Converting AVCHD with Stereo AAC into AC3

[Mark97213]

I'm using a new type of head mounted video camera (Liquid Image Impact Series HD 1080p video goggles) that only renders AAC two-channel Audio in the QuickTime profile files, in either MPEG4 or MOV format. I'd like to re-author these into AC3 instead of just AAC, but without a loss of image quality ... hopefully without rebuilding each file from scratch.

I have tried a couple different programs in conjunction with Mediainfo to match the settings, such as Xilisoft Blu-ray Creator 2, Super, but I end up with a slightly degraded picture quality of the final conversion.

Is there any one particular authoring program that can re-author to encode in AC3 or maybe even DTS without a picture quality loss? I don't really see how re-mixing the audio stream would effect the video stream so I'm wondering if that's just the price to pay for re-authoring or a limitation in the programs I've used this far. Is there a better tool that a novice might utilize instead?

I am FAR from a pro at much of this so any criticisms and/or all advice, is greatly appreciated.

[intracube]

The degradation you're seeing is because the software is re-encoding the video as well as the audio. You could give Avidemux a try as it has an option to 'copy' the video while re-encoding the audio.

I run Linux (I assume you use Windows - it's worth putting your system details in your profile) so it's difficult to give software suggestions but Avidemux should do what you want.

[Mark97213]

Thank you for the response. I finally edited my PC details, so thank you for the reminder. Well I fired Avidemux up and first, it detects my file as it should as H.264, but it references "B-Frames" and says: it can lead to a crash andor stuttering. Avidemux can use another mode which is safe but YOU WILL LOSE FRAME ACCURACY.

I've seen the B-Frames referrence before.

[poisondeathray]

You can ignore the warning because you are just copying video the stream , or use avidemux 2.6 (beta) and you won't get the warning (it handles AVC better)
http://avidemux.razorbyte.com.au/