24p question

[mk23]

Here's another 24p question,

I understand that when you shoot 24p video the camera captures at 29.97 but marks the 24 frames so that the extra frames could be removed in editing. Now here's my question, if the 24p footage will then be displayed on screen that displays at 29.97 (all NTSC) doesn't that mean that extra frames will be added once again?, this makes the whole process seem pointless

in other words, if NTSC has to display at 30fps because of electricity, does that mean 24p footage on NTSC screens will be actually 30 fps with some blank frames or something, and does that mean that when using anything other than the projector in the theatre we're better off shooting and displaying 30 frames ???

Thanks

[guns1inger]

Most NTSC DVDs taken from film shot movies are 23.976 progressive, however they have 2:3 pulldown flags applied to the stream. If you play them back on a standard interlaced TV, you will get 29.970 fps to the display. If you play them back on a progressive player to a progressive TV via component connections, you get 23.976. The play creates the missing frames on the fly.

[mk23]

If you play them back on a progressive player to a progressive TV via component connections, you get 23.976. The play creates the missing frames on the fly.

I think when you play back from a progressive player to a progressive TV you will get the benefit of progressive scanning, but as I understand it, if the display is NTSC then it must display at 30fps and that is because of the electric current going into it, just like in europe or in a PAL system it plays at 25 fps because of different cycles in the electricity.

If what I'm saying is correct then I guess my question still stands.

[edDV]

Here's another 24p question,

I understand that when you shoot 24p video the camera captures at 29.97 but marks the 24 frames so that the extra frames could be removed in editing. Now here's my question, if the 24p footage will then be displayed on screen that displays at 29.97 (all NTSC) doesn't that mean that extra frames will be added once again?, this makes the whole process seem pointless

in other words, if NTSC has to display at 30fps because of electricity, does that mean 24p footage on NTSC screens will be actually 30 fps with some blank frames or something, and does that mean that when using anything other than the projector in the theatre we're better off shooting and displaying 30 frames ???

Thanks

All this depends on the type of camcorder doing the shooting. Very few camcorders are capable of 24p. Here is one of the cheapest, the Panasonic DVX-100p.
http://www.adamwilt.com/24p/

Most of the issues are spelled out in that FAQ. A camera capable of shooting 24p (23.976 actually) must add fields to pad out to 29.97 for 480i DV or DigiBeta format recording. This is done in a different way than normal 2:3 telecine. "Advanced 24p" uses a 2:3:3:2:2:3:3:2 field repeat pattern that actually looks jerky if viewed at 29.97. It isn't intended to be viewed until converted back to 23.976p on the editing timeline.

After editing a 23.976p master, distribution copies can be made in various formats including:

1. Normal telecined 29.97 480i + analog format copies.
2. PAL 25 fps 576i (run 4% fast or speed converted to 25 fps)
3. Progressive 23.976 fps 480p DVD.
The DVD player converts this to 480i (29.97 telecined)
or 480p with full frames repeated 3:2:3:2:3:2 to play at 59.94 frames per second on a progressive TV.
4. Progressive 576p PAL DVD
5. Upconversion to 720p/59.94 frames per second
6. Upconversion and telecined to 29.97 fps 1080i
7. Transfer to 24 fps film
8. Etc. -- you can convert 24p to almost anything else. That is why TV shows are shot 24p.

Above we used a SD camera example. The same process is used for 1080p/23.976 High Def cameras or film used for shooting major TV series for world distribution. The same issues apply except 1080p 23.976 masters get down converted for 720p, 1080i, 576p, 576i, 480p and 480i.

It should be noted that 24P has serious disadvantages requiring carefull shooting technique from heavy tripods, steadycams or highly skilled handheld camera operators.
Pans, zooms and exposure must be more tightly controlled and artificial lighting is often needed. All of the above points one to film school to gain these skills.

[mk23]

Thanks edDV,

I already a panasonic hvx and I capture and edit on 24frame timelines in Final cut all the time, I have no issues with it what so ever, but the thing is I was taught in school that any NTSC display because of the type of electricity it uses has a refresh rate of 60 hz and so it has to produce images at 30 fps while in PAL the refresh rate is 50 hz so it becomes 25 fps, I researched a bit on my own and all information I could find on any type of display supports this info, so I am left wondering if televisions and monitors are restricted to certain frames per second like 30 for NTSC then what is the use of trying to make footage that does not match that.

[mk23]

I guess the only ones who will truly benefit from the 24p mode on cameras like the panasonic dvx and hvx are people who will transfer the footage to actual film or will use it in PAL land where the native 25fps is almost 24

[jagabo]

If you're making DVDs 24p has a lot fewer pixels-per-second to be encoded. So you get better picture quality at equivalent bitrates. And Progressive MPEG encoding results in less chroma channel artifacting than interlaced encoding.

[TBoneit]

One nit picking point. NTSC is not 30fps. It is 29.97 fps, it started out at 30 fps for b&w and when color was introduced the frame rate changed. There was a quite good thread here on that subject.

the difference is small enough that older TVs at that time could still work.

[edDV]

The AC power frequency was an important issue in the early days of television (1930's to 1960's). The TV scan rate had to match power frequency or hum bars would roll through the picture or interfere with audio. I'll spare the "electrical" details.

Also in the early days, broadcasters lacked any means to synchonize their equipment except from power line frequency which was common throughout the region.

It was for these and other reasons that local video standards followed power frequency.

By the time color came along in the mid 50's, equipment had evolved to the point where synchronization was electronic rather than electric but there was a need for backward compatibility for color TV. It was decided to make the system work with the millions of existing monochrome TV sets as well so 60Hz (59.94Hz for color), or 50Hz for Europe and others got locked into the standard.

Today, if you operate 60Hz equipment in 50Hz areas you need to pay attention to hum and shooting under flourescent lights can cause flicker. If you were going to build a 60Hz cable system in a 50Hz power region, you may find many other isolation issues.

Thanks edDV,

...so I am left wondering if televisions and monitors are restricted to certain frames per second like 30 for NTSC then what is the use of trying to make footage that does not match that.

If you intend your video only to be viewed locally, you would just shoot 480i/29.97 or 576i/25.

You would shoot 24p if
1. You intended to distribute to the worldwide broadcast channel. It is possible to electronically standards convert 480i to 576i but at the broadcast level, that is considered second rate suitable only for news or sports.
2. You want to release on film.
3. You want to archive for the future as 24p.
4. You want to shoot "film style" with all the pros (few) and cons (many).

In North America, most TV sets are restricted to 29.97 frame rates. This is beginning to change for some of the HDTV sets that may accept 25 fps (as monochrome or as YPbPr). All HDTV ATSC tuners must accept 480p/23.976, 720p/23.976 or 1080p/23.976 but not the other inputs.

(added)
23.976 ATSC is not currently being used but probably will be in the future to be more bandwidth effeicient. For example, you could transmit two 720p/23.976 HD movies at the same bitrate as one 720p/59.94 channel as now broadcast. The TV tuner itself has the capability to frame repeat 23.976 to 59.94 frames per second.

In Europe, most newer TV sets will "play" NTSC through tricks but rarely are truely multi-standard. HDTV may change that.

[mk23]

If you're making DVDs 24p has a lot fewer pixels-per-second to be encoded. So you get better picture quality at equivalent bitrates. And Progressive MPEG encoding results in less chroma channel artifacting than interlaced encoding.

I know that encoding less frames per second will give better quality per specific size, and the chroma artifacts in progressive V.S interlaced is good to know especially for keying.

[mk23]

edDV:

Thanks,nice post, thats really what I was wondering about, I see so many people that are goin crazy over the new 24p option coming out in new video cameras and they think if they shoot 24p that it will be just like watchin film, but you're confirming what I thought, which is that it will only have same fps as film in rare cases.

[edDV]

If you're making DVDs 24p has a lot fewer pixels-per-second to be encoded. So you get better picture quality at equivalent bitrates. And Progressive MPEG encoding results in less chroma channel artifacting than interlaced encoding.

I know that encoding less frames per second will give better size to quality ratio, and the chroma artifacts in progressive V.S interlaced is good to know especially for keying.

If chroma keying is a prioity, you wouldn't be shooting 4:1:1 DV format especially for the foreground*. Your HVX-200 can shoot DVCPro50 4:2:2 to the P2 flash ram. That would work better for keying. Plan ahead for the scenes that will be keyed.

What kind of work are you doing? Are you doing anything HD?

* if you have to use DV 4:1:1 for chroma key, advice from Ultimatte is to capture the foreground from S-Video. This will average the chroma into smoother edges at the cost of sharpness.

[jagabo]

I usually use shoot 30p with my DV camcorder.

[edDV]

edDV:

Thanks,nice post, thats really what I was wondering about, I see so many people that are goin crazy over the new 24p option coming out in new video cameras and they think if they shoot 24p that it will be just like watchin film, but you're confirming what I thought, which is that it will only have same fps as film in rare cases.

For standard NTSC TV sets, 23.976 gets telecined to 29.97 (59.94 fields per second).

For progressive TV sets, 23.976 gets frame repeated to 59.94 frames per second. The motion is still film like 23.976 but the frame repeat solves the flicker issue.

Movie projectors also repeat frames 2x to 48Hz or 3x to 72Hz to reduce flicker.

PAL interlace field repeats at a 50Hz rate.

PAL progressive display systems repeat full frames 2x to 50Hz or 4x to 100Hz.

Most people have a flicker tolerence somewhere around 48-60Hz. When I go to Europe the 50Hz TV flicker drives me nuts for a few days until the brain adapts.

[mk23]

if chroma keying is a prioity, you wouldn't be shooting 4:1:1 DV format especially for the foreground. Your HVX-200 can shoot DVCPro50 4:2:2 to the P2 flash ram. That would work better for keying. Plan ahead for the scenes that will be keyed.

What kind of work are you doing? Are you doing anything HD?

Yeah, I try to shoot dvcprohd, it gives the raw footage huge sizes, but id rather have the raw stuff as uncompressed as possible plus the color sampling is better than dv, so I only use dv when I need to record a whole lot of footage. I only have one 4gb p2 (theyre so darn expensive) so only 4 minutes of HD at full rez on the p2, but you dont really need a p2 if you can have a laptop around,you can just live capture full rez into final cut or premiere without any storage media in the camera, which is what I do (god bless firewire).

I'm still in film school (although we use digital not film), all my stuff is mainly experimental, just practicing to get the technique down. I worked on a couple local music vids and short films but no project to call my own, saving the good scripts to when I'm more experienced, now i'm just happy to practice whatever.

what about you, don't tell me your interest in this stuff is just as a hobby, what kind of video work do you do?

[edDV]

if chroma keying is a prioity, you wouldn't be shooting 4:1:1 DV format especially for the foreground. Your HVX-200 can shoot DVCPro50 4:2:2 to the P2 flash ram. That would work better for keying. Plan ahead for the scenes that will be keyed.

What kind of work are you doing? Are you doing anything HD?

Yeah, I try to shoot dvcprohd, it gives the raw footage huge sizes, but id rather have the raw stuff as uncompressed as possible plus the color sampling is better than dv, so I only use dv when I need to record a whole lot of footage. I only have one 4gb p2 (theyre so darn expensive) so only 4 minutes of HD at full rez on the p2, but you dont really need a p2 if you can have a laptop around,you can just live capture full rez into final cut or premiere without any storage media in the camera, which is what I do (god bless firewire).

DVCProHD is 960x720p/59.94 or 1280x1080i/29.97 but both are 4:2:2 which will help chroma key. By contrast HDCAM is 3:1:1 (1440x1080 luma, 480x1080 chroma) or more luma, less chroma. A good workman uses the proper tools.

I'm still in film school (although we use digital not film), all my stuff is mainly experimental, just practicing to get the technique down. I worked on a couple local music vids and short films but no project to call my own, saving the good scripts to when I'm more experienced, now i'm just happy to practice whatever.

what about you, don't tell me your interest in this stuff is just as a hobby, what kind of video work do you do?

Experiment while you have access to that good equipment.

I was full on in this industry from the broadcast equipment engineering side from the early 80's to mid 90's. I've tried to stay current while doing more management. I run a small consulting business to post houses on the side and do my own video production projects. I'm also a hobbiest on the DVD authoring side.

[mk23]

I run a small consulting business to post houses on the side and do my own video production projects. I'm also a hobbiest on the DVD authoring side.

The whole engineering thing is way out of my league, my head hurts when it comes to numbers and the heavy technical stuff , but I'm always interested in the creative side, pre during or post production , so If any of your projects are posted online or you got a website or something, I'd love to see.

[edDV]

These days you almost need a consulting engineer to help design a project flow especially for doing greeen screen composites and computer effects integration.

I don't have anything pretty to show you. My HDV projects were just to test equipment here. Serious work will have to wait for the next computer upgrade.

[mk23]

These days you almost need a consulting engineer to help design a project flow especially for doing greeen screen composites and computer effects integration.

yeah and with digital now replacing old analogue stuff and even gradually replacing film, the need for tech people will continue to increase. I think the coming years will be interesting, to see what new equipment will come out and how the media will change.

[edDV]

These days you almost need a consulting engineer to help design a project flow especially for doing greeen screen composites and computer effects integration.

yeah and with digital now replacing old analogue stuff and even gradually replacing film, the need for tech people will continue to increase. I think the coming years will be interesting, to see what new equipment will come out and how the media will change.

I think you will find when you go on the job market that they expect you to be familliar with both the old film technique an the new HD digital technique.

Your potential employer knows more than you will ever need to know about film. They will expect you to fill in the gaps on digital. Don't make the mistake expecting they are digital clueless during the interview. They will know more than you but will be testing your knowledge and experience.