Use an audio which fit with a DVD @ 25 fps on a BluRay @ 23.976 fps

[sirt]

Hi,

Well everything is in the title : I have the same movie in both DVD & BluRay - each one having been remuxed to an mkv with different audios.

On DVD, there is an audio with directory/actor comments. Unfortunately, it doesn't exist on BluRay. So I wonder if I can do something to synchronize DVD audio with BluRay video ? Of course, simply remuxing it like that doesn't work at all and it doesn't seem to be a question of *delay* either. Framerate is certainly the problem : I would need to *convert* audio from 25 fps to 23.976 fps but I am not sure whether it is possible/suitable.

[Qaq]

You need to slow it down with eac3to: https://forum.doom9.org/showthread.php?t=125966

[sirt]

Isn't that supposed to distord audio ? I guess you mean use something like -changeTo23.976. Moreover, does that mean I will have to reencode ?

[sirt]

Well I tried something like that :

eac3to La.track_5.ac3 La.track_5_23976.ac3 -25.000 -changeTo23.976

Resulting track doesn't seem to be distorded but stream size is 312 MO whereas orignal stream size is 85.6 Mo ! Is that normal ? I am not even sure audio has been reencoded or not.

[tebasuna51]

eac3to recode the ac3 5.1 to 640 Kb/s by default, and 2.0 to 448 Kb/s like maybe is the comments track.

To obtain the same size you can include the desired bitrate (like the source), for instance:

eac3to La.track_5.ac3 La.track_5_23976.ac3 -25.000 -changeTo23.976 -192

[Groucho2004]

In addition to tebasuna51's rely, you can obtain the properties of your file like bitrate, number of channels, etc. like this:
eac3to file.ac3

[sirt]

Indeed, thanks, I set proper bitrate (128). And then it is clear : I am forced to reencode to change framerate.

[Music Fan]

To do this I use Hybrid (which uses Sox) which let the choice to change the pitch or not, I believe eac3to don't have this feature when changing audio length ;
http://forum.doom9.org/showthread.php?t=153035

[sirt]

Thanks, do you mean change the pitch because fps has been changed ? Actually, it doesn't seem to be altered. But in the case it would, how would you ajust pitch then in order to compensate ?

[Music Fan]

Thanks, do you mean change the pitch because fps has been changed ?
Yes.

Actually, it doesn't seem to be altered.
I don't remember what does eac3to but I believe it doesn't let any choice, it always (or never) let the pitch as is when changing speed.

But in the case it would, how would you ajust pitch then in order to compensate ?
Hybrid can do this, you have to open your audio file in main window (select "custom" for audio handling) and go to the audio tab to see options (check "reencode" and in encode window select pcm, container wav, keep input sample rate, go in filtering window, check "speed change" -choose from 25 to 23.976- and "adjust pitch" to compensate if needed). Add to audio queue (+ symbol), go back in main window, click on "output file", save in .raw (it will create .wav extension), click on "add to queue" and go to jobs window to start process.
Or select ac3 instead of pcm and save with ac3 extension.

You have to know if your orginial file in 25 fps was already compensated to know if you have to compensate it or not, sometimes it's not easy to be sure.