Jack Port and Integration on MacOSX Stphane Letz Grame, centre de - PowerPoint PPT Presentation

LAD 2004 : Jack Port and Integration on MacOSX Jack Port and Integration on MacOSX Stéphane Letz Grame, centre de création musicale Lyon, France GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Plan • Porting the Linux code to MacOSX • Integration with CoreAudio architecture : the JackOSX project • Jackd evolution : more structure, multi-processor version GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Porting the Linux code • Use of the POSIX shared memory API more reliable on MacOSX • Rewriting the engine audio cycle for a callback-based activation scheme • Using Mach Remote Procedure Call for client activation : the Linux FIFO based code is not used anymore, all clients are activated in a loop inside the Jack engine - - Synchronous RPC are fast because the scheduler is bypassed - - Thread migration : the calling thread parameters (priority, time quantum..) are transferred to the called thread • Client Real-Time threads : fixed priority time constrained threads (period, computation, constraint) • Use an additional real-time thread for client process call GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Drivers • Current one : a PortAudio based driver that can also work on Linux • In development : a more efficient “native” CoreAudio based driver, using the Apple HALOuputUnit component (takes care of all audio stream adaptation) GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Performance • Measuring the audio cycle on a iBook G3/700 using jackd timing code • At 64 frames : client activation time : ~ 50 us (jack_metro in “thru” mode) • At 64 frames : finding the maximum additional latency - jackd only : ~ 5 us (0.5 %) - jackd + 1 jack_metro client : ~ 55 us (3.5 %) - jackd + 1 jack_metro client + moving windows + network access… : up to ~ 260 us - jackd + 2 jack_metro clients : ~ 120 us (7.5 %) - jackd + 2 jack_metro clients + moving windows + network access… : up to ~ 360 us • Maximum additional latency of about 200 us • Really stable • Jackd can be used with 32 frame buffers GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Integration in the CoreAudio architecture MacOSX audio architecture : HAL : Hardware Abstraction Layer in user space : multi-channel audio, real-time thread activation (for Audio callback), mixing for output…, expose the API for applications IOKIT : a C++ based layer that implements generic services for driver developers Drivers : kernel drivers, interaction with the hardware GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX HAL model • A “software interrupt” based model • Each client can use its own buffer size (starting from 14 frames…) • The HAL takes care of waking-up real-time (callback) threads at the right time • All real-time threads run at a fixed priority, but correct thread interleaving is done by the HAL by carefully setting the time-constraint parameters : period, computation, constraint • Drivers usually publish their “native” capabilities : stream and sample format, sample rate, buffer size…. • Application may use optimized (Altivec…) AudioConverter components to convert in their own format if needed • AudioUnits : a plug-in API to be used by host applications GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Jack Audio Router (JAR) The bridge between regular CoreAudio applications and the Jack server • Using JAR, a CoreAudio application becomes a Jack client • A user space driver placed between the HAL and IOKit layer • Implements the HAL “Plug-in API” • Loaded by the HAL like kernel drivers to become available for applications GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX JAR (2) : behaviour • JAR presents itself as an n mono non-interleaved stream , fixed buffer size , fixed sample rate driver • Behaves like a kernel driver for the HAL, will be available like other drivers for applications • Can be used as the default system driver for applications like iTunes, QuickTime Player, DLSSynth… GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX JAR (3) : mapping the CoreAudio API on the Jack API • Parameter query API : AudioDeviceGetProperty • Client activation AudioDeviceAddIOProc ==> jack_client_new jack_client_port_register jack_set_process_callback AudioDeviceStartIOProc ==> jack_client_activate AudioDeviceStopOProc ==> jack_client_deactivate AudioDeviceRemoveIOProc ==> jack_client_port_unregister jack_client_close • Described in global settings : - number of input/ouput jack ports - auto connection with drivers - JAR as default system driver GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Jack Plug-ins, JackPilot • Extend the audio routing capabilities inside plug-ins host applications : track insert….. • JackAU (AudioUnit API) and JackVST (VST API) • JackPilot : global settings : jackd parameters, connections manager Native Jack Clients CoreAudio Applications Pure Data (without plugin support) Reason, iTunes, Quicktime ... JAR Audio Hardware Jack Server JAR Built-In, MOTU 828 … JackVST or JackAU channel insert … CoreAudio Applications JackVST or JackAU (with plugin support) channel insert … Cubase SX, Logic, Max/MSP ... CoreAudio Applications (with plugin support) Cubase SX, Logic, Max/MSP ... GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX JackOSX project • All the components are distributed in a package called JackOSX • Source Forge project : JAR, Jack Plug-ins, CoreAudio drivers • Web site : www.jackosx.com • In collaboration with Johnny Petrantoni and Dan Nigrin GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Synchronization • Allowing transparent synchronization between Jack native clients and CoreAudio applications • Mapping the Jack transport API to the MIDI clock sync API • Converting Jack transport state events to MIDI Start , Stop , Continue, SongPos messages using the CoreMIDI API GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Jack evolution : MacOSX specifics • In MacOSX, the natural way to implement a server/client system is to use the Mach Interface Generator (MIG) to define new Remote Procedure Calls • Synchronous and asynchronous functions can be defined : - function call is actually done using Mach ports and messages - MIG takes care of parameter management - synchronous calls are implemented with send/receive Mach messages that use the fast “thread migration” system • Socket based communications can be completely suppressed • The server defines a public Mach port for client/server communication • When opening, each client defines its own private port for server/client communication - Opening a client : rpc_jack_client_new (mach_port_t server, const char* name, int* refnum…) - Calling the client process callback : rpc_jack_client_process(mach_port_t client, jack_frame_t frames,….) GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Multi-processor version (1) • In the current version , the client graph is sorted to determine an order for client activation each time the graph topology changes • Multi-processor version : activate parallel nodes on different processors - no more “a priori” sorting - a data flow model : a node become runnable when all of its input ports have been filled up GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Multi-processor version (2) • Using system primitives : - describe data dependencies between nodes with semaphores - need of inter-process semaphores • Implementing a “mini” scheduler, for an audio cycle : - starting from the input, find all runnable nodes, put them on a lock-free shared list - one thread per processor that takes a runnable node, execute it, propagate output port “readiness” to connected inputs - re-compute runnable nodes - until all nodes have been executed GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Jackd architecture re-organisation (1) • More structure: - Isolate the server/client communication code - Isolate the client activation code (FIFO on Linux, futexes on kernel 2.6, synchronous RPC on MacOSX, semaphores…) - More secure use of shared memory segment : distinguish between R/W and R only segments on the client side - Move all port data structure and connections to shared memory - Thinking in term of lock-free access whenever possible GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX Jackd architecture re-organisation (2) • More structure : - Moving the FreeWheel code as an autonomous driver - Isolate Watch Dog thread code …… • Fix some API problems : - Memory leak (jack_port_by_id and jack_port_by_name…) - Some state change are not notified to other clients : change of port names… …… GRAME : Centre National de Création Musicale

LAD 2004 : Jack Port and Integration on MacOSX DEMO GRAME : Centre National de Création Musicale