Convert MKV's audio on Mac

[frosse]

How can i convert an MKV file's audio from AC3 to stereo/mp3/aac WITHOUT unsyncing/loosing video quality and ALSO save it as MKV?

A sum up,

IN: MKV, AC3 audio
OUT: MKV, Stereo. No loss in video quality

This has to be done on a mac.

I've tried:
Visualhub - which doesnt save to MKV
Handbrake - which doesnt encode from MKV
ffmpegX - which doesnt save to MKV

How should I do?

[Baldrick]

I'm moving you to our mac section.

[terryj]

Back to an .MKV?

Only way I would know would be to split the file using
a tool from MkvToolnix, create the audio and
video I needed ( Xvid, ac3) by demuxing,
Post process the Ac3 file into mp3 and then
re-create an .mkv from that merged file using MKVMerge,
part of the MkvToolnix set.

don't know how the tools work on newer macs, I'm on a dual 1 PPC Mac.
Also, I don't know if they are even still available for download.

[frosse]

Well it doesnt necessarily have to be saved as MKV.

I plan to use newely released Coreplayer for OSX which supports the following formats:
Audio: MP3, AAC, MKA, WAV, OGG, Speex, WAVPACK, FLAC, MPC, AMR, GSM, ADPCM, ALaw, MuLaw, MIDI, WMA

Video: CoreAVC™ [H.264], AVCHD, MKV, MPEG-1, MPEG-4 part 2 [ASP], DivX, XviD, MJPEG, RLE, MSVIDEO1

Containers: Matroska™(MKV), TS, PS, M2TS, 3GPP, MOV, AVI, MPEG-4, NSV

I'm looking for a way to convert audio from AC3 to something that Coreplayer supports*, like mp3 or AAC. I also dont want to loose any video quality or bitrate. Often they are in x/h264.

So in theory the file could be in an AVI-container, just that it doesnt loose any quality and gets another Audio format.


//Vic

*See "Audio".

[guns1inger]

If the video is H264, and you convert the audio to AAC, why not park it in an mp4 or mov container afterwards ?

[frosse]

With what app and what settings?

Will I loose video quality/bitrate?

[terryj]

Use Merkonk's MoKgVm2DVD app and
set the Video to Pass Through, set the audio
to Mp3, and this will convert it to an .AVI
which will not lose quality, have the audio
you want, and placed into a container that
is widely handled by a lot of apps.

[frosse]

Use Merkonk's MoKgVm2DVD app and
set the Video to Pass Through, set the audio
to Mp3, and this will convert it to an .AVI
which will not lose quality, have the audio
you want, and placed into a container that
is widely handled by a lot of apps.

Thanks alot, there is one problem though. When loading the mkv into MoKgVm2DVD it said it was unable to confirm the length of the movie, the app wanted me to calculate the time in seconds, so I did. After converting the mkv file I can confirm that the video quality is the same and that the audio is in mp3 128kps. BUT the audio is not synced properly, its waaay off where it should be.

Please help me.

Edit: After reading some on different forums I understand that the video x264 in the MKV is in VFR and that AVI only supports CVR and thats whats causing the sync problem. How can I deal with this?

Edit2: After reading some more (http://en.wikipedia.org/wiki/Comparison_of_container_formats) It seems like AVI is the worst format of them all with trouble handling not only VFR but x264 also. So MKV->AVI is a worst case scenario.

Is there a similar app like MoKgVm2DVD that changes audio from AC3 to whatever else but puts the file in a .MOV or .MP4?

[frosse]

Back to an .MKV?

Only way I would know would be to split the file using
a tool from MkvToolnix, create the audio and
video I needed ( Xvid, ac3) by demuxing,
Post process the Ac3 file into mp3 and then
re-create an .mkv from that merged file using MKVMerge,
part of the MkvToolnix set.

don't know how the tools work on newer macs, I'm on a dual 1 PPC Mac.
Also, I don't know if they are even still available for download.

Couldnt I just alter the audio settings from AC3 to mp3/aac/... within MKVtoolnix without demuxing and then saving it to mkv? Unable to try this @ the moment, but will give it a try when I come home.

Edit: Well, I got home, downloaded the app and started demuxing. It gave me an .mka file. I dont get any of this.

Help?

[emmgunn]

Is there a similar app like MoKgVm2DVD that changes audio from AC3 to whatever else but puts the file in a .MOV or .MP4?

I know it doesn't help your present situation, but hopefully in the not too distant future, that will be an option in MoKgVm2DVD. Have you tried extracting using MoKgVm2DVD and then muxing using something like mp4box? I'm guessing that syncing could be tricky. You also might want to take a look at the quality you get with 2-pass xvid. It'll be pretty good if the source is good, and you might find that the little difference that you see might not be worth the effort that it's going to take to pass thru video with no loss in quality.