Hi! I am new to this forum and I was learning about DVD Backups. One of the parts involved was audio compression. So far I was impressed by AAC and I was doing my tests on it ... But I've come across an issue. Dont know if anyone else faced the same but here goes. I chose Nero Digital Audio as the AAC encoder. I used the sample ac3 file of rjamorim on this page http://wiki.hydrogenaudio.org/index.php?title=Multichannel ... I tried using both meGUI and Besweet/BeLight but I noticed that the channel order was messed up. In fact it changed from 5.1 to stereo. Can any1 help me here ? Thanks in advance.

J

If the input of the Nero encoder is in correct order (Microsoft ordering) the output should also be. I'm thinking you have a problem with decoding your ac3 and/or the tools/applications that you are using for this task (maybe it decodes to stereo?).

Another option is that your AAC decoding software outputs the incorrect order.

I thought the possiblity might be with the ac3 decoding. Never considered the possiblity of AAC decoding. How can I check what is being used for decoding and if possible the order of the channels ? Like when i used rjamorim's ac3 file each of the speakers outputted what channel it was supposed 2 play but after reencoding in AAC, the centre channel was played by all speakers, the left and right got a little mixed up. These were my commandline on BeSweet from BeLight,

"C:\Documents and Settings\Wild^Rain\Desktop\besweet15\BeSweet.exe" -core( -input "C:\Documents and Settings\Wild^Rain\Desktop\test files\ac3_test.ac3" -output "C:\Documents and Settings\Wild^Rain\Desktop\test files\ac3test_belight.mp4" -logfile "C:\Documents and Settings\Wild^Rain\Desktop\test files\ac3test_belight.log" ) -azid( -c normal ) -bsn( -cbr 224 -aacprofile_lc -6chnew ) -ota( -g max )

As far as meGUI goes, no major settings to change; I kept the original channels, used VBR of 224, LC profile.

What would you suggest for AC3 decoding ?

I found the error ... the AC3Filter was decoding it to stereo by default. I changed that to 5.1 but now I came across a new issue. When I playback the mp4 file in VLC, the file is played back as a stereo file (centre channel played on all speakers, left front and rear played on both right front and rear speakers, right front and rear channel played on left front and rear speakers) but when played in Winamp, it seems perfect. It made me wonder whether VLC has a good AAC decoder. Menno, what do you think on this ?

J

I think it's pretty good
Maybe they just use it wrong or maybe some setting in VLC? There are software players that look at the channel settings of your soundcard and then determine if they can play more than 2 channels. Could be an issue with that.