24p, 25p, 50i, lots of angst...

Started Jul 15, 2010 | Discussions
mike_2008 Veteran Member • Posts: 5,635
24p, 25p, 50i, lots of angst...

I'm looking for some clarification on frame rates in video. I'm talking exclusively about displaying video on a PAL television or projector.

Some facts:

The PAL version of the nex VG10 measures at 25p and saves at 50i, so it takes 25 frames per second off the sensor and interlaces this to produce 50i.

Most PAL HD televisions work at 50i.

If you exclusively watch video on a 50i device then any 24p or 25p video will be interlaced to 50 fps. Therefore unless you use a device capable of displaying 24p natively there is no benefit to recording in 24p.

If you do have a device that allows native 24p production the VG10 output can be easily deinterlaced to 25p in a video editing package, with little impact as this is the original frame rate at which it was measured.

The vast majority of people in PAL regions will watch their video on their HDTV, at 50i, so it makes sense to use this format by default.

A question:

Unless there is something missing from the above, I fail to understand all the angst about missing 24p from the VG10.

Please enlighten me...

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Jon Rty Veteran Member • Posts: 3,838
Re: 24p, 25p, 50i, lots of angst...

The 24p look is preferred by many cinematographers and is considered the classic movie frame-rate. I'd say as good as every movie you've seen in a cinema has was 24p. Transforming footage from 25p to 24p will introduce judder to the film.

It's also my understanding that de-interlacing can also produce artifacts, especially with footage of lots of movement.

npires
npires Senior Member • Posts: 1,738
Re: 24p, 25p, 50i, lots of angst...

Jon Rty wrote:

It's also my understanding that de-interlacing can also produce artifacts, especially with footage of lots of movement.

Depends how well it's done but it shouldn't also depends on the footage you've shot.

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zepzr Senior Member • Posts: 2,012
Re: 24p, 25p, 50i, lots of angst...

mike_2008 wrote:

I'm looking for some clarification on frame rates in video. I'm talking exclusively about displaying video on a PAL television or projector.

Some facts:

The PAL version of the nex VG10 measures at 25p and saves at 50i, so it takes 25 frames per second off the sensor and interlaces this to produce 50i

But since NTSC is 60i, does VG10 samples it 30p for US model?

Nordstjernen
Nordstjernen Veteran Member • Posts: 6,876
and the

You are right. For a hobbyist that edit his/her own stuff the frame rate of the new Sony videocam should be perfect:

PAL (Europe, Australia, Asia etc.) 25 fps
NTSC (USA, Canada, Japan etc.) 30 fps - or actually 29,97 fps

According to my info film 24 fps complicates slightly the process of transferring a cinematic motion picture to video.

Also, you have the lack of 1080p recording angst, since the highest quality setting for this new Sony E mount video camera is 1080i.

For real work life there should be NO visible differences in quality between 1080i and 1080p.

Specs just for the sake of the specs does seldom tell the whole story, and high specs alone doesn't make a product professional.

I think the frame rate and quality setting for this new videocam is well balanced to make life easy for the hobbyist and serious amateur that want to explore the world of high definition video. This is my point of view.

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OP mike_2008 Veteran Member • Posts: 5,635
Re: and the

Right. I am getting the impression that the video world is full of people who don't understand what they're talking about, but have a fixed idea that if a camera doesn't record 1080p 24 fps then it sucks. Funny how these things get mixed up.

Nordstjernen wrote:

You are right. For a hobbyist that edit his/her own stuff the frame rate of the new Sony videocam should be perfect:

PAL (Europe, Australia, Asia etc.) 25 fps
NTSC (USA, Canada, Japan etc.) 30 fps - or actually 29,97 fps

According to my info film 24 fps complicates slightly the process of transferring a cinematic motion picture to video.

Also, you have the lack of 1080p recording angst, since the highest quality setting for this new Sony E mount video camera is 1080i.

For real work life there should be NO visible differences in quality between 1080i and 1080p.

Specs just for the sake of the specs does seldom tell the whole story, and high specs alone doesn't make a product professional.

I think the frame rate and quality setting for this new videocam is well balanced to make life easy for the hobbyist and serious amateur that want to explore the world of high definition video. This is my point of view.

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zepzr Senior Member • Posts: 2,012
Re: 24p, 25p, 50i, lots of angst...

Jon Rty wrote:

The 24p look is preferred by many cinematographers and is considered the classic movie frame-rate. I'd say as good as every movie you've seen in a cinema has was 24p. Transforming footage from 25p to 24p will introduce judder to the film.

All high-def broadcasts are still done in either 1080i (most) or 720p (a few, Fox, ESPN).

It's also my understanding that de-interlacing can also produce artifacts, especially with footage of lots of movement.

and these artifacts are difficult for most viewers to spot.

Here is from last year year article from cnet
http://reviews.cnet.com/720p-vs-1080p-hdtv/

8. What happens when you feed a 1080i signal to a 1080p TV?

It's converted to 1080p with no resolution conversion. Instead, the 1080i signal is "de-interlaced" for display in 1080p. Some HDTVs do a better job of this de-interlacing process than others, but usually the artifacts caused by improper de-interlacing are difficult for most viewers to spot.

9. Side by side, how do 720p and 1080p TVs match up in head-to-head tests?

We spend a lot of time looking at a variety of source material on a variety of TVs in our video lab here at CNET's offices in New York. When I wrote my original article over three years ago, many 1080p TVs weren't as sharp as they claimed to be on paper. By that, I mean a lot of older 1080p sets couldn't necessarily display all 2 million-plus pixels in the real world--technically, speaking, they couldn't "resolve" every line of a 1080i or 1080p test pattern.

That's changed in the last few years. Virtually all 1080p sets are now capable of fully resolving 1080i and 1080p material, though not every 1080p TV is created equal. As our resident video guru, Senior Editor David Katzmaier explains in his HDTV resolutions feature, Blu-ray serves up another video format, 1080p/24, and not every TV properly displays 1080p/24. The 24 refers to the true frame rate of film-based content, and displaying it in its native format is supposed to give you a picture exactly as the director intended you to see it (for a full explanation, click here).

Whether you're dealing with 1080p/24 or standard 1080p/60, doesn't alter our overall views about 1080p TVs. We still believe that when you're dealing with TVs 50 inches and smaller, the added resolution has only a very minor impact on picture quality. In our tests, we put 720p (or 768p) sets next to 1080p sets, then feed them both the same source material, whether it's 1080i or 1080p, from the highest-quality Blu-ray player. We typically watch both sets for a while, with eyes darting back and forth between the two, looking for differences in the most-detailed sections, such as hair, textures of fabric, and grassy plains. Bottom line: It's almost always very difficult to see any difference--especially from farther than 8 feet away on a 50-inch TV.

I said so much in a 2006 column I wrote called "The case against 1080p," but some readers knocked us for not looking at high-end TVs in our tests. But the fact is, resolution is resolution, and whether you're looking at a Sony or a Westinghouse, 1080p resolution--which relates to picture sharpness--is the same and is a separate issue from black levels and color accuracy.

splugnut2000 Regular Member • Posts: 351
Re: 24p, 25p, 50i, lots of angst...

you're thinking about combing artifacts which arise from de-interlacing, these occur when you use an interlaced CAPTURE method and view on a PROGRESSIVE display. It results from the fact if you do an alternate line scan on a sensor to get the upper/lower field of an output frame, then in the next capture period, you acquire the other field, there will almost always be some movement of the subject during the interval between the upper and lower field capture. When you then de-interlace to turn the interlaced footage to progressive, there is a positional mismatch between subject in the fields and you get something like below at the edges of objects:

iiiiiiiiiiiiiiiiiiiiiiiiii
.....iiiiiiiiiiiiiiiiiiiiiiiiiii
iiiiiiiiiiiiiiiiiiiiiiiiiii
.....iiiiiiiiiiiiiiiiiiiiiiiiiii
iiiiiiiiiiiiiiiiiiiiiiiiiii

With progressive capture this doesn't occur as both fields were captured at the exact same time. Even if this is then recorded in a split field arrangement (interlaced) it wont matter as the deinterlacing just puts the fields back together as they were captured (i.e in progressive with no temporal shift between fields).

In the initial days when mainstream displays started to go natively progressive (LCDs) and most capture was interlaced, this mattered and methods of interpolation were developed to try to reduce the problem using field blending etc, although this reduced resolution.

OP mike_2008 Veteran Member • Posts: 5,635
Re: 24p, 25p, 50i, lots of angst...

OK. First of all, how many people will be using the VG10 to make a feature film to show on 35mm film in a cinema?

Secondly, if you are lucky enough to live in a PAL region and shoot at 50i but render at 25p the movie quality is right there.

In reality in video editors 50i is 50 fields per second and treated as 25 frames per second automatically, so there is really no difference between 50i and 25p. This is particularly true in the case of the VG10 since the source is truly 25p.

Jon Rty wrote:

The 24p look is preferred by many cinematographers and is considered the classic movie frame-rate. I'd say as good as every movie you've seen in a cinema has was 24p. Transforming footage from 25p to 24p will introduce judder to the film.

It's also my understanding that de-interlacing can also produce artifacts, especially with footage of lots of movement.

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OP mike_2008 Veteran Member • Posts: 5,635
Re: 24p, 25p, 50i, lots of angst...

So if I understand this right the VG10 does progressive capture at 25p in PAL and 30p in NTSC, then produces a half resolution field from each 25p frame to produce 50i and 60i video which is then recorded.

In a video editor it can be treated as either as 50i or native 25p without any deinterlacing effects, since it was truly captured at 25p.

splugnut2000 wrote:

With progressive capture this doesn't occur as both fields were captured at the exact same time. Even if this is then recorded in a split field arrangement (interlaced) it wont matter as the deinterlacing just puts the fields back together as they were captured (i.e in progressive with no temporal shift between fields).

In the initial days when mainstream displays started to go natively progressive (LCDs) and most capture was interlaced, this mattered and methods of interpolation were developed to try to reduce the problem using field blending etc, although this reduced resolution.

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Jon Rty Veteran Member • Posts: 3,838
Re: 24p, 25p, 50i, lots of angst...

Yes, but movies are shot in 24p. I've yet to see a non-studio PAL/NTSC to 24p conversion that didn't introduce judder. I'd also say that the main criticism the VG10 was getting was the lack of a 60p option, as well as the lack of higher bit-rates.

As for the article you quoted, yes, usually they're difficult to spot, as like I said you usually need high motion footage to make them visible. If the footage is captured in 25/30p anyway, then storing it as interlaced has as good as no advantages. Besides, the writer of that article doesn't appear to have that high standards, as I personally can spot the difference of 720p and 1080p on a 24" screen.

zepzr wrote:

All high-def broadcasts are still done in either 1080i (most) or 720p (a few, Fox, ESPN).

and these artifacts are difficult for most viewers to spot.

Here is from last year year article from cnet
http://reviews.cnet.com/720p-vs-1080p-hdtv/

8. What happens when you feed a 1080i signal to a 1080p TV?

It's converted to 1080p with no resolution conversion. Instead, the 1080i signal is "de-interlaced" for display in 1080p. Some HDTVs do a better job of this de-interlacing process than others, but usually the artifacts caused by improper de-interlacing are difficult for most viewers to spot.

9. Side by side, how do 720p and 1080p TVs match up in head-to-head tests?

We spend a lot of time looking at a variety of source material on a variety of TVs in our video lab here at CNET's offices in New York. When I wrote my original article over three years ago, many 1080p TVs weren't as sharp as they claimed to be on paper. By that, I mean a lot of older 1080p sets couldn't necessarily display all 2 million-plus pixels in the real world--technically, speaking, they couldn't "resolve" every line of a 1080i or 1080p test pattern.

That's changed in the last few years. Virtually all 1080p sets are now capable of fully resolving 1080i and 1080p material, though not every 1080p TV is created equal. As our resident video guru, Senior Editor David Katzmaier explains in his HDTV resolutions feature, Blu-ray serves up another video format, 1080p/24, and not every TV properly displays 1080p/24. The 24 refers to the true frame rate of film-based content, and displaying it in its native format is supposed to give you a picture exactly as the director intended you to see it (for a full explanation, click here).

Whether you're dealing with 1080p/24 or standard 1080p/60, doesn't alter our overall views about 1080p TVs. We still believe that when you're dealing with TVs 50 inches and smaller, the added resolution has only a very minor impact on picture quality. In our tests, we put 720p (or 768p) sets next to 1080p sets, then feed them both the same source material, whether it's 1080i or 1080p, from the highest-quality Blu-ray player. We typically watch both sets for a while, with eyes darting back and forth between the two, looking for differences in the most-detailed sections, such as hair, textures of fabric, and grassy plains. Bottom line: It's almost always very difficult to see any difference--especially from farther than 8 feet away on a 50-inch TV.

I said so much in a 2006 column I wrote called "The case against 1080p," but some readers knocked us for not looking at high-end TVs in our tests. But the fact is, resolution is resolution, and whether you're looking at a Sony or a Westinghouse, 1080p resolution--which relates to picture sharpness--is the same and is a separate issue from black levels and color accuracy.

splugnut2000 Regular Member • Posts: 351
Re: 24p, 25p, 50i, lots of angst...

yep, thats exactly it.

OP mike_2008 Veteran Member • Posts: 5,635
Re: 24p, 25p, 50i, lots of angst...
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splugnut2000 Regular Member • Posts: 351
Re: 24p, 25p, 50i, lots of angst...

just watched the vimeo "beautiful bali" video shot on the VG10 on a 40 inch LCD and even though its compressed to less than a quarter of the VG10s max bitrate and needs to be scaled for 1080 full screen it looks simply beautiful. The actual footage from the camcorder itself must be stunning. There's also plenty of pans and dolly shots in there with no obvious rolling shutter effects. All in all, superb! - just one little point though Sony, you couldn't stretch throwing in the super slo-motion feature of the NXCAMs could you, or 720p50/60...just a thought.

Jogger
Jogger Veteran Member • Posts: 8,441
are you 100% positive?

Where is your source that it captures progressive but saves in interlace? And, what would be the purpose of this.. seems to add an extra step?

Do you know if this is true for the NEX5 as well?

mike_2008 wrote:

I'm looking for some clarification on frame rates in video. I'm talking exclusively about displaying video on a PAL television or projector.

Some facts:

The PAL version of the nex VG10 measures at 25p and saves at 50i, so it takes 25 frames per second off the sensor and interlaces this to produce 50i.

Most PAL HD televisions work at 50i.

If you exclusively watch video on a 50i device then any 24p or 25p video will be interlaced to 50 fps. Therefore unless you use a device capable of displaying 24p natively there is no benefit to recording in 24p.

If you do have a device that allows native 24p production the VG10 output can be easily deinterlaced to 25p in a video editing package, with little impact as this is the original frame rate at which it was measured.

The vast majority of people in PAL regions will watch their video on their HDTV, at 50i, so it makes sense to use this format by default.

A question:

Unless there is something missing from the above, I fail to understand all the angst about missing 24p from the VG10.

Please enlighten me...

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SchorschB Regular Member • Posts: 308
Re: 24p, 25p, 50i, lots of angst...

Usually, movies are made at 24 full images per second.

Movies on blu-ray discs are also usually stored at a rate of 24 full frames per second.

Why do people like this format and continue to use it? Because it has something like a universal compatibility.

For PAL presentation, you simply run the movie slightly faster, at 25 fps - which presents well on 50Hz (or 100Hz) TV sets; the difference is usually not noticeable. No re-coding required. You simply show each frame two times (four times for 100Hz).

For NTSC presentation, you have two choices:

One is called "3:2 pull-down" and is the only way to present on a conventional TV or cheap LCD/plasma: you present one frame 3 times, and the next one 2 times (12x3 + 12x2 = 60fps). This, however, introduces some choppiness into movements.

The other, much preferred one, requires a more modern TV, with 120Hz (or 240Hz) refresh rate - which these days most HD panels can do (and which you should insist on buying if you want to fully enjoy blu-ray discs). For 120Hz, you simply present each of the 24 frames five times. No change to the original flow of motion is created by this method, no re-coding required.

25 or 50fps material does not play well on NTSC standard devices,
30 or 60fps material does not play well on PAL standard devices -

but 24fps can be played on both with relative ease. That's one of the reasons why it's the standard on blu-ray, too.
--
Georg
-

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mervis50 Regular Member • Posts: 214
Re: 24p, 25p, 50i, lots of angst...

Nice explanation. Thanks.
--
Cheers from Vancouver, Canada

Everdog Veteran Member • Posts: 4,837
Re: 24p, 25p, 50i, lots of angst...

mike_2008 wrote:

So if I understand this right the VG10 does progressive capture at 25p in PAL and 30p in NTSC, then produces a half resolution field from each 25p frame to produce 50i and 60i video which is then recorded.

This is the problem, because then a flat panel display needs to de-interlace the video, which many do poorly. Why the heck can't Sony just output progressive like everyone else?

splugnut2000 Regular Member • Posts: 351
Re: are you 100% positive?

his source is Sony, they state it in their press releases and although I haven't looked into it fully, yes the NEX 5 should be the same.

zepzr Senior Member • Posts: 2,012
Re: are you 100% positive?

Jogger wrote:

Where is your source that it captures progressive but saves in interlace?

because 60i and 30p are same thing (just as 25p and 50i aer identical for PAL) ?

And, what would be the purpose of this.. seems to add an extra step?

To make it simple for playing it on all TV models?

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