How to do an frame rate change from film to pal

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mohanohi
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Hi,
How to do an frame rate change, like speed up an region to 4.271% exactly in ardour?

seablade
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Can you clarify what exactly you are looking to do? It is a bit confusing reading this as it could mean many different things, as there are many related but independent factors you have mentioned thus far.

Seablade

mohanohi
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I have a telecine of film converted to PAL which runs 25 fps. And the sound originally recorded at 24 fps. And it needs to be speed up by 4.271% to exactly sync to the telecine version of PAL visually.

seablade
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Ok in that case, keeping in mind I don't deal with PAL much....

Set your TC Sync to the target frame rate. Set your grid to SMPTE Frames. Then use the region stretch tool to stretch the region to the exact frame that would match your target length. I suspect this is probably the most accurate and simplest way to do this.

Seablade

mohanohi
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Isn't there a way to type those exact values? This wouldn't do any accurate scaling operation.

seablade
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Actually this should allow you to do a pretty exact scaling operation, it just doesn't use percentages. So long as your are syncing Ardour to video to pull the precise frame references you need, it should be pretty precise.

No there is no way to type in percentages or otherwise for time stretch operations, though I am fairly certain that has been a requested feature in Mantis if you wish to comment on it.

Seablade

mohanohi
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Off course it should be essential option because it is universal and exact value for which doing film to PAL speed up is concerned. Eyeballing on video isn't necessary to do sync as an whole movie would end up about an day of labor work doing so. Hence this is exact value to be entered while doing scaling. I will comment on Mantis regard this feature request. Even Audacity has this nifty option via Change tempo filter. Thanks Seablade for your valuable comments and guide. :)

Regards

Mohan

seablade
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Eyeballing on video isn't necessary to do sync as an whole movie would end up about an day of labor work doing so.

You shouldn't be eyeballing if you followed what I mentioned above other than to get the exact reference frame for the original end and the new end(And using the grid options as I mentioned should make this a 30 second process if that). Beyond that it is just double checking to make sure nothing screwy happened(Which honestly shouldn't).

Seablade

mohanohi
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hmmm... English not my native language and not so good at it hence couldn't get hold of what were you saying. :( Sorry.... And regarding time scaling Couldn't do that with ardour and also ardour was crashing when did after doing time scaling for an file of 8 mins? (maybe something wrong) :( .. Used audacity and applied Change tempo to 4.175% (this value was worked out by experimenting, weired value though!) and got my problem solved :)

paul
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@mohanohi: just so we're clear, we don't do what you referred to (pullup/pulldown) in Ardour directly because its not the correct way to do this. Pullup/Pulldown is accomplished by changing the master sync source (hardware), which effectively means altering the sample clock rate. What Audacity did will probably work OK, buts it really not how professional systems operate. What you were trying to do, it appears, is just a simple timestretch, nothing related to pullup/pulldown, which instead affects the relationship between audio time and timecode (video) time. Ardour can certainly do this, but but as easily for your particular workflow as audacity.

mohanohi
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@Paul: I am not sure what master sync source is?! Actually the main purpose i did this job which my Sound engineer should have been done is, the telecine work which we given to the lab, had done very bad sound transfer from the optical mono positive of our film. Hence i dumped the telecine copy from dvcam and replaced the audio from the cd which had been given from our sound engineer which was final master. When i replaced the entire thing was out of sync?! Taught it was done for 24fps film and i was searching for right tool for this job. Isn't this the correct workflow? or was there something else as you said altering the sample clock rate (don't know how though) And also i noticed the telecine copy of the audio from lab was somewhat high pitched [not good quality :( ] Don't know whose fault it is, is it either lab or my sound engineer ?! Hmmm.. at last we the producers are the loosers. :(

paul
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@mohanohi: generally when you're running video and audio together, you use a single sync source, such as a blackburst clock. This generates signals which can be sub-divided into appropriate clock signals for both the digital audio equipment and the video. Altering the rate at which the master sync source runs effectively alters the sample rate and/or video rate. In the workflow you're describing its fine to just timestretch the audio, and this is a task best suited for a destructive audio file editor like Audacity, and less for a non-destructive DAW like Ardour (though Ardour could do this too). It sounds as if someone merely resampled the audio at some point (hence the pitch shift) rather than performing a pitch-neutral timeshift on it.

John E
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Unless it's a very short film it's imperative that you use a master clock source for work like this, since you need to guarantee a known number of audio samples per frame of film - not "guess" or "hope", but "guarantee". Time stretching the material will make it run at approximately the right speed but for a lengthy film, "approximately" won't be good enough. The sound will gradually drift away from the picture. You get around this by locking them both to a common sync source - i.e. a master clock.

Note that timecode is not a master clock. Most systems work by snapshotting the timecode when 'Play' gets pressed and from then on, they lock to their own sync source and calculate the timecode internally (i.e. they don't keep reading it every frame). If the sync source is entirely internal to the device, it won't be running at the same speed as some external device (and that's why you get the drift - and hence why you need a common clock source to lock everything together).