Changing audio frame rate?

[architectofpain]

Hello,
This is somewhat related to my last thread (https://forum.videohelp.com/topic369585.html#1979686).

I have an mpeg, which has a frame rate of 23.976 and I have a wav file (that I should convert to ac3) which was taken from an mpeg with a frame rate of 29.970. I want to sync the audio and video and mux them. What program is ideal for converting frame rate without changing pitch? I tried using BeSweet but so far, every option I tried results in a slower pitch. The audio file has a running time of 87:16 (it lacks the soundtrack to a title card and the ending credits that the video source did not contain but I'm not fussed over adding it anymore) and the video runs 90:59 (with the title card and ending credits).

What program/method should I use to convert the frame rate and mux these?

Thanks.

[guns1inger]

Technically, audio does not have a framerate. What is does have is a length. You need to determine what the running time is of the actual section you have audio for, then modify the audio length to match. Audacity can time-stretch without pitch shifting.

[architectofpain]

The audio file is 87:16. The video file has audio for roughly 90:38. I'll give Audacity a go and see what happens. Thanks!

What is the option on Audacity that allows me to stretch the audio length? I can't seem to find it.
EDIT: Found it, but I can't seem to get it right..

[Chris K]

If both movies are exact the same versions (which isn't always the case) then there is no difference in audio length between 23.976 and 29.970.
Then the difference in length you currently deal with is the lack of title and end credits duration (3min 22sec totally). Stretching this will bring audio awefully out of sync.

What you need to do, is to time out the duration of the missing title and add that as a silence to the start of the track. You should be able to do this with Audacity on the wave but it's a bit tricky.

EDIT: Actually not that tricky

1. In Audacity with loaded wave press the home key (will set the cursor to the very start).
2. At the "Generate" menu on top select "Silence..." and enter the desired duration.
3. Then press "generate silence" which will insert it at the cursor position.

Perhaps there are mux apps that let you shift audio with a large amount so you can do it directly but there are others who can tell much more about that.

[t0nee1]

You can try lining up with AVIDemux's audio Shift(ms) tool..Load the mpeg and external wav..Use the shift tool - or + in (ms) and play/preview..Save a new mpg if satisfied with results..

Cheers, T

[architectofpain]

Will give it a go, thank you!

[architectofpain]

Hello everyone,

In relation to my last thread ("Changing Audio Frame Rate") I've stretched the audio file to compensate for the different frame rate between my preferred video source and the source that the audio was derived from. The video runs at 90:59 and the stretched audio runs at 91:02 (including a delay). I've tried starting the audio 3 seconds earlier. While the audio runs closer to the video it does not sync completely. Are there programs that will fix this? I've tried Syncview but I've had a lot of trouble finding an mpeg to avi convertor that will not decrease the bitrate of the video source.

Thanks.

[sebondar]

Does any one know how to change the frame rate from 29.97 to 24 with Audacity? I know that you have to put -4 in the speed change tool if your going from 25 to 24, but thats all.

Thanks,
Serge

[manono]

You don't want to go from 29.97 to 24. It's possible you might want to go from 23.976 to 24, but I can't figure out a good reason for wanting to do that. Why are you doing this?

You're in PAL land (right?) and don't understand 3:2 pulldown and therefore don't understand that (for a movie anyway) interlaced 29.97fps output is the same length as the progressive 23.976fps source.

[dragonkeeper]

Does any one know how to change the frame rate from 29.97 to 24 with Audacity? I know that you have to put -4 in the speed change tool if your going from 25 to 24, but thats all.

Thanks,
Serge

I would use the filter change Tempo, this should alter the length of the clip to with out changing the pitch of the audio.

[Cornucopia]

Re-read ChrisK's and guns1inger's posts. Sounds like you have multiple problems and are trying to fix them all with one method. Won't work that way.

Scott

[sebondar]

I have a fully functional 1080i 29.97 Pro Res file, and I want to make it a standard 1998 x 1080 DCP file. I know the process with After Effects, but not sure how to slow down the audio? I heard it can definitely be done with the speed changer in Audacity.

Thanks again,
Serge

[Cornucopia]

As said before, 29.97->23.976 is (assuming not change in the program content) IDENTICAL in audio length. 23.976->24 is a 0.1% change, which most audio editors deal with by changing the base sample rate so that it stays in sync with the video change. This has the effect of VERY SLIGHTLY chaning the pitch. This is usually not noticeable to most people. BTW, this (29.97->24) is a speed UP, not DOWN.

Scott

[sebondar]

Scott,

Your right. Great info.

Thank you so much,

Serge

[ranosb]

29.97->23.976
Audacity/Effect/Change Tempo/Percent change -20, changes tempo without changing pitch...

Most Pal to NTSC is -4.096 [25fps > 23.976fps]

[Disco Makberto]

Well, in the case of music video clips, I used to determine the BPM's of the original audio, the replacement audio, and then I matched BPM's. To be more clear, let's say that my music video clip has a defective audio, so I am logically interested in replacing it with a non-defective audio. However, my replacement audio has a different speed which is reflected in its BPM (which is different than the BPM of my original audio). So my approach was to simply match the BPM of the replacement audio to that of the original audio, create a new audio matching the BPM of the original audio, and then use the newly created audio in lieu of the defective audio. I just would like to ask, is there something wrong in this approach? Please note that I am taking here about music video clips only; obviously, this is not the way to go for long videos or whole movies.

Carlos Albert
Disco Makberto

[Cornucopia]

Please enlighten us as to how people are supposed to determine BPM from speech? Or sound effects?

Scott

[Disco Makberto]

Scott,

Are you talking about speech or sound effects of audio within a music video clip? If so, then that is not possible. For instance, for the sake of argument, let's say that we are going to deal with the original full-length video of "Thriller" by Michael Jackson. As this is sort of a mini-movie with speech and stuff, calculating the BPM for audio replacement does not work. On the other hand, if we want to replace just the normal "Thriller" song within a custom-made video clip, then calculating the BPM for audio replacement does work. This can be done for most of Michael Jackson's music video clips, but of course, there are exceptions such as the above-mentioned original full-length video of "Thriller".

Take care,

Carlos Albert
Disco Makberto

[Cornucopia]

Yes, I knew this. I was just trying to get you to make it clear to others that what you suggested is NOT POSSIBLE for feature-length movies as they include plenty of moments in the title where there are both multiple BPM musics as well as speaking-only segments and soundeffects-only segments. Also your idea would not work for more complex pieces of music where BMP changes throughout the length of the piece (as in many orchestral works).

Maybe you didn't notice, but the OP mentioned a running time of ~90 minutes. That pretty much puts it in the ball park of a feature film (or home movie), NOT a music video.

Scott

[Disco Makberto]

You are absolutely right, Scott. That is why I said, in my original post: "Please note that I am taking here about music video clips only; obviously, this is not the way to go for long videos or whole movies." On a related note, thank you for bringing to my attention the fact that many orchestral works don't work with my method. I hadn't thought of that, and of course, you are certainly right. My experience has been basically limited to disco music video clips and, as disco music is highly repetitive, the BPM method fits for the most part.

Thanks again,

Carlos Albert
Disco Makberto

[Gabes]

Not sure if is the right place to write but I'll try my luck

I was having a movie at 50 fps. I encoded it with ripbot but after it finished it the movie was running 2x time faster! (I used my basic settings)

So I re-encoded it and changing the fps speed to 23.97. The video lenght increased from 1:20:00 to 2:00:00 not so with the audio. Still at 1:20:00 h

All I want is to change the "fps" (I heard there is no fps for audio) to be optimized for my video. Any suggests or ideas?

[Bad Cyborg]

Sorry for this late post. I've only now reached this thread via Google.

To all having the same problem as Gabes, message me and I'll help you in whatever way I can. However, it's imperative that you take the time to learn to use Virtualdub, AVIsynth, Xvid4PSP or Avidemux (if you're on Mac or Linux). Any of these 4 programs will convert audio and video from PAL to NTSC and vice versa.

Additionally, you should also learn how to use Srestore plug-in for AVIsynth if you want to restore field-blended PAL video back to 23.976 FPS.

[Gabes]

I fixed by adding in ripbot fps=25 (in the script)