[phvrc2nt]

there's been a proliferation of aac files on the net.
the good thing is that their file size is very light to download.

the downside.
dts / dd receivers cannot understand how to properly decode the signal.

can anyone please help or post a guide on how to convert aac 5.1 to ac3 5.1?
xbmc for the moment doesnt support on-the-fly encoding.

thanks thanks!

[officeboy]

I have been re encoding with avidemux and it works pretty well. You can just stream copy the video, and reencode the audio. Some AAC files have the audio in a different order and that dosn't work out right, but generally it's pretty good, and only takes 10min.

[phvrc2nt]

I have been re encoding with avidemux and it works pretty well. You can just stream copy the video, and reencode the audio. Some AAC files have the audio in a different order and that dosn't work out right, but generally it's pretty good, and only takes 10min.

thanks for he suggestion. will run thru this later... will post feedback as soon... thanks again..

[phvrc2nt]

tried avidemux. failed almost all the time for me.

my aac files are in mkv format. probably this is the main reason.

any other suggestions to conver aac 5.1 to ac3 5.1 would be most welcome.
thanks...

[officeboy]

Is it failing when it opens (like program crashes or can't read file), when it starts re-encoding, or does the resulting file just not work?

[uncertainty]

I use megui....quick but dirty.....

http://sourceforge.net/projects/megui/

[officeboy]

Funny, I just tried meGUI (since I have some mp4's with the audio channels mixed up and I wanted to see if it did a better job then avidemux) and it won't even read the files.
I get error of "Unable to render the file, you probably don't have the correct filters installed".
And an error of "Cannot play back the file. The format is not supported." when trying to just do the audio into an AC3 file.

Grumble Grumble AAC...

[officeboy]

I'll update since I think i got this working for mp4/aac files where the center is sent to the left.

1. Demux or split files up with Yamb. (extract all streams to raw)
   
2. Turn aac file into wav
   Code:

   faad -o "output.wav" "input.aac"
3. Turn wav into ac3
   Code:

   aften -b [bitrate] "input.wav" "output.ac3"
4. Mux files into mkv or something, MeGUI has these tools.
   

Takes about 400% longer then avidemux but it gets the channel order right. (for some reason this only affects 20% of mp4 files I come across.

[phvrc2nt]

@ officeboy.
it encodes but never finish the files.

@uncertainty
will try megui...
will update the post as soon...

[phvrc2nt]

I'll update since I think i got this working for mp4/aac files where the center is sent to the left.

1. Demux or split files up with Yamb. (extract all streams to raw)
   
2. Turn aac file into wav
   Code:

   faad -o "output.wav" "input.aac"
3. Turn wav into ac3
   Code:

   aften -b [bitrate] "input.wav" "output.ac3"
4. Mux files into mkv or something, MeGUI has these tools.
   

Takes about 400% longer then avidemux but it gets the channel order right. (for some reason this only affects 20% of mp4 files I come across.

will this result to multi channel audio or just stereo outputs? im not sure if wav can handle multiple channels...

[goonie]

I'd suggest switching to using handbrake. http://www.handbrake.fr. i've converted hundreds of iso's to mkv and it works beautifully every time.

[officeboy]

will this result to multi channel audio or just stereo outputs? im not sure if wav can handle multiple channels...

It retains all the channels.

I'd suggest switching to using handbrake. http://www.handbrake.fr. i've converted hundreds of iso's to mkv and it works beautifully every time.

And can you get handbreak to only encode the audio and just copy or leave the video stream alone? Iso encoding is one thing but there is no point reencoding video just to change the audio.

[phvrc2nt]

ok. i finally got it right after several trials...

this is how i did it.

1.First off, you need several programs
1.1. FAAD
1.2. AFTEN
1.3. YAMB

2. Place FAAD and AFTEN on the same folder. A new folder would be recommended.

3. Install YAMB.

4. After installation, run YAMB and extract the AAC audio stream. Save it on the folder you created containing AFTEN and FAAD. Shorter file names are recommended since this will be accessed on a DOS window. I use "a.aac"

5. After extraction, run the following commands in DOS WINDOW in succession.
5.1 faad -o a.wav a.aac (dont worry about the senseless file names since you will not need these files anyway when you're all done; a.wav < or whatever you wish > a.aac < or whatever file name you used on step 4.
5.2 del a.aac <or whatever file name you used on step 4.> since you don't need this file any further
5.3 aften -b 640 a.wav a.ac3 <640 is my recommended bitrate to ensure you've covered every detail of the wave file. you an also use lower if you prefer.>
5.4 del a.wav same as 5.2, this file is uneccesary.

6. fire up YAMB, open the mp4 file you extracted the AAC audio from. drag drop the a.ac3 file we created a while back. uncheck the AAC stream. choose the directory you wish to save the new file. finish.

[officeboy]

Good to hear that you got it working.
If you prefer mkv's then mkvmerge works well for making them. (Better then meGUI that I mentioned earlier)

[ikons]

MediaCoder is also a good all in one tool http://www.mediacoderhq.com/index.htm