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selig
Guru
Joined: 31 Jul 2005
Posts: 425
Location: Prague, Czech Republic
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 Posted: Wed Apr 16, 2008 12:34 pm Post subject: Converting 5.1 DVD audio to ogg vorbis |
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Hello! I have got an audio DVD with 5.1 sound and I would like to convert that into ogg vorbis... from what I have seen, this format should support 5.1 sound but I really don't know how to extract it from a DVD and encode it. I can extract stereo sound (downmixed) without a problem, but what to do if I want to keep 5.1?
The best option for me would be mplayer / mencoder / vorbis-tools... any hints?
Thanks a lot! |
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Gusar
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Joined: 09 Apr 2005
Posts: 2665
Location: Slovenia
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| Posted: Wed Apr 16, 2008 1:14 pm Post subject: |
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| Vorbis does not really support 5.1 audio. There's no channel coupling, so the channels will be encoded as 6 separate streams. To get decent quality, you would therefore need such a high bitrate that it would be better to keep the original AC3 audio. If you really want 5.1 audio, I suggest you use AAC, in particular NeroAAC (because faac is crap). Or you could keep the original audio. |
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selig
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Joined: 31 Jul 2005
Posts: 425
Location: Prague, Czech Republic
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| Posted: Tue Apr 22, 2008 7:30 pm Post subject: |
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Well this particular disc which I have in mind has got such a high audio bitrate (the 20 mins or so of audio on it take up more than 900 MB) that savings from converting it to ogg would be fairly decent... I understand that encoding each channel separately would amount to about the same as setting the encoding mode to "stereo" for mp3s. The question is if I can actually fit those streams into one file and get them played back correctly - that would be enough for me.
But if this is too complicated I will just convert the original into flac.  |
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Gusar
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Joined: 09 Apr 2005
Posts: 2665
Location: Slovenia
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| Posted: Wed Apr 23, 2008 8:56 am Post subject: |
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| selig wrote: | | The question is if I can actually fit those streams into one file and get them played back correctly - that would be enough for me. |
Not with vorbis. Apart from no channel coupling, there's no standardized channel order either. So if you want to make sure that the file will play correctly everywhere, use AAC. Assuming you have the VOB on your disk, it would look like this:
| Code: | $ mkfifo audiodump.wav
$ neroAacEnc -ignorelength -q 0.17 -if audiodump.wav -of audio.mp4 & mplayer -really-quiet -vc null -vo null -aid 128 -channels 6 -ao pcm:fast:file=audiodump.wav yourmovie.vob |
-aid 128 is usually the first audio stream, play the file normally and look at the mplayer output to find out the correct number for the stream you want to encode. And neroAacEnc -q 0.17 gives a file around 130 kbit/s, which is good enough for me. If it's not for you, just increase the number a bit.
One other thing: if you have wine installed, use the windows version of NeroAac, it's faster. |
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