/*****************************************************************************
- * input_clock.c: Clock/System date conversions, stream management
+ * input_clock.c: Clock/System date convertions, stream management
*****************************************************************************
- * Copyright (C) 1999, 2000 VideoLAN
- * $Id: input_clock.c,v 1.1 2001/01/24 19:05:55 massiot Exp $
+ * Copyright (C) 1999-2001 VideoLAN
+ * $Id: input_clock.c,v 1.27 2001/12/07 18:33:08 sam Exp $
*
* Authors: Christophe Massiot <massiot@via.ecp.fr>
*
*****************************************************************************/
#include "defs.h"
-#include "config.h"
+#include <string.h> /* memcpy(), memset() */
+#include <sys/types.h> /* off_t */
+
#include "common.h"
+#include "intf_msg.h"
#include "threads.h"
#include "mtime.h"
-#include "intf_msg.h"
#include "stream_control.h"
#include "input_ext-intf.h"
#include "input_ext-dec.h"
+#include "input_ext-plugins.h"
+
+/*
+ * DISCUSSION : SYNCHRONIZATION METHOD
+ *
+ * In some cases we can impose the pace of reading (when reading from a
+ * file or a pipe), and for the synchronization we simply sleep() until
+ * it is time to deliver the packet to the decoders. When reading from
+ * the network, we must be read at the same pace as the server writes,
+ * otherwise the kernel's buffer will trash packets. The risk is now to
+ * overflow the input buffers in case the server goes too fast, that is
+ * why we do these calculations :
+ *
+ * We compute a mean for the pcr because we want to eliminate the
+ * network jitter and keep the low frequency variations. The mean is
+ * in fact a low pass filter and the jitter is a high frequency signal
+ * that is why it is eliminated by the filter/average.
+ *
+ * The low frequency variations enable us to synchronize the client clock
+ * with the server clock because they represent the time variation between
+ * the 2 clocks. Those variations (ie the filtered pcr) are used to compute
+ * the presentation dates for the audio and video frames. With those dates
+ * we can decode (or trash) the MPEG2 stream at "exactly" the same rate
+ * as it is sent by the server and so we keep the synchronization between
+ * the server and the client.
+ *
+ * It is a very important matter if you want to avoid underflow or overflow
+ * in all the FIFOs, but it may be not enough.
+ */
+
+/*****************************************************************************
+ * Constants
+ *****************************************************************************/
+
+/* Maximum number of samples used to compute the dynamic average value.
+ * We use the following formula :
+ * new_average = (old_average * c_average + new_sample_value) / (c_average +1)
+ */
+#define CR_MAX_AVERAGE_COUNTER 40
-#include "input.h"
+/* Maximum gap allowed between two CRs. */
+#define CR_MAX_GAP 1000000
/*****************************************************************************
- * input_ClockToSysdate: converts a movie clock to system date
+ * ClockToSysdate: converts a movie clock to system date
*****************************************************************************/
-mtime_t input_ClockToSysdate( input_thread_t * p_input,
- pgrm_descriptor_t * p_pgrm, mtime_t i_clock )
+static void ClockNewRef( input_thread_t * p_input, pgrm_descriptor_t * p_pgrm,
+ mtime_t i_clock, mtime_t i_sysdate );
+static mtime_t ClockToSysdate( input_thread_t * p_input,
+ pgrm_descriptor_t * p_pgrm, mtime_t i_clock )
{
mtime_t i_sysdate = 0;
if( p_pgrm->i_synchro_state == SYNCHRO_OK )
{
- i_sysdate = (i_clock - p_pgrm->cr_ref)
- * p_input->stream.control.i_rate
- * 300
- / 27
- / DEFAULT_RATE
- + p_pgrm->sysdate_ref;
+ i_sysdate = (mtime_t)(i_clock - p_pgrm->cr_ref)
+ * (mtime_t)p_input->stream.control.i_rate
+ * (mtime_t)300;
+ i_sysdate /= 27;
+ i_sysdate /= 1000;
+ i_sysdate += (mtime_t)p_pgrm->sysdate_ref;
}
return( i_sysdate );
}
/*****************************************************************************
- * input_ClockNewRef: writes a new clock reference
+ * ClockCurrent: converts current system date to clock units
+ *****************************************************************************
+ * Caution : the synchro state must be SYNCHRO_OK for this to operate.
+ *****************************************************************************/
+static mtime_t ClockCurrent( input_thread_t * p_input,
+ pgrm_descriptor_t * p_pgrm )
+{
+ return( (mdate() - p_pgrm->sysdate_ref) * 27 * DEFAULT_RATE
+ / p_input->stream.control.i_rate / 300
+ + p_pgrm->cr_ref );
+}
+
+/*****************************************************************************
+ * ClockNewRef: writes a new clock reference
*****************************************************************************/
-void input_ClockNewRef( input_thread_t * p_input, pgrm_descriptor_t * p_pgrm,
- mtime_t i_clock )
+static void ClockNewRef( input_thread_t * p_input, pgrm_descriptor_t * p_pgrm,
+ mtime_t i_clock, mtime_t i_sysdate )
{
p_pgrm->cr_ref = i_clock;
- p_pgrm->sysdate_ref = mdate();
+ /* this is actually a kludge, but it gives better results when scr
+ * is zero in DVDs: we are 3-4 ms in advance instead of sometimes
+ * 100ms late */
+ p_pgrm->sysdate_ref = ( p_pgrm->last_syscr && !i_clock )
+ ? p_pgrm->last_syscr
+ : i_sysdate ;
+}
+
+/*****************************************************************************
+ * input_ClockInit: reinitializes the clock reference after a stream
+ * discontinuity
+ *****************************************************************************/
+void input_ClockInit( pgrm_descriptor_t * p_pgrm )
+{
+ p_pgrm->last_cr = 0;
+ p_pgrm->last_syscr = 0;
+ p_pgrm->cr_ref = 0;
+ p_pgrm->sysdate_ref = 0;
+ p_pgrm->delta_cr = 0;
+ p_pgrm->c_average_count = 0;
+}
+
+/*****************************************************************************
+ * input_ClockManageControl: handles the messages from the interface
+ *****************************************************************************
+ * Returns UNDEF_S if nothing happened, PAUSE_S if the stream was paused
+ *****************************************************************************/
+int input_ClockManageControl( input_thread_t * p_input,
+ pgrm_descriptor_t * p_pgrm, mtime_t i_clock )
+{
+ int i_return_value = UNDEF_S;
+
+ vlc_mutex_lock( &p_input->stream.stream_lock );
+
+ if( p_input->stream.i_new_status == PAUSE_S )
+ {
+ int i_old_status;
+ vlc_mutex_lock( &p_input->stream.control.control_lock );
+ i_old_status = p_input->stream.control.i_status;
+
+ p_input->stream.control.i_status = PAUSE_S;
+ vlc_cond_wait( &p_input->stream.stream_wait,
+ &p_input->stream.stream_lock );
+ p_pgrm->last_syscr = 0;
+ ClockNewRef( p_input, p_pgrm, i_clock, mdate() );
+
+ if( p_input->stream.i_new_status == PAUSE_S )
+ {
+ /* PAUSE_S undoes the pause state: Return to old state. */
+ p_input->stream.control.i_status = i_old_status;
+ p_input->stream.i_new_status = UNDEF_S;
+ p_input->stream.i_new_rate = UNDEF_S;
+ }
+
+ /* We handle i_new_status != PAUSE_S below... */
+ vlc_mutex_unlock( &p_input->stream.control.control_lock );
+
+ i_return_value = PAUSE_S;
+ }
+
+ if( p_input->stream.i_new_status != UNDEF_S )
+ {
+ vlc_mutex_lock( &p_input->stream.control.control_lock );
+
+ p_input->stream.control.i_status = p_input->stream.i_new_status;
+
+ ClockNewRef( p_input, p_pgrm, i_clock,
+ ClockToSysdate( p_input, p_pgrm, i_clock ) );
+
+ if( p_input->stream.control.i_status == PLAYING_S )
+ {
+ p_input->stream.control.i_rate = DEFAULT_RATE;
+ p_input->stream.control.b_mute = 0;
+ }
+ else
+ {
+ p_input->stream.control.i_rate = p_input->stream.i_new_rate;
+ p_input->stream.control.b_mute = 1;
+
+ /* Feed the audio decoders with a NULL packet to avoid
+ * discontinuities. */
+ input_EscapeAudioDiscontinuity( p_input );
+ }
+
+ p_input->stream.i_new_status = UNDEF_S;
+ p_input->stream.i_new_rate = UNDEF_S;
+
+ vlc_mutex_unlock( &p_input->stream.control.control_lock );
+ }
+
+ vlc_mutex_unlock( &p_input->stream.stream_lock );
+
+ return( i_return_value );
+}
+
+/*****************************************************************************
+ * input_ClockManageRef: manages a clock reference
+ *****************************************************************************/
+void input_ClockManageRef( input_thread_t * p_input,
+ pgrm_descriptor_t * p_pgrm, mtime_t i_clock )
+{
+ if( ( p_pgrm->i_synchro_state != SYNCHRO_OK ) || ( i_clock == 0 ) )
+ {
+ /* Feed synchro with a new reference point. */
+ ClockNewRef( p_input, p_pgrm, i_clock, mdate() );
+ p_pgrm->i_synchro_state = SYNCHRO_OK;
+
+ if( p_input->stream.b_pace_control
+ && p_input->stream.p_selected_program == p_pgrm )
+ {
+ p_pgrm->last_cr = i_clock;
+ mwait( ClockToSysdate( p_input, p_pgrm, i_clock ) );
+ }
+ else
+ {
+ p_pgrm->last_cr = 0;
+ p_pgrm->last_syscr = 0;
+ p_pgrm->delta_cr = 0;
+ p_pgrm->c_average_count = 0;
+ }
+ }
+ else
+ {
+ if ( p_pgrm->last_cr != 0 &&
+ ( (p_pgrm->last_cr - i_clock) > CR_MAX_GAP
+ || (p_pgrm->last_cr - i_clock) < - CR_MAX_GAP ) )
+ {
+ /* Stream discontinuity, for which we haven't received a
+ * warning from the stream control facilities (dd-edited
+ * stream ?). */
+ intf_WarnMsg( 1, "Clock gap, unexpected stream discontinuity" );
+ input_ClockInit( p_pgrm );
+ p_pgrm->i_synchro_state = SYNCHRO_START;
+ input_EscapeDiscontinuity( p_input, p_pgrm );
+ }
+
+ p_pgrm->last_cr = i_clock;
+
+ if( p_input->stream.b_pace_control
+ && p_input->stream.p_selected_program == p_pgrm )
+ {
+ /* We remember the last system date to be able to restart
+ * the synchro we statistically better continuity, after
+ * a zero scr */
+ p_pgrm->last_syscr = ClockToSysdate( p_input, p_pgrm, i_clock );
+
+ /* Wait a while before delivering the packets to the decoder.
+ * In case of multiple programs, we arbitrarily follow the
+ * clock of the first program. */
+ mwait( p_pgrm->last_syscr );
+
+ /* Now take into account interface changes. */
+ input_ClockManageControl( p_input, p_pgrm, i_clock );
+ }
+ else
+ {
+ /* Smooth clock reference variations. */
+ mtime_t i_extrapoled_clock = ClockCurrent( p_input, p_pgrm );
+
+ /* Bresenham algorithm to smooth variations. */
+ if( p_pgrm->c_average_count == CR_MAX_AVERAGE_COUNTER )
+ {
+ p_pgrm->delta_cr = ( p_pgrm->delta_cr
+ * (CR_MAX_AVERAGE_COUNTER - 1)
+ + ( i_extrapoled_clock - i_clock ) )
+ / CR_MAX_AVERAGE_COUNTER;
+ }
+ else
+ {
+ p_pgrm->delta_cr = ( p_pgrm->delta_cr
+ * p_pgrm->c_average_count
+ + ( i_extrapoled_clock - i_clock ) )
+ / (p_pgrm->c_average_count + 1);
+ p_pgrm->c_average_count++;
+ }
+ }
+ }
+}
+
+/*****************************************************************************
+ * input_ClockGetTS: manages a PTS or DTS
+ *****************************************************************************/
+mtime_t input_ClockGetTS( input_thread_t * p_input,
+ pgrm_descriptor_t * p_pgrm, mtime_t i_ts )
+{
+ if( p_pgrm->i_synchro_state == SYNCHRO_OK )
+ {
+ return( ClockToSysdate( p_input, p_pgrm, i_ts + p_pgrm->delta_cr )
+ + DEFAULT_PTS_DELAY
+ + (p_main->i_desync > 0 ? p_main->i_desync : 0) );
+ }
+ else
+ {
+ return 0;
+ }
}