5.1 AC3 framerate conversion

[Dr.Rock]

I have a 5.1 (6 channel) AC3 audio file which I extracted from a 23.976 fps movie. The audio file plays fine, so I know it extracted OK. I need to convert it into 25 fps (NTSC to PAL) for which I'm using BeSweet. The audio shrinks to the correct duration, however the new AC3 file loses the 5.1 format and becomes stereo. How do I retain the 5.1 format when I do the time conversion? Is there a BeSweet setting I need to change? I tried enabling the "Create 5.1 AC3" option, but that makes the resultant audio distorted and unrecognisable.

Any tips would be greatly appreciated.

Thanks.

[mats.hogberg]

AFAIK, very hard to do, and rarely worth the effort. I think you have to decode AC3 to 6 wavs, do a "frame rate conversion" of the wavs, then reencode those to 5.1 AC3 again.

/Mats

[daphy]

The audio shrinks to the correct duration

am I right , it must be longer: NTSC 23.976 fps to PAL 25 fps ~> +4%

as mats.hogberg said, you have to decode the single channels (all 6 of course) and lenghten the tracks to fit the 25 fps, then recode to one AC3.

I suggest to do this in two steps, it gives you the opportunity to check the stream´s synchronity before you encode to AC3 - maybe you should check out another encoder - other free solutions are f.e. HeadAC3 (beware you have to chose a version from december 2004 or later others as they from the homepage doesn´t do the best possible job) or WaveWizard (recommend) -> dig here for both :P

Why are intend to do such a project? Even in NTSC-land all TVs should replay PAL coded films? I guess you want to replace the audio track with one you´ve found somewhere

[mats.hogberg]

am I right , it must be longer: NTSC 23.976 fps to PAL 25 fps ~> +4% question.gif

No, you're wrong. I guess Dr Rock (like I use to do) patches the video from 23.976 fps to 25 fps. As # of frames don't change, the movie will have a shorter play time (23.976/25) - hence a shorter audio track is needed.

/Mats

[dvd3500]

Even in NTSC-land all TVs should replay PAL coded films

Nope. I know of many people whose players are very picky...

[anaboland]

Use AC3machine with Besweet, it has many options including output as 5.1. I've used it many times when doing framerate conversions, i found that many times i needed to check the Auto Gain Find Control option to prevent distortion on very loud scenes.

This gives 5.1 Ac3 files.

[daphy]

@ mats.hogberg
You right ~> -4%

Use AC3machine with Besweet, it has many options including output as 5.1.

that´s basically the same as he tried before, maybe my suggestion brings a diffrent result

[anaboland]

@ mats.hogberg
You right ~> -4%

Use AC3machine with Besweet, it has many options including output as 5.1.

that´s basically the same as he tried before, maybe my suggestion brings a diffrent result

Can't argue with that, but using Ac3machine with Besweet and correct settings has always allowed me to input a 23.967 fps 5.1 track, change the frame rate and output a undistorted 25 fps 5.1 track file ready for import into aurthoring software, who knows????????????

I know it works as i done it many times when converting Xvid etc

Its always a good idea to run ac3fix on the extracted .ac3 files as they sometimes have faults.

When i was new to encoding i did find the Ac3machine GUI easier to use than Besweets, so perhaps Dr.Rock's simply missing a setting somewhere??