convert audio from PAL to NTSC

[Ankin]

hi everyone,
what I wanted to do was take an audio track from one DVD and put it into another DVD, but one of them turned out to be in PAL and the other one is in NTSC. Is it possible to convert a track without a significant loss in quality? Or will it totally screw it up I shouldn't even bother? thanks

edit: ok, i just realized it sin't really a video question, my bad

[manono]

Is it possible to convert a track without a significant loss in quality?

Yes it's possible to convert. And yes, there will be quality loss. You didn't say what kind of audio it is, but I always first convert the audio from PAL to NTSC WAV. BeSweet has a preset for that. Then I reencode the slowed down WAV file to AC3 audio. For freeware maybe Aften is good, unless you have access to a commercial AC3 encoder.

[Ankin]

You didn't say what kind of audio it is, but I always first convert the audio from PAL to NTSC WAV

that's basicly a movie audio track
thanks for your advice, I'll give it try!! Also found this old topic https://forum.videohelp.com/topic371573.html, I guess I should try Audacity or Avanti as well

[fitch.j]

I dont understand the issue you think you have here.

If the source is coming from a different DvD, then it's not going to be syncing with the new dvd no? So there is no need to stretch the time is there?

[Ankin]

If the source is coming from a different DvD, then it's not going to be syncing with the new dvd no?

the basic difference between those DVDs is the number of frames per second. It's 29,97 for NTSC video and 25 for PAL video. And once you stretch (or shrink) the audio track to match the other standard, it should match the video. At least that's how I imagine it
Or am I wrong?? it worked with subtitles...

[Gavino]

But why shrink or stretch at all?
Audio files don't have an associated 'frames per second', just a duration.

[AlanHK]

what I wanted to do was take an audio track from one DVD and put it into another DVD, but one of them turned out to be in PAL and the other one is in NTSC. Is it possible to convert a track

Depending on how the various DVDs were made, the duration may be the same (no conversion necessary), or it might be a 25/23.976 conversion, or some other method.

But also, they are quite possibly different edits of the movie, in which case syncing would be impossible.

Anyway, when I have replaced a soundtrack with one from another version I use Audacity: "open" the soundtrack of the video you are going to keep, and then "import" a new track from the other.
Use Audacity's tools to move and stretch the second track to match the first. If bits are missing, just use the original track.
Finally mute or delete the original track and export the rest as AC3.

This assumes both tracks are stereo, if you use multi-channel sound, I can't help you, though I believe it's possible in Audacity.

DVD audio is normally pretty high quality so running it through Audacity -- effectively converting to WAVE and back to AC3 -- should not make any noticeable degradation.

Note that the latest version of Audacity can be configured to use ffmpeg for import and export, which simplifies the process considerably.

[AlanHK]

the basic difference between those DVDs is the number of frames per second. It's 29,97 for NTSC video and 25 for PAL video. And once you stretch (or shrink) the audio track to match the other standard, it should match the video. At least that's how I imagine it
Or am I wrong?? it worked with subtitles...

Subtitles may be timed according to frame number (as in ASS format), or seconds (as in SRT). If frames obviously you do need to scale them. But if time, then maybe or maybe not.

[Ankin]

But why shrink or stretch at all?
Audio files don't have an associated 'frames per second', just a duration.

You're right, they don't have an associated 'frames per second' value, but they do have a "speed", meaning how fast they run. An "amount of audio" played back in one second for a PAL video corresponds to 25 frames and for a NTSC video it corresponds to 29.97 frames. So it kind of runs faster for NTSC than it does for PAL and hance the duration difference (29.97/25 = 1.2). Then again, I'm no pro, it just seems reasonable to me

[Ankin]

This assumes both tracks are stereo, if you use multi-channel sound, I can't help you, though I believe it's possible in Audacity.

DVD audio is normally pretty high quality so running it through Audacity -- effectively converting to WAVE and back to AC3 -- should not make any noticeable degradation.

Unfortunately it is multi-channel sound, but anyway my main concern was the quality loss. I just didn't want to get deep into that only find out the result would be crappy anyway, so thanks a lot for your help!

[manono]

So it kind of runs faster for NTSC than it does for PAL and hance the duration difference (29.97/25 = 1.2).

Be very careful there. Most NTSC movies are encoded at 23.976fps (with pulldown applied to output 29.97fps). So, ordinarily when converting from PAL to NTSC you slow the audio, and not speed it up. Anyway, stretching the audio by a factor of 1.2 as you're suggesting will make it unlistenable.

[dphirschler]

You can do multi-channel. Split the audio into 5 mono wavs. You can use AviSynth to do this. You can also use AviSynth to changes the speed to match the NTSC. Then use Aften to re-encode to 5.1 AC3.

In AviSynth, check into the following functions:

assumeFPS(23.976,sync_audio=TRUE)
getChannel

I forgot to mention. Get the NicAudio plugin for AviSynth so you can open the ac3 file.


Darryl

[Gavino]

You're right, they don't have an associated 'frames per second' value, but they do have a "speed", meaning how fast they run. An "amount of audio" played back in one second for a PAL video corresponds to 25 frames and for a NTSC video it corresponds to 29.97 frames. So it kind of runs faster for NTSC than it does for PAL and hance the duration difference (29.97/25 = 1.2).

I still don't get this. One second of audio is one second of audio whether it's in a PAL video or in a NTSC video (assuming they have the same sampling rates, eg 48kHz). So the audio doesn't run faster or slower.

Perhaps I'm confused because it's not clear to me if you are simply transferring an audio track from one DVD to another wholly unconnected one, or whether the 2nd DVD is the 'same' movie as the first, but has a different duration.

[dphirschler]

Gavino, it's like this. In the US the movie plays at 23.976 FPS (and then telecined to 29.97 FPS, but the audio remains the same). But in Europe, the same movie will be sped up 4% so that it plays at 25 FPS to match their television standard. The Europeans are used to hearing audio slightly sped up. But in order to use the audio for a US movie, it must be slowed down to 23.976.

Now none of this matters if the DVD is video (such as a live sporting event, newscast, or some concerts) instead of film. The audio stays the same in that case.


Darryl

[tomlee59]

The short version is this:

1) There may be no change in duration at all. In that case, no need to do any conversion of any kind.
2) There might be a duration ratio of 25/23.976 (never 1.2!). In that case, he might have to adjust the duration by 4%. Audacity is great for this.
3) These two discs might be different edits of the same movie. If the edits are significant in any way, then syncing will require huge amounts of manual labor.

[johns0]

I still don't get this. One second of audio is one second of audio whether it's in a PAL video or in a NTSC video (assuming they have the same sampling rates, eg 48kHz). So the audio doesn't run faster or slower.

Lots of dvds which are ntsc are converted to pal and are sped up in the process so a 2 hour ntsc film will be running at around 1 hour and 54 minutes in pal format,if you wanted to have the 1 hour 54 min pal track to play at the right speed back to ntsc at 2 hours you would have to slow down the pal track to match the ntsc track regardless of sampling rate.

[Gavino]

Yes, I understand that perfectly.
But as far as I can see, the OP hasn't made clear which of tomlee59's three cases (if any) apply here.
Hence my confusion. My original interpretation, probably wrong, was that he just wanted to take an audio track from one video and use it on another (unrelated) one, so there was no issue of sychronisation involved.

[johns0]

The op has to see if there is a time difference with the track.

[Ankin]

My original interpretation, probably wrong, was that he just wanted to take an audio track from one video and use it on another (unrelated) one, so there was no issue of sychronisation involved.

oh, my bad. That's the same video, just a better quality, and unfortunately another standard

The op has to see if there is a time difference with the track.

ok, thanks. I kind of took it for granted that there would be a time difference. well, it is a newbie section

Be very careful there. Most NTSC movies are encoded at 23.976fps (with pulldown applied to output 29.97fps)

thanks for the info, I had no idea. googling "pulldown"