Originally posted by: Doctor M
Hmm. First let me nit-pick and say that technically PAL audio isn't time stretched, it is time compressed since the runtime is less than the original. It runs faster, hence the increased frequency. Correcting it requires time expansion. For most PAL material, like it or not, that's really the best alternative out there if you're turning it back to NTSC.
Still time stretching, its just whats its called. Also, this isnt what normally would be done to return PAL audo to NTSC audio speed, as the vast majority of PAL audio is just sped up by 4.096%, not pitch shifted or time stretched in any way. So you just need to slow it down (resample it) by 4.096% and its back to the normal speed and pitch again. Its just in this bizarre case we have here where the original pitch was preserved with pitch shifting/time stretching.
I dont think you get what i mean. time stretching does it as one job, with pitch shifting you need to do it in two stages. To get it from PAL to NTSC speed, first slow down the track (resample it) to get it playing to the correct length (4.096% slower), then pitch shift it up by 4.096%.
From what I'm seeing with soundforge though, pitchshifting doesn't seem to be done on a percentage basis making this much more wobbly a problem to deal with.
Hmm. First let me nit-pick and say that technically PAL audio isn't time stretched, it is time compressed since the runtime is less than the original. It runs faster, hence the increased frequency. Correcting it requires time expansion. For most PAL material, like it or not, that's really the best alternative out there if you're turning it back to NTSC.
Still time stretching, its just whats its called. Also, this isnt what normally would be done to return PAL audo to NTSC audio speed, as the vast majority of PAL audio is just sped up by 4.096%, not pitch shifted or time stretched in any way. So you just need to slow it down (resample it) by 4.096% and its back to the normal speed and pitch again. Its just in this bizarre case we have here where the original pitch was preserved with pitch shifting/time stretching.
Commenting on the rest (and I could be butt-ass wrong):
As far as pitchshifting. Typically it would not be needed as it only changes the frequency, not the actual speed/length of a clip. In this case (and I thought my ears were playing tricks on me too when I heard the butch C3PO) time expansion is STILL needed. Otherwise when the framerate is slowed to 24fps, the audio will run too short. We are (unfortunately for me) finding that evidentily it will need ADDITIONAL pitchshifting to reverse the whole process they put it through.
As far as pitchshifting. Typically it would not be needed as it only changes the frequency, not the actual speed/length of a clip. In this case (and I thought my ears were playing tricks on me too when I heard the butch C3PO) time expansion is STILL needed. Otherwise when the framerate is slowed to 24fps, the audio will run too short. We are (unfortunately for me) finding that evidentily it will need ADDITIONAL pitchshifting to reverse the whole process they put it through.
I dont think you get what i mean. time stretching does it as one job, with pitch shifting you need to do it in two stages. To get it from PAL to NTSC speed, first slow down the track (resample it) to get it playing to the correct length (4.096% slower), then pitch shift it up by 4.096%.
From what I'm seeing with soundforge though, pitchshifting doesn't seem to be done on a percentage basis making this much more wobbly a problem to deal with.
Just playing in SoundForge, to pitch shift up by 4.096%, you need to increase the pitch by 69.5 cents, and to pitch shift it down by 4.096%, you need to decrease it by -72.4 cents. In my mind they should be plus and minus the same value, but Sound Forge doesnt seem to think so, I'm going by the transposition ratio at the bottom of the window, either up to 1.04096, or down to 0.95904.