Audio encoding AAC to AC3 for multiAVCHD authoring

[ejai]

I am currently creating blu-ray disks using multiAVCHD, my issue is with transcoding the video. Most of the times my videos that are not blu-ray standard which causes them to be re-encoded by multiAVCHD causing audio sync issues.

The videos are mpeg4 with AAC audio, I need to convert the audio to AC3 to abide by the blu-ray standard. I was wondering if there is a program that will convert the audio portion of the mp4 file from AAC to AC3 without re-encoding the entire video?

[poisondeathray]

multiavchd can encode the audio to ac3 , since you're using it anyways. Sometimes the channel arrangement is different in aac than ac3 (there is option to remap channels in multiavchd)

If you want to do it yourself with extra steps, you could demux the audio with yamb, convert the audio (lame xp, audacity, megui, audacity , foobar2k , eac3to etc..) then mux it back in with yamb

[ejai]

Thanks for the reply, my issue was the audio going out of sync when using multiAVCHD. I really don't want to use another software but it seems that I might have to.

[poisondeathray]

How do you know it's the audio and not the video that's causing the sync issue?

What kind of mpeg4 ? "mpeg4" can mean about 20 different things

e.g. mpeg-4 asp (part 2) is divx, xvid,
mpeg-4 avc (part10) is h.264, avc

Where is the video from ? Is it variable frame rate ? Use mediainfo (view=>text) and copy & paste the text information back here

[ejai]

When I get home I will try what you said, I'm sure it's a H.264 video. Your right it might be the video and not so much the audio. I'll look further into it later, thanks.

[Bonie81]

The best way is as said by poisondeathray

...If you want to do it yourself with extra steps, you could demux the audio with yamb, convert the audio (lame xp, audacity, megui, audacity , foobar2k , eac3to etc..) then mux it back in with yamb...

Alternatively convert mp4+aac to avi+mp3/ac3 using good video converter.

[ejai]

Thanks for the advice, I was able to resolve the issue. I seperated the audio and used Nero to change it to AC3 and then I combined the audio and video and now the video is in proper sync.

Thanks again.