On Fri, Apr 07, 2006 at 12:29:58PM -0600, William Ferrell wrote: > This HOWTO attempts to document how the whole thing fits together, how > to implement it on your own system, and how to use it in production at > a karaoke (or really any DJ'ed) show.
This is really spiffy. I'm not sure how easily I'm going to be able to integrate it with the control-top I want to construct (which I've finally, at least, sketched out, and am trying to learn Glade to mock up), but... > The JACK Audio Connection Kit is a real-time virtual mixing board for > Linux (and possibly other platforms; I haven't yet investigated this) I understand JACK has been ported successfully to OS/X now, which probably isn't too surprising. > that uses a low-latency server and protocol to connect sound > applications and devices to each other. It can control all sorts of > real hardware (sound cards, MIDI controllers, etc.) and can accept > inputs from just about anything (media players, MIDI controllers, > etc.) for both audio and control. Specifically, it can talk to my Phase 26 USB box, with 3 stereo outputs (I'm very much a "real mixing board" kind of guy). > JACK includes a useful tool, qjackctl, that will be used in this HOWTO > to configure JACK and to automate patching our different tools > together. You do *not* want to try to play with JACK without qj; take my word on this. > This HOWTO uses JACK Rack for two things: first, it is used to perform > the actual pitch-shifting work when needed (audio from PyKaraoke is > passed to JACK Rack instead of straight ot the sound card). Second, it > performs crossfading work; I use different audio sources > (specifically, XMMS and MPlayer) during my shows, and smoothly > transitioning from them to CD+G music and back is important. JACK Rack > is, in this configuration, the only piece of software on the chain > that is connected to the sound card. All audio playback runs through > JACK Rack whether it is doing anything to the sound or not. Can JR, or the modules it encases, be controlled by DBus (or any other message passing facility)? > It supports MP3, Ogg Vorbis, WAV, FLAC, and all sorts of other audio > formats. It can play video (via MPlayer, actually), but we want manual > control over that kind of thing so we'll only be using XMMS for audio. Mplayer is sort of ungainly for playing audio directly, isn't it? > MPlayer is a multimedia player for Linux. It supports audio and video > playback, tons of media formats, lots of output devices and types, and > has more features than I can adequately count here. Here's a curious idea: I wonder how hard it would be to recast Kelvin's rendering code as an Mplayer codec? Did we already talk about this? > For our purposes, we'll simply be chaining it to JACK as an audio > source (letting it do its own thing for video, if needed) so we can > crossfade between it and the filler music XMMS provides. How *are* you deconflicting video output sources, anyway? > 1.5 Tom's Audio Processing LADSPA Plugins > > http://tap-plugins.sourceforge.net/ > > This set of plugins, compatible with JACK Rack, includes the one we > want: pitch shifting. This is what will provide us with digital > pitch-shifting for CD+G playback. Really, it can affect all sound, but > we just want it to affect CD+G. Ah; it's TAP that's doing it. > 2. Setting Up the Parts > > It's beyond the scope of this HOWTO to document the > installation/configuration procedure for the software used; if you're > using a modern Linux distribution (like Debian, Ubuntu, or Gentoo), > its package management system should already have these packages > available. Note: SuSE, in particular, tends to have an out of date JACK; I wouldn't be surprised to find that other distros do as well -- Will? Could you document the version numbers of all your components? > 2.1. Configuring ALSA to Talk to JACK > > By default, ALSA just talks to your real sound device. We want it to > default to connecting to JACK instead, though, so it's necessary to > create a .asoundrc file. It belongs in the home directory of the > account you're using for production shows. Just edit ~/.asoundrc and > you should be fine. Its contents should be: > > pcm.!default { > type plug > slave { pcm "jack" } > } > > pcm.jack { > type jack > playback_ports { > 0 alsa_pcm:playback_1 > 1 alsa_pcm:playback_2 > } > capture_ports { > 0 alsa_pcm:capture_1 > 1 alsa_pcm:capture_2 > } > } > > Test that this is working properly by starting JACK (run qjackctl and > start a JACK server), then watch the "Connections" bay as you run > "aplay somefile.mp3" -- you should see a new client appear, and it > will probably automatically connect to the sound card (this is JACK's > default behavior). This is *nice* detail, Will. > 2.2. Setting Up the Sound Processor (JACK Rack) > > Start up JACK Rack (the command is "jack-rack"). It will start with an > empty effects stack, which is what we want. Do you mention where is the best place to start all this stuff? .profile for the login account? /etc/rc.*? > PyKaraoke needs no modifications because it uses SDL, which honors > .asoundrc. MPlayer needs to be told either to use JACK or SDL as its > audio output method: > > # mplayer -ao sdl ... > -or- > # mplayer -ao jack ... You can configure that in mplayer.conf, right? > Fire off an MPlayer instance with a song to make sure it appears as a > client in the qjackctl Connections window. > > If you're using MPlayer with SDL, you'll notice that PyKaraoke and > MPlayer appear pretty much the same within the Connections window. > That's an important detail later. Because you're cheating? :-) > I've posted this HOWTO at > http://willfe.com/index.php/Pitch-shifting_With_PyKaraoke_and_JACK_HOWTO > as well. I'll get it formatted properly here in a few minutes. And, BTW; kudos on the site; blogging with MW isn't easy. Cheers, -- jra -- Jay R. Ashworth [EMAIL PROTECTED] Designer Baylink RFC 2100 Ashworth & Associates The Things I Think '87 e24 St Petersburg FL USA http://baylink.pitas.com +1 727 647 1274 A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on Usenet and in e-mail? ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. 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