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Help? 25 fps to 24 fps pitch shift

  • 17-01-2010 12:56AM
    #1
    JJV
    Registered Users, Registered Users 2 Posts: 168 ✭✭


    I'm looking for some info please. A director e-mailed me to say a film I did some music for last year is going to print & as a result is going from 25 frames per second to 24 frames per second. As a result, the music is being pitched down & he is not happy with this.

    Does anyone have any experience with this type of problem. I imagine I will have to pitch the original audio up (using melodyne) so that when the transfer happens the audio comes back down to the original pitch.

    But what percentage of a semitone is the change between 25 & 24 fps?

    All very confusing. Thanks for any info.

    www.jjvernon.com


Comments

  • #2
    woodsdenis
    Registered Users, Registered Users 2 Posts: 535 ✭✭✭woodsdenis


    JJV wrote: »
    I'm looking for some info please. A director e-mailed me to say a film I did some music for last year is going to print & as a result is going from 25 frames per second to 24 frames per second. As a result, the music is being pitched down & he is not happy with this.

    Does anyone have any experience with this type of problem. I imagine I will have to pitch the original audio up (using melodyne) so that when the transfer happens the audio comes back down to the original pitch.

    But what percentage of a semitone is the change between 25 & 24 fps?

    All very confusing. Thanks for any info.

    www.jjvernon.com



    -4.1% = 0.492 semitones. This happens all the time with music done to video and then transferred to film. Why is this such an issue ? If you have to do it there are Dolby tools for this type of thing.
    You need really high quality pitch shifting for this. If you pitch shift up and then deliver it will be pitch shifted down again on transfer to be be in concert pitch. Thats 2 pitch shift conversions, Could be very funky.
    Will it sound that bad half a semitone down and only 1 pitch conversion.


  • #3
    JJV
    Registered Users, Registered Users 2 Posts: 168 ✭✭JJV


    Thanks a million Denis, that was exactly the info I was looking for. I have passed it on to the director. Seems there is going to be a compromise in the audio either way - either 1 x pitch change & music half a semitone flat or 2 x pitch changes & audio at concert.

    www.jjvernon.com


  • #4
    PaulBrewer
    Registered Users, Registered Users 2 Posts: 7,790 ✭✭✭PaulBrewer


    Interesting problem - one would think there's an industry standard solution other than a Dolby one - Is that not the case ?


  • #5
    Obi-Jim
    Registered Users, Registered Users 2 Posts: 90 ✭✭Obi-Jim


    I thought people did this in pro tools in post production, with the pull up and pull down of the sample rate. (record it back in again with the sample rate pulled up, then playback at regular sample rate. Or just convert it digitally)

    But yea, i wouldn't have thought the shift was so much. I figured this happens all the time. Because if something is recorded to film, then the audio is recorded at the same speed and therefore will have to be changed, at some point, if that recording is ever put on dvd.

    Am i missing something?

    (but i thought this would have been an assignment of whomever was doing the film conversion for him, not a concern of yours)


  • #6
    woodsdenis
    Registered Users, Registered Users 2 Posts: 535 ✭✭✭woodsdenis


    PaulBrewer wrote: »
    Interesting problem - one would think there's an industry standard solution other than a Dolby one - Is that not the case ?

    http://www.gearslutz.com/board/post-production-forum/457801-best-time-stretching-algorithm-pulldowns.html

    many different ways of doing this as you can see. Obi wan is
    correct, this is an issue for the post/ transfer people.


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  • #7
    studiorat
    Closed Accounts Posts: 6,408 ✭✭✭studiorat


    The idea of up sampling before converting would make sense too. Would have thought the Post Production boys would have had something to do this for years. They call it harmonizing if I remember correctly.

    I also would have thought that it could be done with time compression or expansion rather than pitch shifting.
    .... 35mm or 16mm negative at 2K resolution with a proprietary film recorder. The audio from your master tape is transferred to timecode DAT, and then transferred to optical sound negative in Dolby SR (for 35mm) or mono (for 16mm). PAL audio is time-expanded 4% to play back at 24 fps without altering the pitch of voices. The picture and soundtrack negatives are then printed to positive film on a contact printer. The resulting print is compatible with any movie theater system, worldwide.

    http://www.dvfilm.com


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