Convert AC3 framerate

[Kal]

Hi all,

I have a movie encoded @ 23.976 fps. I would like to add french ac3 track which has a framerate of 25fps.

Do you think it's possible to modify the the framerate from 25fps to 23.976 lossless?

Regards,
Kal

[ACrowley]

You can mux it into mkv with mkvmerge .
Its possible to set a timecode.txt File for 25fps, so the remuxed Video runs clean (lossless) at 25fps and you can mux your Pal Audio.

Otherwise you must reencode it and make a timestretch

1. Besweet AC3 to wave with pal-ntsc
2. reencode wave with aften

[tebasuna51]

Hi all,

I have a movie encoded @ 23.976 fps. I would like to add french ac3 track which has a framerate of 25fps.

Do you think it's possible to modify the the framerate from 25fps to 23.976 lossless?

Sorry, but ac3 audio never had 23.976 or 25 fps.

If is 48 Khz have a audio frame each 32 ms, or 31.25 fps.

[Kal]

You can mux it into mkv with mkvmerge .
Its possible to set a timecode.txt File for 25fps, so the remuxed Video runs clean (lossless) at 25fps and you can mux your Pal Audio.

Otherwise you must reencode it and make a timestretch

1. Besweet AC3 to wave with pal-ntsc
2. reencode wave with aften


I didn't know we could do that with mkv. Unfortunaly, i want to keep my english ac3 track which is for the 23.976 movie version. So i will have to conver in wave and then encode in ac3, too bad :(

Kal

[tebasuna51]

So i will have to conver in wave and then encode in ac3, too bad

Like I say you the ac3 framerate is the same for NTSC or PAL movie: 31.25.

Maybe you don't need reencode.

[shon3i]

Yes it is have same fps but don't have same durations. Audio track from 23.976 movie have longer duration. So audio from 25 fps movie must be streched, but process isn't lossless at all.

[tebasuna51]

This is the problem, we have two audio tracks from different movies with different duration, maybe different offset, credits, scenes, ...

If the video is well converted (a 100 meters race of 10 sec. in NTSC is also 10 sec. in PAL and not a new world record of 9.59 sec.), the audio don't need to be modified.

Of course, to change the audio track duration, we need decompress, stretch (lose quality) and recompress (lose quality).