View Full Version : AC3 => Stereo customizable channel-mapping
when i watch movies with ac3-sound, i don't get an option to set up sound to my stereo-system.
this can be done with almost every windows-players (see example on http://home.c2i.net/ffffffffff/wmc_audio.gif (windows media player classic)), so how about an option on xbox media player too?
almost everybody i know don't have an ac3-system, as they use tv or similar to watch movies.
i'm tired of watching movies with low speech and high effects/music volume!
would be nice to get some feedback, atleast some url's where i can read more or anything at all. thanks :)
what ?
channel mapping? thats practical with a mouse & a mousepointer, not with a controller
if something else, i don't understand...
okay, i'll try to explain.
an ac3-track contain info for many channels (like those listed at my picture posted).
when outputting ac3 to a stereo system (e.g. my tv), it will only send left and right channels, whilst center speaker-channel (speech/talking in movies) is not sent. thus the low volume on speech when i play movies (some low-volume speech is still sent to left and right channels). center channel is mostly only for speech, and effects/music is almost always located in left/right channels inside the ac3-track.
thus when i play ac3-tracks on my xbox, i get high volume on effects/music and low volume on speech.
in media player classic on windows, i can set this center-channel to output to stereo, and this will fix the speech issue.
a dev has told me in the past that when we hand a 6ch source like ac3 to the mcp-x, and tell it to output in stereo, it mixes the "extra" channels into the 2front channels.
that would mean you are wrong :o
speedster
2005-08-08, 23:08
try in audio setup change it to analogue and set output to all speakers that should do it.
speedster. i have it set to analogue. that means i have no options :(
speedster
2005-08-08, 23:23
can i just get this right
you have your xbox linked to your tv using scart??
your sound is coming via scart and the speech section of your ac3 avis is lower than your effects?
if so has your tv got pro logic??? it maybe the speaker settings are wrong on the tv itself if its pro logic
i think the problem flour has is that 5.1 sound is usually mixed with a very high dynamic range.
this means the difference between the level of talk and the level of effects like explosions is very high. this is done by intend by the sound mixers.
in a movie an explosion or a shot should be much louder than two people talking, more like in real life.
when this sound is downmixed to stereo the high dynamic range remains. this is why people usually say that 5.1 sound too low.
normal stereo sound is usually processed with dynamic range compression. this means the low sound levels are amplified and the high sound levels are lowered. the low and high levels are squezed together.
this is why especially music dvds often contain an extra 2.0 audio track in addition to the 5.1 track.
to address flour's problem with low 5.1 sound xbmc would have to perform this dynamic range compression. i don't know whether mpc-x can do this in hardware? otherwise this would have to be moved to the feature reqs forum. :cool:
bernd
okay, i've finally located a clip that test ac3 sound. it's located at http://home.no/bluesector/6ch_ac3_in_avi.7z (600kb, open in winrar).
it seems now that after watching other movies, i've not experienced anything like i first posted you about. thus the first movie i saw on xbox must have been incorrectly encoded. i'm sorry that i didn't test this more throughly before complaining...
but!
when i play that clip that tests 6ch ac3, the xbox do not play the lfe (low frequency effect) channel! and this one plays fine on my windows system. i'm posting this to the feature request forum.
maybe it would be possible to make an option, that increases the volume of the center signal (or even better decreases everything but the center signal, to avoid clipping) before mixing it to the stereo channels. no idea if something like that is doable or desireable, but it would to a certain extend help with the problem, that spoken dialogue is often so much quieter than the explosions etc. making it hard to find the right volume when watching movies at night, without waking up the whole house :)
maybe it would be possible to make an option, that increases the volume of the center signal (or even better decreases everything but the center signal, to avoid clipping) before mixing it to the stereo channels.
i second the "center channel gain" idea. with a receiver you can manually adjust the gain on the seperate channels but there is no option to do this once it has been downsampled to stereo.
"center channel gain" should be a slider from 0% to 100% which is a linear combination of the center channel with the other channels.
... or maybe you should do it like this.
0% -> 0% center 100% other
50% -> 100% center 100% other
100% -> 100% center 0% other
Gamester17
2005-08-11, 10:43
@hotzenpl0tz/asteron, that's off-topic, what you are asking for is "normalization (http://www.xboxmediaplayer.de/cgi-bin/forums/ikonboard.pl?act=st;f=4;t=275)" and/or "dynamic range compression (http://www.xboxmediaplayer.de/cgi-bin/forums/ikonboard.pl?act=st&f=4&t=4660)" or even a equalizer (http://www.xboxmediaplayer.de/cgi-bin/forums/ikonboard.pl?act=st;f=4;t=6754).
...not the user controlled "ac3 => stereo customizable channel-mapping" for the downmixing filter request fluor started this topic for :hmm:
ps! xbmc not downmixing lfe is also off-topic, but that sounds like a bug (or coding misstake) so i submitted a report for it here (link) (http://sourceforge.net/tracker/index.php?func=detail&aid=1255686&group_id=87054&atid=581838)when i play that clip that tests 6ch ac3, the xbox do not play the lfe (low frequency effect) channel!