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Re: does a quicktime tool exist for this?

I am not a developer, but read the various QT lists as I find many of the topics very interesting. This post caught my attention as its process I do all the time to convert 25fps clips to 24fps clips for film projects.

I use Cinema Tools to convert the frame rates of QT movies. CT will alter a QT movies properties so that a clip that used to play at 25fps can play (with a 1:1 frame ratio) at 24fps. There are also options for 23.98, 29.97 and 30fps. It does not dupe frames, it just changes the playback speed (1:1).

I often need to do this on systems without Cinema Tools and wondered if there was a way to change the properties of the QT file without Cinema Tools. Not knowing very much about the technical aspects of the operation performed by CT, the other day I tried duping a clip and making one 24fps and the other 25fps (using Cinema Tools 2.2). Then I loaded them both in Dumpster and went through comparing the various values side by side. I found that with a QT movie with one video track and a timecode track I could alter two values in Dumpster to make a 25fps movie become a 24fps movie (1:1). I could not get the timecode to remain as a 25fps code as Cinema Tolls does and this is rather crucial for film work, but first things first. I tried altering the TC tracks timeScale also, as Cinema Tools seems to, but that made the TC go very wild, so I think there are other important values attached to this process.

Here are things I changed to alter a 25fps clip to 24fps:

IN THE MOVIE HEADER
'moov' / 'mvhd' / timeScale = 2400

IN THE VIDEO TRACK
'moov' / 'trak' / 'mdia' / 'mdhd' / timeScale = 2400


To see what else CT was altering I made a log of all the changed values. I'm sorry if this is a bit obvious, like I said I'm feeling my way in the dark here, so I just recorded anything that changed and tried to establish a pattern:

IN THE MOVIE HEADER
'moov' / 'mvhd' / nextTrackID = +2 to the value
'moov' / 'mvhd' / timeScale = 2400

IN THE VIDEO TRACK
'moov' / 'trak' / 'tkhd' / trackID = +2 to the value
'moov' / 'trak' / 'mdia' / 'mdhd' / timeScale = 2400
'moov' / 'trak' / 'mdia' / 'hdlr' / componentFlagsMask = $00010153
'moov' / 'trak' / 'mdia' / 'minf' / 'hdlr' / componentFlagsMask = $00010167

IN THE TIMECODE TRACK
'moov' / 'trak' / 'tkhd' / trackID = +2 to the value
'moov' / 'trak' / 'mdia' / 'mdhd' / timeScale = 2400
'moov' / 'trak' / 'mdia' / 'hdlr' / componentFlagsMask = $00010157
'moov' / 'trak' / 'mdia' / 'minf' / 'hdlr' / componentFlagsMask = $00010167
'moov' / 'trak' / 'mdia' / 'minf' / 'stbl' / 'stsd' / srcRefType = `

These appeared to be the standard values after the CT conversion from 25 to 24. I tried doing them all manually, but found that the TC would never remain at 25fps. At this point I decided I should go looking for help and then I saw this thread. Don't want to hijack it, but has anyone got any ideas or information on what is going on (I do understand the timeScale value I think).

Would it be possible to create a small app or Applescript to perform this sort of task? A kind of Cinema Tools frame rate stand alone app.

Kind regards
Mark


email@hidden asked:

Hello list-

Does a tool that allows you to change the frame rate of file exist? I'm
looking for something that just tells the QuickTime file to be played back
at a certain rate and then be able to save it.

For example, if I had an image sequence that I read into QuickTime as
24.00fps but later discover the media should actually be at 23.976, I'd like
to just adjust the frame rate of the file rather than having to re-import
the whole thing.

Thanks,
Jamie
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References: 
 >Re: does a quicktime tool exist for this? (From: Frank Lowney <email@hidden>)



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