Audacity for audio speedup

[ukb008]

Hi

In Audacity, what are the exact steps for changing an audio file taken from a 25 fps movie for muxing with a 23.976 fps one?

The Audacity's profuse documentation could not help because, perhaps, they were ...too technical for me. :confused:

Thanks and regards.

[yetanotherid]

Work out the percentage difference in movie duration, import the audio into Audacity (from the project menu), highlight the track and use the Change Tempo effect to change the tempo by the appropriate amount, or you can set a new length instead of changing it by percentage. Export the audio as a stereo wave file or MP3 etc.
Assuming the only difference between the two videos is the frame rate (which isn't necessarily the case), have you considered changing the 23.976 video to 25fps instead of re-encoding the audio?

Alternatively HDConvertToX is a free encoder GUI which has a function to automatically convert audio in the way you're wanting to convert it. I can't say I've tried it myself though. You'll find it via Google.

[ukb008]

Work out the percentage difference in movie duration, import the audio into Audacity (from the project menu), highlight the track and use the Change Tempo effect to change the tempo by the appropriate amount, or you can set a new length instead of changing it by percentage. Export the audio as a stereo wave file or MP3 etc.

:thanks:

Assuming the only difference between the two videos is the frame rate (which isn't necessarily the case)

This is ominous, but true. Very often the audio and video durations are not the same.

What do I do if they aren't?

have you considered changing the 23.976 video to 25fps instead of re-encoding the audio?

That sounds safer. What method do you suggest for this?

Alternatively HDConvertToX is a free encoder GUI which has a function to automatically convert audio in the way you're wanting to convert it. I can't say I've tried it myself though. You'll find it via Google.

Thanks again. I'll try it, and report back.

My regards.

[yetanotherid]

This is ominous, but true. Very often the audio and video durations are not the same.

What do I do if they aren't?

Your best guess.... Trial and error.....
Sorry, if there's an easier way I'm missing it.
And of course there's no guarantee you'll get the video and audio to line up anyway, it depends how the original was converted to each format. Theoretically 24fps film is just played at 23.976fps for NTSC and sped up to 25fps for PAL, but there's other techniques which can make what you're trying to do impossible.

That sounds safer. What method do you suggest for this?

It depends on the video type/container. Generally VirtualDub for AVI, MKVToolNix for MKV or YAMB for MP4. All 3 will open their appropriate file types, let you change the frame rate, add or delete streams etc and then save the output without having to re-encode.

[dansrfe]

eac3to input.wav output.extension -25.000 -changeto23.976

[ukb008]

Thanks, PROs. You have my regards.