自学教程：C++ snd_seq_ev_clear函数代码示例

    void sendMessageNow (const MidiMessage& message)    {        if (message.getRawDataSize() > maxEventSize)        {            maxEventSize = message.getRawDataSize();            snd_midi_event_free (midiParser);            snd_midi_event_new (maxEventSize, &midiParser);        }        snd_seq_event_t event;        snd_seq_ev_clear (&event);        snd_midi_event_encode (midiParser,                               message.getRawData(),                               message.getRawDataSize(),                               &event);        snd_midi_event_reset_encode (midiParser);        snd_seq_ev_set_source (&event, 0);        snd_seq_ev_set_subs (&event);        snd_seq_ev_set_direct (&event);        snd_seq_event_output (seqHandle, &event);        snd_seq_drain_output (seqHandle);    }

void MIDIDevice::feedBack(t_input_channel channel, t_input_value value){	/* MIDI devices can have only 128 notes or controllers */	if (channel < 128)	{		snd_seq_event_t ev;		MIDIInput* plugin;		plugin = static_cast<MIDIInput*> (parent());		Q_ASSERT(plugin != NULL);		Q_ASSERT(plugin->alsa() != NULL);		Q_ASSERT(m_address != NULL);		/* Setup an event structure */		snd_seq_ev_clear(&ev);		snd_seq_ev_set_dest(&ev, m_address->client, m_address->port);		snd_seq_ev_set_subs(&ev);		snd_seq_ev_set_direct(&ev);		/* Send control change, channel 1 (0) */		snd_seq_ev_set_controller(&ev, 0, channel, value >> 1);		snd_seq_event_output(plugin->alsa(), &ev);		snd_seq_drain_output(plugin->alsa());		/* Send note on/off, channel 1 (0) */		if (value == 0)			snd_seq_ev_set_noteoff(&ev, 0, channel, 0);		else			snd_seq_ev_set_noteon(&ev, 0, channel, value >> 1);		snd_seq_event_output(plugin->alsa(), &ev);		snd_seq_drain_output(plugin->alsa());	}

void stop_midireceiver (JackVST *jvst){	int err; 	snd_seq_event_t event;	snd_seq_t *seq2 = create_sequencer ("jfstquit", true);		jvst->midiquit = 1;		snd_seq_connect_to (seq2, 0, snd_seq_client_id (jvst->seq),0);	snd_seq_ev_clear      (&event);	snd_seq_ev_set_direct (&event);	snd_seq_ev_set_subs   (&event);	snd_seq_ev_set_source (&event, 0);	snd_seq_ev_set_controller (&event,1,0x80,50);		if ((err = snd_seq_event_output (seq2, &event)) < 0) {		fst_error ("cannot send stop event to midi thread: %s/n",			   snd_strerror (err));	}	snd_seq_drain_output (seq2);	snd_seq_close (seq2);	pthread_join (jvst->midi_thread,NULL);	snd_seq_close (jvst->seq);}

static void Func_NoteOn( int channel, int key, int velocity ){    snd_seq_event_t ev;    snd_seq_ev_clear(&ev);    snd_seq_ev_set_noteon(&ev, channel, key, velocity);    sequence_event(&ev);}

static void Func_PolyAftertouch( int channel, int key, int pressure ){    snd_seq_event_t ev;    snd_seq_ev_clear(&ev);    snd_seq_ev_set_keypress(&ev, channel, key, pressure);    sequence_event(&ev);}

void MIDIDevice::outputDMX(const QByteArray& universe){    MIDIOut* plugin = static_cast<MIDIOut*> (parent());    Q_ASSERT(plugin != NULL);    Q_ASSERT(plugin->alsa() != NULL);    Q_ASSERT(m_address != NULL);    /* Setup a common event structure for all values */    snd_seq_event_t ev;    snd_seq_ev_clear(&ev);    snd_seq_ev_set_dest(&ev, m_address->client, m_address->port);    snd_seq_ev_set_subs(&ev);    snd_seq_ev_set_direct(&ev);    /* Since MIDI devices can have only 128 real channels, we don't       attempt to write more than that */    for (unsigned char channel = 0; channel < MAX_MIDI_DMX_CHANNELS;            channel++)    {        /* Scale 0-255 to 0-127 */        char scaled = DMX2MIDI(universe[channel]);        /* Since MIDI is so slow, we only send values that are           	   actually changed. */        if (m_values[channel] == scaled)            continue;        /* Store the changed MIDI value */        m_values[channel] = scaled;        if (mode() == Note)        {            if (scaled == 0)            {                /* 0 is sent as a note off command */                snd_seq_ev_set_noteoff(&ev, midiChannel(),                                       channel, scaled);            }            else            {                /* 1-127 is sent as note on command */                snd_seq_ev_set_noteon(&ev, midiChannel(),                                      channel, scaled);            }            snd_seq_event_output(plugin->alsa(), &ev);        }        else        {            /* Control change */            snd_seq_ev_set_controller(&ev, midiChannel(),                                      channel, scaled);            snd_seq_event_output_buffer(plugin->alsa(), &ev);        }    }    /* Make sure that all values go to the MIDI endpoint */    snd_seq_drain_output(plugin->alsa());}

static void note_on(int note, real_t power) {  snd_seq_event_t ev;  if (debug>1) 	fprintf(stderr, "midimatch: (%ld) note on:  note:%-3d p:%.2f name:%[email
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