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720p V 1080i: Whats Better For Fast-action Sport?


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So guys... I don't want you to rehash what you've said... but is that a fair summary?

I think your terminology is off. What you are calling is 1080i25 is really 1080i50 since there are 50 frames per second (with every other line) as you've said. And that is the reason 1080i50 is potentially better than 1080p24 even though the actual amount of picture data transmitted is the same. A good deinterlacer is part of that.

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Not too bad a summary, GregA. I am interspersing some comments in bold brown.

I don't think there is any debate that 1080p24 is better than 720p24 which is better than 576p24. True [though these would be rare TV transmission formats].

Likewise, 1080p50 is better than 1080i25 ("i25" seems to be used in different ways on different websites... I mean that both refresh 50 times a second, but the "i25" only does every 2nd line during each refresh). Obviously the i25 is half the data so much smaller transmission!. The potential benefit of 50 full frames over 50 interlaced frames per second disappears if the source material is 25fps progressive (e.g. sped-up 24fps film). I note that HD-DVD and Blu-ray releases have as their source 24fps film. True 1080p50/60 hardly exists at the consumer level outside of animations created by games software.

I'd like to summarise my understanding of the debate... someone will tell me if /where I've misunderstood.

The debate starts when you compare 1080p25 with 1080i25. 1080p25 is not a common transmission format, although it is a common source format as mentioned above for sped-up film. The interlaced refreshes 50 times a second, but only half the lines, while the progressive refreshes 25 times a second but all the lines. Then we get more confusing by adding 720p50 into the equation. 720p50 is a common transmission format but many broadasters feed it 720p25 — sped-up 24fps film again.

It seems the most vocal in this thread say that 1080i25 is better because there are 50 new pictures a second. Even though it's interlaced, they say a good deinterlacer can effectively compensate for missing lines (the latest developments doing particularly good jobs).

Thus, they say, 1080i25 looks pretty close to 1080p50. Hence 1080i25 is better than 1080p25 [This may not quite reflect the relative weights in the argument. I think the argument goes like this: 1080i gives superior static resolution to 720p and is adequate for fast motion also. I am not sure there has been much debate about 1080i25 vs 1080p50.]

Back to the beginning - we know 1080p50 is better than 720p50.

But what about 1080i25? Does it REALLY look like 1080p50? or because of the approximations, does 720p50 look better?

Note that although deinterlacers are getting better and better, for the really fast motion stuff they still simplify the picture to 540 lines... [Only the fast moving part of the picture; just to clarify.]

I think the answer is that IF you have a 1080p screen, and the latest & best deinterlacers, then 1080i is best ... since it will still downgrade to half resolution when it's moving fast, but we can't notice it because it's moving fast (and when it slows down it gives the full resolution). [Yes, this seems true for most program material.]

... If you have a 768line screen then 720p will be better - but if you're watching 1080i then make sure you have a good deinterlacer. [How a 1080 screen performs relative to a 768 screen when they are both fed 720 material, would be a whole separate debate in itself.]

So guys... I don't want you to rehash what you've said... but is that a fair summary?

What I think we lack is critical opinions on whether some fast action sport might look better in a 720p format rather than a 1080i format. In Australia the 720p would be at 50fps, and the 1080i would be at (25 odd +25 even) fields per second.

I could imagine that squash, with its small ball that can move across the entire playing area in a fraction of a second would be very difficult to capture with a video camera. The movement of the players would be very rapid too. It is conceivable that 720p could look better than 1080i. Some people may have eyesight than can perceive an actual benefit of a 720p full frame refresh, over a 1080i field refresh pus adaptive deinterlacing, with this type of rapidly moving action.

In Australia, this discussion is somewhat academic, as there seems to be little 720p fast-action sport telecast by ABC HD, our only 720p broadcaster.

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Region 4 encompasses South America and Mexico, both NTSC areas, so region 4 DVD’s can be NTSC, however Australia and New Zealand are PAL ONLY.

If you get an NTSC DVD here it is an import NOT intended for the Australian market.

Most modern TV’s are multi standard, so NTSC DVD’s will display on them, but older TV’s are often PAL only and are not NTSC compatible.

owen....i read ur posts

and i read them again

and again

and again

and i think " i really need to learn a hell of of a lot before i can begin to understand wat this bloke is saying"

but it is good....its y we are here

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...

American material

For those without access to their own off-air recorded transport streams of genuine progressive material, there's a clip of some 59.94fps basketball referred to here. The file, clip.ts, is 25MB and is at a genuine 59.94 unique frames per second, in a 1280x720 format. [it appears to be from a cable or satellite service.] I've sampled some of this frame by frame, and have noticed that the players move quite some significant distance, even in 1/59.94 of a second! ...

I've been searching the net for comments in support of 720p over 1080i for sport and although there are plenty of brief comments to that effect, there are also many opinions expressed that 1080i is preferred because of its detail, even for sport.

This afternoon I prepared some simple gif animations to satisfy my own curiosity. I post them here in case anyone else finds them interesting. :)

To keep file sizes manageable (the result gifs vary from about 1MB to about 1.7MB), I proceeded as follows:

A. Slow motion cropped 720p (the crop is equivalent to 1/12th of the picture height)

1. Captured
11
17
frames from the basketball 1280x720 clip above (frames 183 to
193
now 199
).

2. Re-sampled each frame into blocks of 12x12 pixels, i.e. 1/12th of the height of the 1280x720 format, or equivalent to 60 vertical pixels of a 1280x720 screen.

3. Animated them as a 640x360 gif with 0.2sec per frame. This produced an equivalent cropped (1/12) and blown up (x6) section of a 720p source.

Result is here. Although the movement is reasonably smooth, it is difficult to see what is going on.

B. Slow motion cropped 1080i weighted deinterlacing

1. Captured 1
7
frames from the basketball 1280x720 clip above (frames 183 to 19
9
); also captured frame 182.

3. For odd numbered frames, removed lines 9-16, 25-32, 41-48 etc

4. For even numbered frames, removed lines 1-8, 17-24, 33-40, etc

5. Resampled each frame into blocks of 8x8 pixels (as a 1080 screen has 3/2 times the vertical resolution of a 720 screen).

6. The 1
7
new frames thus created were equivalent to alternating fields in a cropped 1080i video. However if displayed raw without any interlacing protocol (as
), the flickering was very disturbing, although the detail was better than with the 720p crop above.

7. There were many possible deinterlacing methods that could have been attempted. I chose a simple weighted method which can be described as follows.

Each field when it first comes into view is shown at original strength. It is then allowed to persist at 75% strength during the next "frame".

This is crudely similar to what used to happen many years ago with CRTs displaying interlaced source material.

8. Animated the 1
7
weighted interlaced frames as a 640x360 gif with 0.2sec per frame. (This allowed a same size comparison with the more coarsely resampled version above.)

Result with the weighted deinterlacing is here. I personally find this more satisfactory than A above, as there is significantly more detail.

With a sophisticated motion adaptive deinterlacing protocol, non-moving parts of a 1080i image (e.g. the spectators, and the floor of the basketball court) should look as smooth and detailed as 1080p. A common unsophisticated method of deinterlacing is "weave", where the immediate prior field is maintained into the next field at full intensity. This method has the disadvantage that where there is movement, the movement becomes overlaid between "frames".

Result with weave deinteracing is here . This is pretty smooth. However, the shape of the ball varies strangely.

C. Slow motion cropped 1080p

1. Captured 1
7
frames from the basketball 1280x720 clip above (frames 183 to 19
9
).

2. Re-sampled each frame into blocks of 8x8 pixels, i.e. 1/8th of the vertical resolution of a 1080x720 screen or 90 pixels. (A 1920x1080 screen has 90 pixels to every 60 pixels of a 1080x720 screen.)

3. Animated them as a 640x360 gif with 0.2sec per frame. (This allows for comparison with the animations above.)

Result is here. This is definitely the best image, which comes as no surprise.

_______________________________________

Although the above gif animations are low resolution they may serve to give a feel for what is going on. They suggest:

  • 1080p gives detail and smoothness.
  • 1080i, with a deinterlacing protocol, is not as smooth as 1080p.
  • 720p gives better smoothness than 1080i, but noticeably less detail. There is a question to be addressed of whether the smoothness comes at too great a sacrifice of detail.

The images produced in the gif animations above are equivalent to looking at just 1/12 of the height of a 720p screen (60 pixels of height), or 1/12 of the height of a 1080i/p screen (90 pixels of height). The effects might apply when watching a football match with some action occurring at the far end of the playing field, and with the tv camera not yet zoomed in on that action.

Another limitation is that the gifs are set to display at a very low speed (200mS per frame instead of the original 16.7mS per frame). But I think this may help rather than hinder, in gaining an impression of what is going on. As a reference point, the frame rate for cinematic film is 24fps, or 41.7mS per frame.

My opinion

The above exercise has firmed up in my own mind my opinion that 1080i is likely to be a superior format to 720p, even for fast action sport. Fortunately, in my view, 1080i is the predominant HD format in Australia (9HD, 10HD).

The ABC uses 720p for HD. 7HD uses 576p (an unfortunate choice for a major network), but has recently upgraded to 1080i for Sydney and Melbourne — hopefully other locations will follow in due course. SBS HD uses 576p (presumably because of budgetary constraints, and it may not be true 576p - see Dvb-t Lcn List, A List of Channel Available on Digital here).

Cable networks are offering choice of program material (for a price), but are not offering high defintion.

Edited by MLXXX
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I've been searching the net for comments in support of 720p over 1080i for sport and although there are plenty of brief comments to that effect, there are also many opinions expressed that 1080i is preferred because of its detail, even for sport.

In my quest of comparing 720p and 1080i, I requested a sample clip of a recent NBA Game shown on ABCHD in 720p60. A very kind individual uploaded a 720p as well a 1080i sample clip. This individual does not know if the 1080i clip is the original (i.e if ABCHD decided to film and broadcast a game in 1080i) or if it was converted by the person who captured the footage. Also what was done to the original captured footage is unknown.

720p60 - 39sec - 12Mbit - 61MB

1080i60 - 39sec - 14Mbit - 66MB

I viewed the frames in virtualdubmod and was surprised to see pixelation in both formats which makes it difficult to compare. At the moment, I'm still analysing but for now, I cannot see anymore detail in the 1080i clip than the 720p clip.

I would be interested if anyone can analyse the above 2 files and give their opinion on picture quality.

Incidently I recently watched the NBA Finals, Games 1 and 2 in 720p30 at a 3-4mbps bitrate (re-encoded in x264 at a reduced frame rate of 29.97fps). The picture was definitely smoother, however not as much pixelation compared to the above 2 higher bitrate files. Go figure.

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Part 1

The 61MB file downloaded in about 2 hours. It's a significantly better picture quality 720p59.94 clip of American basketball than the 25MB clip (which I suspect may have been received by cable) I used for my gif animations above.

The logos suggest the camerawork may have been by ESPN (a cable network) and that the video may have been relayed or rebroadcast by the American Broadcasting Company. I see that both ESPN and ABC have adopted 720p59.94 as their high definition TV format.

I have yet to start downloading the 66MB file. (There seems to be a 2 hour waiting period for a second free download from the website host.)

===================================

Part 2

The 66MB file downloaded fairly fast (in 8 minutes).

It's of a basketball match at a different venue. There's nowhere near the image quality of the 61MB clip. I extracted a frame 13 seconds into the clip, where the player's face had been stationary long enough for interlacing effects not to interfere. That 1920x1080 frame does not have the colour saturation, or sharpness of many of the 1280x720 frames from the 61MB clip.

The logos are again of ESPN and of the American ABC. Given that these networks use 720p rather than 1080i, I have to assume the 1080i was probably introduced at a later stage in the image processing. However I haven't minutely examined frames, and probably will not attempt to do so. I've examined some footage from some live Australian 1080i50 and it is clearer than the 1080i59.94 of the 66MB file.

Alpha, thanks very much for organising the uploads. The 61MB file is excellent. You can quickly step through it frame by frame and observe the changes in detail of the MPEG encoding. When the movement slows down, the detail sharpens. Where there are major changes in picture content, for example a quick pan, the detail falls away considerably.

I have read that slow motion is one area where 720p excels. That is evident when stepping through the frames in the 61MB file.

Cheers.

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Unless you can guarantee the video was shot in 720p and 1080i (not converted, recompressed etc), any comparison is pointless.

ABC in the US usually used 720p for sport, so it is HIGHLY unlikely it was shot in both 720p and 1080i.

Rather then stuff about comparing still frames etc, just watch some full motion video on a big screen. If the differences are not obvious they are not worth worrying about.

There is very little chance of finding any video that was shot in both 720p and 1080i.

I have native 720p and 1080i video, but never with the same content.

I have yet to see any 720p that looks as detailed as 1080i.

Be very careful about what you use to play 1080i video.

For the best deinterlacing you need an 8 series nVidia card. I’ve only tested an 8800, but 8500 and 8600 cards should be similar.

To use the hardware deinterlacing you will need a suitable video decoder that enables hardware acceleration and a player that preferably can use VMR9 full screen exclusive renderless mode. Other modes won’t run as smoothly and may provide only 540 lines.

YUV mixing should be disabled, as it always forces 540 line output in my experience.

I use a resolution test pattern encoded into 1080i Mpg2 video to check if I am getting 1080 lines and not 540. It’s easy to see on the test pattern, but it can be very difficult to tell just looking at normal video.

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For the best deinterlacing you need an 8 series nVidia card. I’ve only tested an 8800, but 8500 and 8600 cards should be similar.

There is a (limited) video quality comparison of the 2900XT, 8800GTS, and 8600GTS here using the HQV HD tests. It shows the 2900XT & 8800GTS equal and trailing the 8600GTS for SD DVD, and the 8800GTS & 8600GTS equal and trailing the 2900XT for HD content.

But I'd not rush to draw conclusions from it, given that it was a rather limited test.

Adrian

EDIT: Corrections -- thanks MLXXX.

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Unfortunately the ExtremeTech article is not worth the paper it is printed on, and since it a web page that’s not a lot.

There are many variables that affect performance significantly, such as decoder used, the player application used, the video renderer used, as well as setting used. There will also be significant differences between video types (Mpeg2, VC1, h.264).

It’s complicated mess to sort out and ExtremeTech did not address any of these very important factors.

The Silicon Optics HQV test scores are also very suspect. You need to know the results of all the individual tests to get an idea of the real performance, as the overall score includes factors that have nothing to do with deinterlacing and as well as unusual types of interlaced video content that is rarely if ever encountered.

Bad edit detection and correction for 1080i is still broken in the 8800 drivers, which will also affect test scores.

When those factors are removed, the score can be radically different. The tests also often have little relevance in real life situations, which is what really matters.

I will wait until I have tested these cards personally under known conditions with real video content before I would make any judgment.

On line reviewers usually don’t have the experience or knowledge required to properly conduct worthwhile evaluations of video related issues.

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Unfortunately the ExtremeTech article is not worth the paper it is printed on, and since it a web page that’s not a lot.

Touche

I was looking forward to your deconstruction of the review. And you didn't disappoint! :-)

I've also read that the HQV tests are questionable due to the company using the results to promote their own systems ...

Adrian

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Corrections in red:

There is a (limited) video quality comparison of the 2900XT, 8800GTS, and 8600GTS here using the HQV HD tests. It shows the 2900XT & 8800GTS equal and trailing the 8600GTS for SD DVD, and the 8800GTS & 8600GTS equal and trailing the 2900XT for HD content.

But I'd not rush to draw conclusions from it, given that it was a rather limited test.

Adrian

The text states:

The newer Nvidia 8600 GTS seemed to offer noticeably better quality in the HQV DVD quality tests. It outperformed the 8800 GTS in the color bar test, and beat out ATI in film detail and some of the more exotic cadence patterns.

On the HD front, the tables are somewhat reversed. The AMD card was noticeably better in the HD noise test, even when the Nvidia noise reduction control was cranked to about 50%. And both Nvidia cards fared poorly in the Film Resolution Loss test.

I'd tend to agree with Owen's and Adrian's reservations, though.

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That 61MB 720 p 59.94 fps MPEG2 clip Adrian organised above has been useful for a few experiments I've carried out on the impact of interlacing.

The first thing I did was to convert the MPEG2 clip to an uncompressed [progressive] AVI. This allowed it to be further processed using VirtualDub.

The steps in the further processing were:

1. Save the uncompressed AVI as a high quality DivX
*
compressed AVI. This compressed file became the the reference file:
720 p 60

2. Convert the MPEG2 clip to an uncompressed interlaced AVI
**
. De-interlace using a motion adapative VirtualDub deinterlacing filter
***
and save as an uncompressed de-interlaced AVI. Save that using the DivX codec. This compressed file became the comparison version:
720 i 60

3. Using the uncompressed progressive AVI, loaded into VirtualDub, discard every second frame and save using DivX. This compressed file became the comparison version
720 p 30

4. Using the uncompressed de-interlaced AVI, pixelate
****
into 2x2 pixel squares and save using DivX. This compressed file became the comparison version
cropped 1080 i 60
(This is how one qadrant of a 1920x1080i screen might appear if the source image were in the 1920x1080i format.)

5. Using the uncompressed progressive AVI, pixelate intro 3x3 pixel squares and saving usingf DivX. This compressed file became the comparison version
cropped 720 p 60
(This is how one quadrant of a 1280x720p screen might appear if the source image were in the 1920x1080i format.)

My ranking of the image quality of the full size versions was:

1. 720 p 60 Exceptionally smooth, good detail and colour saturation

2. 720 i 60 Less smooth. Image less solid looking.

3. 720 p 30 Even less smooth. A perceptible jerkiness in the movement.

My ranking of the quality of the notionally cropped versions was:

1. 1080 i 60 Reasonably smooth, and with reasonable detail

2. 720 p 60 Smoother than 1, but lacking in detail.

3. At a remote viewing distance (7 metres from a 60" 1920x1080 screen) 720 p 60 Smooth

4. At a remote viewing distance (7 metres from a 60" 1920 x 1080 screen) 1080 i 60 Not as smooth

These results confirm my previous impressions that 1080i gives a better picture than 720p, even with sport; on a 1920x1080 set, at a reasonable viewing distance.

However when viewing under adverse conditions (such as poor eyesight, a small set, or an excessive viewing distance) 720p may look smoother than 1080i, and the added detail of 1080i will not be noticeable. In such a situation, 720p gives the better picture.

Of course if the source is film, it will only be providing 24 or 25 unique frames per second (even if broadcast at a higher frame rate), so smoothness will be compromised from the start. It may be a few years yet before we get to see new movies at, say, 48 true progressive frames per second.

There is one main thing I've learned from this exercise - an appreciation of the smoothness of 720p. Even though I still prefer 1080i!

_______________________

†with an MPEG converter such as here.

*DivX Community Codec 6.6, set to 1080HD mode, 1-pass quality based.

**Using an avs file as follows:

AVISource("720p.avi")

AssumeFrameBased()

SeparateFields()

SelectEvery(4,0,3)

Weave()

VirtualDub.exe loads the avs file and this invokes AviSynth which needs to have been previously installed.

***Smart.vdf (Donald Graft) Ver 2.8 , set to frame-and-field differencing, Cubic interpolate.

****pixellate.vdf (Tom Ford)

A webpage that provides some background on deinterlacing and the use of VirtualDub is here.

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Anyone wishing to experiment may find the following useful:

From this pdf:

The SVT High Definition Multi Format Test Set Version 1.0 Feb.2006

Sveriges Television www.svt.se Lars Haglund 1

The SVT High Definition Multi Format Test Set

1. Introduction

This Document contains information about the
SVT High Definition Multi Format Test Set

picked from the demanding, but not unduly so, multi-genre TV-program ‘Fairytale’ (by SVT)

mastered in 3840x2160p/50.

All sequences from this set may be distributed freely (complete or in parts) as long as the

copyright and the restrictions of the use of the sequences are not violated.

This document has to be distributed with any part of the test set that is distributed.

It is not allowed to charge a fee for the distribution of the sequences. Anybody receiving

material from this data set is kindly asked to further distribute these sequences to other parties

to reach a super distribution effect.

All sequences from this set were filmed in 50 fps with professional, high end 65mm film

equipment by SVT in October 2004. The utmost care has been taken when converting the

film into digital data, the same applies for all conversion steps applied afterwards.

The data itself comes in various different resolutions which are widely used – all in 50 Hz

motion portrayal. Lower resolutions were gained by filtering the 2160p/50 master. At all

resolutions the bit depth is full interval 16 bits per (RGB) colour plane to obtain the very high

quality of the original shots.

Details concerning shooting of the sequences and post-processing steps can be found in the

section ‘Technical Information’.

The test sequences are downloadable from here. The explanatory material states: "These sequences may only be used for the purpose of developing, testing and presenting technology standards." Available formats include 1280x720 p50 and 1920x1080 p50, and 1920x1080 i25*, all derived from the original 3840x2160 p50.

Note the format is of individual frames in sgi format. A freeware individual frame viewer and converter (XnView v1.91.1) can be downloaded from here.

Each frame of the 500 frames (numbered 07111 to 07610) from the 1080p ftp download site is 12.4MB, so the total download would be about 6.25GB. The 720p frames are about 5.53MB each, i.e. about 2.8GB for the 500 frames.

It could be someone has already downloaded these, assembled them into a movie, compressed the video, and uploaded the result somewhere.

*i25 as used here means 50 fields per second, resulting in 25 interleaved frames. Each frame available for download is therefore a weave of two fields (even and odd lines) captured 1/50th of a second apart in time

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That 61MB 720 p 59.94 fps MPEG2 clip Adrian organised above has been useful for a few experiments I've carried out on the impact of interlacing.

The first thing I did was to convert the MPEG2 clip to an uncompressed [progressive] AVI. This allowed it to be further processed using VirtualDub.

The steps in the further processing were:

1. Save the uncompressed AVI as a high quality DivX
*
compressed AVI. This compressed file became the the reference file:
720 p 60

2. Convert the MPEG2 clip to an uncompressed interlaced AVI
**
. De-interlace using a motion adapative VirtualDub deinterlacing filter
***
and save as an uncompressed de-interlaced AVI. Save that using the DivX codec. This compressed file became the comparison version:
720 i 60

3. Using the uncompressed progressive AVI, loaded into VirtualDub, discard every second frame and save using DivX. This compressed file became the comparison version
720 p 30

4. Using the uncompressed de-interlaced AVI, pixelate
****
into 2x2 pixel squares and save using DivX. This compressed file became the comparison version
cropped 1080 i 60
(This is how one qadrant of a 1920x1080i screen might appear if the source image were in the 1920x1080i format.)

5. Using the uncompressed progressive AVI, pixelate intro 3x3 pixel squares and saving usingf DivX. This compressed file became the comparison version
cropped 720 p 60
(This is how one quadrant of a 1280x720p screen might appear if the source image were in the 1920x1080i format.)

My ranking of the image quality of the full size versions was:

1. 720 p 60 Exceptionally smooth, good detail and colour saturation

2. 720 i 60 Less smooth. Image less solid looking.

3. 720 p 30 Even less smooth. A perceptible jerkiness in the movement.

My ranking of the quality of the notionally cropped versions was:

1. 1080 i 60 Reasonably smooth, and with reasonable detail

2. 720 p 60 Smoother than 1, but lacking in detail.

3. At a remote viewing distance (7 metres from a 60" 1920x1080 screen) 720 p 60 Smooth

4. At a remote viewing distance (7 metres from a 60" 1920 x 1080 screen) 1080 i 60 Not as smooth

These results confirm my previous impressions that 1080i gives a better picture than 720p, even with sport; on a 1920x1080 set, at a reasonable viewing distance.

However when viewing under adverse conditions (such as poor eyesight, a small set, or an excessive viewing distance) 720p may look smoother than 1080i, and the added detail of 1080i will not be noticeable. In such a situation, 720p gives the better picture.

Of course if the source is film, it will only be providing 24 or 25 unique frames per second (even if broadcast at a higher frame rate), so smoothness will be compromised from the start. It may be a few years yet before we get to see new movies at, say, 48 true progressive frames per second.

There is one main thing I've learned from this exercise - an appreciation of the smoothness of 720p. Even though I still prefer 1080i!

_______________________

†with an MPEG converter such as here.

*DivX Community Codec 6.6, set to 1080HD mode, 1-pass quality based.

**Using an avs file as follows:

AVISource("720p.avi")

AssumeFrameBased()

SeparateFields()

SelectEvery(4,0,3)

Weave()

VirtualDub.exe loads the avs file and this invokes AviSynth which needs to have been previously installed.

***Smart.vdf (Donald Graft) Ver 2.8 , set to frame-and-field differencing, Cubic interpolate.

****pixellate.vdf (Tom Ford)

A webpage that provides some background on deinterlacing and the use of VirtualDub is here.

You seem to have lost the plot with this one mate.

There are so many issues I don’t know where to start.

Compression issues, poor deinterlacing etc.

1080i 60 from a 1080i video camera is 60 frames per second when deinterlaced, if it looks less smooth then 720p 60 something is not working as it should.

I agree that 720p may look more solid some of the time, but I can’t agree that it’s smoother.

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Owen it could be that if I had used bob deinterlacing for the whole of each frame there would have been no apparent loss in fluidity, but I thought it better to use a motion adapative technique and preserve some of the vertical and horizontal detail. I might try a simple bob to see how it looks. Another issue is colour which is encoded fairly coarsely to begin with.

___________________________________________________________________________

Viewing the original 59.94fps 720p clip frames one by one I found there was a lot of movement from one frame to the next.

The first step in generating 59.94 fps 720i was to eliminate odd lines from half of the frames (say the odd numbered frames), and even lines from the other half of the frames; and obtained 720i.

I could have just presented that to my 1920x1080 television and allowed it to do the de-interlacing, but I thought it better to use a methodology that was repeatable and known*.

I used a motion adaptive deinterlacing filter. (I was able to preview the de-interlacing frame by frame using VirtualDub. I saw that is was quite effective. It cleaned up the interlacing artefacts very nicely, but left the rest of the image intact.)

The filter allowed some sections of the 59.94i frames I had generated to be left as a weave of the current interlaced field (say odd lines), and of the immediate prior interlaced field (say even lines).

The filter caused the faster moving sections to be bobbed, such that the progressive frames generated contained only the current interlaced field in those sections. The bobbed sections were of course not as detailed as the woven sections, giving a somewhat fuzzy appearance to quick movement in the processed progressive frames; in comparison with the original progressive frames. I think this effect was exacerbated because the original 720p material was quite sharp.

When shown at full speed the final result (after interlacing the original, and deinterlacing to get back to a progressive format for ease of display) was a lack of solidity, and a certain lack of smoothness. The smoothness was better though than the method of removing every second frame of the original progressive source to generate 29.97 fps progressive.

The compression codec was at generous settings.

* I could perhaps have changed the pc desktop resolution to 720i59.94, and used a player that would output at that resolution, but I didn't bother. The rescaling in the 1920x1080 TV would have been a variable too.

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The most likely cause of the less then perfect motion you experienced with your manufactured 720i 60 is the deinterlacer you are using. If it where generating the consistent 60 frames per second it should, you should not see any worse motion then you get with 720p 60.

For example, simple bob deinterlacing should always deliver perfect 60fps motion, no if’s or but’s. Motion should always look the same as 720p 60.

A really good deinterlacer should always provide motion equivalent to bob, but much better vertical resolution in motion and no artifacts.

All the software deinterlacers I have used have been mediocre at best for true interlaced source, and none produce the sort of result I get with the 8800 hardware deinterlacing.

Donald’s “Smart” deinterlacer is pretty basic and hardly up to the job you are asking of it, so don’t make any judgments based in its performance.

The deinterlacer in the SXRD is reasonable but not in the same class as the 8800.

720i 60 is not a valid video format, so the deinterlacers will probably not know what to do with it.

The Sony HD STB has to deinterlace 576i before it upscales it to 1080i for output. Again, it only does a reasonable job, as one would expect form an inexpensive consumer product. Horizontal scrolling text shows up its limitations noticeably.

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Owen,

How are you accessing hardware deinterlacing for the 8800 ?

With the 8600GTS I have not been able to surpass the video performance of the Sony HD-STB nor have I found any deinterlacing options within the Nvidia software for the 8x00 cards in either XP or Vista.

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The most likely cause of the less then perfect motion you experienced with your manufactured 720i 60 is the deinterlacer you are using. If it where generating the consistent 60 frames per second it should, you should not see any worse motion then you get with 720p 60.

For example, simple bob deinterlacing should always deliver perfect 60fps motion, no if’s or but’s. Motion should always look the same as 720p 60.

A really good deinterlacer should always provide motion equivalent to bob, but much better vertical resolution in motion and no artifacts. ...

Yes Owen, you were right; there was a problem with the "smart" deinterlacing filter. Although it looked good from frame to frame, it somehow didn't work when the frames were put together. I have to admit that yesterday was the first time I'd used AviSynth or VirtualDub and after a bit of experimenting with interlacing filters I chose the filter that appeared to give the best result in the preview pane VirtualDub provides. I could have overlooked something.

In the last hour or so, I've obtained smooth results from all of the following alternative methods:

  • Saving the manufactured 720i59.94 avi with the DivX codec set to preserve interlacing, and leaving it to Zoomplayer (using a DivX codec of course) to play the avi on a 1920x1080p desktop.
  • Saving the manufactured 720i59.94 avi with the DivX codec set to deinterlace, and leaving it to Zoomplayer (using a DivX codec) to play the avi on a 1920x1080p desktop.
  • Using VirtualDub to bob the fields*, bring them back to full height, and save the result with DivX codec set to a progressive source. This was then played on Zoomplayer.

The last method was the least sharp, which was to be expected.

So I am going to have to revise what I said last night at post #114 above. Interlacing need not reduce the fluidity of the motion. Hence my comments about 720p looking better than 1080i when viewed from a remote distance have to be withdrawn. I no longer have any real evidence to support that view, as the deinterlacing method I used, appears to be suspect.

However despite this, the interlaced versions of the clip are not as solid looking as progressive versions of the clip. This is not all that surprising, as half of the lines are discarded from each of the progressive source frames. Something has to give.

Cheers.

_________________________

* This required loading the fields in separately. The avs file read:

AVISource("720p.avi")

AssumeFrameBased()

SeparateFields()

The internal field bob filter of VirtualDub was used, with quarter scanline adjustment settings.

As well the internal resize filter was used set to resize the half height frames back to 1280x720 (using bicubic resampling).

Then every second frame (they became duplicates) was discarded.

The final result was 720p 59.94

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Owen,

How are you accessing hardware deinterlacing for the 8800 ?

With the 8600GTS I have not been able to surpass the video performance of the Sony HD-STB nor have I found any deinterlacing options within the Nvidia software for the 8x00 cards in either XP or Vista.

I use DNTV Live and either the nVidia decoder or the Cyberlink decoder that came with Power DVD 7.3, both with hardware assistance (DXVA) enabled. Neither are perfect as they occasionally loose the plot on some content.

I really don’t watch free to air TV. The Sony STB and the tuner in my HTPC have seen maybe two hours use between them in the last 4 months.

I did watch some motor racing on channel 7 (SD) about 3 weeks ago, and was swapping between the PC and the STB to see how they compared. Overall picture quality is very similar, but the horizontal scrolling text (ticker) on the bottom of the screen was noticeably better on the HTPC. The text was clean and free of flicker, where as via the STB it was ragged and flickery. The deinterlacer in the SXRD may be better then the one in the STB, but unless we change the output format on the STB to watch 576i or 1080i we have to live with what the STB does with 576i.

When I first installed the STB I spend an hour or so viewing 1080 HD loops and comparing it to the PC. Even though the STB is connected via the $2 Component cables that came with it, there was only a subtle difference between it and the HTPC connected via HDMI at 1080p. The STB is running 1080i output so that the DRC settings can be used on the SXRD. The DRC can be adjusted to give a sharper picture then is possible without it, but sharper is not better and the picture was cleaner via the PC. I generally find the picture better with DRC disabled.

I have no doubt that a HDMI cable would provide a cleaner image from the STB then a $2 Component cable, but I cant be bothered to get one just to watch a few hours of FTA TV in a year.

A PC is not the ideal device to watch live FTA TV IMHO as it’s not as consistent as a STB, although they can work fine. The family 86cm CRT runs digital free to air from a HTPC all the time (no STB) and gets heaps of problem free use.

For recorded content I wont use anything but a HTPC. Foxtel-Austar is also better when processed via the PC.

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Thanks Owen for the reply.

With regard to DXVA being enabled with either the nvidia or Cyberlink powerDVD 7.3 decoder, have you been able to confirm whether or not hardware acceleration is actually engaged and is there any difference in picture quality if DXVA is not enabled ?

I have no doubt that a HDMI cable would provide a cleaner image from the STB then a $2 Component cable, but I can't be bothered to get one just to watch a few hours of FTA TV in a year.

I have the HD-STB connected to the SXRD via HDMI.

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Hey Owen drsmith, how did the Channel 7 footy (1080i) look on Sunday afternoon on your SXRD??

I didn't watch it. I thought only 10 was broadcasting one game per week in HD. I can't see any mention of 7 broadcasting AFL in HD here.

I use DNTV Live and either the nVidia decoder or the Cyberlink decoder that came with Power DVD 7.3, both with hardware assistance (DXVA) enabled. Neither are perfect as they occasionally loose the plot on some content.

I have done some experimentation with DNTVLive! in XP with a segment of tennis recorded about six months ago.

With the Cyberlink Power DVD 7.3 decoder there is definately an improvement in picture quality with DxVA enabled.

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Anyone wishing to experiment may find the following useful:

From this pdf:

The SVT High Definition Multi Format Test Set Version 1.0 Feb.2006

Sveriges Television www.svt.se Lars Haglund 1

The SVT High Definition Multi Format Test Set

1. Introduction

This Document contains information about the
SVT High Definition Multi Format Test Set

picked from the demanding, but not unduly so, multi-genre TV-program ‘Fairytale’ (by SVT)

mastered in 3840x2160p/50.

All sequences from this set may be distributed freely (complete or in parts) as long as the

copyright and the restrictions of the use of the sequences are not violated.

This document has to be distributed with any part of the test set that is distributed.

It is not allowed to charge a fee for the distribution of the sequences. Anybody receiving

material from this data set is kindly asked to further distribute these sequences to other parties

to reach a super distribution effect.

All sequences from this set were filmed in 50 fps with professional, high end 65mm film

equipment by SVT in October 2004. The utmost care has been taken when converting the

film into digital data, the same applies for all conversion steps applied afterwards.

The data itself comes in various different resolutions which are widely used – all in 50 Hz

motion portrayal. Lower resolutions were gained by filtering the 2160p/50 master. At all

resolutions the bit depth is full interval 16 bits per (RGB) colour plane to obtain the very high

quality of the original shots.

Details concerning shooting of the sequences and post-processing steps can be found in the

section ‘Technical Information’.

The test sequences are downloadable from here. The explanatory material states: "These sequences may only be used for the purpose of developing, testing and presenting technology standards." Available formats include 1280x720 p50 and 1920x1080 p50, and 1920x1080 i25*, all derived from the original 3840x2160 p50.

Note the format is of individual frames in sgi format. A freeware individual frame viewer and converter (XnView v1.91.1) can be downloaded from here.

Each frame of the 500 frames (numbered 07111 to 07610) from the 1080p ftp download site is 12.4MB, so the total download would be about 6.25GB. The 720p frames are about 5.53MB each, i.e. about 2.8GB for the 500 frames.

It could be someone has already downloaded these, assembled them into a movie, compressed the video, and uploaded the result somewhere.

*i25 as used here means 50 fields per second, resulting in 25 interleaved frames. Each frame available for download is therefore a weave of two fields (even and odd lines) captured 1/50th of a second apart in time

I have made up some very short videos using frames from the SVT High Definition Multi Format Test Set above. They are a means of "presenting technology standards" but are for use at own risk. Although I have taken care, I cannot guarantee the technical standard of the videos.

They are as follows:

Clip1: CrowdRun720p50.avi 19.23MB 20Mbps

Clip2: CrowdRun1080i25.avi 24.12MB 25Mbps

Clip3: CrowdRun1080p50.avi 31.8MB 33Mbps

As web bandwith is limited, I'd ask that if you download you please save, so that you do not need to download the same file more than once.

They are each 10 seconds long, and show exactly the same picture content -- a crowd of people running. It appears to be a cross-country run, with a very large number of participants. This represents a challenge for any video compression algorithm.

Rather than doing my own resizing or conversions from progressive to interlaced, I simply downloaded the relevant source frames already of the apropriate format, converted them to bmp images, loaded them into VirtualDub, and saved them with ffdshowddshowfilter set for H.264 compression (one pass - 85% quality).

I originally tried MPEG2 compression but the file sizes became very high for reasonable quality. I found the H.264 encoding was effective with the progressive material, even at low bitrates. (In contrast, the interlaced material needed a certain minimum bitrate or it would become "sketchy" and difficult to watch.)

Comparing the visual quality

  • There seems no doubt clip 3 is the best; giving smoothness and detail.
  • Clip 1 is easy to watch, being quite smooth.
  • Clip 2 has a certain disjointedness [the exact appearance will depend on the characteristics of the de-interlacing for the viewing device], but could be said to have more detail than clip 1.

I think I am more inclined towards clip 1 than clip 2, despite my usual preference for 1080i, with less fast moving material.

I have not found much true 1080p material on the web. Although called 1080p it is usually from 24fps [or 25fps] film.

It's a pity, because true 1080 p50 can look very impresssive.

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