1 /*****************************************************************************
2 * input_clock.c: Clock/System date convertions, stream management
3 *****************************************************************************
4 * Copyright (C) 1999-2004 VideoLAN (Centrale Réseaux) and its contributors
7 * Authors: Christophe Massiot <massiot@via.ecp.fr>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
22 *****************************************************************************/
24 /*****************************************************************************
26 *****************************************************************************/
30 #include <vlc/input.h>
31 #include "input_internal.h"
34 * DISCUSSION : SYNCHRONIZATION METHOD
36 * In some cases we can impose the pace of reading (when reading from a
37 * file or a pipe), and for the synchronization we simply sleep() until
38 * it is time to deliver the packet to the decoders. When reading from
39 * the network, we must be read at the same pace as the server writes,
40 * otherwise the kernel's buffer will trash packets. The risk is now to
41 * overflow the input buffers in case the server goes too fast, that is
42 * why we do these calculations :
44 * We compute a mean for the pcr because we want to eliminate the
45 * network jitter and keep the low frequency variations. The mean is
46 * in fact a low pass filter and the jitter is a high frequency signal
47 * that is why it is eliminated by the filter/average.
49 * The low frequency variations enable us to synchronize the client clock
50 * with the server clock because they represent the time variation between
51 * the 2 clocks. Those variations (ie the filtered pcr) are used to compute
52 * the presentation dates for the audio and video frames. With those dates
53 * we can decode (or trash) the MPEG2 stream at "exactly" the same rate
54 * as it is sent by the server and so we keep the synchronization between
55 * the server and the client.
57 * It is a very important matter if you want to avoid underflow or overflow
58 * in all the FIFOs, but it may be not enough.
61 /* p_input->i_cr_average : Maximum number of samples used to compute the
62 * dynamic average value.
63 * We use the following formula :
64 * new_average = (old_average * c_average + new_sample_value) / (c_average +1)
68 static void ClockNewRef( input_clock_t * p_pgrm,
69 mtime_t i_clock, mtime_t i_sysdate );
71 /*****************************************************************************
73 *****************************************************************************/
75 /* Maximum gap allowed between two CRs. */
76 #define CR_MAX_GAP 2000000
78 /* Latency introduced on DVDs with CR == 0 on chapter change - this is from
80 #define CR_MEAN_PTS_GAP 300000
82 /*****************************************************************************
83 * ClockToSysdate: converts a movie clock to system date
84 *****************************************************************************/
85 static mtime_t ClockToSysdate( input_thread_t *p_input,
86 input_clock_t *cl, mtime_t i_clock )
88 mtime_t i_sysdate = 0;
90 if( cl->i_synchro_state == SYNCHRO_OK )
92 i_sysdate = (mtime_t)(i_clock - cl->cr_ref)
93 * (mtime_t)p_input->i_rate
97 i_sysdate += (mtime_t)cl->sysdate_ref;
103 /*****************************************************************************
104 * ClockCurrent: converts current system date to clock units
105 *****************************************************************************
106 * Caution : the synchro state must be SYNCHRO_OK for this to operate.
107 *****************************************************************************/
108 static mtime_t ClockCurrent( input_thread_t *p_input,
111 return( (mdate() - cl->sysdate_ref) * 27 * INPUT_RATE_DEFAULT
112 / p_input->i_rate / 300
116 /*****************************************************************************
117 * ClockNewRef: writes a new clock reference
118 *****************************************************************************/
119 static void ClockNewRef( input_clock_t *cl,
120 mtime_t i_clock, mtime_t i_sysdate )
122 cl->cr_ref = i_clock;
123 cl->sysdate_ref = i_sysdate ;
126 /*****************************************************************************
127 * input_ClockInit: reinitializes the clock reference after a stream
129 *****************************************************************************/
130 void input_ClockInit( input_clock_t *cl, vlc_bool_t b_master, int i_cr_average )
132 cl->i_synchro_state = SYNCHRO_START;
139 cl->c_average_count = 0;
141 cl->i_cr_average = i_cr_average;
143 cl->b_master = b_master;
147 /*****************************************************************************
148 * input_ClockManageControl: handles the messages from the interface
149 *****************************************************************************
150 * Returns UNDEF_S if nothing happened, PAUSE_S if the stream was paused
151 *****************************************************************************/
152 int input_ClockManageControl( input_thread_t * p_input,
153 input_clock_t *cl, mtime_t i_clock )
157 int i_return_value = UNDEF_S;
159 vlc_mutex_lock( &p_input->stream.stream_lock );
161 if( p_input->stream.i_new_status == PAUSE_S )
165 vlc_mutex_lock( &p_input->stream.control.control_lock );
166 i_old_status = p_input->stream.control.i_status;
167 p_input->stream.control.i_status = PAUSE_S;
168 vlc_mutex_unlock( &p_input->stream.control.control_lock );
170 vlc_cond_wait( &p_input->stream.stream_wait,
171 &p_input->stream.stream_lock );
172 ClockNewRef( p_pgrm, i_clock, p_pgrm->last_pts > mdate() ?
173 p_pgrm->last_pts : mdate() );
175 if( p_input->stream.i_new_status == PAUSE_S )
177 /* PAUSE_S undoes the pause state: Return to old state. */
178 vlc_mutex_lock( &p_input->stream.control.control_lock );
179 p_input->stream.control.i_status = i_old_status;
180 vlc_mutex_unlock( &p_input->stream.control.control_lock );
182 p_input->stream.i_new_status = UNDEF_S;
183 p_input->stream.i_new_rate = UNDEF_S;
186 /* We handle i_new_status != PAUSE_S below... */
188 i_return_value = PAUSE_S;
191 if( p_input->stream.i_new_status != UNDEF_S )
193 vlc_mutex_lock( &p_input->stream.control.control_lock );
195 p_input->stream.control.i_status = p_input->stream.i_new_status;
197 ClockNewRef( p_pgrm, i_clock,
198 ClockToSysdate( p_input, p_pgrm, i_clock ) );
200 if( p_input->stream.control.i_status == PLAYING_S )
202 p_input->stream.control.i_rate = DEFAULT_RATE;
203 p_input->stream.control.b_mute = 0;
207 p_input->stream.control.i_rate = p_input->stream.i_new_rate;
208 p_input->stream.control.b_mute = 1;
210 /* Feed the audio decoders with a NULL packet to avoid
211 * discontinuities. */
212 input_EscapeAudioDiscontinuity( p_input );
215 val.i_int = p_input->stream.control.i_rate;
216 var_Change( p_input, "rate", VLC_VAR_SETVALUE, &val, NULL );
218 val.i_int = p_input->stream.control.i_status;
219 var_Change( p_input, "state", VLC_VAR_SETVALUE, &val, NULL );
221 p_input->stream.i_new_status = UNDEF_S;
222 p_input->stream.i_new_rate = UNDEF_S;
224 vlc_mutex_unlock( &p_input->stream.control.control_lock );
227 vlc_mutex_unlock( &p_input->stream.stream_lock );
229 return( i_return_value );
235 /*****************************************************************************
236 * input_ClockSetPCR: manages a clock reference
237 *****************************************************************************/
238 void input_ClockSetPCR( input_thread_t *p_input,
239 input_clock_t *cl, mtime_t i_clock )
241 if( ( cl->i_synchro_state != SYNCHRO_OK ) ||
242 ( i_clock == 0 && cl->last_cr != 0 ) )
244 /* Feed synchro with a new reference point. */
245 ClockNewRef( cl, i_clock,
246 cl->last_pts + CR_MEAN_PTS_GAP > mdate() ?
247 cl->last_pts + CR_MEAN_PTS_GAP : mdate() );
248 cl->i_synchro_state = SYNCHRO_OK;
250 if( p_input->b_can_pace_control && cl->b_master )
252 cl->last_cr = i_clock;
253 if( !p_input->b_out_pace_control )
255 mtime_t i_wakeup = ClockToSysdate( p_input, cl, i_clock );
256 while( (i_wakeup - mdate()) / CLOCK_FREQ > 1 )
258 msleep( CLOCK_FREQ );
259 if( p_input->b_die ) i_wakeup = mdate();
268 cl->c_average_count = 0;
273 if ( cl->last_cr != 0 &&
274 ( (cl->last_cr - i_clock) > CR_MAX_GAP
275 || (cl->last_cr - i_clock) < - CR_MAX_GAP ) )
277 /* Stream discontinuity, for which we haven't received a
278 * warning from the stream control facilities (dd-edited
280 msg_Warn( p_input, "clock gap, unexpected stream discontinuity" );
281 input_ClockInit( cl, cl->b_master, cl->i_cr_average );
284 input_EscapeDiscontinuity( p_input );
288 cl->last_cr = i_clock;
290 if( p_input->b_can_pace_control && cl->b_master )
292 /* Wait a while before delivering the packets to the decoder.
293 * In case of multiple programs, we arbitrarily follow the
294 * clock of the selected program. */
295 if( !p_input->b_out_pace_control )
297 mtime_t i_wakeup = ClockToSysdate( p_input, cl, i_clock );
298 while( (i_wakeup - mdate()) / CLOCK_FREQ > 1 )
300 msleep( CLOCK_FREQ );
301 if( p_input->b_die ) i_wakeup = mdate();
305 /* FIXME Not needed anymore ? */
307 /* Now take into account interface changes. */
308 input_ClockManageControl( p_input, cl, i_clock );
313 /* Smooth clock reference variations. */
314 mtime_t i_extrapoled_clock = ClockCurrent( p_input, cl );
316 /* Bresenham algorithm to smooth variations. */
317 cl->delta_cr = ( cl->delta_cr * (cl->i_cr_average - 1)
318 + ( i_extrapoled_clock - i_clock ) )
324 /*****************************************************************************
325 * input_ClockGetTS: manages a PTS or DTS
326 *****************************************************************************/
327 mtime_t input_ClockGetTS( input_thread_t * p_input,
328 input_clock_t *cl, mtime_t i_ts )
330 if( cl->i_synchro_state != SYNCHRO_OK )
333 cl->last_pts = ClockToSysdate( p_input, cl, i_ts + cl->delta_cr );
334 return cl->last_pts + p_input->i_pts_delay;