Rui Nuno Capela wrote: I'm having difficulty understanding what the difference is between jack midi clients and alsa sequencer midi clients. Could you possibly give me some examples of which programs will show up as jack clients and which as alsa sequencer clients ? Does it make a difference to the way one uses them, or the facilities that jack offers them? In other words, what is the reason for having separate tabs ? Can one not connect a jack midi client to an alsa sequencer port then ? Sorry to be bombarding you with questions, but in the absence of documentation, it seems to be the only way to get an understanding of jack. Fritz

On Tue, Sep 23, 2008 at 12:04:39AM +0200, Christoph Eckert wrote: Rather ideological and not very informative IMHO. To understand how all this fits together you need to know the following. 1. The bottom layer: ALSA audio and ALSA raw midi. On most (nearly all) linux systems these are the drivers handling audio and midi devices respectively. A program can use these directly, but then it is limited to connecting to hardware devices only. 2. Interconnecting applications and hardware: Jack and ALSA midi sequencer. Jack can interconnect audio programs that are written to use it to each other and to an audio card. To talk to the audio card Jack uses the ALSA driver in mose cases. This is what you see in the 'AUDIO' tab in qjackctl. The ALSA midi sequencer does the same for midi. It can connect applications to each other and to physical midi interfaces (raw ALSA ports). This is what you see in the 'ALSA' tab of qjackctl. 3. Jack midi replacing ALSA midi sequencer. Using the ALSA midi sequencer can be hard (for a programmer) and also it has had serious problems with timing, mainly because of lack of high-resolution timer support in Linux until recent times. This has resulted in the development of midi-in-Jack, which can (almost) be used as a replacement for the ALSA midi sequencer. It has its pros and cons. This is what you see in the 'MIDI' tab in qjackctl. Currently the two midi routing system coexist, and this leads to some confusion. In qjackctl you have three options for midi-in-Jack: 1. 'None' - this means that Jack will not use any ALSA midi devices. Applications that use midi-in-jack (e.g. Aeolus) will still show up in the 'MIDI' tab, but you can't connect them to any physical ALSA midi ports, only to other apps (if there are any other). 2. 'Raw' - this means that Jack will grab the raw ALSA (hardware) midi devices, and convert them into Jack midi ports with rather useless names. The same devices are still shown in the 'ALSA' tab, but you will notice you can't connect them there anymore - they are usually supporting only one client, and Jack has already taken them. This means that applications that only support connecting to ALSA midi sequencer can't be connected to physical midi devices anymore. In the dreams of the Jack midi developers, such apps will soon cease to exists, and if that happens the 'raw' option is the normal one to use. 3. 'Seq' - this means Jack will convert *all* ALSA sequencer ports into Jack midi ports. The original ones remain accessible in the 'ALSA' tab. Now Aeolus has both an ALSA midi sequencer port, and a midi-in-Jack port. You will see Aeolus in both the 'MIDI' and 'ALSA' tabs. If you use 'Raw', you will have to use the Jack connection to connect Aeolus to a keyboard. If you use 'Seq' you can make the connection in either system. Also if you use 'Seq' there will be two Jack-midi ports for Aeolus: the Jack-midi port that Aeolus creates, and a Jack-midi copy of the ALSA sequencer port of Aeolus, shown as system:playback_#, with # some number. Don't use the latter. What happens if you do that is that the midi data from your keyboard will follow a rather long route: Raw ALSA -> Jack port -> Jack port -> ALSA sequencer -> Aeolus. The most direct route is still the one in the 'ALSA' tab: Raw ALSA -> ALSA sequencer -> Aeolus. Ciao, -- FA Laboratorio di Acustica ed Elettroacustica Parma, Italia Wie der Mond heute Nacht aussieht ! Ist es nicht ein seltsames Bild ?

Hi, [...] right, and IMO even confusing. Seems I should better shut up when it's time to go to bed :) . Cheers, ce

Arnold Krille wrote: +1 ( see also wiki.linuxmusicians.com )