/*****************************************************************************
* input_clock.c: Clock/System date convertions, stream management
*****************************************************************************
* Copyright (C) 1999, 2000 VideoLAN
* $Id: input_clock.c,v 1.18 2001/06/27 09:53:57 massiot Exp $
*
* Authors: Christophe Massiot <massiot@via.ecp.fr>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
*****************************************************************************/
/*****************************************************************************
* Preamble
*****************************************************************************/
#include "defs.h"
#include <string.h> /* memcpy(), memset() */
#include <sys/types.h> /* off_t */
#include "config.h"
#include "common.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.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
/* Maximum gap allowed between two CRs. */
#define CR_MAX_GAP 1000000
/*****************************************************************************
* ClockToSysdate: converts a movie clock to system date
*****************************************************************************/
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 = (mtime_t)(i_clock - p_pgrm->cr_ref)
* (mtime_t)p_input->stream.control.i_rate
* (mtime_t)300
/ (mtime_t)27
/ (mtime_t)DEFAULT_RATE
+ (mtime_t)p_pgrm->sysdate_ref;
}
return( i_sysdate );
}
/*****************************************************************************
* 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
*****************************************************************************/
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 = p_pgrm->last_syscr ? 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 );
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_pgrm );
}
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.pp_programs[0] == 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.pp_programs[0] == p_pgrm )
{
/* Wait a while before delivering the packets to the decoder.
* In case of multiple programs, we arbitrarily follow the
* clock of the first program. */
p_pgrm->last_syscr = ClockToSysdate( p_input, p_pgrm, i_clock );
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 );
}
else
{
return 0;
}
}