even upload them directly to youtube from the camera. Sadly no Vimeo support yet.

720p sample
http://vimeo.com/22043269

1080i sample 1
http://vimeo.com/22043403

1080i sample 2
http://vimeo.com/22043559


Here are the 1080p variants for good measure

1080p @ 30 FPS 80% slow motion
http://vimeo.com/22045193


1080p @ 24 FPS
http://vimeo.com/22044182
 
Last edited:
I think the videos above show exactly why we need the hack for the GH2. Even the 1080p variants are bit starved in this type of scene.
 
Thanks for sharing mpgxsvchd, here are the specs from 3 of the clips :-

720 60p
General / Container Stream #1
Total Video Streams for this File.................1
Total Audio Streams for this File.................1
Total Subtitle Streams for this File..............1
Video Codecs Used.................................AVC
Audio Codecs Used.................................AC3
SubTitle Codecs Used..............................PGS
File Format.......................................BDAV
Play Time.........................................4s 953ms
Total File Size...................................10.4 MiB
Total Stream BitRate..............................17.5 Mbps
Video Stream #1
Codec (Human Name)................................AVC
Codec (FourCC)....................................27
Codec Profile.....................................High@L4.0
Frame Width.......................................1 280 pixels
Frame Height......................................720 pixels
Frame Rate........................................59.940 fps
Total Frames......................................299
Display Aspect Ratio..............................16:9
Scan Type.........................................Progressive
Color Space.......................................YUV
Codec Settings (Summary)..........................2 Ref Frames
QF (like Gordian Knot)............................0.300
Codec Settings (CABAC)............................No
Codec Settings (Reference Frames).................2
Video Stream Length...............................4s 988ms
Video Stream BitRate..............................16.6 Mbps
Video Stream BitRate Mode.........................VBR
Bit Depth.........................................8 bits
Video Stream Size.................................9.86 MiB (95%)
Audio Stream #1
Codec.............................................AC-3
Codec (FourCC)....................................129
Audio Stream Length...............................5s 24ms
Audio Stream BitRate..............................192 Kbps
Audio Stream BitRate Mode.........................CBR
Number of Audio Channels..........................2
Audio Channel's Positions.........................Front: L R
Sampling Rate.....................................48.0 KHz
Bit Depth.........................................16 bits
Audio Stream Delay................................676ms
Audio Stream Size.................................118 KiB (1%)
Subtitle Stream #1
Format............................................PGS
Codec ID..........................................144

1080 60i

General / Container Stream #1
Total Video Streams for this File.................1
Total Audio Streams for this File.................1
Total Subtitle Streams for this File..............1
Video Codecs Used.................................AVC
Audio Codecs Used.................................AC3
SubTitle Codecs Used..............................PGS
File Format.......................................BDAV
Play Time.........................................7s 588ms
Total File Size...................................15.2 MiB
Total Stream BitRate..............................16.7 Mbps
Video Stream #1
Codec (Human Name)................................AVC
Codec (FourCC)....................................27
Codec Profile.....................................High@L4.0
Frame Width.......................................1 920 pixels
Frame Height......................................1 080 pixels
Frame Rate........................................29.970 fps
Total Frames......................................223
Display Aspect Ratio..............................16:9
Scan Type.........................................Interlaced
Scan Order........................................TFF
Color Space.......................................YUV
Codec Settings (Summary)..........................2 Ref Frames
QF (like Gordian Knot)............................0.255
Codec Settings (CABAC)............................No
Codec Settings (Reference Frames).................2
Video Stream Length...............................7s 440ms
Video Stream BitRate..............................15.9 Mbps
Video Stream BitRate Mode.........................VBR
Bit Depth.........................................8 bits
Video Stream Size.................................14.1 MiB (92%)
Audio Stream #1
Codec.............................................AC-3
Codec (FourCC)....................................129
Audio Stream Length...............................7s 552ms
Audio Stream BitRate..............................192 Kbps
Audio Stream BitRate Mode.........................CBR
Number of Audio Channels..........................2
Audio Channel's Positions.........................Front: L R
Sampling Rate.....................................48.0 KHz
Bit Depth.........................................16 bits
Audio Stream Delay................................889ms
Audio Stream Size.................................177 KiB (1%)
Subtitle Stream #1
Format............................................PGS
Codec ID..........................................144

1080 24p

General / Container Stream #1
Total Video Streams for this File.................1
Total Audio Streams for this File.................1
Total Subtitle Streams for this File..............1
Video Codecs Used.................................AVC
Audio Codecs Used.................................AC3
SubTitle Codecs Used..............................PGS
File Format.......................................BDAV
Play Time.........................................6s 320ms
Total File Size...................................17.0 MiB
Total Stream BitRate..............................22.5 Mbps
Video Stream #1
Codec (Human Name)................................AVC
Codec (FourCC)....................................27
Codec Profile.....................................High@L4.0
Frame Width.......................................1 920 pixels
Frame Height......................................1 080 pixels
Frame Rate........................................23.976 fps
Total Frames......................................142
Display Aspect Ratio..............................16:9
Scan Type.........................................Progressive
Color Space.......................................YUV
Codec Settings (Summary)..........................2 Ref Frames
QF (like Gordian Knot)............................0.430
Codec Settings (CABAC)............................No
Codec Settings (Reference Frames).................2
Video Stream Length...............................5s 922ms
Video Stream BitRate..............................21.4 Mbps
Video Stream BitRate Mode.........................VBR
Bit Depth.........................................8 bits
Video Stream Size.................................15.1 MiB (89%)
Audio Stream #1
Codec.............................................AC-3
Codec (FourCC)....................................129
Audio Stream Length...............................6s 48ms
Audio Stream BitRate..............................192 Kbps
Audio Stream BitRate Mode.........................CBR
Number of Audio Channels..........................2
Audio Channel's Positions.........................Front: L R
Sampling Rate.....................................48.0 KHz
Bit Depth.........................................16 bits
Audio Stream Delay................................889ms
Audio Stream Size.................................142 KiB (1%)
Subtitle Stream #1
Format............................................PGS
Codec ID..........................................144

Cheers

Paul
 
Thanks for the clips.. and...

EWWWWW... I shall pass on 1080i. Don't like the live look, scaling wasn't so bad...not great but not bad, but yuck on the artifacting... all in all a look I would never want.
 
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