Question about 1080i and 720p formats

[mr-scarface]

OK so football matches are broadcasted in 1080i over satellite then they get captured and then released as 720p format. I've always disliked how motion looks in 1080i. 720p shows the motion more smoothly. But 1080i has the clearer picture due to higher resolution. Have I gone wrong somewhere? What do others prefer?

edit: Well I just read this post from edDV on another thread:

Not mentioned so far is the way motion is handled 1080i vs. 720p.

1280x720p has lower stationary resolution vs. 1920x1080i. For a still scene 1080i and 1080p show essentially the same picture at full 1920x1080 resolution. When an object is in motion, 720p delivers a full frame picture every 1/60th second (1/50th for "PAL"). Thus for fast action (e.g. think hockey with fast camera pan/zoom and fast object motion), there is no TV processing required to deliver a sequence of full resolution frames.

1080i delivers alternating odd and even lines (1920x540 resolution) every 1/60 sec for a full frame every ~1/30th second. It does this in approximately the same bandwidth or bit rate of 720p. When an object is in motion there is spatial displacement between odd and even lines of the same frame. For an interlace TV, this poses no problem since the TV is capable of sequential display of each field. The human eye processes the image into a 60 frame rate equivalent image through persistence of vision. The eye is tuned to resolve motion as vectors (direction) ignoring object detail until the motion slows. So for an interlace TV, 1080i is perceived by the human eye as near equivalent of 1080p at half the bandwidth. The Kell factor and other issues cause ~20% vertical resolution loss for interlace scan but since most TV aspect ratios are wider than high this isn't a serious tradeoff.

So if all HDTV sets were interlace (like a 1080i CRT or projector), 1080i would be close to a no brainer choice except for high action sports*. Remember, with high motion, the eye discounts resolution.

The spoiler for 1080i is the trend to progressive scan display technology. Progressive scan can't display 1080i as a sequence of 1/60th second fields. Unprocessed 1080i is displayed as 1/30th sec frames with horizontal combed lines during motion. The human eye can't process this image. Line split during motion is not perceived as directional motion but as un-natural artifacting (horizontally biased). For this reason, 1080i must be processed by the TV (deinterlace or inverse telecine) to make the image acceptable and predictable to the human eye.

Early HDTV sets had poor image processing. They mainly relied on blend deinterlace to average or blur out 1080i line comb during motion. This made the image look motion laggy/blurred. Over time inverse telecine and motion adaptive bob deinterlace techniques were added to better track motion vectors. Deinterlacers are getting better each model year with advancements showing first in the high end models. Budget models use 2-3 yr old "hand me down" deinterlace technology.

So, if you buy a cheaper flat screen TV, 720p may deliver a more motion natural image even if resolution is upscaled. A higher end HDTV will better handle 1080i source with fewer artifacts.


* progressive also has advantage for "white paper" text and graphics display. A white background tends to flicker more with 60Hz interlace scan.

So 1080i can be converted into 720p. And this 720p won't have the motion issue of the 1080i?

[edDV]

So did that answer your question? It depends where the conversion takes place.

In a 1920x1080p TV, sport 1080i/29.97 is deinterlaced to 1080p/59.94 or 1080p/119.88 (aka 120Hz) by various means. The result smooths motion at the possible expense of digital artifacts. Deinterlacer quality varies, usually by age and money spent on the TV. The premium HDTV sets have better deinterlacers.

If your HDTV has lower 1366x768 resolution, then the 1080i is first deinterlaced to 1080p, then downscaled.

[mr-scarface]

Yeah it totally did. But I'm curious as to how they convert a 1080i feed which looks bad in motion sequences, into a progressive 720 that looks good in motion.

[edDV]

Yeah it totally did. But I'm curious as to how they convert a 1080i feed which looks bad in motion sequences, into a progressive 720 that looks good in motion.

A 1080i/29.97 field is 1920x960* and progressive. This is down scaled to 1280x720p then you have 1280x720p/59.94.

BTW, a good TV will upscale 1920x960* fields to 1920x1080 frames for 1920x1080p/59.94.



*Correction 1920x540 instead of1920x960 (late night math). 1080/2=540

[mr-scarface]

Pretty cool. thanks.

I watched a football match which was 720p25, thinking it was a 1080i format when I watched it. I didn't like how it looked in motion(must have been due to the 25 framerate), so I just told myself that I'll steer clear of the 1080i. But my TV is actually pretty good (Panasonic Viera G15 series) and the 1080i's actually might look decent on it. I will try watching one and report back.

[edDV]

Pretty cool. thanks.

I watched a football match which was 720p25, thinking it was a 1080i format when I watched it. I didn't like how it looked in motion(must have been due to the 25 framerate), so I just told myself that I'll steer clear of the 1080i. But my TV is actually pretty good (Panasonic Viera G15 series) and the 1080i's actually might look decent on it. I will try watching one and report back.

How were you playing 720p/25?

Most US HDTV sets reject PAL frame rates. Not sure about Canada.

[mr-scarface]

Through XBMC. It has a built in player. Normally I use MPC-HC but nowadays I strictly use xbmc's internal player.

[edDV]

Well the display card would have converted to 59.94 so there would have been losses.

[poisondeathray]

You must mean "football" as in "soccer" or broadcast somewhere from Europe ? That's the only reason why you would have 720p25

"football" as in NFL/CFL would be 1080i/59.94 and 720p/59.94

Are you sure it's 720p25 and not 720p50 ? Motion won't look so good with 720p25

[mr-scarface]

Well the display card would have converted to 59.94 so there would have been losses.

Not sure what you mean exactly. The video card on my pc converted the framerate from 25 to 59.94? Why would it do that and what kind of losses are we talking about?
Sorry I'm not that well versed in this kind of stuff...kinda new to it and still learning a whole lot

You must mean "football" as in "soccer" or broadcast somewhere from Europe ? That's the only reason why you would have 720p25

"football" as in NFL/CFL would be 1080i/59.94 and 720p/59.94

Are you sure it's 720p25 and not 720p50 ? Motion won't look so good with 720p25

That's correct, I meant soccer. And yeah it was most likely broadcasted from Europe as it's from SkysportHD1. Definitely sure it was 720p. Here are the details:

UCL 10-11 - Last 16 - 1st. Leg - Arsenal FC vs. FC Barcelona - 2011.02.16 - 720p25 HDTV DD2.0 - English - MASSA
Video Codec: H264
Video Bitrate: 3500kbps
Video FPS: 25
Video Resolution: 1280x720

Audio Codec: AC3
Audio Bitrate: 384Kbps
Audio Channels: Stereo

Size: 2.72 GB
Language: English

It actually doesn't look that bad, but I did notice the motion. Anyhow, you think 1080i releases would look better in motion than 720p25?

[edDV]

Well the display card would have converted to 59.94 so there would have been losses.

Not sure what you mean exactly. The video card on my pc converted the framerate from 25 to 59.94? Why would it do that and what kind of losses are we talking about?
Sorry I'm not that well versed in this kind of stuff...kinda new to it and still learning a whole lot

Most laptops output video at NTSC rates (29.97 fps 59.94 fields per second). Check your display settings to see if PAL rates are supported (25 fps 50 fields per second). This would be rare. Also, most North American TV sets will refuse to play PAL.

When you play PAL in your computer player, it gets resampled to NTSC rates in the laptop's display card. This process is lossy.

[jagabo]

1080i video has as much motion information as 720p (50 images per second PAL, 59.94 NTSC). Your 1080i video isn't being handled properly if motions aren't as smooth as in an equivalent 720p video.

If you are converting, you need to convert to a format that supports interlaced video (and use a player that bob deinterlaces during playback), or bob deinterlace before encoding.

Each frame of 1080i video contains two half pictures taken at two different times, 1/50 second apart in PAL. One half picture is in all the even scan lines, one in all the odd scan lines. So you have two images that are 1080x540. When properly displayed you see each of those separately and sequentially. So 25 interlaced frames become 50 different pictures.

The problem when displaying that on a progressive display is that you have to fill in the missing scan lines in each of those 1920x540 images -- to fill the 1920x1080 display. Different techniques result in different qualities.

[neomaine]

So did that answer your question? It depends where the conversion takes place.

In a 1920x1080p TV, sport 1080i/29.97 is deinterlaced to 1080p/59.94 or 1080p/119.88 (aka 120Hz) by various means. The result smooths motion at the possible expense of digital artifacts. Deinterlacer quality varies, usually by age and money spent on the TV. The premium HDTV sets have better deinterlacers.

If your HDTV has lower 1366x768 resolution, then the 1080i is first deinterlaced to 1080p, then downscaled.

If I remember correctly, some TVs even downscale to 720p and then to the native 768p.

[poisondeathray]

UCL 10-11 - Last 16 - 1st. Leg - Arsenal FC vs. FC Barcelona - 2011.02.16 - 720p25 HDTV DD2.0 - English - MASSA
Video Codec: H264
Video Bitrate: 3500kbps
Video FPS: 25
Video Resolution: 1280x720

It actually doesn't look that bad, but I did notice the motion. Anyhow, you think 1080i releases would look better in motion than 720p25?

As described above, 1080i50 would have essentially the same motion characteristics as 720p50

BUT you don't have 720p50. You have 720p25. The sample you have has been single rate deinterlaced. i.e 1/2 the motion information is discarded

So yes, 1080i50 would look better in motion than 720p25 .

[jagabo]

Note that 1080i25 and 1080i50 are the same thing. Marketing just decided 50 sounded better than 25.

[mr-scarface]

Thanks a lot for the responses guys

Your 1080i video isn't being handled properly if motions aren't as smooth as in an equivalent 720p video.

If you are converting, you need to convert to a format that supports interlaced video (and use a player that bob deinterlaces during playback), or bob deinterlace before encoding.

I actually haven't watched a 1080i one. I thought the 720p25 was a 1080i at first. Gonna try a 1080i match and see how it looks.

Should I be tweaking any settings in the xbmc internal player?

[edDV]

Thanks a lot for the responses guys

Your 1080i video isn't being handled properly if motions aren't as smooth as in an equivalent 720p video.

If you are converting, you need to convert to a format that supports interlaced video (and use a player that bob deinterlaces during playback), or bob deinterlace before encoding.

I actually haven't watched a 1080i one. I thought the 720p25 was a 1080i at first. Gonna try a 1080i match and see how it looks.

Should I be tweaking any settings in the xbmc internal player?

Try MPC-HC. On recent machines with NVIDIA HD Purevideo, it self configures itself well. Maybe not on an x800 Radeon which was pre AVIVO HD. Try it

[mr-scarface]

ed, I used to have xbmc set up in a way where it would minimize the xbmc window and launch the video files in mpc-hc. Then when you're done watching the video, it closes mpc-hc and goes back to xbmc.
But mpc-hc was causing me playback problems on quite a few HD videos, especially 1080p ones. Sometimes it would stutter, and lots of times the audio would lose sync. Very frustrating.

I had tried many different renderers in the mpc options. Installed CoreAVC, disabled other decoders that shouldn't be running, etc. But the problems would still arise. Dxva was always enabled too - nvidia cuda or something like that it was called. Perhaps updating the video drivers to an even more recent version would have helped, but I never bothered.
Also, there was a flickering problem in mph-hc when the HD videos were being read from the media server (my desktop PC).
When you move those files straight onto the laptop, the flickering problem was gone. However, the random stuttering problems and audio sync problems were not. They would still show up once in a while. I'm sure the flickering issue is probably something simple, but I couldn't figure it out.

Ever since I got the new version of xbmc, I stuck with its internal player, and I haven't had a single hiccup on HD videos since! Now I'm sure there's a way to fix the mpc problem since it's a more advanced player than xbmc's internal one, but I just don't have the patience for it.

Plus another advantage of using the xbmc built-in player is that it doesn't need to minimize it every time you launch a video file...and it can even keep a small window of the video playing in the corner of xbmc while you browse your video/music library.

[edDV]

Well the machines you have listed are a generation or two earlier than my current machines that are all Core2 duo or quad with Win Vista,7 or Mac OSX Leopard. Display cards are mostly NVIDIA GT or GS. I have Linux on some older Pentium machines and VLC does OK for SD. I'm not watching many downloads, but much time shifted ATSC or cable transport streams.

[jagabo]

1080p24 and higher frame rates, or 720p50, generally require either a dual core CPU at around 2 GHz (and a multithreaded h.264 decoder) or GPU based decoding. I don't think the X800 has GPU decoding.

[mr-scarface]

You guys are looking at my desktop PC. Have a look at the laptop, it's a dual core with nvidia hardware acceleration.

My laptop is connected to my HDTV via HDMI

[edDV]

You guys are looking at my desktop PC. Have a look at the laptop, it's a dual core with nvidia hardware acceleration.

My laptop is connected to my HDTV via HDMI

What CPU/Graphics chipset?

For instance, I have a Compaq laptop with 1.8 GHz AMD Athlon 64 X2 Dual-Core Mobile Technology TK-55 and NVIDIA GeForce Go 6100 that will not play 720p or 1080i h.264 but will play MPeg2 TS.

[mr-scarface]

AMD Turion dual core RM70 2.0GHZ
Nvidia 8200m G
It's there in my details below the desktop info.

Not the fastest laptop out there, but certainly capable of HD playback, especially with the hardware acceleration.

[edDV]

Your CPU is on the weak side for software only solutions but the 8200m should support various Blu-Ray formats with a configured player.

[mr-scarface]

Your CPU is on the weak side for software only solutions but the 8200m should support various Blu-Ray formats with a configured player.

yeah it supports most formats. I havent run across a problem using the xbmc player, but the mpc player would give headaches, as I previously described. Must be an issue with the decoder, encoder or renderer that mpc is using, or something to that extent. Or perhaps mpc itself - since it plays fine on the xbmc player. Kinda confusing

[jagabo]

Note that not all h.264 features are supported by DXVA. So some videos will not play back properly with GPU decoding.

[mr-scarface]

The CPU is probably too weak to read the higher bitrate ones without the help of the gpu. A low-midrange laptop will not usually play HD perfectly anyway. The high-end laptops I am sure do.

I will need to buy one of those acer revo devices or something. Something that does justice to the TV set