gstreamer/ext/alsa/gstalsamidisrc.c
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C

/* GStreamer
* Copyright (C) 2014 Antonio Ospite <ao2@ao2.it>
*
* gstalsamidisrc.c: Source element for ALSA MIDI sequencer events
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:element-alsamidisrc
* @title: alsamidisrc
* @see_also: #GstPushSrc
*
* The alsamidisrc element is an element that fetches ALSA MIDI sequencer
* events and makes them available to elements understanding
* audio/x-midi-events in their sink pads.
*
* It can be used to generate notes from a MIDI input device.
*
* ## Example launch line
* |[
* gst-launch -v alsamidisrc ports=129:0 ! fluiddec ! audioconvert ! autoaudiosink
* ]|
* This pipeline will listen for events from the sequencer device at port 129:0,
* and generate notes using the fluiddec element.
*
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include "gstalsamidisrc.h"
GST_DEBUG_CATEGORY_STATIC (gst_alsa_midi_src_debug);
#define GST_CAT_DEFAULT gst_alsa_midi_src_debug
/*
* The MIDI specification declares some status bytes undefined:
*
* - 0xF4 System common - Undefined (Reserved)
* - 0xF5 System common - Undefined (Reserved)
* - 0xF9 System real-time - Undefined (Reserved)
* - 0xFD System real-time - Undefined (Reserved)
*
* See: http://www.midi.org/techspecs/midimessages.php#2
*
* Some other documents define status 0xf9 as a tick message with a period of
* 10ms:
*
* - http://www.blitter.com/~russtopia/MIDI/~jglatt/tech/midispec/tick.htm
* - http://www.sequencer.de/synth/index.php/MIDI_Format#0xf9_-_MIDI_Tick
*
* Even if non-standard it looks like this convention is quite widespread.
*
* For instance Fluidsynth uses 0xF9 as a "midi tick" message:
* http://sourceforge.net/p/fluidsynth/code-git/ci/master/tree/fluidsynth/src/midi/fluid_midi.h#l62
*
* And then so does the midiparse element in order to be compatible with
* Fluidsynth and the fluiddec element.
*
* Do the same to behave like midiparse.
*/
#define MIDI_TICK 0xf9
#define MIDI_TICK_PERIOD_MS 10
/* Functions specific to the Alsa MIDI sequencer API */
#define DEFAULT_BUFSIZE 65536
#define DEFAULT_CLIENT_NAME "alsamidisrc"
#define DEFAULT_POLL_TIMEOUT_MS (MIDI_TICK_PERIOD_MS / 2)
static int
init_seq (GstAlsaMidiSrc * alsamidisrc)
{
int ret;
ret = snd_seq_open (&alsamidisrc->seq, "default", SND_SEQ_OPEN_DUPLEX, 0);
if (ret < 0) {
GST_ERROR_OBJECT (alsamidisrc, "Cannot open sequencer - %s",
snd_strerror (ret));
goto error;
}
ret = snd_seq_set_client_name (alsamidisrc->seq, DEFAULT_CLIENT_NAME);
if (ret < 0) {
GST_ERROR_OBJECT (alsamidisrc, "Cannot set client name - %s",
snd_strerror (ret));
goto error_seq_close;
}
return 0;
error_seq_close:
snd_seq_close (alsamidisrc->seq);
error:
return ret;
}
/* Parses one or more port addresses from the string */
static int
parse_ports (const char *arg, GstAlsaMidiSrc * alsamidisrc)
{
gchar **ports_list;
guint i;
int ret = 0;
GST_DEBUG_OBJECT (alsamidisrc, "ports: %s", arg);
/*
* Assume that ports are separated by commas.
*
* Commas are used instead of spaces because those are valid in client
* names.
*/
ports_list = g_strsplit (arg, ",", 0);
alsamidisrc->port_count = g_strv_length (ports_list);
alsamidisrc->seq_ports = g_try_new (snd_seq_addr_t, alsamidisrc->port_count);
if (!alsamidisrc->seq_ports) {
GST_ERROR_OBJECT (alsamidisrc, "Out of memory");
ret = -ENOMEM;
goto out_free_ports_list;
}
for (i = 0; i < alsamidisrc->port_count; i++) {
gchar *port_name = ports_list[i];
ret = snd_seq_parse_address (alsamidisrc->seq, &alsamidisrc->seq_ports[i],
port_name);
if (ret < 0) {
GST_ERROR_OBJECT (alsamidisrc, "Invalid port %s - %s", port_name,
snd_strerror (ret));
goto error_free_seq_ports;
}
}
goto out_free_ports_list;
error_free_seq_ports:
g_free (alsamidisrc->seq_ports);
out_free_ports_list:
g_strfreev (ports_list);
return ret;
}
static int
create_port (GstAlsaMidiSrc * alsamidisrc)
{
int ret;
ret = snd_seq_create_simple_port (alsamidisrc->seq, DEFAULT_CLIENT_NAME,
SND_SEQ_PORT_CAP_WRITE |
SND_SEQ_PORT_CAP_SUBS_WRITE,
SND_SEQ_PORT_TYPE_MIDI_GENERIC | SND_SEQ_PORT_TYPE_APPLICATION);
if (ret < 0)
GST_ERROR_OBJECT (alsamidisrc, "Cannot create port - %s",
snd_strerror (ret));
return ret;
}
static void
connect_ports (GstAlsaMidiSrc * alsamidisrc)
{
int i;
int ret;
for (i = 0; i < alsamidisrc->port_count; ++i) {
ret =
snd_seq_connect_from (alsamidisrc->seq, 0,
alsamidisrc->seq_ports[i].client, alsamidisrc->seq_ports[i].port);
if (ret < 0)
/* Issue a warning and try the other ports */
GST_WARNING_OBJECT (alsamidisrc, "Cannot connect from port %d:%d - %s",
alsamidisrc->seq_ports[i].client, alsamidisrc->seq_ports[i].port,
snd_strerror (ret));
}
}
/* GStreamer specific functions */
static GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE ("src",
GST_PAD_SRC,
GST_PAD_ALWAYS,
GST_STATIC_CAPS ("audio/x-midi-event"));
#define DEFAULT_PORTS NULL
enum
{
PROP_0,
PROP_PORTS,
PROP_LAST,
};
#define _do_init \
GST_DEBUG_CATEGORY_INIT (gst_alsa_midi_src_debug, "alsamidisrc", 0, "alsamidisrc element");
#define gst_alsa_midi_src_parent_class parent_class
G_DEFINE_TYPE_WITH_CODE (GstAlsaMidiSrc, gst_alsa_midi_src, GST_TYPE_PUSH_SRC,
_do_init);
static void gst_alsa_midi_src_set_property (GObject * object, guint prop_id,
const GValue * value, GParamSpec * pspec);
static void gst_alsa_midi_src_get_property (GObject * object, guint prop_id,
GValue * value, GParamSpec * pspec);
static gboolean gst_alsa_midi_src_start (GstBaseSrc * basesrc);
static gboolean gst_alsa_midi_src_stop (GstBaseSrc * basesrc);
static GstFlowReturn
gst_alsa_midi_src_create (GstPushSrc * src, GstBuffer ** buf);
static void
gst_alsa_midi_src_class_init (GstAlsaMidiSrcClass * klass)
{
GObjectClass *gobject_class;
GstElementClass *gstelement_class;
GstBaseSrcClass *gstbase_src_class;
GstPushSrcClass *gstpush_src_class;
gobject_class = G_OBJECT_CLASS (klass);
gstelement_class = GST_ELEMENT_CLASS (klass);
gstbase_src_class = GST_BASE_SRC_CLASS (klass);
gstpush_src_class = GST_PUSH_SRC_CLASS (klass);
gobject_class->set_property = gst_alsa_midi_src_set_property;
gobject_class->get_property = gst_alsa_midi_src_get_property;
g_object_class_install_property (gobject_class, PROP_PORTS,
g_param_spec_string ("ports", "Ports",
"Comma separated list of sequencer ports (e.g. client:port,...)",
DEFAULT_PORTS, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
gst_element_class_set_static_metadata (gstelement_class,
"AlsaMidi Source",
"Source",
"Push ALSA MIDI sequencer events around", "Antonio Ospite <ao2@ao2.it>");
gst_element_class_add_static_pad_template (gstelement_class, &srctemplate);
gstbase_src_class->start = GST_DEBUG_FUNCPTR (gst_alsa_midi_src_start);
gstbase_src_class->stop = GST_DEBUG_FUNCPTR (gst_alsa_midi_src_stop);
gstpush_src_class->create = GST_DEBUG_FUNCPTR (gst_alsa_midi_src_create);
}
static void
gst_alsa_midi_src_init (GstAlsaMidiSrc * alsamidisrc)
{
alsamidisrc->ports = DEFAULT_PORTS;
gst_base_src_set_format (GST_BASE_SRC (alsamidisrc), GST_FORMAT_TIME);
gst_base_src_set_live (GST_BASE_SRC (alsamidisrc), TRUE);
}
static void
gst_alsa_midi_src_set_property (GObject * object, guint prop_id,
const GValue * value, GParamSpec * pspec)
{
GstAlsaMidiSrc *src;
src = GST_ALSA_MIDI_SRC (object);
switch (prop_id) {
case PROP_PORTS:
g_free (src->ports);
src->ports = g_value_dup_string (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
gst_alsa_midi_src_get_property (GObject * object, guint prop_id, GValue * value,
GParamSpec * pspec)
{
GstAlsaMidiSrc *src;
g_return_if_fail (GST_IS_ALSA_MIDI_SRC (object));
src = GST_ALSA_MIDI_SRC (object);
switch (prop_id) {
case PROP_PORTS:
g_value_set_string (value, src->ports);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static GstBuffer *
prepare_buffer (GstAlsaMidiSrc * alsamidisrc, gpointer data, guint size)
{
GstClockTime time;
gpointer local_data;
GstBuffer *buffer;
buffer = gst_buffer_new ();
time = alsamidisrc->tick * MIDI_TICK_PERIOD_MS * GST_MSECOND;
GST_BUFFER_DTS (buffer) = time;
GST_BUFFER_PTS (buffer) = time;
GST_BUFFER_OFFSET (buffer) = time;
GST_BUFFER_DURATION (buffer) = MIDI_TICK_PERIOD_MS * GST_MSECOND;
local_data = g_memdup (data, size);
gst_buffer_append_memory (buffer,
gst_memory_new_wrapped (0, local_data, size, 0, size, local_data,
g_free));
GST_MEMDUMP_OBJECT (alsamidisrc, "MIDI data:", local_data, size);
alsamidisrc->tick += 1;
return buffer;
}
static void
push_buffer (GstAlsaMidiSrc * alsamidisrc, gpointer data, guint size,
GstBufferList * buffer_list)
{
gst_buffer_list_add (buffer_list, prepare_buffer (alsamidisrc, data, size));
}
static void
push_tick_buffer (GstAlsaMidiSrc * alsamidisrc, GstBufferList * buffer_list)
{
alsamidisrc->buffer[0] = MIDI_TICK;
push_buffer (alsamidisrc, alsamidisrc->buffer, 1, buffer_list);
}
static GstFlowReturn
gst_alsa_midi_src_create (GstPushSrc * src, GstBuffer ** buf)
{
GstAlsaMidiSrc *alsamidisrc;
GstBufferList *buffer_list;
long size_ev = 0;
int err;
int ret;
guint len;
alsamidisrc = GST_ALSA_MIDI_SRC (src);
buffer_list = gst_buffer_list_new ();
snd_seq_poll_descriptors (alsamidisrc->seq, alsamidisrc->pfds,
alsamidisrc->npfds, POLLIN);
/*
* The file descriptors are polled with a timeout _less_ than 10ms (the MIDI
* tick period) in order not to loose events because of possible overlaps
* with MIDI ticks.
*
* If the polling times out (no new events) then a MIDI-tick event gets
* generated in order to keep the pipeline alive and progressing.
*
* If new events are present, then they are decoded and queued in
* a buffer_list. One buffer per event will be queued, all with different
* timestamps (see the prepare_buffer() function); maybe this can be
* optimized but a as a proof-of-concept mechanism it works OK.
*/
ret = poll (alsamidisrc->pfds, alsamidisrc->npfds, DEFAULT_POLL_TIMEOUT_MS);
if (ret < 0) {
GST_ERROR_OBJECT (alsamidisrc, "ERROR in poll: %s", strerror (errno));
} else if (ret == 0) {
push_tick_buffer (alsamidisrc, buffer_list);
} else {
/* There are events available */
do {
snd_seq_event_t *event;
err = snd_seq_event_input (alsamidisrc->seq, &event);
if (err < 0)
break; /* Processed all events */
if (event) {
size_ev =
snd_midi_event_decode (alsamidisrc->parser, alsamidisrc->buffer,
DEFAULT_BUFSIZE, event);
if (size_ev < 0) {
/* ENOENT indicates an event that is not a MIDI message, silently skip it */
if (-ENOENT == size_ev) {
GST_WARNING_OBJECT (alsamidisrc,
"Warning: Received non-MIDI message");
push_tick_buffer (alsamidisrc, buffer_list);
} else {
GST_ERROR_OBJECT (alsamidisrc,
"Error decoding event from ALSA to output: %s",
strerror (-size_ev));
goto error;
}
} else {
push_buffer (alsamidisrc, alsamidisrc->buffer, size_ev, buffer_list);
}
}
} while (err > 0);
}
len = gst_buffer_list_length (buffer_list);
if (len == 0)
goto error;
/* Pop the _last_ buffer in the list */
*buf = gst_buffer_copy (gst_buffer_list_get (buffer_list, len - 1));
gst_buffer_list_remove (buffer_list, len - 1, 1);
--len;
/*
* If there are no more buffers left, free the list, otherwise push all the
* _previous_ buffers left in the list.
*
* The one popped above will be pushed last when this function returns.
*/
if (len == 0)
gst_buffer_list_unref (buffer_list);
else
gst_pad_push_list (GST_BASE_SRC (src)->srcpad, buffer_list);
return GST_FLOW_OK;
error:
gst_buffer_list_unref (buffer_list);
return GST_FLOW_ERROR;
}
static gboolean
gst_alsa_midi_src_start (GstBaseSrc * basesrc)
{
GstAlsaMidiSrc *alsamidisrc;
int ret;
alsamidisrc = GST_ALSA_MIDI_SRC (basesrc);
alsamidisrc->tick = 0;
alsamidisrc->port_count = 0;
ret = init_seq (alsamidisrc);
if (ret < 0)
goto err;
if (alsamidisrc->ports) {
ret = parse_ports (alsamidisrc->ports, alsamidisrc);
if (ret < 0)
goto error_seq_close;
}
ret = create_port (alsamidisrc);
if (ret < 0)
goto error_free_seq_ports;
connect_ports (alsamidisrc);
ret = snd_seq_nonblock (alsamidisrc->seq, 1);
if (ret < 0) {
GST_ERROR_OBJECT (alsamidisrc, "Cannot set nonblock mode - %s",
snd_strerror (ret));
goto error_free_seq_ports;
}
snd_midi_event_new (DEFAULT_BUFSIZE, &alsamidisrc->parser);
snd_midi_event_init (alsamidisrc->parser);
snd_midi_event_reset_decode (alsamidisrc->parser);
snd_midi_event_no_status (alsamidisrc->parser, 1);
alsamidisrc->buffer = g_try_malloc (DEFAULT_BUFSIZE);
if (alsamidisrc->buffer == NULL)
goto error_free_parser;
alsamidisrc->npfds =
snd_seq_poll_descriptors_count (alsamidisrc->seq, POLLIN);
alsamidisrc->pfds =
g_try_malloc (sizeof (*alsamidisrc->pfds) * alsamidisrc->npfds);
if (alsamidisrc->pfds == NULL)
goto error_free_buffer;
return TRUE;
error_free_buffer:
g_free (alsamidisrc->buffer);
error_free_parser:
snd_midi_event_free (alsamidisrc->parser);
error_free_seq_ports:
g_free (alsamidisrc->seq_ports);
error_seq_close:
snd_seq_close (alsamidisrc->seq);
err:
return FALSE;
}
static gboolean
gst_alsa_midi_src_stop (GstBaseSrc * basesrc)
{
GstAlsaMidiSrc *alsamidisrc;
alsamidisrc = GST_ALSA_MIDI_SRC (basesrc);
g_free (alsamidisrc->pfds);
g_free (alsamidisrc->buffer);
snd_midi_event_free (alsamidisrc->parser);
g_free (alsamidisrc->seq_ports);
snd_seq_close (alsamidisrc->seq);
return TRUE;
}