[MPlayer-users] Dolby digital .avi file : identification output please

Michael Holland mplayer at golden.wattle.id.au
Mon Jun 5 11:39:50 CEST 2006

Rohit Sharma wrote:
> Hi there,
> I am somewhat confused here trying to rip [I own the DVDs, Like LOTR
> trilogy] the DVDs while retaining Dolby digital tracks.

I just use "-oac copy" to keep the original AC3 soundtrack. You may need 
-aid or -alang to select the correct soundtrack.

> If any of you have an avi file with proper dolby digital / DTS sound
> track retained which you play using SPDIF for your digital amp using

Interesting! I get:
	lotr-3b.avi: RIFF (little-endian) data, AVI, 720 x 428, 25.00
	fps, video: DivX 4, audio: Dolby AC3 (stereo, 48000 Hz)

The same as you. Looks like an error in 'file' program, as the AC3
  _is_ 5.1, not stereo, as reported by mplayer.

BTW, mplayer will also make a similar "mistake" when using the "-hwac3"
option for playback, and report the data as "ac3 2.0". I'm told its
not a bug, but it sure had me confused.

> I am confused between whether to use hwdts, hwac3 while encoding

These are _playback_ options (read the man page). Why re-encode the 
audio at all?

> stereo. But then I am not sure how hardware decoding of DTS/DD takes
> place within my amp [all SPDIF cables are stereo, so it may be stored
> inside as encapsulated and may have been meant to be decoded by my amp].

Huh - what???  SPDIF is digital. You just send the AC3 data as read from
the DVD. No audio decoding is needed on the PC, so mplayer and ALSA 
don't really need to know if its stereo, 5.1 or quadraphonic.

> If someone has an authoritative answer to what does Linux returns on
> seeing a 6 channel dolby digital track within an avi file, I would have
> something to compare my results against.

I hope the previous para clarifies that. Just tell mplayer to send the 
RAW undecoded data, and let your amplifier worry about it.

> Many thanks,
> Rohit

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