convert pal 5.1 sound to 23.976 frames

[tommcd64]

I have a file with 5.1 surround but the frame rate is 25(pal). I can convert the video easily using avisynth and my video encoder. How can I convert the framerate of the audio and maintain the 5.1? I tried using besweet and it will convert the framerate but it also converts the audio to 2 channel surround(pro logic).

[tommcd64]

I found 2 routes I can go but I am not sure which one is the best way to do it. I can use bewsweet to convert the 5.1 to a 2 channel surround and use the pal to ntsc preset and then use soft encode to go back to 5.1. The other method is to use besweet to convert to 6 wave files using the pal to ntsc preset and then use soft encode to go back to 5.1. Which would be the preferred method to maintain as much sound quality as possible?

[tgm4883]

You might not want to listen to this as i have no advanced knowledge on the subject, but something to think about. If you convert it to 2 channel audio first wouldn't it just scrap the other 4 channels and when you convert it back into 5.1 it would have to copy the other 4 channels from the 2 channel audio? Not sure if this is how it works, but it is something to think about.

[spectroelectro]

USing BeSweet witht he AC3Machine front end I am pretty sure you can convert AC3 to AC3. THere is a PAL-to-NTSC switch you just have to click on and it will do that automatically.
BeSweet with the AC3Machine front end looks like your best bet. I've used it extensively, sounds superb, works fast. Youc anfind it at
www.doom9.org

[tommcd64]

Thanks for the info. I used the ac3machine to convert the framerate of the sound file and it was out of sync. Believe it or not I used the original 5.1 sound file and it synced up perfectly regardless of the framerate change in the video!

[mh2360]

USing BeSweet witht he AC3Machine front end I am pretty sure you can convert AC3 to AC3. THere is a PAL-to-NTSC switch you just have to click on and it will do that automatically.
BeSweet with the AC3Machine front end looks like your best bet. I've used it extensively, sounds superb, works fast. Youc anfind it at
www.doom9.org

I did a conversion from 23.976 to 25 and my stand-alone wouldn't play the audio. It played ok on my PC though. I dont know if this is because of Besweet or my Pioneer 343.

[adam]

tommcd64 it might have desynced after doing the PROPER audio conversion because you did your video conversion IMPROPERLY.

Most mpg encoders allow you to do one of two things when changing framerates. Either you can use frame decimation/duplication which just copys or throws out frames to change the fps, or you can do the conversion the correct way and keep the frames as they are but physically speed up the playback speed.

If you do the former than the audio does not need to be adjusted but you will get choppy playback. Fps should never be changed this way.

Only if you properly slow the film down from 25fps to 23.976fps will you need to also slow your audio down.

[wildcatfan]

USing BeSweet witht he AC3Machine front end I am pretty sure you can convert AC3 to AC3. THere is a PAL-to-NTSC switch you just have to click on and it will do that automatically.
BeSweet with the AC3Machine front end looks like your best bet. I've used it extensively, sounds superb, works fast. Youc anfind it at
www.doom9.org

I did a conversion from 23.976 to 25 and my stand-alone wouldn't play the audio. It played ok on my PC though. I dont know if this is because of Besweet or my Pioneer 343.

Besweet uses the wrong byte order (Or used to, I haven't used it in a while, I assume it still does) and some players have problems with the AC3 files it produces, notably Pioneers.

[tommcd64]

Adam, I am not sure what method was used for the video. I used tmpgenc plus and used the template and tmpgenc did the video conversion for me. I am not sure what method tmpgenc uses.

[adam]

By default TMPGenc uses the very bad method of frame duplication/decimation. This is why your audio didn't sync up. You can make TMPGenc do the PAL-NTSC conversion correctly by enabling the "do not framerate conversion" filter on the advanced tab.

I strongly recommend that in future conversions of this type you enable this filter and then process the audio in BeSweet using the PAL-NTSC setting. The audio and video will properly sync and your playback motion should be smooth now since no frames have been removed.

[mh2360]

The latest version of Besweet has new settings for AC3 and DTS. What "Endians" setting would I use for max compatabilty?

[mh2360]

AH! never mind, all is explained in this thread....

https://www.videohelp.com/forum/archive/t129419.html

[tommcd64]

Thanks for the info Adam. I will try that next time.

[Flave]

So Adam, if you were doing this in CCE and I understand you correctly, you would use an AssumeFPS(23.976) in your AVISynth script to do the PAL->NTSC frame rate conversion? In this case, would the 5.1 audio require any conversion?

[adam]

Correct Flave you would use assumefps. This command keeps the # of frames the same, and just speeds them up or slows them down to change the fps. The convertfps command uses frame duplication/decimation.

Since you are physically slowing down the playback speed of your movie, yes you must adjust the audio speed as well. You could use the PAL->NTSCfilm option in BeSweet to do the conversion.