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

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It’s a shame you have invalidated your test by using un optimised h.264 compression.

The video should have been left in its original form, or at the very least compressed with optimised Mpeg2, which is what we use for TV transmission.

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It’s a shame you have invalidated your test by using un optimised h.264 compression.

The video should have been left in its original form, or at the very least compressed with optimised Mpeg2, which is what we use for TV transmission.

The original form (bmp) for the 1080p immediately prior to compression was 2.90GB, for the 1080i it was 1.45GB, and for the 720p it was 1.29GB.

The compression factor used was more in line with HD-DVD than with free to air.

There was little point in multiple pass encoding, as the picture content was highly changeable through the whole of the 10 seconds of the clip.

[1080p of course is not an existing FTA or high definition disk (HD-DVD or Bluray) format.]

I found that lower compression factors were a little less kind for the 1080i than the 720p or 1080p. [both bottom field first and top field first options for the interlaced format were tried.]

In addition to Mpeg 2 and H.264, a DivX codec was tried.

To my eyes, the three picture formats preserved their different characters, irrespective of the compression codec.

I was more interested in the basic characteristics of the formats than how curent bit-rate limitations of FTA further reduce the quality.

With no compression, the 1080i avi will play on Zoomplayer only at a reduced speed, even with clip size reduced to 50 frames (2 seconds' worth). I may experiment further with playing the frames uncompressed, or with very mild compression, and report the result.

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Try watching uncompressed video at full speed for say 10 seconds to get a feel for how it performs. If your system cant cope, you cant do a valid comparison.

The problem will be getting good hardware deinterlacing working with uncompressed content. PC replay systems are not optimised for uncompressed video, and ineffective deinterlacing will ruin your comparison.

h.264 or the PC playbacks systems for it have big problems with 1080i in my experience. 1080i in Mpeg2 works faultlessly on the same system because PC systems are now well optimised to handle 1080i in Mpeg2 format.

If you want to create 1080i in Mpeg2 you will need a professional grade compression codec to do it justice.

I’ll download the original source video and see if I can play it properly on my system if you like. I’m very used to watching 1080i content and I’ll know if it does not look the way it should.

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Owen thanks for your comments.

The download of the 1080i frames is about 3GB (250 frames at 12Mb each in SGI format). The five hundred 2160p frames come in at about 23GB :blink: if they are needed. [They show film grain and are probaby not the best as 2160p source material as such, but might be useful for deriving a lower resolution for test purposes, such as 576p.]

As a work around for the uncompressed playback issue, I've been able to play cropped versions of the 1080i and 1080p avi's I created, at full speed. The cropping was to remove 600 pixels from the left, 600 from the right, and 504 from the top, thus reducing the 1080i or p to 576i or p. The resulting 576p played superbly.

There was still the issue of deinterlacing with the resulting 576i. I used the Smooth Deinterlacer (Gunnar Thalin) filter with VirtualDub* and the output was indeed very smooth, and easy on the eye.

I then compared the uncompressed 576p (cropped from the uncompressed 1080p) with the uncompressed 576i (deinterlaced from the cropped 1080i). Both were very smooth, but the 576p had noticeably more detail.

The quest

I would observe that there is no reason why the deinterlacing that a graphics card does cannot be emulated in software, even if the emulation is much slower.

We seem to be on a quest to find a deinterlacing system that provides smooth motion and detail, in circumstances where only 540 lines are refreshed each 1/50th of a second, and a lot of the image detail changes appreciably each 1/50th of a second; in comparison with a system where 720 lines are refreshed each 1/50th of a second.

It is often stated that 720p is better for fast-action sport than 1080i. At this stage I have not seen evidence to contradict that position.

* An Avisynth File was needed to load in the uncompressed 576i, as follows:

AVISource("576isource1.avi")

AssumeFrameBased()

ComplementParity()

SeparateFields()

This split the 250 interlaced frames into 500 half-height 576i frames; which the Smooth Deinterlacer filter assembled into 500 full height progressive frames.

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Owen has recently started a new thread: Is 1080p Superior To 1080i ?, The answer may not be what you expect. That is prompting me to provide some further video samples. They tend to confirm my impressions of a few months ago.

The first two samples use the 1080p still frames from the Crowd Run sequence. (See post #125 above for a description of where this material originated). And the third sample uses 720p still frames from the same sequence.

The steps to create the raw frames were as follows:

1080i50

Load the 500 1080p50 frames [in bmp format, converted from sgi] into Virtualdub using an AviSynth script that creates interlaced frames. Use the Virtualdub level filter to map video levels 0-255 to 16-235, and save as an uncompressed AVI. Without the mapping, black detail would be lost in the later Mpeg2 encoding.

1080p25

Load the 500 1080p50 frames into Virtualdub. Save them as an uncompressed AVI, discarding each second frame, and use the level filter to map the intensity levels.

720p

Load the 500 720p50 frames into Virtualdub. Save them as an uncompressed AVI after setting the level filter.

It was then possible using a trial version of Main Concept Pro to encode the raw files as interlaced (upper field first) or progressive as the case required, using a data rate of approximately 25Mbps, which is a typical rate for encoding Blu-ray disks.

The results (each file is about 35MB) are:

1. CrowdRun25Mbps-1080i50.m2v downloadable from
.

2. CrowdRun25Mbps-1080p25.m2v downloadable from
.

3. CrowdRun25Mbps--720p50.m2v downloadable from
.

As download bandwidth is strictly limited, I'd ask that anyone performing a download makes a point of saving the file, so as to avoid any need to download a particular file more than once. [The bandwidth resets at the end of each month.]

It's interesting that the smoothness of the 720p50 makes the runners appear not to be running as fast.

I suggest this old thread might be allowed to lapse, unless someone has specific comments about 720p vs 1080i.

Edited by MLXXX

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What a joke, that looks like one field of 1080i video (540 lines), or simple bob deinterlacing.

The guy needs to re-evaluate his image capture methods, no way 1080i ever looks like that when displayed properly.

If I ever saw anything like that on my display I would be looking for what the hell was wrong with the replay system.

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