doc/jackdbus.html

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 682 <body class="article">
 683 <div id="header">
 684 <h1>(LADI) jackdbus</h1>
 685 </div>
 686 <div id="content">
 687 <div id="preamble">
 688 <div class="sectionbody">
 689 <div class="paragraph"><p><span class="image">
 690 <a class="image" href="https://github.com/LADI/jackdbus/actions">
 691 <img src="https://github.com/LADI/jackdbus/actions/workflows/build.yml/badge.svg" alt="Build status badge">
 692 </a>
 693 </span>
 694 <span class="image">
 695 <a class="image" href="https://repology.org/metapackage/jack-audio-connection-kit/versions">
 696 <img src="https://repology.org/badge/tiny-repos/jack-audio-connection-kit.svg" alt="Repology bandge">
 697 </a>
 698 </span></p></div>
 699 </div>
 700 </div>
 701 <div class="sect1">
 702 <h2 id="_overview">Overview</h2>
 703 <div class="sectionbody">
 704 <div class="paragraph"><p>This software imlements D-Bus endpoint for JACK server.</p></div>
 705 </div>
 706 </div>
 707 <div class="sect1">
 708 <h2 id="_brief_history">Brief History</h2>
 709 <div class="sectionbody">
 710 <div class="paragraph"><p>Initial version of <a href="https://github.com/LADI/jackdbus">jackdbus</a> was created
 711 as part of LADI project and was ad-hoc modification of JACK1 codebase.
 712 jackdbus for JACK1 was maintained first as a setup of ad-hoc patches,
 713 then via Mercural and then via Git.
 714 In 2008/2009, jackdbus was ported to jackdmp codebase along with an implementation
 715 of the newly designed for the new need control API for JACK.
 716 The result of this merge became known as
 717 <a href="https://web.archive.org/web/20170106162202/http://lac.linuxaudio.org/2009/cdm/Thursday/01_Letz/01.pdf">JACK2</a>.
 718 As of 2022, jackdbus is again maintained in LADI project.
 719 The jackaudio.org version of jackdbus is considered older/alternative
 720 implementation.</p></div>
 721 <div class="paragraph"><p>For LADI specific issues, submit issues or pull request to LADI project.
 722 For related discussions, you are invited to join
 723 <a href="https://libera.chat/">Libera.Chat</a> channel #ladi</p></div>
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 780 EQn3XQAAAABJRU5ErkJggg==">
 781 </td>
 782 <td class="content">Do not submit LADI specific issues to jackaudio project.</td>
 783 </tr></table>
 784 </div>
 785 </div>
 786 </div>
 787 <div class="sect1">
 788 <h2 id="_d_bus_access">D-Bus access</h2>
 789 <div class="sectionbody">
 790 <div class="paragraph"><p>D-Bus is an object model that provides IPC mechanism.
 791 D-Bus supports autoactivation of objects,
 792 thus making it simple and reliable to code a "single instance" application or daemon,
 793 and to launch applications and daemons on demand when their services are needed.</p></div>
 794 <div class="paragraph"><p>Improvements over classical "jackd" approach:</p></div>
 795 <div class="ulist"><ul>
 796 <li>
 797 <p>
 798 Simplified single thread model for control and monitor
 799    applications. Various D-Bus language bindings make it trivial to
 800    write control and monitor applications using scripting languages
 801    like Python, Ruby, Perl, etc..
 802 </p>
 803 </li>
 804 <li>
 805 <p>
 806 A log file is available for inspection even when autoactivation
 807    happens by the first launched JACK application.
 808 </p>
 809 </li>
 810 <li>
 811 <p>
 812 A real configuration file is used to persist settings to be
 813    manipulated through configuration interface of JACK D-Bus object.
 814 </p>
 815 </li>
 816 <li>
 817 <p>
 818 Improved graph inspection and control mechanism. JACK graph is
 819    versioned. Connections, ports and clients have unique
 820    (monotonically increasing) numeric IDs.
 821 </p>
 822 </li>
 823 <li>
 824 <p>
 825 High level abstraction of JACK settings. Allows applications that
 826    can configure JACK to expose parameters that were not known at
 827    compile (or tarball release) time. Recent real world examples are
 828    the JACK MIDI driver parameters and support for FFADO driver in
 829    QJackCtl. Upgrading of JACK requires upgrade of QJackCtl in order
 830    to make new settings available in the GUI.
 831 </p>
 832 </li>
 833 </ul></div>
 834 <div class="sect2">
 835 <h3 id="_how_it_works">How it works</h3>
 836 <div class="sect3">
 837 <h4 id="_autoactivation_and_starting_stopping_jack_server">Autoactivation and starting/stopping JACK server</h4>
 838 <div class="paragraph"><p>First, application that issues D-Bus method call to JACK controller object,
 839 causes D-Bus session daemon to activate the object by starting the jackdbus executable.
 840 Activating controller object does not start the server.
 841 Instead controller object has several interfaces.
 842 The most important of them is the control interface.
 843 Control interface contains methods for starting and stopping JACK server,
 844 loading and unloading of internal clients (netjack),
 845 setting buffer size and resetting xrun counter.
 846 It also contains methods for querying information required by monitoring
 847 applications:</p></div>
 848 <div class="ulist"><ul>
 849 <li>
 850 <p>
 851 whether JACK server is started
 852 </p>
 853 </li>
 854 <li>
 855 <p>
 856 whether JACK server is running in realtime mode
 857 </p>
 858 </li>
 859 <li>
 860 <p>
 861 sample rate
 862 </p>
 863 </li>
 864 <li>
 865 <p>
 866 DSP load
 867 </p>
 868 </li>
 869 <li>
 870 <p>
 871 current buffer size
 872 </p>
 873 </li>
 874 <li>
 875 <p>
 876 latency
 877 </p>
 878 </li>
 879 <li>
 880 <p>
 881 xrun counter
 882 </p>
 883 </li>
 884 </ul></div>
 885 <div class="paragraph"><p>JACK server autostart is achieved by libjack calling "jack server start" method of
 886 JACK control D-Bus interface.</p></div>
 887 </div>
 888 <div class="sect3">
 889 <h4 id="_jack_settings">JACK settings</h4>
 890 <div class="paragraph"><p>Applications that want to manage JACK settings can query
 891 and set all settings that were traditionally specified as
 892 jackd command-line parameters.
 893 Interface abstraction provides virtual tree of parameter
 894 containers with container leaves that contain parameters.
 895 Parameters are accessed using simple addressing scheme (array of strings)
 896 where address defines path to parameter, like "drivers", "alsa", "dither".</p></div>
 897 <div class="paragraph"><p>Overview of the tree of standard settings’ addresses:</p></div>
 898 <div class="ulist"><ul>
 899 <li>
 900 <p>
 901 "engine"
 902 </p>
 903 </li>
 904 <li>
 905 <p>
 906 "engine", "driver"
 907 </p>
 908 </li>
 909 <li>
 910 <p>
 911 "engine", "realtime"
 912 </p>
 913 </li>
 914 <li>
 915 <p>
 916 "engine", &#8230;more engine parameters
 917 </p>
 918 </li>
 919 <li>
 920 <p>
 921 "driver", "device"
 922 </p>
 923 </li>
 924 <li>
 925 <p>
 926 "driver", &#8230;more driver parameters
 927 </p>
 928 </li>
 929 <li>
 930 <p>
 931 "drivers", "alsa", "device"
 932 </p>
 933 </li>
 934 <li>
 935 <p>
 936 "drivers", "alsa", &#8230;more alsa driver parameters
 937 </p>
 938 </li>
 939 <li>
 940 <p>
 941 "drivers", &#8230;more drivers
 942 </p>
 943 </li>
 944 <li>
 945 <p>
 946 "internals", "netmanager", "multicast ip"
 947 </p>
 948 </li>
 949 <li>
 950 <p>
 951 "internals", "netmanager", &#8230;more netmanager parameters
 952 </p>
 953 </li>
 954 <li>
 955 <p>
 956 "internals", &#8230;more internals
 957 </p>
 958 </li>
 959 </ul></div>
 960 <div class="paragraph"><p>JACK settings are persisted.
 961 I.e. they are automatically saved by jackdbus when they are set.
 962 Next time user starts JACK server, last saved settings will be automatically used.
 963 Changing JACK settings through the configure D-Bus interface takes effect on next
 964 JACK server start.
 965 On the fly change of the buffer size, as available in the libjack
 966 (jack.h) API, is also possible through the control D-Bus interface.</p></div>
 967 </div>
 968 <div class="sect3">
 969 <h4 id="_jack_parameter_constraints">JACK parameter constraints</h4>
 970 <div class="paragraph"><p>JACK internal modules that provide parameters visible through control API can provide
 971 information about parameter valid range (like realtime priority) or
 972 whether parameter should be presented as enumeration.
 973 Enumeration parameters can be strict and non-strict.
 974 Example of strict enum parameter is dither parameter of ALSA driver,
 975 it has only predefined valid values: "shaped noise",
 976 "rectangular", "triangualr" and "none".</p></div>
 977 <div class="paragraph"><p>Example of non-strict parameter is device parameter of ALSA driver.
 978 It is useful to provide some detected device strings as choices to user,
 979 but still allow user to specify custom string that ALSA layer is supposed to
 980 understand.</p></div>
 981 </div>
 982 <div class="sect3">
 983 <h4 id="_jack_patchbay">JACK patchbay</h4>
 984 <div class="paragraph"><p>In order to simplify patchbay applications, extended functionality is provided.
 985 There is a method that returns the current graph state.
 986 Graph state has unique monotonically increasing version number
 987 and contains info about all clients, their ports and connections.
 988 Connections, ports and clients have unique numeric IDs
 989 that are guaranteed not to be reused.
 990 Notifica tions about graph changes are provided using
 991 D-Bus signals.</p></div>
 992 </div>
 993 </div>
 994 <div class="sect2">
 995 <h3 id="_jack_d_bus_enabled_applications">JACK D-Bus enabled applications</h3>
 996 <div class="sect3">
 997 <h4 id="_jack_control">jack_control</h4>
 998 <div class="paragraph"><p>JACK contains "jack_control" executable a 300 lines of Python exposing
 999 JACK D-Bus functionality. It allows chained execution of several commands.
1000 For example "jack control ds alsa dps midi-driver raw eps realtime on
1001 eps relatime-priority 70 start" selects ALSA driver, enables JACK MIDI
1002 raw backend, enables realtime mode, sets realtime priority to 70 and starts
1003 JACK server.</p></div>
1004 </div>
1005 <div class="sect3">
1006 <h4 id="_ladi_tools">LADI Tools</h4>
1007 <div class="paragraph"><p>LADI Tools is a set of programs to configure, control and monitor JACK.
1008 It provides tray icon, Window Maker style dockapp,
1009 G15 keyboard LCD display integration application,
1010 configuration utility for managing JACK settings
1011 and log file monitor application.</p></div>
1012 <div class="paragraph"><p>All tools are written in Python.</p></div>
1013 </div>
1014 <div class="sect3">
1015 <h4 id="_patchage">Patchage</h4>
1016 <div class="paragraph"><p>Patchage, the ubiquitous canvas modular patch bay can be compiled to use
1017 D-Bus instead of libjack to communicate with JACK.</p></div>
1018 <div class="paragraph"><p>Doing so also enables JACK server start/stop functionality in Patchage.</p></div>
1019 </div>
1020 <div class="sect3">
1021 <h4 id="_ladi_session_handler_ladish">LADI Session handler (LADISH)</h4>
1022 <div class="paragraph"><p>LADISH, a rewrite of LASH session handler
1023 uses D-Bus to communicate with JACK.</p></div>
1024 <div class="paragraph"><p>Various JACK related features are implemented:</p></div>
1025 <div class="ulist"><ul>
1026 <li>
1027 <p>
1028 Saving of JACK settings as part of "studio" session.
1029 </p>
1030 </li>
1031 <li>
1032 <p>
1033 Handling of "JACK server crash" scenario: restarting JACK server,
1034 notifying JACK applications that JACK server reappeared so they
1035 can reconnect to it, and restoring JACK connections.
1036 </p>
1037 </li>
1038 </ul></div>
1039 </div>
1040 </div>
1041 </div>
1042 </div>
1043 <div class="sect1">
1044 <h2 id="_references">References</h2>
1045 <div class="sectionbody">
1046 <div class="olist arabic"><ol class="arabic">
1047 <li>
1048 <p>
1049 <a href="https://web.archive.org/web/20170106162202/http://lac.linuxaudio.org/2009/cdm/Thursday/01_Letz/01.pdf">What&#8217;s new in JACK2?</a>
1050 </p>
1051 </li>
1052 </ol></div>
1053 </div>
1054 </div>
1055 </div>
1056 <div id="footnotes"><hr></div>
1057 <div id="footer">
1058 <div id="footer-text">
1059 Last updated
1060  2023-03-08 10:15:31 EET
1061 </div>
1062 </div>
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