Is it better to shoot a TV commercial in 29.97fps or 30fps?

[Barry_Green]

Except that with regards to interlaced video two fields captured 1/60th (or 1/50th) appart make up a unit of time called we've decided to call a frame.

Yes, exactly. And we all decided that the sun revolved around the earth, too -- but that didn't make it so. And two disparate moments in time (fields) arbitrarily grouped together, doesn't become a "frame", even though that's the word that's used to describe a pair of fields.

When I think about frames and footage the first thing that comes to me is a defined unit of time.

We all do. But that's the problem... what you're calling a "frame" in interlaced video is actually TWO units of time. A progressive frame is a snapshot of time. An interlaced "frame" isn't. It's two different units in time, which are sliced up and packed in the same box (which, unfortunately, someone long ago decided to call that mismatched pair of fields a "frame" and we've been stuck with that erroneous nomenclature ever since.)

but the frame is the fraction of a second I get to cut with.

And in terms of editing, yes, that's right. Fields are grouped into pairs and called a "frame", and that's all the NLE lets you work with.

so, coming full circle, 60 fields per second and 30 interlaced frames per second are two ways to describe the same thing.

You are correct, both those terms describe the same thing.
What David and I have a problem with is that if you have a choice of what to call it, why not call it by the more accurate, more descriptive term? 30p tells you there's 30 motion samples per second. 60i tells you there's 60 motion samples per second. 30i just confuses things -- what is it? Is it 30 motion samples per second? That'd make it the equivalent of 15 "interlaced frames", wouldn't it? How does that make sense?

If you say "60i" (like all the camera manufacturers do) then you know exactly what you're getting -- 60 motion samples per second, in interlaced fields. If you say 30p you know exactly what you're getting -- 30 progressive frames per second. If you call NTSC video "29.97", what are you getting? Which is it? It could be either -- but it's obviously one, and not the other. So the name is confusing.

Eventually we all had to get used to the idea that the sun didn't revolve around the earth, but the earth revolves around the sun. Equally, we're all going to have to get used to the idea that "29.97", while a common name, is just deceptive and confusing, and if the goal of communication is to make your intent clearly and easily understood, then we should stop using the confusing, old name and migrate to the proper names -- 60i (or 59.94i) and 60p (or 59.94p) and 30p (or 29.97p) and 24p (or 23.976p).

 

[adkimery]

And in terms of editing, yes, that's right. Fields are grouped into pairs and called a "frame", and that's all the NLE lets you work with.

I meant to expand on this a little more but I apparently side tracked myself. I'm going to go out on limb and say you and Dave shoot more than I do (I edit and haven't shot for years). So I think it's interesting that when the word 'frame' pops up your guys first reaction is to think about it in terms of what's happening at the head of the camera and my first reaction is to think about it in terms of what's coming out the back of the camera.

Eventually we all had to get used to the idea that the sun didn't revolve around the earth, but the earth revolves around the sun. Equally, we're all going to have to get used to the idea that "29.97", while a common name, is just deceptive and confusing, and if the goal of communication is to make your intent clearly and easily understood, then we should stop using the confusing, old name and migrate to the proper names -- 60i (or 59.94i) and 60p (or 59.94p) and 30p (or 29.97p) and 24p (or 23.976p).

I'm all for uniform naming but whatever you call it, interlaced still requires an explanation. If you call it 29.97 frames per second interlaced you have to explain that it's 2 fields recorded 1/60th of a second apart. If you call it 60i you still have to explain why the frame rate is 29.97 even though the camera is set to "60". The only route that doesn't require an explanation is to banish interlaced to the history books but unfortunately that's not going to happen anytime soon.


-Andrew

 

[Barry_Green]

It will happen, just not soon enough.

 

[adkimery]

It will happen, just not soon enough.

A number of years ago I convinced the place I was working at to stop shooting in 1080i60 and switch over to 720p60. Initially they were reluctant because 1080 is the bigger of the two numbers but I did some 720p60/1080i60 split-screen tests and no one could tell which was which watching only a few feet away on a 45" monitor. After that they were sold. Going progressive also alleviated other problems related to interlacing such as compression for the web, graphics and speed ramps.

For work that needs to happen at 60hz I'll happily stick w/720p60 until 1080p60 becomes viable.

 

[David Jimerson]

I meant to expand on this a little more but I apparently side tracked myself. I'm going to go out on limb and say you and Dave shoot more than I do (I edit and haven't shot for years). So I think it's interesting that when the word 'frame' pops up your guys first reaction is to think about it in terms of what's happening at the head of the camera and my first reaction is to think about it in terms of what's coming out the back of the camera.

I do all the editing as well, and what I see on a 29.97 timeline is two motion samples being treated as one. This is why, if I shoot 59.94 (not often), I generally create my own timeline and edit by pure frame stops (in 60p) instead of timecode. I get at all of the motion samples that way, not just every other. It is not at all difficult to match this up with any delivery needs.

 

[Razz16mm]

59.94 is broadcast timing for 1080i, interlaced. 29.97 is broadcast timing for 720p. If you are producing for broadcast, your deliverable should be in one or the other of these formats. Which is determined by the broadcast format of the station or network you are delivering to.

 

[David Jimerson]

59.94 is broadcast timing for 1080i, interlaced. 29.97 is broadcast timing for 720p. If you are producing for broadcast, your deliverable should be in one or the other of these formats. Which is determined by the broadcast format of the station or network you are delivering to.

Why would 29.97 be the "broadcast timing" for 720p? It's broadcast at 60p. (The station above, for example, asked for 59.94.)

I think you may have typed that backwards, and the label of "29.97" for 1080i is at the heart of the problem we've been discussing here. They may call it "29.97," but it's really 59.94.

If things were broadcast at an actual 29.97, nothing -- no news, no sports, no reality TV, no soap operas, nothing -- would ever look "live." And that would be a BIG problem for sports, sports being the main reason 720p broadcasters choose 720p.

Here's the bottom line, getting back to the OP's question:

Of the NTSC-based frame rates -- 60i, 60p, 30p, 24p -- you can choose and shoot ANY of them and still be able to deliver for broadcast on any NTSC-region TV station/network without losing the look/motion cadence of that frame rate. You do NOT have to choose your frame rate based on the delivery requirements. Shoot the frame rate you want your footage to LOOK like, full stop.

 

[David W. Jones]

Here's the bottom line, getting back to the OP's question:

Of the NTSC-based frame rates -- 60i, 60p, 30p, 24p -- you can choose and shoot ANY of them and still be able to deliver for broadcast on any NTSC-region TV station/network without losing the look/motion cadence of that frame rate. You do NOT have to choose your frame rate based on the delivery requirements. Shoot the frame rate you want your footage to LOOK like, full stop.

This^

 

[Razz16mm]

Why would 29.97 be the "broadcast timing" for 720p? It's broadcast at 60p. (The station above, for example, asked for 59.94.)

I think you may have typed that backwards, and the label of "29.97" for 1080i is at the heart of the problem we've been discussing here. They may call it "29.97," but it's really 59.94.

If things were broadcast at an actual 29.97, nothing -- no news, no sports, no reality TV, no soap operas, nothing -- would ever look "live." And that would be a BIG problem for sports, sports being the main reason 720p broadcasters choose 720p.

Here's the bottom line, getting back to the OP's question:

Of the NTSC-based frame rates -- 60i, 60p, 30p, 24p -- you can choose and shoot ANY of them and still be able to deliver for broadcast on any NTSC-region TV station/network without losing the look/motion cadence of that frame rate. You do NOT have to choose your frame rate based on the delivery requirements. Shoot the frame rate you want your footage to LOOK like, full stop.

Broadcast standard timing is still based on NTSC analog timing. The fractional shift in timing is to prevent beat frequency strobing with 60Hz AC powerline frequency. There is no visible difference between 30p and 29.97p, they are essentially the same. Nobody broadcasts 60p currently, there is not bandwidth allotted to support it. 59.94 is interlaced only. The effective spatial resolution for moving images is essentially the same for 1080i and 720p. Broadcast standard timecode is set to 29.97 drop frame for 720p, and 59.94 drop frame for 1080i. If you edit in or deliver in a different time base the usual result is problems with audio sync when the footage is recompressed and encoded for broadcast, not a difference in visual quality. All broadcast is at 30 frames per second progressive or 60 fields per second, still 30fps, interlaced. If the station is asking for 59.94 they are broadcasting 1080i.

 

[Razz16mm]

To clarify the above. The ATSC standard does allow for 1080p 30(29.97) and 720p 60(59.94) broadcast using the full 6mHz channel bandwith allotment. But I don't know of many stations that do this. Most allocate half the bandwith allotment to 720 30p or 1080i 59.94 HD broadcast and divide the rest of it among one or two additional 480p/i SD 4:3 channels plus data services to enhance their advertising revenue streams.

 

[David Jimerson]

Nobody broadcasts 60p currently, there is not bandwidth allotted to support it. 59.94 is interlaced only. The effective spatial resolution for moving images is essentially the same for 1080i and 720p. Broadcast standard timecode is set to 29.97 drop frame for 720p, and 59.94 drop frame for 1080i. If you edit in or deliver in a different time base the usual result is problems with audio sync when the footage is recompressed and encoded for broadcast, not a difference in visual quality. All broadcast is at 30 frames per second progressive or 60 fields per second, still 30fps, interlaced. If the station is asking for 59.94 they are broadcasting 1080i.

That cannot be so, as I've seen plenty of actual 720/60p. As I said, if it weren't 59.94, nothing would look live, and that would be a major problem for sports. (And the station above specifically asked for 720/60p anyway.)

Nobody broadcasts 1080/60p, that is true.

Broadcast standard timing is still based on NTSC analog timing. The fractional shift in timing is to prevent beat frequency strobing with 60Hz AC powerline frequency. There is no visible difference between 30p and 29.97p, they are essentially the same.

I'm not referring to the 1000/1001 NTSC frame rate offset. I'm referring to 29.97 vs. 59.94.

 

[David Jimerson]

Here, for example, are ABC's specifications:

2

This document provides technical specifications for those producing high definition interstitial
material (commercials, promotion, PSA, etc.) for playback on the ABC Television Network. ABC
will not normally modify any supplied audio or video parameters,
providing the following technical
requirements are met. ABC reserves the right to reject materials that are delivered with
parameters exceeding the specifications outlined in this document.
Summary of Technical Specifications
•
Scanning format: 720p,59.94 frames per second.

As of January 2013.

http://abcallaccess.com/wp-content/...ial-Tech-Specs-final-updated-January-2013.pdf

 

[Razz16mm]

Here, for example, are ABC's specifications:



As of January 2013.

http://abcallaccess.com/wp-content/...ial-Tech-Specs-final-updated-January-2013.pdf

I stand corrected on the 720p 59.94 thing. The main point I am emphasizing is that you should for most consistent and predictable results shoot, edit, and deliver at the same time base reference and that is ultimately determined by the preferred delivery format.

 

[David Jimerson]

I stand corrected on the 720p 59.94 thing. The main point I am emphasizing is that you should for most consistent and predictable results shoot, edit, and deliver at the same time base reference and that is ultimately determined by the preferred delivery format.

Obviously you have to deliver according to their requirements.

But shooting and editing are entirely different things from delivery.

You pick your shooting frame rate because it's what you want your footage to look like. That's it, end of story. What it looks like, not what you'll deliver it as.

All TV dramas are shot in 24p, not the 60i or 60p they're broadcast as. Many comedies are shot at 30p. That's picked for the look, not the broadcast delivery format.

If you shoot everything as the 59.94i or 59.94p of the delivery format, everything will look like live TV. That's fine if it's what you want your thing to be, but it's not fine if you don't.

And as for editing, you should match the timeline to your footage. All delivery options are still available to you.

 

[kostas]

But shooting and editing are entirely different things from delivery.

You pick your shooting frame rate because it's what you want your footage to look like.

From this I understand that if you shoot something in 24/25p and deliver it to 30p, for instance, it will look different from shooting the same thing in 30p and delivering to 30p. Is that true?
And to what extent? In my example 30fps should provide a smoother looking motion than 24/25p. While converting 24/25 to 30p aren't we smoothing out motion to make it look like it was shot on 30p?

 

[David Jimerson]

From this I understand that if you shoot something in 24/25p and deliver it to 30p, for instance, it will look different from shooting the same thing in 30p and delivering to 30p. Is that true?

It is true; it will be different from shooting 30p.

And to what extent?

It'll be a terrible conversion.

What I said was in the context of shooting a frame rate and delivering for broadcast, which in the NTSC world is at 59.94. You can shoot any NTSC-based frame rate and export at 59.94 for broadcast, and it'll look correct for the shooting frame rate. 24p and 30p will still look like 24p and 30p even though it's delivered in a 59.94 stream. The same is true for 25p delivered for broadcast in Europe, which is 50.000.

If you are NOT delivering for broadcast, you can almost always shoot and deliver the same frame rate, or at the very least, you can deliver at the same rate AS broadcast (such as PAL DVD). So, you can always choose the frame rate you want your footage to look like.

I cannot think of anything where you'd be required to deliver as 30p. You won't be required to for broadcast and you don't use it for DVD or Blu-ray. If you want it for the web, then shoot 30p. 24p/25p exported to 30p is the worst conversion you can make, because the result will be very choppy or have a lot of ghosting, depending on how you decide to interpolate the frames. But for the web, you can and should shoot and deliver at the frame rate you want your project to look like. But YOU get to choose the delivery frame rate, so you are free to shoot whatever you think is appropriate.

So, if you shoot 24p or 25p, and you're delivering to the web, deliver as 24p or 25p. There's no reason to convert to 30p.

If you have the option of shooting 24p or 25p, as you seem to, because they're almost identical in appearance, shoot 25p if you're delivering to PAL broadcast (50.000), and shoot 24p if you're delivering to NTSC broadcast (59.94).

In my example 30fps should provide a smoother looking motion than 24/25p. While converting 24/25 to 30p aren't we smoothing out motion to make it look like it was shot on 30p?

No. You only have so many motion samples. You need MORE motion samples for movement to be smoother. If you export out as 30p, you don't create new motions, so nothing is smoother. You're still seeing 24 or 25 movements per second, only they'll be re-arranged in a way that they'll look pretty bad.

All of this, too, is explained and demonstrated in the 24p & Frame Rates tutorial, which is 90% of the reason I created it.