XBMP (XBox Media Player)

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frodo and monkeyhappy are working on it & almost cracked it
True AC3/DTS pass-through (DVD & AVI movies with AC3/DTS)
www.xboxmediaplayer.de/cgi-bin/ib31/ikonboard.cgi?
act=ST;f=3;t=6021

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Related Feature Request "Pass-through for AC3"
http://sourceforge.net/tracker/index.php?
func=detail&aid=812209&group_id=64793&atid=508681


Also quoting jmarshall:

1. The XBox has onboard AC3 5.1 encoding in it's MCP-X
(Audio processor). It can encode ac3 surround from 6 (or
more if they're downmixed) channels of content. This allows
game developers to easily create surround sound effects +
soundtracks.

2. There is currently no way that I know of to bypass the
MCPx and write direct to the audio output buffers. This is
clearly possible (Microsoft dash does it, as does DVD-X2) but
I have found no documentation on how to do it, and the DVD-
X2 guys have either not got the code anymore, or are not
releasing it for whatever reasons.

This then leaves us with the following: We can either
attempt to get the AC3 or DTS or whatever through the MCP-
X unscathed, or decode in software and let the MCP-X
reencode it. Unfortunately, the MCP-X upsamples everything
to 24bit/48kHz which ofcourse screws up any compressed
stream. Thus, we are currently forced to decode in software
and then let the MCP-X recode it after it's upsampled and
done whatever else it wants. This is why DTS is currently
not supported, as we can't decode it in software.

As for "sound quality" you can do a couple of things about
this:

Disable all the Sound processing features. In particular,
disable the "Enhance stereo", "Always output to all
speakers"
and "Amplify Audio" - that will mean that the sound will get to

the MCP-X without being rogered by mplayer's "effects".

I personally have no problem with the sound quality. I agree
that it could be a little better, but generally it is very good at
doing the decoding/resampling/reencoding.

I use avi's with the AC3 track unaltered from the DVD - works
fine and sounds good. Not quite as good as playing the
actual DVD with Microsoft's Dash, but reasonably close.

If you or anyone else knows of a way to write direct to the
audio output buffers BYPASSING the MCP-X, please get in
contact and let me know. I'll implement it immediately.

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Note to all developers wanting to port/code this into XBMP!
MPlayer 1.0pre1 released September 01 2003
www.mplayerhq.hu
One this that is new in it and relative to this FR is:
"Codecs/demuxers support: hwac3: DTS passthru support"

PS! Changed this FR topic summery to read "DTS pass-
through", as have created a seprate FR for "DTS decoding":
http://sourceforge.net/tracker/index.php?
func=detail&aid=799840&group_id=64793&atid=508681

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Agree that DTS pass-through is a must,
but decoding be nice too (if no DTS amp):

"BeSure" direct VOB/AC3 to CD audio (inc DTS) conversion.
http://dspguru.doom9.net/
---------------------
DTS / AVI Filters - allows AVI/DTS muxing and playback
http://www.doom9.org/Soft21/Filters/test.rar
---------------------
BeSweet - Audio Transcoder (inc DTS support)
http://dspguru.doom9.net

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DTS Audio and DD 5.1 audio pass-thru is a must and should be
fairly easily implemented. Mplayer already can handle this - it
should be just a matter of setting up the hardware so that it can
pump the audio through without any decoding. This IMO is one
of the biggest things holding XBMP and the XBox from being a
quality entertainment centre.

Note that dvd2x has DTS and DD pass through support.

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In addition, it would be great if it can playback *.dts files
and .wav files encoded in DTS...
Or alternately, pass through DTS and AC3 files to allow
decoding by home theaters - as I believe DVD-X and
XBOX itself allow....

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Hypercube Transcoder Open Source DTS filter
http://hypercube.is.dreaming.org/
(inc. RAW PCM output support)
Only support DTS 5.1 yet but plans for 7.1
(Maybe its code could be use to add DTS)

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any news about DTS Audio CD?

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Second this idea

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Addition: AviMux GUI 1.11 now allows you to mux DTS audio
into an AVI (requires special DirectShow filters and a DTS
playback filter, see test.rar attatched) but this feature is
currently in beta stage. ...maybe this filter could be used as a
base for this support?

More info on DTS muxing can be found here
http://forum.doom9.org/showthread.php?s=&threadid=41052