[Meow]

Originally Posted by Ghitulescu

Slowing is possible, as well as speeding it up, just that is not lossless - it can't be lossless.

Yeah, as I said in my post.
I was just wondering if there's a way to slow it down in a way that I'd lose a minimal amount of audio quality.

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Originally Posted by tebasuna51

Yes, then correct me if next comments are wrong.


For instance you have a video clip with 120 frames than played at 120 fps have a real duration of 1 second.

And you change the fps to 60 to obtain a wrong duration of 2 seconds for these 120 frames.



When playback at 2x you recover the correct duration of 1 second for these 120 frames.

Now you have the real audio of 1 second of duration than want to mux to fake 60 fps video.

I don't know what do the playback 2x with the audio, even some players can mute the audio when select a double speed for the video.

But, in theory, the change of video fps to half (120 -> 60 fps) is equivalent to change the audio samplerate to half (48000 -> 24000 Hz).

Then the 48000 samples of 1 second real audio are played in 2 seconds at 24 KHz.
Maybe the player at 2x recover the original samplerate and play the 48000 samples in 1 second lossless.

You can try this solution. Remember, is change the samplerate, not resample the audio or change the duration.

Resample:
When you resample 48000 samples 48 KHz to 24 KHz you obtain 24000 samples with 1 second of duration. Lossy conversion.

Change duration:
When you drag the audio with 48000 samples 1 second in Vegas, over a 2 seconds video, it convert the 48000 samples in 96000 samples to obtain 2 seconds played at 48 KHz. Lossy conversion.

And we need 48000 samples 48 KHz = 1 second, the same 48000 samples played at 24 KHz = 2 seconds.
Lossless conversion (the samples are untouched).
We hope than playback at 2x recover the real duration without modify the samples.

I don't know if Vegas can do it, but yes any audio editor (Audition, SoundForge, Goldwave, Audacity,...).

Sounds cool, but I'm quite sure this wont work.
And I tried it as well (not sure if I did it wrong tho)

This would be the result on the Sony Vegas timeline:


Video is slowed down to half, and audio's samplerate has been changed to half.
So now half of the video is just no sound, and anyways when I playback halved samplerate on YouTube with 2x playback speed, it's just actually in 2x speed.
So the first half of the video sounds like chipmunks, and in the second half there's no sound.

So I guess YouTube will just simply play it back with 2x speed.
Here's how to seconds go in 2x playback:

So yeah.