root/branches/ppalmers-streaming/src/libstreaming/amdtp/AmdtpTransmitStreamProcessor.cpp

Revision 720, 23.4 kB (checked in by ppalmers, 13 years ago)

first working version of the reworked streaming code

Line 
1 /*
2  * Copyright (C) 2005-2007 by Pieter Palmers
3  *
4  * This file is part of FFADO
5  * FFADO = Free Firewire (pro-)audio drivers for linux
6  *
7  * FFADO is based upon FreeBoB.
8  *
9  * This library is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License version 2.1, as published by the Free Software Foundation;
12  *
13  * This library is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with this library; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
21  * MA 02110-1301 USA
22  */
23
24 #include "AmdtpTransmitStreamProcessor.h"
25 #include "AmdtpPort.h"
26 #include "../StreamProcessorManager.h"
27
28 #include "../util/cycletimer.h"
29
30 #include <netinet/in.h>
31 #include <assert.h>
32
33 // in ticks
34 // as per AMDTP2.1:
35 // 354.17us + 125us @ 24.576ticks/usec = 11776.08192 ticks
36 #define DEFAULT_TRANSFER_DELAY (11776U)
37
38 #define TRANSMIT_TRANSFER_DELAY DEFAULT_TRANSFER_DELAY
39
40 namespace Streaming
41 {
42
43 /* transmit */
44 AmdtpTransmitStreamProcessor::AmdtpTransmitStreamProcessor ( int port, int dimension )
45         : StreamProcessor ( ePT_Transmit, port )
46         , m_dimension ( dimension )
47         , m_dbc ( 0 )
48 {}
49
50 bool
51 AmdtpTransmitStreamProcessor::generatePacketHeader (
52     unsigned char *data, unsigned int *length,
53     unsigned char *tag, unsigned char *sy,
54     int cycle, unsigned int dropped, unsigned int max_length )
55 {
56     struct iec61883_packet *packet = ( struct iec61883_packet * ) data;
57     /* Our node ID can change after a bus reset, so it is best to fetch
58     * our node ID for each packet. */
59     packet->sid = m_handler->getLocalNodeId() & 0x3f;
60
61     packet->dbs = m_dimension;
62     packet->fn = 0;
63     packet->qpc = 0;
64     packet->sph = 0;
65     packet->reserved = 0;
66     packet->dbc = m_dbc;
67     packet->eoh1 = 2;
68     packet->fmt = IEC61883_FMT_AMDTP;
69
70     *tag = IEC61883_TAG_WITH_CIP;
71     *sy = 0;
72
73     signed int fc;
74     uint64_t presentation_time;
75     unsigned int presentation_cycle;
76     int cycles_until_presentation;
77
78     uint64_t transmit_at_time;
79     unsigned int transmit_at_cycle;
80     int cycles_until_transmit;
81
82     // FIXME: should become a define
83     // the absolute minimum number of cycles we want to transmit
84     // a packet ahead of the presentation time. The nominal time
85     // the packet is transmitted ahead of the presentation time is
86     // given by TRANSMIT_TRANSFER_DELAY (in ticks), but in case we
87     // are too late for that, this constant defines how late we can
88     // be.
89     const int min_cycles_before_presentation = 1;
90     // FIXME: should become a define
91     // the absolute maximum number of cycles we want to transmit
92     // a packet ahead of the ideal transmit time. The nominal time
93     // the packet is transmitted ahead of the presentation time is
94     // given by TRANSMIT_TRANSFER_DELAY (in ticks), but we can send
95     // packets early if we want to. (not completely according to spec)
96     const int max_cycles_to_transmit_early = 5;
97
98 try_block_of_frames:
99     debugOutput ( DEBUG_LEVEL_ULTRA_VERBOSE, "Try for cycle %d\n", cycle );
100     // check whether the packet buffer has packets for us to send.
101     // the base timestamp is the one of the next sample in the buffer
102     ffado_timestamp_t ts_head_tmp;
103     m_data_buffer->getBufferHeadTimestamp ( &ts_head_tmp, &fc ); // thread safe
104
105     // the timestamp gives us the time at which we want the sample block
106     // to be output by the device
107     presentation_time = ( uint64_t ) ts_head_tmp;
108     m_last_timestamp = presentation_time;
109
110     // now we calculate the time when we have to transmit the sample block
111     transmit_at_time = substractTicks ( presentation_time, TRANSMIT_TRANSFER_DELAY );
112
113     // calculate the cycle this block should be presented in
114     // (this is just a virtual calculation since at that time it should
115     //  already be in the device's buffer)
116     presentation_cycle = ( unsigned int ) ( TICKS_TO_CYCLES ( presentation_time ) );
117
118     // calculate the cycle this block should be transmitted in
119     transmit_at_cycle = ( unsigned int ) ( TICKS_TO_CYCLES ( transmit_at_time ) );
120
121     // we can check whether this cycle is within the 'window' we have
122     // to send this packet.
123     // first calculate the number of cycles left before presentation time
124     cycles_until_presentation = diffCycles ( presentation_cycle, cycle );
125
126     // we can check whether this cycle is within the 'window' we have
127     // to send this packet.
128     // first calculate the number of cycles left before presentation time
129     cycles_until_transmit = diffCycles ( transmit_at_cycle, cycle );
130
131     debugOutput ( DEBUG_LEVEL_VERY_VERBOSE,
132                 "Gen HDR: CY=%04u, TC=%04u, CUT=%04d, TST=%011llu (%04u), TSP=%011llu (%04u)\n",
133                 cycle,
134                 transmit_at_cycle, cycles_until_transmit,
135                 transmit_at_time, ( unsigned int ) TICKS_TO_CYCLES ( transmit_at_time ),
136                 presentation_time, ( unsigned int ) TICKS_TO_CYCLES ( presentation_time ) );
137
138     // two different options:
139     // 1) there are not enough frames for one packet
140     //      => determine wether this is a problem, since we might still
141     //         have some time to send it
142     // 2) there are enough packets
143     //      => determine whether we have to send them in this packet
144     if ( fc < ( signed int ) m_syt_interval )
145     {
146         // not enough frames in the buffer,
147         debugOutput ( DEBUG_LEVEL_VERBOSE,
148                     "Insufficient frames: N=%02d, CY=%04u, TC=%04u, CUT=%04d\n",
149                     fc, cycle, transmit_at_cycle, cycles_until_transmit );
150         // we can still postpone the queueing of the packets
151         // if we are far enough ahead of the presentation time
152         if ( cycles_until_presentation <= min_cycles_before_presentation )
153         {
154             // we are too late
155             // meaning that we in some sort of xrun state
156             // signal xrun situation ??HERE??
157             m_xruns++;
158             // we send an empty packet on this cycle
159             return false;
160         }
161         else
162         {
163             // there is still time left to send the packet
164             // we want the system to give this packet another go
165     //             goto try_packet_again; // UGLY but effective
166             // unfortunatly the try_again doesn't work very well,
167             // so we'll have to either usleep(one cycle) and goto try_block_of_frames
168
169             // or just fill this with an empty packet
170             // if we have to do this too often, the presentation time will
171             // get too close and we're in trouble
172             return false;
173         }
174     }
175     else
176     {
177         // there are enough frames, so check the time they are intended for
178         // all frames have a certain 'time window' in which they can be sent
179         // this corresponds to the range of the timestamp mechanism:
180         // we can send a packet 15 cycles in advance of the 'presentation time'
181         // in theory we can send the packet up till one cycle before the presentation time,
182         // however this is not very smart.
183
184         // There are 3 options:
185         // 1) the frame block is too early
186         //      => send an empty packet
187         // 2) the frame block is within the window
188         //      => send it
189         // 3) the frame block is too late
190         //      => discard (and raise xrun?)
191         //         get next block of frames and repeat
192
193         if ( cycles_until_transmit <= max_cycles_to_transmit_early )
194         {
195             // it's time send the packet
196             m_dbc += fillDataPacketHeader ( packet, length, m_last_timestamp );
197             return true;
198         }
199         else if ( cycles_until_transmit < 0 )
200         {
201             // we are too late
202             debugOutput ( DEBUG_LEVEL_VERBOSE,
203                         "Too late: CY=%04u, TC=%04u, CUT=%04d, TSP=%011llu (%04u)\n",
204                         cycle,
205                         transmit_at_cycle, cycles_until_transmit,
206                         presentation_time, ( unsigned int ) TICKS_TO_CYCLES ( presentation_time ) );
207
208             // however, if we can send this sufficiently before the presentation
209             // time, it could be harmless.
210             // NOTE: dangerous since the device has no way of reporting that it didn't get
211             //       this packet on time.
212             if ( cycles_until_presentation <= min_cycles_before_presentation )
213             {
214                 // we are not that late and can still try to transmit the packet
215                 m_dbc += fillDataPacketHeader ( packet, length, m_last_timestamp );
216                 return true;
217             }
218             else   // definitely too late
219             {
220                 // remove the samples
221                 m_data_buffer->dropFrames ( m_syt_interval );
222                 // signal some xrun situation ??HERE??
223                 m_xruns++;
224                 // try a new block of frames
225                 goto try_block_of_frames; // UGLY but effective
226             }
227         }
228         else
229         {
230             debugOutput ( DEBUG_LEVEL_VERY_VERBOSE,
231                         "Too early: CY=%04u, TC=%04u, CUT=%04d, TST=%011llu (%04u), TSP=%011llu (%04u)\n",
232                         cycle,
233                         transmit_at_cycle, cycles_until_transmit,
234                         transmit_at_time, ( unsigned int ) TICKS_TO_CYCLES ( transmit_at_time ),
235                         presentation_time, ( unsigned int ) TICKS_TO_CYCLES ( presentation_time ) );
236 #ifdef DEBUG
237             if ( cycles_until_transmit > max_cycles_to_transmit_early + 1 )
238             {
239                 debugOutput ( DEBUG_LEVEL_VERY_VERBOSE,
240                             "Way too early: CY=%04u, TC=%04u, CUT=%04d, TST=%011llu (%04u), TSP=%011llu (%04u)\n",
241                             cycle,
242                             transmit_at_cycle, cycles_until_transmit,
243                             transmit_at_time, ( unsigned int ) TICKS_TO_CYCLES ( transmit_at_time ),
244                             presentation_time, ( unsigned int ) TICKS_TO_CYCLES ( presentation_time ) );
245             }
246 #endif
247             // we are too early, send only an empty packet
248             return false;
249         }
250     }
251     return true;
252 }
253
254 bool
255 AmdtpTransmitStreamProcessor::generatePacketData (
256     unsigned char *data, unsigned int *length,
257     unsigned char *tag, unsigned char *sy,
258     int cycle, unsigned int dropped, unsigned int max_length )
259 {
260     struct iec61883_packet *packet = ( struct iec61883_packet * ) data;
261     if ( m_data_buffer->readFrames ( m_syt_interval, ( char * ) ( data + 8 ) ) )
262     {
263         // process all ports that should be handled on a per-packet base
264         // this is MIDI for AMDTP (due to the need of DBC)
265         if ( !encodePacketPorts ( ( quadlet_t * ) ( data+8 ), m_syt_interval, packet->dbc ) )
266         {
267             debugWarning ( "Problem encoding Packet Ports\n" );
268         }
269         debugOutput ( DEBUG_LEVEL_VERY_VERBOSE, "XMIT DATA: TSP=%011llu (%04u)\n",
270                     cycle, m_last_timestamp, ( unsigned int ) TICKS_TO_CYCLES ( m_last_timestamp ) );
271         return true;
272     }
273     else
274     {
275         return false;
276     }
277 }
278
279 bool
280 AmdtpTransmitStreamProcessor::generateSilentPacketHeader (
281     unsigned char *data, unsigned int *length,
282     unsigned char *tag, unsigned char *sy,
283     int cycle, unsigned int dropped, unsigned int max_length )
284 {
285     struct iec61883_packet *packet = ( struct iec61883_packet * ) data;
286     debugOutput ( DEBUG_LEVEL_VERY_VERBOSE, "XMIT NONE: CY=%04u, TSP=%011llu (%04u)\n",
287                 cycle, m_last_timestamp, ( unsigned int ) TICKS_TO_CYCLES ( m_last_timestamp ) );
288
289     /* Our node ID can change after a bus reset, so it is best to fetch
290     * our node ID for each packet. */
291     packet->sid = m_handler->getLocalNodeId() & 0x3f;
292
293     packet->dbs = m_dimension;
294     packet->fn = 0;
295     packet->qpc = 0;
296     packet->sph = 0;
297     packet->reserved = 0;
298     packet->dbc = m_dbc;
299     packet->eoh1 = 2;
300     packet->fmt = IEC61883_FMT_AMDTP;
301
302     *tag = IEC61883_TAG_WITH_CIP;
303     *sy = 0;
304
305     m_dbc += fillNoDataPacketHeader ( packet, length );
306     return true;
307 }
308
309 bool
310 AmdtpTransmitStreamProcessor::generateSilentPacketData (
311     unsigned char *data, unsigned int *length,
312     unsigned char *tag, unsigned char *sy,
313     int cycle, unsigned int dropped, unsigned int max_length )
314 {
315     return true; // no need to do anything
316 }
317
318 unsigned int AmdtpTransmitStreamProcessor::fillDataPacketHeader (
319     struct iec61883_packet *packet, unsigned int* length,
320     uint32_t ts )
321 {
322
323     packet->fdf = m_fdf;
324
325     // convert the timestamp to SYT format
326     uint16_t timestamp_SYT = TICKS_TO_SYT ( ts );
327     packet->syt = ntohs ( timestamp_SYT );
328
329     *length = m_syt_interval*sizeof ( quadlet_t ) *m_dimension + 8;
330
331     return m_syt_interval;
332 }
333
334 unsigned int AmdtpTransmitStreamProcessor::fillNoDataPacketHeader (
335     struct iec61883_packet *packet, unsigned int* length )
336 {
337
338     // no-data packets have syt=0xFFFF
339     // and have the usual amount of events as dummy data (?)
340     packet->fdf = IEC61883_FDF_NODATA;
341     packet->syt = 0xffff;
342
343     // FIXME: either make this a setting or choose
344     bool send_payload=true;
345     if ( send_payload )
346     {
347         // this means no-data packets with payload (DICE doesn't like that)
348         *length = 2*sizeof ( quadlet_t ) + m_syt_interval * m_dimension * sizeof ( quadlet_t );
349         return m_syt_interval;
350     }
351     else
352     {
353         // dbc is not incremented
354         // this means no-data packets without payload
355         *length = 2*sizeof ( quadlet_t );
356         return 0;
357     }
358 }
359
360 unsigned int
361 AmdtpTransmitStreamProcessor::getPacketsPerPeriod()
362 {
363     return ( m_manager->getPeriodSize() ) /m_syt_interval;
364 }
365
366 bool AmdtpTransmitStreamProcessor::prepareChild()
367 {
368     debugOutput ( DEBUG_LEVEL_VERBOSE, "Preparing (%p)...\n", this );
369     switch ( m_manager->getNominalRate() )
370     {
371         case 32000:
372             m_syt_interval = 8;
373             m_fdf = IEC61883_FDF_SFC_32KHZ;
374             break;
375         case 44100:
376             m_syt_interval = 8;
377             m_fdf = IEC61883_FDF_SFC_44K1HZ;
378             break;
379         default:
380         case 48000:
381             m_syt_interval = 8;
382             m_fdf = IEC61883_FDF_SFC_48KHZ;
383             break;
384         case 88200:
385             m_syt_interval = 16;
386             m_fdf = IEC61883_FDF_SFC_88K2HZ;
387             break;
388         case 96000:
389             m_syt_interval = 16;
390             m_fdf = IEC61883_FDF_SFC_96KHZ;
391             break;
392         case 176400:
393             m_syt_interval = 32;
394             m_fdf = IEC61883_FDF_SFC_176K4HZ;
395             break;
396         case 192000:
397             m_syt_interval = 32;
398             m_fdf = IEC61883_FDF_SFC_192KHZ;
399             break;
400     }
401
402     iec61883_cip_init (
403         &m_cip_status,
404         IEC61883_FMT_AMDTP,
405         m_fdf,
406         m_manager->getNominalRate(),
407         m_dimension,
408         m_syt_interval );
409
410     for ( PortVectorIterator it = m_Ports.begin();
411             it != m_Ports.end();
412             ++it )
413     {
414         if ( ( *it )->getPortType() == Port::E_Midi )
415         {
416             // we use a timing unit of 10ns
417             // this makes sure that for the max syt interval
418             // we don't have rounding, and keeps the numbers low
419             // we have 1 slot every 8 events
420             // we have syt_interval events per packet
421             // => syt_interval/8 slots per packet
422             // packet rate is 8000pkt/sec => interval=125us
423             // so the slot interval is (1/8000)/(syt_interval/8)
424             // or: 1/(1000 * syt_interval) sec
425             // which is 1e9/(1000*syt_interval) nsec
426             // or 100000/syt_interval 'units'
427             // the event interval is fixed to 320us = 32000 'units'
428             if ( ! ( *it )->useRateControl ( true, ( 100000/m_syt_interval ),32000, false ) )
429             {
430                 debugFatal ( "Could not set signal type to PeriodSignalling" );
431                 return false;
432             }
433             break;
434         }
435     }
436
437     debugOutput ( DEBUG_LEVEL_VERBOSE, "Prepared for:\n" );
438     debugOutput ( DEBUG_LEVEL_VERBOSE, " Samplerate: %d, FDF: %d, DBS: %d, SYT: %d\n",
439                 m_manager->getNominalRate(), m_fdf, m_dimension, m_syt_interval );
440     debugOutput ( DEBUG_LEVEL_VERBOSE, " PeriodSize: %d, NbBuffers: %d\n",
441                 m_manager->getPeriodSize(), m_manager->getNbBuffers() );
442     debugOutput ( DEBUG_LEVEL_VERBOSE, " Port: %d, Channel: %d\n",
443                 m_port,m_channel );
444     return true;
445 }
446
447 /*
448 * compose the event streams for the packets from the port buffers
449 */
450 bool AmdtpTransmitStreamProcessor::processWriteBlock ( char *data,
451         unsigned int nevents, unsigned int offset )
452 {
453     bool no_problem=true;
454
455     for ( PortVectorIterator it = m_PeriodPorts.begin();
456             it != m_PeriodPorts.end();
457             ++it )
458     {
459
460         if ( ( *it )->isDisabled() ) {continue;};
461
462         //FIXME: make this into a static_cast when not DEBUG?
463
464         AmdtpPortInfo *pinfo=dynamic_cast<AmdtpPortInfo *> ( *it );
465         assert ( pinfo ); // this should not fail!!
466
467         switch ( pinfo->getFormat() )
468         {
469             case AmdtpPortInfo::E_MBLA:
470                 if ( encodePortToMBLAEvents ( static_cast<AmdtpAudioPort *> ( *it ), ( quadlet_t * ) data, offset, nevents ) )
471                 {
472                     debugWarning ( "Could not encode port %s to MBLA events", ( *it )->getName().c_str() );
473                     no_problem=false;
474                 }
475                 break;
476             case AmdtpPortInfo::E_SPDIF: // still unimplemented
477                 break;
478             default: // ignore
479                 break;
480         }
481     }
482     return no_problem;
483 }
484
485 bool AmdtpTransmitStreamProcessor::transmitSilenceBlock ( char *data,
486         unsigned int nevents, unsigned int offset )
487 {
488     bool problem = false;
489     for ( PortVectorIterator it = m_PeriodPorts.begin();
490             it != m_PeriodPorts.end();
491             ++it )
492     {
493         //FIXME: make this into a static_cast when not DEBUG?
494         AmdtpPortInfo *pinfo=dynamic_cast<AmdtpPortInfo *> ( *it );
495         assert ( pinfo ); // this should not fail!!
496
497         switch ( pinfo->getFormat() )
498         {
499             case AmdtpPortInfo::E_MBLA:
500                 if ( encodeSilencePortToMBLAEvents ( static_cast<AmdtpAudioPort *> ( *it ), ( quadlet_t * ) data, offset, nevents ) )
501                 {
502                     debugWarning ( "Could not encode port %s to MBLA events", ( *it )->getName().c_str() );
503                     problem = true;
504                 }
505                 break;
506             case AmdtpPortInfo::E_SPDIF: // still unimplemented
507                 break;
508             default: // ignore
509                 break;
510         }
511     }
512     return problem;
513 }
514
515 /**
516 * @brief decode a packet for the packet-based ports
517 *
518 * @param data Packet data
519 * @param nevents number of events in data (including events of other ports & port types)
520 * @param dbc DataBlockCount value for this packet
521 * @return true if all successfull
522 */
523 bool AmdtpTransmitStreamProcessor::encodePacketPorts ( quadlet_t *data, unsigned int nevents, unsigned int dbc )
524 {
525     bool ok=true;
526     quadlet_t byte;
527
528     quadlet_t *target_event=NULL;
529     unsigned int j;
530
531     for ( PortVectorIterator it = m_PacketPorts.begin();
532             it != m_PacketPorts.end();
533             ++it )
534     {
535
536 #ifdef DEBUG
537         AmdtpPortInfo *pinfo=dynamic_cast<AmdtpPortInfo *> ( *it );
538         assert ( pinfo ); // this should not fail!!
539
540         // the only packet type of events for AMDTP is MIDI in mbla
541         assert ( pinfo->getFormat() ==AmdtpPortInfo::E_Midi );
542 #endif
543
544         AmdtpMidiPort *mp=static_cast<AmdtpMidiPort *> ( *it );
545
546         // we encode this directly (no function call) due to the high frequency
547         /* idea:
548         spec says: current_midi_port=(dbc+j)%8;
549         => if we start at (dbc+stream->location-1)%8,
550         we'll start at the right event for the midi port.
551         => if we increment j with 8, we stay at the right event.
552         */
553         // FIXME: as we know in advance how big a packet is (syt_interval) we can
554         //        predict how much loops will be present here
555         // first prefill the buffer with NO_DATA's on all time muxed channels
556
557         for ( j = ( dbc & 0x07 ) +mp->getLocation(); j < nevents; j += 8 )
558         {
559
560             quadlet_t tmpval;
561
562             target_event= ( quadlet_t * ) ( data + ( ( j * m_dimension ) + mp->getPosition() ) );
563
564             if ( mp->canRead() )   // we can send a byte
565             {
566                 mp->readEvent ( &byte );
567                 byte &= 0xFF;
568                 tmpval=htonl (
569                         IEC61883_AM824_SET_LABEL ( ( byte ) <<16,
570                                                     IEC61883_AM824_LABEL_MIDI_1X ) );
571
572                 debugOutput ( DEBUG_LEVEL_ULTRA_VERBOSE, "MIDI port %s, pos=%d, loc=%d, dbc=%d, nevents=%d, dim=%d\n",
573                             mp->getName().c_str(), mp->getPosition(), mp->getLocation(), dbc, nevents, m_dimension );
574                 debugOutput ( DEBUG_LEVEL_ULTRA_VERBOSE, "base=%p, target=%p, value=%08X\n",
575                             data, target_event, tmpval );
576
577             }
578             else
579             {
580                 // can't send a byte, either because there is no byte,
581                 // or because this would exceed the maximum rate
582                 tmpval=htonl (
583                         IEC61883_AM824_SET_LABEL ( 0,IEC61883_AM824_LABEL_MIDI_NO_DATA ) );
584             }
585
586             *target_event=tmpval;
587         }
588
589     }
590     return ok;
591 }
592
593
594 int AmdtpTransmitStreamProcessor::encodePortToMBLAEvents ( AmdtpAudioPort *p, quadlet_t *data,
595         unsigned int offset, unsigned int nevents )
596 {
597     unsigned int j=0;
598
599     quadlet_t *target_event;
600
601     target_event= ( quadlet_t * ) ( data + p->getPosition() );
602
603     switch ( p->getDataType() )
604     {
605         default:
606         case Port::E_Int24:
607         {
608             quadlet_t *buffer= ( quadlet_t * ) ( p->getBufferAddress() );
609
610             assert ( nevents + offset <= p->getBufferSize() );
611
612             buffer+=offset;
613
614             for ( j = 0; j < nevents; j += 1 )   // decode max nsamples
615             {
616                 *target_event = htonl ( ( * ( buffer ) & 0x00FFFFFF ) | 0x40000000 );
617                 buffer++;
618                 target_event += m_dimension;
619             }
620         }
621         break;
622         case Port::E_Float:
623         {
624             const float multiplier = ( float ) ( 0x7FFFFF00 );
625             float *buffer= ( float * ) ( p->getBufferAddress() );
626
627             assert ( nevents + offset <= p->getBufferSize() );
628
629             buffer+=offset;
630
631             for ( j = 0; j < nevents; j += 1 )   // decode max nsamples
632             {
633
634                 // don't care for overflow
635                 float v = *buffer * multiplier;  // v: -231 .. 231
636                 unsigned int tmp = ( ( int ) v );
637                 *target_event = htonl ( ( tmp >> 8 ) | 0x40000000 );
638
639                 buffer++;
640                 target_event += m_dimension;
641             }
642         }
643         break;
644     }
645
646     return 0;
647 }
648 int AmdtpTransmitStreamProcessor::encodeSilencePortToMBLAEvents ( AmdtpAudioPort *p, quadlet_t *data,
649         unsigned int offset, unsigned int nevents )
650 {
651     unsigned int j=0;
652
653     quadlet_t *target_event;
654
655     target_event= ( quadlet_t * ) ( data + p->getPosition() );
656
657     switch ( p->getDataType() )
658     {
659         default:
660         case Port::E_Int24:
661         case Port::E_Float:
662         {
663             for ( j = 0; j < nevents; j += 1 )   // decode max nsamples
664             {
665                 *target_event = htonl ( 0x40000000 );
666                 target_event += m_dimension;
667             }
668         }
669         break;
670     }
671
672     return 0;
673 }
674
675 } // end of namespace Streaming
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