diff options
Diffstat (limited to 'Documentation/sound/alsa/seq_oss.html')
| -rw-r--r-- | Documentation/sound/alsa/seq_oss.html | 409 |
1 files changed, 409 insertions, 0 deletions
diff --git a/Documentation/sound/alsa/seq_oss.html b/Documentation/sound/alsa/seq_oss.html new file mode 100644 index 00000000000..d9776cf60c0 --- /dev/null +++ b/Documentation/sound/alsa/seq_oss.html @@ -0,0 +1,409 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<HTML> +<HEAD> + <TITLE>OSS Sequencer Emulation on ALSA</TITLE> +</HEAD> +<BODY> + +<CENTER> +<H1> + +<HR WIDTH="100%"></H1></CENTER> + +<CENTER> +<H1> +OSS Sequencer Emulation on ALSA</H1></CENTER> + +<HR WIDTH="100%"> +<P>Copyright (c) 1998,1999 by Takashi Iwai +<TT><A HREF="mailto:iwai@ww.uni-erlangen.de"><iwai@ww.uni-erlangen.de></A></TT> +<P>ver.0.1.8; Nov. 16, 1999 +<H2> + +<HR WIDTH="100%"></H2> + +<H2> +1. Description</H2> +This directory contains the OSS sequencer emulation driver on ALSA. Note +that this program is still in the development state. +<P>What this does - it provides the emulation of the OSS sequencer, access +via +<TT>/dev/sequencer</TT> and <TT>/dev/music</TT> devices. +The most of applications using OSS can run if the appropriate ALSA +sequencer is prepared. +<P>The following features are emulated by this driver: +<UL> +<LI> +Normal sequencer and MIDI events:</LI> + +<BR>They are converted to the ALSA sequencer events, and sent to the corresponding +port. +<LI> +Timer events:</LI> + +<BR>The timer is not selectable by ioctl. The control rate is fixed to +100 regardless of HZ. That is, even on Alpha system, a tick is always +1/100 second. The base rate and tempo can be changed in <TT>/dev/music</TT>. + +<LI> +Patch loading:</LI> + +<BR>It purely depends on the synth drivers whether it's supported since +the patch loading is realized by callback to the synth driver. +<LI> +I/O controls:</LI> + +<BR>Most of controls are accepted. Some controls +are dependent on the synth driver, as well as even on original OSS.</UL> +Furthermore, you can find the following advanced features: +<UL> +<LI> +Better queue mechanism:</LI> + +<BR>The events are queued before processing them. +<LI> +Multiple applications:</LI> + +<BR>You can run two or more applications simultaneously (even for OSS sequencer)! +However, each MIDI device is exclusive - that is, if a MIDI device is opened +once by some application, other applications can't use it. No such a restriction +in synth devices. +<LI> +Real-time event processing:</LI> + +<BR>The events can be processed in real time without using out of bound +ioctl. To switch to real-time mode, send ABSTIME 0 event. The followed +events will be processed in real-time without queued. To switch off the +real-time mode, send RELTIME 0 event. +<LI> +<TT>/proc</TT> interface:</LI> + +<BR>The status of applications and devices can be shown via <TT>/proc/asound/seq/oss</TT> +at any time. In the later version, configuration will be changed via <TT>/proc</TT> +interface, too.</UL> + +<H2> +2. Installation</H2> +Run configure script with both sequencer support (<TT>--with-sequencer=yes</TT>) +and OSS emulation (<TT>--with-oss=yes</TT>) options. A module <TT>snd-seq-oss.o</TT> +will be created. If the synth module of your sound card supports for OSS +emulation (so far, only Emu8000 driver), this module will be loaded automatically. +Otherwise, you need to load this module manually. +<P>At beginning, this module probes all the MIDI ports which have been +already connected to the sequencer. Once after that, the creation and deletion +of ports are watched by announcement mechanism of ALSA sequencer. +<P>The available synth and MIDI devices can be found in proc interface. +Run "<TT>cat /proc/asound/seq/oss</TT>", and check the devices. For example, +if you use an AWE64 card, you'll see like the following: +<PRE> OSS sequencer emulation version 0.1.8 + ALSA client number 63 + ALSA receiver port 0 + + Number of applications: 0 + + Number of synth devices: 1 + + synth 0: [EMU8000] + type 0x1 : subtype 0x20 : voices 32 + capabilties : ioctl enabled / load_patch enabled + + Number of MIDI devices: 3 + + midi 0: [Emu8000 Port-0] ALSA port 65:0 + capability write / opened none + + midi 1: [Emu8000 Port-1] ALSA port 65:1 + capability write / opened none + + midi 2: [0: MPU-401 (UART)] ALSA port 64:0 + capability read/write / opened none</PRE> +Note that the device number may be different from the information of +<TT>/proc/asound/oss-devices</TT> +or ones of the original OSS driver. Use the device number listed in <TT>/proc/asound/seq/oss</TT> +to play via OSS sequencer emulation. +<H2> +3. Using Synthesizer Devices</H2> +Run your favorite program. I've tested playmidi-2.4, awemidi-0.4.3, gmod-3.1 +and xmp-1.1.5. You can load samples via <TT>/dev/sequencer</TT> like sfxload, +too. +<P>If the lowlevel driver supports multiple access to synth devices (like +Emu8000 driver), two or more applications are allowed to run at the same +time. +<H2> +4. Using MIDI Devices</H2> +So far, only MIDI output was tested. MIDI input was not checked at all, +but hopefully it will work. Use the device number listed in <TT>/proc/asound/seq/oss</TT>. +Be aware that these numbers are mostly different from the list in +<TT>/proc/asound/oss-devices</TT>. +<H2> +5. Module Options</H2> +The following module options are available: +<UL> +<LI> +<TT>maxqlen</TT></LI> + +<BR>specifies the maximum read/write queue length. This queue is private +for OSS sequencer, so that it is independent from the queue length of ALSA +sequencer. Default value is 1024. +<LI> +<TT>seq_oss_debug</TT></LI> + +<BR>specifies the debug level and accepts zero (= no debug message) or +positive integer. Default value is 0.</UL> + +<H2> +6. Queue Mechanism</H2> +OSS sequencer emulation uses an ALSA priority queue. The +events from <TT>/dev/sequencer</TT> are processed and put onto the queue +specified by module option. +<P>All the events from <TT>/dev/sequencer</TT> are parsed at beginning. +The timing events are also parsed at this moment, so that the events may +be processed in real-time. Sending an event ABSTIME 0 switches the operation +mode to real-time mode, and sending an event RELTIME 0 switches it off. +In the real-time mode, all events are dispatched immediately. +<P>The queued events are dispatched to the corresponding ALSA sequencer +ports after scheduled time by ALSA sequencer dispatcher. +<P>If the write-queue is full, the application sleeps until a certain amount +(as default one half) becomes empty in blocking mode. The synchronization +to write timing was implemented, too. +<P>The input from MIDI devices or echo-back events are stored on read FIFO +queue. If application reads <TT>/dev/sequencer</TT> in blocking mode, the +process will be awaked. + +<H2> +7. Interface to Synthesizer Device</H2> + +<H3> +7.1. Registration</H3> +To register an OSS synthesizer device, use <TT>snd_seq_oss_synth_register</TT> +function. +<PRE>int snd_seq_oss_synth_register(char *name, int type, int subtype, int nvoices, + snd_seq_oss_callback_t *oper, void *private_data)</PRE> +The arguments <TT>name</TT>, <TT>type</TT>, <TT>subtype</TT> and +<TT>nvoices</TT> +are used for making the appropriate synth_info structure for ioctl. The +return value is an index number of this device. This index must be remembered +for unregister. If registration is failed, -errno will be returned. +<P>To release this device, call <TT>snd_seq_oss_synth_unregister function</TT>: +<PRE>int snd_seq_oss_synth_unregister(int index),</PRE> +where the <TT>index</TT> is the index number returned by register function. +<H3> +7.2. Callbacks</H3> +OSS synthesizer devices have capability for sample downloading and ioctls +like sample reset. In OSS emulation, these special features are realized +by using callbacks. The registration argument oper is used to specify these +callbacks. The following callback functions must be defined: +<PRE>snd_seq_oss_callback_t: + int (*open)(snd_seq_oss_arg_t *p, void *closure); + int (*close)(snd_seq_oss_arg_t *p); + int (*ioctl)(snd_seq_oss_arg_t *p, unsigned int cmd, unsigned long arg); + int (*load_patch)(snd_seq_oss_arg_t *p, int format, const char *buf, int offs, int count); + int (*reset)(snd_seq_oss_arg_t *p); +Except for <TT>open</TT> and <TT>close</TT> callbacks, they are allowed +to be NULL. +<P>Each callback function takes the argument type snd_seq_oss_arg_t as the +first argument. +<PRE>struct snd_seq_oss_arg_t { + int app_index; + int file_mode; + int seq_mode; + snd_seq_addr_t addr; + void *private_data; + int event_passing; +};</PRE> +The first three fields, <TT>app_index</TT>, <TT>file_mode</TT> and +<TT>seq_mode</TT> +are initialized by OSS sequencer. The <TT>app_index</TT> is the application +index which is unique to each application opening OSS sequencer. The +<TT>file_mode</TT> +is bit-flags indicating the file operation mode. See +<TT>seq_oss.h</TT> +for its meaning. The <TT>seq_mode</TT> is sequencer operation mode. In +the current version, only <TT>SND_OSSSEQ_MODE_SYNTH</TT> is used. +<P>The next two fields, <TT>addr</TT> and <TT>private_data</TT>, must be +filled by the synth driver at open callback. The <TT>addr</TT> contains +the address of ALSA sequencer port which is assigned to this device. If +the driver allocates memory for <TT>private_data</TT>, it must be released +in close callback by itself. +<P>The last field, <TT>event_passing</TT>, indicates how to translate note-on +/ off events. In <TT>PROCESS_EVENTS</TT> mode, the note 255 is regarded +as velocity change, and key pressure event is passed to the port. In <TT>PASS_EVENTS</TT> +mode, all note on/off events are passed to the port without modified. <TT>PROCESS_KEYPRESS</TT> +mode checks the note above 128 and regards it as key pressure event (mainly +for Emu8000 driver). +<H4> +7.2.1. Open Callback</H4> +The <TT>open</TT> is called at each time this device is opened by an application +using OSS sequencer. This must not be NULL. Typically, the open callback +does the following procedure: +<OL> +<LI> +Allocate private data record.</LI> + +<LI> +Create an ALSA sequencer port.</LI> + +<LI> +Set the new port address on arg->addr.</LI> + +<LI> +Set the private data record pointer on arg->private_data.</LI> +</OL> +Note that the type bit-flags in port_info of this synth port must NOT contain +<TT>TYPE_MIDI_GENERIC</TT> +bit. Instead, <TT>TYPE_SPECIFIC</TT> should be used. Also, <TT>CAP_SUBSCRIPTION</TT> +bit should NOT be included, too. This is necessary to tell it from other +normal MIDI devices. If the open procedure succeeded, return zero. Otherwise, +return -errno. +<H4> +7.2.2 Ioctl Callback</H4> +The <TT>ioctl</TT> callback is called when the sequencer receives device-specific +ioctls. The following two ioctls should be processed by this callback: +<UL> +<LI> +<TT>IOCTL_SEQ_RESET_SAMPLES</TT></LI> + +<BR>reset all samples on memory -- return 0 +<LI> +<TT>IOCTL_SYNTH_MEMAVL</TT></LI> + +<BR>return the available memory size +<LI> +<TT>FM_4OP_ENABLE</TT></LI> + +<BR>can be ignored usually</UL> +The other ioctls are processed inside the sequencer without passing to +the lowlevel driver. +<H4> +7.2.3 Load_Patch Callback</H4> +The <TT>load_patch</TT> callback is used for sample-downloading. This callback +must read the data on user-space and transfer to each device. Return 0 +if succeeded, and -errno if failed. The format argument is the patch key +in patch_info record. The buf is user-space pointer where patch_info record +is stored. The offs can be ignored. The count is total data size of this +sample data. +<H4> +7.2.4 Close Callback</H4> +The <TT>close</TT> callback is called when this device is closed by the +applicaion. If any private data was allocated in open callback, it must +be released in the close callback. The deletion of ALSA port should be +done here, too. This callback must not be NULL. +<H4> +7.2.5 Reset Callback</H4> +The <TT>reset</TT> callback is called when sequencer device is reset or +closed by applications. The callback should turn off the sounds on the +relevant port immediately, and initialize the status of the port. If this +callback is undefined, OSS seq sends a <TT>HEARTBEAT</TT> event to the +port. +<H3> +7.3 Events</H3> +Most of the events are processed by sequencer and translated to the adequate +ALSA sequencer events, so that each synth device can receive by input_event +callback of ALSA sequencer port. The following ALSA events should be implemented +by the driver: +<BR> +<TABLE BORDER WIDTH="75%" NOSAVE > +<TR NOSAVE> +<TD NOSAVE><B>ALSA event</B></TD> + +<TD><B>Original OSS events</B></TD> +</TR> + +<TR> +<TD>NOTEON</TD> + +<TD>SEQ_NOTEON +<BR>MIDI_NOTEON</TD> +</TR> + +<TR> +<TD>NOTE</TD> + +<TD>SEQ_NOTEOFF +<BR>MIDI_NOTEOFF</TD> +</TR> + +<TR NOSAVE> +<TD NOSAVE>KEYPRESS</TD> + +<TD>MIDI_KEY_PRESSURE</TD> +</TR> + +<TR NOSAVE> +<TD>CHANPRESS</TD> + +<TD NOSAVE>SEQ_AFTERTOUCH +<BR>MIDI_CHN_PRESSURE</TD> +</TR> + +<TR NOSAVE> +<TD NOSAVE>PGMCHANGE</TD> + +<TD NOSAVE>SEQ_PGMCHANGE +<BR>MIDI_PGM_CHANGE</TD> +</TR> + +<TR> +<TD>PITCHBEND</TD> + +<TD>SEQ_CONTROLLER(CTRL_PITCH_BENDER) +<BR>MIDI_PITCH_BEND</TD> +</TR> + +<TR> +<TD>CONTROLLER</TD> + +<TD>MIDI_CTL_CHANGE +<BR>SEQ_BALANCE (with CTL_PAN)</TD> +</TR> + +<TR> +<TD>CONTROL14</TD> + +<TD>SEQ_CONTROLLER</TD> +</TR> + +<TR> +<TD>REGPARAM</TD> + +<TD>SEQ_CONTROLLER(CTRL_PITCH_BENDER_RANGE)</TD> +</TR> + +<TR> +<TD>SYSEX</TD> + +<TD>SEQ_SYSEX</TD> +</TR> +</TABLE> + +<P>The most of these behavior can be realized by MIDI emulation driver +included in the Emu8000 lowlevel driver. In the future release, this module +will be independent. +<P>Some OSS events (<TT>SEQ_PRIVATE</TT> and <TT>SEQ_VOLUME</TT> events) are passed as event +type SND_SEQ_OSS_PRIVATE. The OSS sequencer passes these event 8 byte +packets without any modification. The lowlevel driver should process these +events appropriately. +<H2> +8. Interface to MIDI Device</H2> +Since the OSS emulation probes the creation and deletion of ALSA MIDI sequencer +ports automatically by receiving announcement from ALSA sequencer, the +MIDI devices don't need to be registered explicitly like synth devices. +However, the MIDI port_info registered to ALSA sequencer must include a group +name <TT>SND_SEQ_GROUP_DEVICE</TT> and a capability-bit <TT>CAP_READ</TT> or +<TT>CAP_WRITE</TT>. Also, subscription capabilities, <TT>CAP_SUBS_READ</TT> or <TT>CAP_SUBS_WRITE</TT>, +must be defined, too. If these conditions are not satisfied, the port is not +registered as OSS sequencer MIDI device. +<P>The events via MIDI devices are parsed in OSS sequencer and converted +to the corresponding ALSA sequencer events. The input from MIDI sequencer +is also converted to MIDI byte events by OSS sequencer. This works just +a reverse way of seq_midi module. +<H2> +9. Known Problems / TODO's</H2> + +<UL> +<LI> +Patch loading via ALSA instrument layer is not implemented yet.</LI> +</UL> + +</BODY> +</HTML> |