On Sun, 2006-08-27 at 19:03 +0100, `Zidane Tribal wrote: > hello all. > > I'm trying to put together various dvd's with 5.1 ac3 audio tracks. > Can anyone point me in the right direction to some documentation on how > i would normalise the audio? > > Basically, some of the video's are too loud, others too quiet. I know > transcode itself will let me increase or decrease the volume by a > specific amount, but i would need to discover how much i need to inc/dec > each track and then re-transcode the audio adjusting each track by a > specific amount. what would be really spiffy is something like > normalise in batch mode, which would allow me to have, say, 10 ac3 > tracks, scan them all and normalise them all to 12db. > > does such a thing exist? if not, can anyone point me towards some > documentation on how to convert ac3 5.1 surround into different channels > so i can normalise them as wavs, then re-mux and transcode them back > into an ac3? > > any help would be much appreciated. > > `Zidane. > >
ok, now i know i'm replying to my own mail, but hopefully this should keep it in the same thread ;) after much man-page reading and fiddling around, it would seem i can use mplayer to extract each individual audio track in turn, as follows: mplayer -channels 6 -af channels=1:1:1:1 ./x-men-1.vob mplayer -channels 6 -af channels=1:1:2:1 ./x-men-1.vob mplayer -channels 6 -af channels=1:1:3:1 ./x-men-1.vob (etc... for all six channels) where:- mplayer -channels 6 -af channels=no-of-output-channels:no-of-routes:map-channel-X:to-channel-X now i can get each channel out on its own, it shouldn't be too much trouble to fiddle around with transcoding it to, say, wav, and using something to normalise it. however, this leads me to another curious quandry. after digging around to try to find out which channel number represented which 'speaker', i came accross the ac3 spec here http://www.atsc.org/standards/a_52b.pdf which implies there can be 8 different track layouts (table 5.8 is the part that defines them). so, the question now becomes, does anyone know of a tool that can give me the 'acmod' feild, so that i know which track is which? preferably something cli-based, as i want to incorperate this into a shell script. many thanks in advance if anyone can point me in the direction of something that could tell me which trach is which 'speaker'. `Zidane.
