root/trunk/libffado/src/libutil/TimestampedBuffer.cpp

/*
 * Copyright (C) 2005-2007 by Pieter Palmers
 *
 * This file is part of FFADO
 * FFADO = Free Firewire (pro-)audio drivers for linux
 *
 * FFADO is based upon FreeBoB.
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */

#include "libutil/Atomic.h"
#include "libieee1394/cycletimer.h"

#include "TimestampedBuffer.h"
#include "assert.h"

// FIXME: note that it will probably be better to use a DLL bandwidth that is 
//        dependant on the sample rate


// #define DLL_BANDWIDTH (4800/48000.0)
#define DLL_BANDWIDTH (0.01)
#define DLL_PI        (3.141592653589793238)
#define DLL_SQRT2     (1.414213562373095049)
#define DLL_OMEGA     (2.0*DLL_PI*DLL_BANDWIDTH)
#define DLL_COEFF_B   (DLL_SQRT2 * DLL_OMEGA)
#define DLL_COEFF_C   (DLL_OMEGA * DLL_OMEGA)

#define ENTER_CRITICAL_SECTION { \
    pthread_mutex_lock(&m_framecounter_lock); \
    }
#define EXIT_CRITICAL_SECTION { \
    pthread_mutex_unlock(&m_framecounter_lock); \
    }

namespace Util {

IMPL_DEBUG_MODULE( TimestampedBuffer, TimestampedBuffer, DEBUG_LEVEL_VERBOSE );

TimestampedBuffer::TimestampedBuffer(TimestampedBufferClient *c)
    : m_event_buffer(NULL), m_cluster_buffer(NULL),
      m_event_size(0), m_events_per_frame(0), m_buffer_size(0),
      m_bytes_per_frame(0), m_bytes_per_buffer(0),
      m_enabled( false ), m_transparent ( true ),
      m_wrap_at(0xFFFFFFFFFFFFFFFFLLU),
      m_Client(c), m_framecounter(0),
      m_tick_offset(0.0),
      m_buffer_tail_timestamp(0.0),
      m_buffer_next_tail_timestamp(0.0),
      m_dll_e2(0.0), m_dll_b(DLL_COEFF_B), m_dll_c(DLL_COEFF_C),
      m_nominal_rate(0.0), m_update_period(0)
{
    pthread_mutex_init(&m_framecounter_lock, NULL);

}

TimestampedBuffer::~TimestampedBuffer() {
    ffado_ringbuffer_free(m_event_buffer);
    free(m_cluster_buffer);
}

/**
 * \brief Set the nominal rate in frames/timeunit
 *
 * Sets the nominal rate in frames per time unit. This rate is used
 * to initialize the DLL that will extract the effective rate based
 * upon the timestamps it gets fed.
 *
 * @param r rate
 * @return true if successful
 */
bool TimestampedBuffer::setNominalRate(float r) {
    m_nominal_rate=r;
    debugOutput(DEBUG_LEVEL_VERBOSE," nominal rate=%e set to %e\n",
                                    m_nominal_rate, r);
    return true;
}

/**
 * \brief Set the nominal update period (in frames)
 *
 * Sets the nominal update period. This period is the number of frames
 * between two timestamp updates (hence buffer writes)
 *
 * @param n period in frames
 * @return true if successful
 */
bool TimestampedBuffer::setUpdatePeriod(unsigned int n) {
    m_update_period=n;
    return true;
}

/**
 * \brief set the value at which timestamps should wrap around
 * @param w value to wrap at
 * @return true if successful
 */
bool TimestampedBuffer::setWrapValue(ffado_timestamp_t w) {
    m_wrap_at=w;
    return true;
}
#include <math.h>

/**
 * \brief return the effective rate
 *
 * Returns the effective rate calculated by the DLL.
 *
 * @return rate (in timeunits/frame)
 */
float TimestampedBuffer::getRate() {
    ffado_timestamp_t diff;
    
    ENTER_CRITICAL_SECTION;
    diff=m_buffer_next_tail_timestamp - m_buffer_tail_timestamp;
    EXIT_CRITICAL_SECTION;
    
    debugOutput(DEBUG_LEVEL_VERY_VERBOSE,"getRate: %f/%f=%f\n",
        (float)(diff),
        (float)m_update_period,
        ((float)(diff))/((float) m_update_period));
    
    // the maximal difference we can allow (64secs)
    const ffado_timestamp_t max=m_wrap_at/((ffado_timestamp_t)2);

    if(diff > max) {
        diff -= m_wrap_at;
    } else if (diff < -max) {
        diff += m_wrap_at;
    }

    float rate=((float)diff)/((float) m_update_period);
    if (rate<0.0) debugError("rate < 0! (%f)\n",rate);
    if (fabsf(m_nominal_rate - rate)>(m_nominal_rate*0.1)) {
        debugWarning("(%p) rate (%10.5f) more that 10%% off nominal (rate=%10.5f, diff="TIMESTAMP_FORMAT_SPEC", update_period=%d)\n",
                     this, rate,m_nominal_rate,diff, m_update_period);

        return m_nominal_rate;
    } else {
        return rate;
    }
}

/**
 * \brief Sets the size of the events
 * @param s event size in bytes
 * @return true if successful
 */
bool TimestampedBuffer::setEventSize(unsigned int s) {
    m_event_size=s;

    m_bytes_per_frame=m_event_size*m_events_per_frame;
    m_bytes_per_buffer=m_bytes_per_frame*m_buffer_size;

    return true;
}

/**
 * \brief Sets the number of events per frame
 * @param n number of events per frame
 * @return true if successful
 */
bool TimestampedBuffer::setEventsPerFrame(unsigned int n) {
    m_events_per_frame=n;

    m_bytes_per_frame=m_event_size*m_events_per_frame;
    m_bytes_per_buffer=m_bytes_per_frame*m_buffer_size;

    return true;
}
/**
 * \brief Sets the buffer size in frames
 * @param n number frames
 * @return true if successful
 */
bool TimestampedBuffer::setBufferSize(unsigned int n) {
    m_buffer_size=n;

    m_bytes_per_frame=m_event_size*m_events_per_frame;
    m_bytes_per_buffer=m_bytes_per_frame*m_buffer_size;

    return true;
}

/**
 * Sets the buffer offset in ticks.
 *
 * A positive value means that the buffer is 'delayed' for nticks ticks.
 *
 * @note These offsets are only used when reading timestamps. Any function
 *       that returns a timestamp will incorporate this offset.
 * @param nframes the number of ticks (positive = delay buffer)
 * @return true if successful
 */
bool TimestampedBuffer::setTickOffset(ffado_timestamp_t nticks) {
    debugOutput(DEBUG_LEVEL_VERBOSE,"Setting ticks offset to "TIMESTAMP_FORMAT_SPEC"\n",nticks);

    // JMW: I think we need to update the internal DLL state to take account
    // of the new offset.  Doing so certainly makes for a smoother MOTU
    // startup.
    ENTER_CRITICAL_SECTION;
    m_buffer_tail_timestamp = m_buffer_tail_timestamp - m_tick_offset + nticks;
    m_buffer_next_tail_timestamp = (ffado_timestamp_t)((double)m_buffer_tail_timestamp + m_dll_e2);
    m_tick_offset=nticks;
    EXIT_CRITICAL_SECTION;

    return true;
}

/**
 * \brief Returns the current fill of the buffer
 *
 * This returns the buffer fill of the internal ringbuffer. This
 * can only be used as an indication because it's state is not
 * guaranteed to be consistent at all times due to threading issues.
 *
 * In order to get the number of frames in the buffer, use the
 * getBufferHeadTimestamp, getBufferTailTimestamp
 * functions
 *
 * @return the internal buffer fill in frames
 */
unsigned int TimestampedBuffer::getBufferFill() {
    return ffado_ringbuffer_read_space(m_event_buffer)/(m_bytes_per_frame);
}

/**
 * \brief Initializes the TimestampedBuffer
 *
 * Initializes the TimestampedBuffer, should be called before anything else
 * is done.
 *
 * @return true if successful
 */
bool TimestampedBuffer::init() {
    return true;
}

/**
 * \brief Resets the TimestampedBuffer
 *
 * Resets the TimestampedBuffer, clearing the buffers and counters.
 * (not true yet: Also resets the DLL to the nominal values.)
 *
 * \note when this is called, you should make sure that the buffer
 *       tail timestamp gets set before continuing
 *
 * @return true if successful
 */
bool TimestampedBuffer::clearBuffer() {
    debugOutput(DEBUG_LEVEL_VERBOSE, "Clearing buffer\n");
    ffado_ringbuffer_reset(m_event_buffer);
    resetFrameCounter();
    return true;
}

/**
 * \brief Prepares the TimestampedBuffer
 *
 * Prepare the TimestampedBuffer. This allocates all internal buffers and
 * initializes all data structures.
 *
 * This should be called after parameters such as buffer size, event size etc.. are set,
 * and before any read/write operations are performed.
 *
 * @return true if successful
 */
bool TimestampedBuffer::prepare() {
    debugOutput(DEBUG_LEVEL_VERBOSE,"Preparing buffer (%p)\n",this);
    debugOutput(DEBUG_LEVEL_VERBOSE," Size=%u events, events/frame=%u, event size=%ubytes\n",
                                        m_buffer_size,m_events_per_frame,m_event_size);

    debugOutput(DEBUG_LEVEL_VERBOSE," update period %u\n",
                                    m_update_period);
    debugOutput(DEBUG_LEVEL_VERBOSE," nominal rate=%f\n",
                                    m_nominal_rate);

    debugOutput(DEBUG_LEVEL_VERBOSE," wrapping at "TIMESTAMP_FORMAT_SPEC"\n",m_wrap_at);

    assert(m_buffer_size);
    assert(m_events_per_frame);
    assert(m_event_size);

    assert(m_nominal_rate != 0.0L);
    assert(m_update_period != 0);

    if( !(m_event_buffer=ffado_ringbuffer_create(
            (m_events_per_frame * m_buffer_size) * m_event_size))) {
        debugFatal("Could not allocate memory event ringbuffer\n");
        return false;
    }

    // allocate the temporary cluster buffer
    if( !(m_cluster_buffer=(char *)calloc(m_events_per_frame,m_event_size))) {
            debugFatal("Could not allocate temporary cluster buffer\n");
        ffado_ringbuffer_free(m_event_buffer);
        return false;
    }

    // init the DLL
    m_dll_e2=m_nominal_rate * (float)m_update_period;

    m_dll_b=((float)(DLL_COEFF_B));
    m_dll_c=((float)(DLL_COEFF_C));
    
    // this will init the internal timestamps to a sensible value
    setBufferTailTimestamp(m_buffer_tail_timestamp);
    
    return true;
}

/**
 * @brief Insert a dummy frame to the head buffer
 *
 * Writes one frame of dummy data to the head of the buffer.
 * This is to assist the phase sync of several buffers.
 * 
 * Note: currently the dummy data is added to the tail of the
 *       buffer, but without updating the timestamp.
 *
 * @return true if successful
 */
bool TimestampedBuffer::writeDummyFrame() {

    unsigned int write_size=m_event_size*m_events_per_frame;
    
    char dummy[write_size]; // one frame of garbage
    memset(dummy,0,write_size);

    // add the data payload to the ringbuffer
    if (ffado_ringbuffer_write(m_event_buffer,dummy,write_size) < write_size)
    {
//         debugWarning("writeFrames buffer overrun\n");
        return false;
    }

//     incrementFrameCounter(nframes,ts);
    
    // increment without updating the DLL
    ENTER_CRITICAL_SECTION;
    m_framecounter++;
    EXIT_CRITICAL_SECTION;
    
    return true;
}

/**
 * @brief Write frames to the buffer
 *
 * Copies \ref nframes of frames from the buffer pointed to by \ref data to the
 * internal ringbuffer. The time of the last frame in the buffer is set to \ref ts.
 *
 * @param nframes number of frames to copy
 * @param data pointer to the frame buffer
 * @param ts timestamp of the last frame copied
 * @return true if successful
 */
bool TimestampedBuffer::writeFrames(unsigned int nframes, char *data, ffado_timestamp_t ts) {

    unsigned int write_size=nframes*m_event_size*m_events_per_frame;

    if (m_transparent) {
        // while disabled, we don't update the DLL, nor do we write frames
        // we just set the correct timestamp for the frames
        setBufferTailTimestamp(ts);
    } else {
        // add the data payload to the ringbuffer
        size_t written = ffado_ringbuffer_write(m_event_buffer, data, write_size);
        if (written < write_size)
        {
            debugWarning("ringbuffer full, %u, %u\n", write_size, written);
            return false;
        }
        incrementFrameCounter(nframes,ts);
    }
    return true;
}

/**
 * @brief Preload frames into the buffer
 *
 * Preload \ref nframes of frames from the buffer pointed to by \ref data to the
 * internal ringbuffer. Does not care about transparency. Keeps the buffer head or tail
 * timestamp constant.
 *
 * @note not thread safe
 *
 * @param nframes number of frames to copy
 * @param data pointer to the frame buffer
 * @param keep_head_ts if true, keep the head timestamp constant. If false, keep the
 *                     tail timestamp constant.
 * @return true if successful
 */
bool TimestampedBuffer::preloadFrames(unsigned int nframes, char *data, bool keep_head_ts) {
    unsigned int write_size = nframes * m_event_size * m_events_per_frame;
    // add the data payload to the ringbuffer
    size_t written = ffado_ringbuffer_write(m_event_buffer, data, write_size);
    if (written < write_size)
    {
        debugWarning("ringbuffer full, request: %u, actual: %u\n", write_size, written);
        return false;
    }
    
    // make sure the head timestamp remains identical
    signed int fc;
    ffado_timestamp_t ts;

    if (keep_head_ts) {
        getBufferHeadTimestamp(&ts, &fc);
    } else {
        getBufferTailTimestamp(&ts, &fc);
    }
    // update frame counter
    m_framecounter += nframes;
    if (keep_head_ts) {
        setBufferHeadTimestamp(ts);
    } else {
        setBufferTailTimestamp(ts);
    }

    return true;
}

/**
 * @brief Drop frames from the head of the buffer
 *
 * drops \ref nframes of frames from the head of internal buffer
 *
 * @param nframes number of frames to drop
 * @return true if successful
 */
bool
TimestampedBuffer::dropFrames(unsigned int nframes) {
    unsigned int read_size = nframes * m_event_size * m_events_per_frame;
    ffado_ringbuffer_read_advance(m_event_buffer, read_size);
    decrementFrameCounter(nframes);
    return true;
}

/**
 * @brief Read frames from the buffer
 *
 * Copies \ref nframes of frames from the internal buffer to the data buffer pointed
 * to by \ref data.
 *
 * @param nframes number of frames to copy
 * @param data pointer to the frame buffer
 * @return true if successful
 */
bool TimestampedBuffer::readFrames(unsigned int nframes, char *data) {

    unsigned int read_size=nframes*m_event_size*m_events_per_frame;

    if (m_transparent) {
        return true; // FIXME: the data still doesn't make sense!
    } else {
        // get the data payload to the ringbuffer
        if ((ffado_ringbuffer_read(m_event_buffer,data,read_size)) < read_size)
        {
            debugWarning("readFrames buffer underrun\n");
            return false;
        }
        decrementFrameCounter(nframes);
    }
    return true;
}

/**
 * @brief Performs block processing write of frames
 *
 * This function allows for zero-copy writing into the ringbuffer.
 * It calls the client's processWriteBlock function to write frames
 * into the internal buffer's data area, in a thread safe fashion.
 *
 * It also updates the timestamp.
 *
 * @param nbframes number of frames to process
 * @param ts timestamp of the last frame written to the buffer
 * @return true if successful
 */
bool TimestampedBuffer::blockProcessWriteFrames(unsigned int nbframes, ffado_timestamp_t ts) {

    debugOutput( DEBUG_LEVEL_VERY_VERBOSE, "Transferring period...\n");
    int xrun;
    unsigned int offset=0;

    ffado_ringbuffer_data_t vec[2];
    // we received one period of frames
    // this is period_size*dimension of events
    unsigned int events2write=nbframes*m_events_per_frame;
    unsigned int bytes2write=events2write*m_event_size;

    /* write events2write bytes to the ringbuffer
    *  first see if it can be done in one read.
    *  if so, ok.
    *  otherwise write up to a multiple of clusters directly to the buffer
    *  then do the buffer wrap around using ringbuffer_write
    *  then write the remaining data directly to the buffer in a third pass
    *  Make sure that we cannot end up on a non-cluster aligned position!
    */
    unsigned int cluster_size=m_events_per_frame*m_event_size;

    while(bytes2write>0) {
        int byteswritten=0;

        unsigned int frameswritten=(nbframes*cluster_size-bytes2write)/cluster_size;
        offset=frameswritten;

        ffado_ringbuffer_get_write_vector(m_event_buffer, vec);

        if(vec[0].len==0) { // this indicates a full event buffer
            debugError("Event buffer overrun in buffer %p, fill: %u, bytes2write: %u \n",
                       this, ffado_ringbuffer_read_space(m_event_buffer), bytes2write);
            debugShowBackLog();
            return false;
        }

        /* if we don't take care we will get stuck in an infinite loop
        * because we align to a cluster boundary later
        * the remaining nb of bytes in one write operation can be
        * smaller than one cluster
        * this can happen because the ringbuffer size is always a power of 2
        */
        if(vec[0].len<cluster_size) {

            // encode to the temporary buffer
            xrun = m_Client->processWriteBlock(m_cluster_buffer, 1, offset);

            if(xrun<0) {
                // xrun detected
                debugError("Frame buffer underrun in buffer %p\n",this);
                return false;
            }

            // use the ringbuffer function to write one cluster
            // the write function handles the wrap around.
            ffado_ringbuffer_write(m_event_buffer,
                         m_cluster_buffer,
                         cluster_size);

            // we advanced one cluster_size
            bytes2write-=cluster_size;

        } else { //

            if(bytes2write>vec[0].len) {
                // align to a cluster boundary
                byteswritten=vec[0].len-(vec[0].len%cluster_size);
            } else {
                byteswritten=bytes2write;
            }

            xrun = m_Client->processWriteBlock(vec[0].buf,
                         byteswritten/cluster_size,
                         offset);

            if(xrun<0) {
                    // xrun detected
                debugError("Frame buffer underrun in buffer %p\n",this);
                return false; // FIXME: return false ?
            }

            ffado_ringbuffer_write_advance(m_event_buffer, byteswritten);
            bytes2write -= byteswritten;
        }

        // the bytes2write should always be cluster aligned
        assert(bytes2write%cluster_size==0);

    }

    incrementFrameCounter(nbframes,ts);

    return true;

}

/**
 * @brief Performs block processing read of frames
 *
 * This function allows for zero-copy reading from the ringbuffer.
 * It calls the client's processReadBlock function to read frames
 * directly from the internal buffer's data area, in a thread safe
 * fashion.
 *
 * @param nbframes number of frames to process
 * @return true if successful
 */
bool TimestampedBuffer::blockProcessReadFrames(unsigned int nbframes) {

    debugOutput( DEBUG_LEVEL_VERY_VERBOSE, "Reading %u from buffer (%p)...\n", nbframes, this);

    int xrun;
    unsigned int offset=0;

    ffado_ringbuffer_data_t vec[2];
    // we received one period of frames on each connection
    // this is period_size*dimension of events

    unsigned int events2read=nbframes*m_events_per_frame;
    unsigned int bytes2read=events2read*m_event_size;
    /* read events2read bytes from the ringbuffer
    *  first see if it can be done in one read.
    *  if so, ok.
    *  otherwise read up to a multiple of clusters directly from the buffer
    *  then do the buffer wrap around using ringbuffer_read
    *  then read the remaining data directly from the buffer in a third pass
    *  Make sure that we cannot end up on a non-cluster aligned position!
    */
    unsigned int cluster_size=m_events_per_frame*m_event_size;

    while(bytes2read>0) {
        unsigned int framesread=(nbframes*cluster_size-bytes2read)/cluster_size;
        offset=framesread;

        int bytesread=0;

        ffado_ringbuffer_get_read_vector(m_event_buffer, vec);

        if(vec[0].len==0) { // this indicates an empty event buffer
            debugError("Event buffer underrun in buffer %p\n",this);
            return false;
        }

        /* if we don't take care we will get stuck in an infinite loop
        * because we align to a cluster boundary later
        * the remaining nb of bytes in one read operation can be smaller than one cluster
        * this can happen because the ringbuffer size is always a power of 2
                */
        if(vec[0].len<cluster_size) {
            // use the ringbuffer function to read one cluster
            // the read function handles wrap around
            ffado_ringbuffer_read(m_event_buffer,m_cluster_buffer,cluster_size);

            assert(m_Client);
            xrun = m_Client->processReadBlock(m_cluster_buffer, 1, offset);

            if(xrun<0) {
                // xrun detected
                debugError("Frame buffer overrun in buffer %p\n",this);
                    return false;
            }

            // we advanced one cluster_size
            bytes2read-=cluster_size;

        } else { //

            if(bytes2read>vec[0].len) {
                // align to a cluster boundary
                bytesread=vec[0].len-(vec[0].len%cluster_size);
            } else {
                bytesread=bytes2read;
            }

            assert(m_Client);
            xrun = m_Client->processReadBlock(vec[0].buf, bytesread/cluster_size, offset);

            if(xrun<0) {
                // xrun detected
                debugError("Frame buffer overrun in buffer %p\n",this);
                return false;
            }

            ffado_ringbuffer_read_advance(m_event_buffer, bytesread);
            bytes2read -= bytesread;
        }

        // the bytes2read should always be cluster aligned
        assert(bytes2read%cluster_size==0);
    }

    decrementFrameCounter(nbframes);

    return true;
}

/**
 * @brief Sets the buffer tail timestamp.
 *
 * Set the buffer tail timestamp to \ref new_timestamp. This will recalculate
 * the internal state such that the buffer's timeframe starts at
 * \ref new_timestamp.
 *
 * This is thread safe.
 *
 * @note considers offsets
 *
 * @param new_timestamp
 */
void TimestampedBuffer::setBufferTailTimestamp(ffado_timestamp_t new_timestamp) {

    // add the offsets
    ffado_timestamp_t ts=new_timestamp;
    ts += m_tick_offset;

    if (ts >= m_wrap_at) {
        ts -= m_wrap_at;
    } else if (ts < 0) {
        ts += m_wrap_at;
    }

#ifdef DEBUG
    if (new_timestamp >= m_wrap_at) {
        debugWarning("timestamp not wrapped: "TIMESTAMP_FORMAT_SPEC"\n",new_timestamp);
    }
    if ((ts >= m_wrap_at) || (ts < 0 )) {
        debugWarning("ts not wrapped correctly: "TIMESTAMP_FORMAT_SPEC"\n",ts);
    }
#endif

    ENTER_CRITICAL_SECTION;

    m_buffer_tail_timestamp = ts;

    m_dll_e2=m_update_period * (double)m_nominal_rate;
    m_buffer_next_tail_timestamp = (ffado_timestamp_t)((double)m_buffer_tail_timestamp + m_dll_e2);

    EXIT_CRITICAL_SECTION;

    debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "for (%p) to "
                                          TIMESTAMP_FORMAT_SPEC" => "TIMESTAMP_FORMAT_SPEC", NTS="
                                          TIMESTAMP_FORMAT_SPEC", DLL2=%f, RATE=%f\n",
                this, new_timestamp, ts, m_buffer_next_tail_timestamp, m_dll_e2, getRate());

}

/**
 * @brief Sets the buffer head timestamp.
 *
 * Set the buffer tail timestamp such that the buffer head timestamp becomes
 * \ref new_timestamp. This does not consider offsets, because it's use is to
 * make sure the following is true after setBufferHeadTimestamp(x):
 *   x == getBufferHeadTimestamp()
 *
 * This is thread safe.
 *
 * @param new_timestamp
 */
void TimestampedBuffer::setBufferHeadTimestamp(ffado_timestamp_t new_timestamp) {

#ifdef DEBUG
    if (new_timestamp >= m_wrap_at) {
        debugWarning("timestamp not wrapped: "TIMESTAMP_FORMAT_SPEC"\n",new_timestamp);
    }
#endif

    ffado_timestamp_t ts = new_timestamp;

    ENTER_CRITICAL_SECTION;

    // add the time
    ts += (ffado_timestamp_t)(m_nominal_rate * (float)m_framecounter);

    if (ts >= m_wrap_at) {
        ts -= m_wrap_at;
    } else if (ts < 0) {
        ts += m_wrap_at;
    }

    m_buffer_tail_timestamp = ts;

    m_dll_e2=m_update_period * (double)m_nominal_rate;
    m_buffer_next_tail_timestamp = (ffado_timestamp_t)((double)m_buffer_tail_timestamp + m_dll_e2);

    EXIT_CRITICAL_SECTION;

    debugOutput(DEBUG_LEVEL_VERBOSE, "for (%p) to "TIMESTAMP_FORMAT_SPEC" => "
                                          TIMESTAMP_FORMAT_SPEC", NTS="TIMESTAMP_FORMAT_SPEC", DLL2=%f, RATE=%f\n",
                this, new_timestamp, ts, m_buffer_next_tail_timestamp, m_dll_e2, getRate());

}

/**
 * @brief Synchronize the buffer head to a specified timestamp
 *
 * Try to synchronize the buffer head to a specific timestamp. This
 * can mean adding or removing samples to/from the buffer such that
 * the buffer head aligns with the specified timestamp. The alignment
 * is within ts +/- Tsample/2
 *
 * @param target the timestamp to align to
 * @return true if alignment succeeded, false if not 
 */
bool
TimestampedBuffer::syncBufferHeadToTimestamp(ffado_timestamp_t target)
{
    uint64_t ts_head;
    uint64_t ts_target=(uint64_t)target;
    signed int fc;
    int32_t lag_ticks;
    float lag_frames;

    ffado_timestamp_t ts_head_tmp;
    getBufferHeadTimestamp(&ts_head_tmp, &fc);
    ts_head=(uint64_t)ts_head_tmp;
    // if target > ts_head then the wanted buffer head timestamp
    // is later than the actual. This means that we (might) have to drop
    // some frames.
    lag_ticks=diffTicks(ts_target, ts_head);
    float rate=getRate();
    
    assert(rate!=0.0);

    lag_frames=(((float)lag_ticks)/rate);
    
    debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): HEAD=%llu, TS=%llu, diff=%ld = %10.5f frames (rate=%10.5f)\n",
                                      this, ts_head, ts_target, lag_ticks, lag_frames, rate);

    if (lag_frames>=1.0) {
        // the buffer head is too early
        // ditch frames until the buffer head is on time
        char dummy[getBytesPerFrame()]; // one frame of garbage
        int frames_to_ditch=(int)roundf(lag_frames);
        debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): ditching %d frames (@ ts=%lld)\n",this,frames_to_ditch,ts_target);
        
        while (frames_to_ditch--) {
            readFrames(1, dummy);
        }
        
    } else if (lag_frames<=-1.0) {
        // the buffer head is too late
        // add some padding frames
        int frames_to_add=(int)roundf(lag_frames);
        debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): adding %d frames (@ ts=%lld)\n",this,-frames_to_add,ts_target);
        
        while (frames_to_add++) {
             writeDummyFrame();
        }
    }
    getBufferHeadTimestamp(&ts_head_tmp, &fc);
    ts_head=(uint64_t)ts_head_tmp;
    debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): new HEAD=%llu, fc=%d, target=%llu, new diff=%lld\n",
                                      this, ts_head, fc, ts_target, diffTicks(ts_target, ts_head));
    // FIXME: of course this doesn't always succeed
    return true;
}

/**
 * @brief Synchronize the buffer tail to a specified timestamp
 *
 * Try to synchronize the buffer tail to a specific timestamp. This
 * can mean adding or removing samples to/from the buffer such that
 * the buffer tail aligns with the specified timestamp. The alignment
 * is within ts +/- Tsample/2
 *
 * @param target the timestamp to align to
 * @return true if alignment succeeded, false if not 
 */
bool
TimestampedBuffer::syncBufferTailToTimestamp(ffado_timestamp_t target)
{
    uint64_t ts_tail;
    uint64_t ts_target=(uint64_t)target;
    signed int fc;
    int32_t lag_ticks;
    float lag_frames;

    debugWarning("Untested\n");
    
    ffado_timestamp_t ts_tail_tmp;
    getBufferTailTimestamp(&ts_tail_tmp, &fc);
    ts_tail=(uint64_t)ts_tail_tmp;
    // if target < ts_tail then the wanted buffer head timestamp
    // is later than the actual. This means that we (might) have to drop
    // some frames.
    lag_ticks=diffTicks(ts_tail, ts_target);
    float rate=getRate();
    
    assert(rate!=0.0);

    lag_frames=(((float)lag_ticks)/rate);
    
    debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): HEAD=%llu, TS=%llu, diff=%ld = %10.5f frames (rate=%10.5f)\n",
                                      this, ts_tail, ts_target, lag_ticks, lag_frames, rate);

    if (lag_frames>=1.0) {
        // the buffer head is too early
        // ditch frames until the buffer head is on time
        char dummy[getBytesPerFrame()]; // one frame of garbage
        int frames_to_ditch=(int)roundf(lag_frames);
        debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): ditching %d frames (@ ts=%lld)\n",this,frames_to_ditch,ts_target);
        
        while (frames_to_ditch--) {
            readFrames(1, dummy);
        }
        
    } else if (lag_frames<=-1.0) {
        // the buffer head is too late
        // add some padding frames
        int frames_to_add=(int)roundf(lag_frames);
        debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): adding %d frames (@ ts=%lld)\n",this,-frames_to_add,ts_target);
        
        while (frames_to_add++) {
             writeDummyFrame();
        }
    }
    getBufferHeadTimestamp(&ts_tail_tmp, &fc);
    ts_tail=(uint64_t)ts_tail_tmp;
    debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): new HEAD=%llu, fc=%d, target=%llu, new diff=%lld\n",
                                      this, ts_tail, fc, ts_target, diffTicks(ts_target, ts_tail));
    // FIXME: of course this doesn't always succeed
    return true;
}

/**
 * @brief correct lag
 *
 * Try to synchronize the buffer tail to a specific timestamp. This
 * can mean adding or removing samples to/from the buffer such that
 * the buffer tail aligns with the specified timestamp. The alignment
 * is within ts +/- Tsample/2
 *
 * @param target the timestamp to align to
 * @return true if alignment succeeded, false if not 
 */
bool
TimestampedBuffer::syncCorrectLag(int64_t lag_ticks)
{
    float lag_frames;
    float rate=getRate();
    assert(rate!=0.0);

    lag_frames=(((float)lag_ticks)/rate);
    if (lag_frames >= 1.0) {
        // the buffer head is too late
        // add some padding frames
        int frames_to_add=(int)roundf(lag_frames);
        debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): adding %d frames\n",this,frames_to_add);

        while (frames_to_add++) {
             writeDummyFrame();
        }
    } else if (lag_frames <= -1.0) {
        // the buffer head is too early
        // ditch frames until the buffer head is on time
        char dummy[getBytesPerFrame()]; // one frame of garbage
        int frames_to_ditch=(int)roundf(lag_frames);
        debugOutput( DEBUG_LEVEL_VERBOSE, "(%p): ditching %d frames\n",this,-frames_to_ditch);

        while (frames_to_ditch--) {
            readFrames(1, dummy);
        }
    }
    return true;
}

/**
 * \brief return the timestamp of the first frame in the buffer
 *
 * This function returns the timestamp of the very first sample in
 * the StreamProcessor's buffer. It also returns the framecounter value
 * for which this timestamp is valid.
 *
 * @param ts address to store the timestamp in
 * @param fc address to store the associated framecounter in
 */
void TimestampedBuffer::getBufferHeadTimestamp(ffado_timestamp_t *ts, signed int *fc) {
    // NOTE: this is still ok with threads, because we use *fc to compute
    //       the timestamp
    *fc = m_framecounter;
    *ts=getTimestampFromTail(*fc);
}

/**
 * \brief return the timestamp of the last frame in the buffer
 *
 * This function returns the timestamp of the last frame in
 * the StreamProcessor's buffer. It also returns the framecounter
 * value for which this timestamp is valid.
 *
 * @param ts address to store the timestamp in
 * @param fc address to store the associated framecounter in
 */
void TimestampedBuffer::getBufferTailTimestamp(ffado_timestamp_t *ts, signed int *fc) {
    ENTER_CRITICAL_SECTION;
    *fc = m_framecounter;
    *ts = m_buffer_tail_timestamp;
    EXIT_CRITICAL_SECTION;
}

/**
 * @brief Get timestamp for a specific position from the buffer tail
 *
 * Returns the timestamp for a position that is nframes earlier than the
 * buffer tail
 *
 * @param nframes number of frames
 * @return timestamp value
 */
ffado_timestamp_t TimestampedBuffer::getTimestampFromTail(int nframes)
{
    // ts(x) = m_buffer_tail_timestamp -
    //         (m_buffer_next_tail_timestamp - m_buffer_tail_timestamp)/(samples_between_updates)*(x)
    ffado_timestamp_t diff;
    float rate;
    ffado_timestamp_t timestamp;
    
    ENTER_CRITICAL_SECTION;

    diff = m_buffer_next_tail_timestamp - m_buffer_tail_timestamp;
    timestamp = m_buffer_tail_timestamp;
    
    EXIT_CRITICAL_SECTION;
    
    if (diff < 0) diff += m_wrap_at;
    rate = (float)diff / (float)m_update_period;

    timestamp -= (ffado_timestamp_t)((nframes) * rate);

    if(timestamp >= m_wrap_at) {
        timestamp -= m_wrap_at;
    } else if(timestamp < 0) {
        timestamp += m_wrap_at;
    }

    return timestamp;
}

/**
 * @brief Get timestamp for a specific position from the buffer head
 *
 * Returns the timestamp for a position that is nframes later than the
 * buffer head
 *
 * @param nframes number of frames
 * @return timestamp value
 */
ffado_timestamp_t TimestampedBuffer::getTimestampFromHead(int nframes)
{
    return getTimestampFromTail(m_framecounter-nframes);
}

/**
 * Resets the frame counter, in a atomic way. This
 * is thread safe.
 */
void TimestampedBuffer::resetFrameCounter() {
    ENTER_CRITICAL_SECTION;
    m_framecounter = 0;
    EXIT_CRITICAL_SECTION;
}

/**
 * Decrements the frame counter in a thread safe way.
 *
 * @param nbframes number of frames to decrement
 */
void TimestampedBuffer::decrementFrameCounter(int nbframes) {
    ENTER_CRITICAL_SECTION;
    m_framecounter -= nbframes;
    EXIT_CRITICAL_SECTION;
}

/**
 * Increments the frame counter in a thread safe way.
 * Also updates the timestamp.
 *
 * @note the offsets defined by setTicksOffset and setFrameOffset
 *       are added here.
 *
 * @param nbframes the number of frames to add
 * @param new_timestamp the new timestamp
 */
void TimestampedBuffer::incrementFrameCounter(int nbframes, ffado_timestamp_t new_timestamp) {

    // add the offsets
    ffado_timestamp_t diff;
    
    ENTER_CRITICAL_SECTION;
    diff = m_buffer_next_tail_timestamp - m_buffer_tail_timestamp;
    EXIT_CRITICAL_SECTION;

    if (diff < 0) diff += m_wrap_at;

#ifdef DEBUG
    float rate=(float)diff / (float)m_update_period;
#endif

    ffado_timestamp_t ts = new_timestamp;
    ts += m_tick_offset;

    if (ts >= m_wrap_at) {
        ts -= m_wrap_at;
    } else if (ts < 0) {
        ts += m_wrap_at;
    }

#ifdef DEBUG
    if (new_timestamp >= m_wrap_at) {
        debugWarning("timestamp not wrapped: "TIMESTAMP_FORMAT_SPEC"\n", new_timestamp);
    }
    if ((ts >= m_wrap_at) || (ts < 0 )) {
        debugWarning("ts not wrapped correctly: "TIMESTAMP_FORMAT_SPEC"\n",ts);
    }
#endif
// FIXME: JMW: at some points during startup the timestamp doesn't change.
// This still needs to be verified in more detail.  
// if (ts>m_buffer_tail_timestamp-1 && ts<m_buffer_tail_timestamp+1) {
//   ENTER_CRITICAL_SECTION;
//   m_framecounter += nbframes;
//   EXIT_CRITICAL_SECTION;
//   return;
// }
    ffado_timestamp_t pred_buffer_next_tail_timestamp;
    if(nbframes == m_update_period) {
        pred_buffer_next_tail_timestamp = m_buffer_next_tail_timestamp;
    } else {
        debugOutput( DEBUG_LEVEL_VERBOSE,
                     "Number of frames (%u) != update period (%u)\n",
                     nbframes, m_update_period );
        // calculate the predicted timestamp for nframes (instead of m_update_period)
        // after the previous update.
        float rel_step = ((float)nbframes)/((float)m_update_period);
        ENTER_CRITICAL_SECTION; // FIXME: do we need these?
        ffado_timestamp_t corrected_step = (m_buffer_next_tail_timestamp - m_buffer_tail_timestamp) * rel_step;
        pred_buffer_next_tail_timestamp = m_buffer_tail_timestamp + corrected_step;
        EXIT_CRITICAL_SECTION;
        
        debugOutput( DEBUG_LEVEL_VERBOSE,
                     "Updated ("TIMESTAMP_FORMAT_SPEC","TIMESTAMP_FORMAT_SPEC") to ("TIMESTAMP_FORMAT_SPEC","TIMESTAMP_FORMAT_SPEC")\n",
                     m_buffer_tail_timestamp, m_buffer_next_tail_timestamp,
                     m_buffer_tail_timestamp, pred_buffer_next_tail_timestamp);
        
    }
    
    // the difference between the given TS and the one predicted for this time instant
    // this is the error for the DLL
    diff = ts - pred_buffer_next_tail_timestamp;

    // check whether the update is within the allowed bounds
    const float max_deviation = (50.0/100.0); // maximal relative difference considered normal
    ffado_timestamp_t one_update_step = nbframes * getRate();
    ffado_timestamp_t max_abs_diff = one_update_step * (1.0 + max_deviation);
    
    if (diff > max_abs_diff) {
        debugWarning("(%p) difference rather large (+): diff="TIMESTAMP_FORMAT_SPEC", max="TIMESTAMP_FORMAT_SPEC", "TIMESTAMP_FORMAT_SPEC", "TIMESTAMP_FORMAT_SPEC"\n",
            this, diff, max_abs_diff, ts, pred_buffer_next_tail_timestamp);
//         debugShowBackLogLines(40);
    } else if (diff < -max_abs_diff) {
        debugWarning("(%p) difference rather large (-): diff="TIMESTAMP_FORMAT_SPEC", max="TIMESTAMP_FORMAT_SPEC", "TIMESTAMP_FORMAT_SPEC", "TIMESTAMP_FORMAT_SPEC"\n",
            this, diff, -max_abs_diff, ts, pred_buffer_next_tail_timestamp);
//         debugShowBackLogLines(40);
    }

    debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "(%p): diff="TIMESTAMP_FORMAT_SPEC" ",
                this, diff);

    double err = diff;

    debugOutputShort(DEBUG_LEVEL_VERY_VERBOSE, "diff2="TIMESTAMP_FORMAT_SPEC" err=%f\n",
                    diff, err);
    debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "B: FC=%10u, TS="TIMESTAMP_FORMAT_SPEC", NTS="TIMESTAMP_FORMAT_SPEC"\n",
                    m_framecounter, m_buffer_tail_timestamp, pred_buffer_next_tail_timestamp);

    ENTER_CRITICAL_SECTION;
    m_framecounter += nbframes;

    m_buffer_tail_timestamp = pred_buffer_next_tail_timestamp;
    m_buffer_next_tail_timestamp = pred_buffer_next_tail_timestamp + (ffado_timestamp_t)(m_dll_b * err + m_dll_e2);
//    m_buffer_tail_timestamp=ts;
//    m_buffer_next_tail_timestamp += (ffado_timestamp_t)(m_dll_b * err + m_dll_e2);
    
    m_dll_e2 += m_dll_c*err;

    EXIT_CRITICAL_SECTION;

    debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "tail for (%p) to "
                                          TIMESTAMP_FORMAT_SPEC" => "TIMESTAMP_FORMAT_SPEC", NTS="
                                          TIMESTAMP_FORMAT_SPEC", DLL2=%f, RATE=%f\n",
                this, new_timestamp, ts, m_buffer_next_tail_timestamp, m_dll_e2, getRate());

    debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "U: FC=%10u, TS="TIMESTAMP_FORMAT_SPEC", NTS="TIMESTAMP_FORMAT_SPEC"\n",
                    m_framecounter, m_buffer_tail_timestamp, m_buffer_next_tail_timestamp);

    ENTER_CRITICAL_SECTION;
    if (m_buffer_next_tail_timestamp >= m_wrap_at) {
        debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "Unwrapping next tail timestamp: "TIMESTAMP_FORMAT_SPEC"",
                m_buffer_next_tail_timestamp);

        m_buffer_next_tail_timestamp -= m_wrap_at;

        debugOutputShort(DEBUG_LEVEL_VERY_VERBOSE, " => "TIMESTAMP_FORMAT_SPEC"\n",
                m_buffer_next_tail_timestamp);

    }
    EXIT_CRITICAL_SECTION;

    debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "A: TS="TIMESTAMP_FORMAT_SPEC", NTS="TIMESTAMP_FORMAT_SPEC", DLLe2=%f, RATE=%f\n",
                m_buffer_tail_timestamp, m_buffer_next_tail_timestamp, m_dll_e2, rate);


    if(m_buffer_tail_timestamp>=m_wrap_at) {
        debugError("Wrapping failed for m_buffer_tail_timestamp! "TIMESTAMP_FORMAT_SPEC"\n",m_buffer_tail_timestamp);
        debugOutput(DEBUG_LEVEL_VERY_VERBOSE, " IN="TIMESTAMP_FORMAT_SPEC", TS="TIMESTAMP_FORMAT_SPEC", NTS="TIMESTAMP_FORMAT_SPEC"\n",
                    ts, m_buffer_tail_timestamp, m_buffer_next_tail_timestamp);

    }
    if(m_buffer_next_tail_timestamp>=m_wrap_at) {
        debugError("Wrapping failed for m_buffer_next_tail_timestamp! "TIMESTAMP_FORMAT_SPEC"\n",m_buffer_next_tail_timestamp);
        debugOutput(DEBUG_LEVEL_VERY_VERBOSE, " IN="TIMESTAMP_FORMAT_SPEC", TS="TIMESTAMP_FORMAT_SPEC", NTS="TIMESTAMP_FORMAT_SPEC"\n",
                    ts, m_buffer_tail_timestamp, m_buffer_next_tail_timestamp);
    }
    
    if(m_buffer_tail_timestamp==m_buffer_next_tail_timestamp) {
        debugError("Current and next timestamps are equal: "TIMESTAMP_FORMAT_SPEC" "TIMESTAMP_FORMAT_SPEC"\n",
                   m_buffer_tail_timestamp,m_buffer_next_tail_timestamp);
    
    }

    // this DLL allows the calculation of any sample timestamp relative to the buffer tail,
    // to the next period and beyond (through extrapolation)
    //
    // ts(x) = m_buffer_tail_timestamp +
    //         (m_buffer_next_tail_timestamp - m_buffer_tail_timestamp)/(samples_between_updates)*x

}

/**
 * @brief Print status info.
 */
void TimestampedBuffer::dumpInfo() {

    ffado_timestamp_t ts_head;
    signed int fc;
    getBufferHeadTimestamp(&ts_head,&fc);

#ifdef DEBUG
    ffado_timestamp_t diff=(ffado_timestamp_t)ts_head - (ffado_timestamp_t)m_buffer_tail_timestamp;
#endif

    debugOutputShort( DEBUG_LEVEL_NORMAL, "  TimestampedBuffer (%p) info:\n",this);
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  Frame counter         : %d\n", m_framecounter);
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  Events in buffer      : %d\n", getBufferFill());
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  Buffer head timestamp : "TIMESTAMP_FORMAT_SPEC"\n",ts_head);
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  Buffer tail timestamp : "TIMESTAMP_FORMAT_SPEC"\n",m_buffer_tail_timestamp);
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  Next tail timestamp   : "TIMESTAMP_FORMAT_SPEC"\n",m_buffer_next_tail_timestamp);
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  Head - Tail           : "TIMESTAMP_FORMAT_SPEC"\n",diff);
    debugOutputShort( DEBUG_LEVEL_NORMAL, "  rate                  : %f (%f)\n",m_dll_e2,m_dll_e2/m_update_period);
}

} // end of namespace Util