when to use a 24p or 23.976 project

[Scott Davids]

Also this is strictly an option for an adrenaline correct?

[Dom Silverio]

The choice also exist on newer Meridien (version 12) and Symphony systems.

It all comes down to how the audio is recorded.

Read Michael Phillip’s (of Avid) article for EGM –

https://www.editorsguild.com/newsletter/MayJun04/mayjun04_23-24_proj.htm

[Michael Phillips]

I am also doing a seminar for the MPEG in NY next week on this very topic as well as in LA for the MPEG the week after. Check the MPEG site at http://www.editorsguild.com for more details.

Michael

[Chris Bové]

Both 24p and 23.976 are SD, not HD. 720p is HDV.

Roughly put, 23.976 is 24p drop-frame. It’s used a lot for miniDV broadcast stuff. Even if footage is shot 24p or 24pA, I’m told by the brains-in-jars over in Avid Tech Support land to use 23.976 (with pulldown for both on v2.1.5 and above Adrenaline) for anything broadcast. They then go on to say the Adrenaline’s 24p is more for film.

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\`(=)`/…Pixel Monkey
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[Michael Phillips]

First of all, 24p or 23.976 does not define resolution. It only defines a frame rate and image structure (progressive or interlace). 720p is also HDV but also HD with DVCPRO HD from Panasonic.

24p does not exist as a native SD format but does exist in HD. HD can be 1080p/24 or 1080p/23.976. 720 can be 720p/23.976 (which is a 2:3 pulldown into 59.94).

One can think of 23.976 as being drop frame, but it should be clear that drop frame timecode does not exist in 23.976. It is a playback rate counted as 24fps timecode. If you want broadcast time while editing, set the sequence timecode in your timeline to 30fps drop frame.

23.976 does exist in SD (DV cameras) as part of a NTSC signal with either NORMAL or ADVANCED pulldown. In this case, the 24p or the 23.976p (frame rate) refers to the rate at which the image was captured sometimes referred to as the motion resolution. The motion is captured as true 23.976p and then stored as a SD signal compressed as DV with one of two pulldown cadences.

The choice of project type is defined by the frame rate of the camera during production and the audio sample rate. Of course you can cross over into one or the other but you will go through an audio sample rate conversion when doing so since in both cases the sample rate in 48kHz. Changing just picture to the other frame rate and not the audio would have the audio drift by .1%.

The HDW-F500 VTR can take a 23.976p, 24p and 25p tape and play out back at 23.976fps, 24fps, and 25fps. In each case, the audio is staying at 48kHz and the deck is fondly referred to as the world’s most expensive audio sample rate converter… 😉

24 frame based television is done at 23.976 since it allow for a clean 2:3 pulldown inside the NTSC rate of 59.94 fields per second (29.97fps). This is true for film or HD. But film at 24fps get an audio sample rate conversion during the film to tape transfer at 23.976.

24fps is typically used fro feature films since the acquisition is at 24fps and the audio is brought straight in for syncing. In this case, you need true 24fps.

The Avid products allow 24fps and 23.976 timelines to go out as 23.976 or 24fps depending on your final distribution needs.

In the end, a frame is a frame for picture, it just plays back at a given frame rate, but audio is a different issue since 48kHz is a constant and needs to remain at the rate regardless of playback rate – so in many cases it needs to go through a sample rate conversion or analog to digital or digital to analog.

Michael

[Scott Davids]

So i’ve read the article and it still leaves me with questions.. Its basically all about sound then.

Currently the show that I”m on is running composer version 11.2.5 (which does not have the 23.976 project option) and thus are in a 24p project. Our show was shot on the varicam downconverted to digibeta and ingested into our avid. Our production sound is being recorded to dvdram at 29.97 ndf 48k. We are finishing on film but will be conforming the 720P material for upres and filmout.

Sounds like our production then should be using a 23.976 project. Since we are on an older version and don’t have that option, is our only dissadvantage when using our production sound? As of now the editor is cutting with audio off the digibeta (which is digitised with audio matching video sync) and only when need be asks for sound rolls. When we import the sound roll we have to do a time compression filter (.999 conversion) to pull down the fostex dvd ram audio from 48k to 47.952 to be in sync with the video.

Am I correct to assume then if we were cutting in a 23.976 project – the audio would remain at 48k (not be pulled down using video sync) and then in turn our production sound would be in sync with picture running at 23.98 at 48k?

[Scott Davids]

So i’ve read the article and it still leaves me with questions.. Its basically all about sound then.

Currently the show that I”m on is running composer version 11.2.5 (which does not have the 23.976 project option) and thus are in a 24p project. Our show was shot on the varicam downconverted to digibeta and ingested into our avid. Our production sound is being recorded to dvdram at 29.97 ndf 48k. We are finishing on film but will be conforming the 720P material for upres and filmout.

Sounds like our production then should be using a 23.976 project. Since we are on an older version and don’t have that option, is our only dissadvantage when using our production sound? As of now the editor is cutting with audio off the digibeta (which is digitised with audio matching video sync) and only when need be asks for sound rolls. When we import the sound roll we have to do a time compression filter (.999 conversion) to pull down the fostex dvd ram audio from 48k to 47.952 to be in sync with the video.

Am I correct to assume then if we were cutting in a 23.976 vs our current 24p project – the audio would remain at 48k (not be pulled down using video sync) and then in turn our production sound would be in sync with picture running at 23.98 at 48k? or am I completely confused?

sorry for my bad spelling in advance 🙁

[Michael Phillips]

You need to get to 11.8 at the very least to get a 23.976 project type. And yes, working in a 23.976 project would eliminate the need for you to do the sample conversion to maintain 48kHz while changing its duration to be .1% faster to be in sync with 24fps images.

Michael

[Scott Davids]

Is this the only dissadvantage we have on our show in cutting at 24p vs 23.976? (We won’t be changing to a newer version of composer) Thats all I can think of. It only affects sound correct?

[Scott Davids]

PS… thanks Michael.. I’ll try to make that thing at fox – but the westside by 730 is tough when your working at “the Lot”….