path: root/libhb/vfr.c

#include "hb.h"

struct hb_filter_private_s
{
    hb_job_t    * job;
    int           cfr;
    int           input_vrate;
    int           input_vrate_base;
    int           vrate;
    int           vrate_base;
    hb_fifo_t   * delay_queue;
    int           dropped_frames;
    int           extended_frames;
    uint64_t      last_start[4];
    uint64_t      last_stop[4];
    uint64_t      lost_time[4];
    uint64_t      total_lost_time;
    uint64_t      total_gained_time;
    int           count_frames;      // frames output so far
    double        frame_rate;        // 90KHz ticks per frame (for CFR/PFR)
    uint64_t      out_last_stop;     // where last frame ended (for CFR/PFR)
    int           drops;             // frames dropped (for CFR/PFR)
    int           dups;              // frames duped (for CFR/PFR)

    // Duplicate frame detection members
    float         max_metric;   // highest motion metric since
                                // last output frame
    float         frame_metric; // motion metric of last frame
    float         out_metric;   // motion metric of last output frame
    int           sync_parity;
    unsigned      gamma_lut[256];
};

static int hb_vfr_init( hb_filter_object_t * filter,
                        hb_filter_init_t * init );

static int hb_vfr_work( hb_filter_object_t * filter,
                        hb_buffer_t ** buf_in,
                        hb_buffer_t ** buf_out );

static void hb_vfr_close( hb_filter_object_t * filter );
static int hb_vfr_info( hb_filter_object_t * filter, hb_filter_info_t * info );

hb_filter_object_t hb_filter_vfr =
{
    .id            = HB_FILTER_VFR,
    .enforce_order = 1,
    .name          = "Framerate Shaper",
    .settings      = NULL,
    .init          = hb_vfr_init,
    .work          = hb_vfr_work,
    .close         = hb_vfr_close,
    .info          = hb_vfr_info,
};

// Create gamma lookup table.
// Note that we are creating a scaled integer lookup table that will
// not cause overflows in sse_block16() below.  This results in
// small values being truncated to 0 which is ok for this usage.
static void build_gamma_lut( hb_filter_private_t * pv )
{
    int i;
    for( i = 0; i < 256; i++ )
    {
        pv->gamma_lut[i] = 4095 * pow( ( (float)i / (float)255 ), 2.2f );
    }
}

// insert buffer 'succ' after buffer chain element 'pred'.
// caller must guarantee that 'pred' and 'succ' are non-null.
static hb_buffer_t *insert_buffer_in_chain( 
    hb_buffer_t *pred, 
    hb_buffer_t *succ )
{
    succ->next = pred->next;
    pred->next = succ;
    return succ;
}

#define DUP_THRESH_SSE 5.0

// Compute ths sum of squared errors for a 16x16 block
// Gamma adjusts pixel values so that less visible diffreences
// count less.
static inline unsigned sse_block16( hb_filter_private_t *pv, uint8_t *a, uint8_t *b, int stride )
{
    int x, y;
    unsigned sum = 0;
    int diff;
    unsigned *g = pv->gamma_lut;

    for( y = 0; y < 16; y++ )
    {
        for( x = 0; x < 16; x++ )
        {
            diff =  g[a[x]] - g[b[x]];
            sum += diff * diff;
        }
        a += stride;
        b += stride;
    }
    return sum;
}

// Sum of squared errors.  Computes and sums the SSEs for all
// 16x16 blocks in the images.  Only checks the Y component.
static float motion_metric( hb_filter_private_t * pv, hb_buffer_t * a, hb_buffer_t * b )
{
    int bw = a->f.width / 16;
    int bh = a->f.height / 16;
    int stride = a->plane[0].stride;
    uint8_t * pa = a->plane[0].data;
    uint8_t * pb = b->plane[0].data;
    int x, y;
    uint64_t sum = 0;

    for( y = 0; y < bh; y++ )
    {
        for( x = 0; x < bw; x++ )
        {
            sum +=  sse_block16( pv, pa + y * 16 * stride + x * 16,
                                 pb + y * 16 * stride + x * 16, stride );
        }
    }
    return (float)sum / ( a->f.width * a->f.height );;
}

// This section of the code implements video frame rate control.
// Since filters are allowed to duplicate and drop frames (which
// changes the timing), this has to be the last thing done in render.
//
// There are three options, selected by the value of cfr:
//   0 - Variable Frame Rate (VFR) or 'same as source': frame times
//       are left alone
//   1 - Constant Frame Rate (CFR): Frame timings are adjusted so that all
//       frames are exactly vrate_base ticks apart. Frames are dropped
//       or duplicated if necessary to maintain this spacing.
//   2 - Peak Frame Rate (PFR): vrate_base is treated as the peak
//       average frame rate. I.e., the average frame rate (current frame
//       end time divided by number of frames so far) is never allowed to be
//       greater than vrate_base and frames are dropped if necessary
//       to keep the average under this value. Other than those drops, frame
//       times are left alone.
//

static void adjust_frame_rate( hb_filter_private_t *pv, hb_buffer_t **buf_out )
{
    hb_buffer_t *out = *buf_out;

    if ( out && out->size > 0 )
    {
        if ( pv->cfr == 0 )
        {
            ++pv->count_frames;
            pv->out_last_stop = out->s.stop;
            return;
        }

        // compute where this frame would stop if the frame rate were constant
        // (this is our target stopping time for CFR and earliest possible
        // stopping time for PFR).
        double cfr_stop = pv->frame_rate * ( pv->count_frames + 1 );

        hb_buffer_t * next = hb_fifo_see( pv->delay_queue );

        float next_metric = 0;
        if( next )
            next_metric = motion_metric( pv, out, next );

        if( pv->out_last_stop >= out->s.stop )
        {
            ++pv->drops;
            hb_buffer_close( buf_out );

            pv->frame_metric = next_metric;
            if( next_metric > pv->max_metric )
                pv->max_metric = next_metric;

            return;
        }

        if( out->s.start <= pv->out_last_stop &&
            out->s.stop > pv->out_last_stop &&
            next && next->s.stop < cfr_stop )
        {
            // This frame starts before the end of the last output
            // frame and ends after the end of the last output
            // frame (i.e. it straddles it).  Also the next frame
            // ends before the end of the next output frame. If the
            // next frame is not a duplicate, and we haven't seen
            // a changed frame since the last output frame,
            // then drop this frame.
            //
            // This causes us to sync to the pattern of progressive
            // 23.976 fps content that has been upsampled to
            // progressive 59.94 fps.
            if( pv->out_metric > pv->max_metric &&
                next_metric > pv->max_metric )
            {
                // Pattern: N R R N
                //          o   c n
                // N == new frame
                // R == repeat frame
                // o == last output frame
                // c == current frame
                // n == next frame
                // We haven't seen a frame change since the last output
                // frame and the next frame changes. Use the next frame,
                // drop this one.
                ++pv->drops;
                pv->frame_metric = next_metric;
                pv->max_metric = next_metric;
                pv->sync_parity = 1;
                hb_buffer_close( buf_out );
                return;
            }
            else if( pv->sync_parity &&
                     pv->out_metric < pv->max_metric &&
                     pv->max_metric > pv->frame_metric &&
                     pv->frame_metric < next_metric )
            {
                // Pattern: R N R N
                //          o   c n
                // N == new frame
                // R == repeat frame
                // o == last output frame
                // c == current frame
                // n == next frame
                // If we see this pattern, we must not use the next
                // frame when straddling the current frame.
                pv->sync_parity = 0;
            }
            else if( pv->sync_parity )
            {
                // The pattern is indeterminate.  Continue dropping
                // frames on the same schedule
                ++pv->drops;
                pv->frame_metric = next_metric;
                pv->max_metric = next_metric;
                pv->sync_parity = 1;
                hb_buffer_close( buf_out );
                return;
            }

        }

        // this frame has to start where the last one stopped.
        out->s.start = pv->out_last_stop;

        pv->out_metric = pv->frame_metric;
        pv->frame_metric = next_metric;
        pv->max_metric = next_metric;

        // at this point we know that this frame doesn't push the average
        // rate over the limit so we just pass it on for PFR. For CFR we're
        // going to return it (with its start & stop times modified) and
        // we may have to dup it.
        ++pv->count_frames;
        if ( pv->cfr > 1 )
        {
            // PFR - we're going to keep the frame but may need to
            // adjust it's stop time to meet the average rate constraint.
            if ( out->s.stop <= cfr_stop )
            {
                out->s.stop = cfr_stop;
            }
        }
        else
        {
            // we're doing CFR so we have to either trim some time from a
            // buffer that ends too far in the future or, if the buffer is
            // two or more frame times long, split it into multiple pieces,
            // each of which is a frame time long.
            double excess_dur = (double)out->s.stop - cfr_stop;
            out->s.stop = cfr_stop;
            for ( ; excess_dur >= pv->frame_rate; excess_dur -= pv->frame_rate )
            {
                /* next frame too far ahead - dup current frame */
                hb_buffer_t *dup = hb_buffer_copy( out );
                dup->s.new_chap = 0;
                dup->s.start = cfr_stop;
                cfr_stop += pv->frame_rate;
                dup->s.stop = cfr_stop;
                out = insert_buffer_in_chain( out, dup );
                ++pv->dups;
                ++pv->count_frames;
            }
        }
        pv->out_last_stop = out->s.stop;
    }
}

static int hb_vfr_init( hb_filter_object_t * filter,
                        hb_filter_init_t * init )
{
    filter->private_data = calloc( 1, sizeof(struct hb_filter_private_s) );
    hb_filter_private_t * pv = filter->private_data;

    build_gamma_lut( pv );
    pv->cfr = init->cfr;
    pv->input_vrate = pv->vrate = init->vrate;
    pv->input_vrate_base = pv->vrate_base = init->vrate_base;
    if( filter->settings )
    {
        sscanf( filter->settings, "%d:%d:%d",
                &pv->cfr, &pv->vrate, &pv->vrate_base );
    }

    //pv->job = init->job;

    /* Setup FIFO queue for subtitle cache */
    pv->delay_queue = hb_fifo_init( 8, 1 );

    /* VFR IVTC needs a bunch of time-keeping variables to track
      how many frames are dropped, how many are extended, what the
      last 4 start and stop times were (so they can be modified),
      how much time has been lost and gained overall, how much time
      the latest 4 frames should be extended by */
    pv->dropped_frames = 0;
    pv->extended_frames = 0;
    pv->last_start[0] = 0;
    pv->last_stop[0] = 0;
    pv->total_lost_time = 0;
    pv->total_gained_time = 0;
    pv->lost_time[0] = 0; pv->lost_time[1] = 0; pv->lost_time[2] = 0; pv->lost_time[3] = 0;
    pv->frame_metric = 1000; // Force first frame

    if ( pv->cfr == 0 )
    {
        /* Ensure we're using "Same as source" FPS */
        pv->vrate_base = init->vrate_base;
        pv->vrate = init->vrate;
    }
    else if ( pv->cfr == 2 )
    {
        // For PFR, we want the framerate based on the source's actual 
        // framerate, unless it's higher than the specified peak framerate. 
        double source_fps = (double)init->vrate / init->vrate_base;
        double peak_fps = (double)pv->vrate / pv->vrate_base;
        if ( source_fps > peak_fps )
        {
            // peak framerate is lower than source framerate. so signal
            // that the nominal framerate will be changed.
            init->vrate = pv->vrate;
            init->vrate_base = pv->vrate_base;
        }
    }
    else
    {
        // Constant framerate. Signal the framerate we are using.
        init->vrate = pv->vrate;
        init->vrate_base = pv->vrate_base;
    }
    init->cfr = pv->cfr;
    pv->frame_rate = (double)pv->vrate_base * 90000. / pv->vrate;

    return 0;
}

static int hb_vfr_info( hb_filter_object_t * filter,
                        hb_filter_info_t * info )
{
    hb_filter_private_t * pv = filter->private_data;

    if( !pv )
        return 1;

    memset( info, 0, sizeof( hb_filter_info_t ) );
    info->out.vrate_base = pv->vrate_base;
    info->out.vrate = pv->vrate;
    info->out.cfr = pv->cfr;
    if ( pv->cfr == 0 )
    {
        /* Ensure we're using "Same as source" FPS */
        sprintf( info->human_readable_desc, 
                "frame rate: same as source (around %.3f fps)",
                (float)pv->vrate / pv->vrate_base );
    }
    else if ( pv->cfr == 2 )
    {
        // For PFR, we want the framerate based on the source's actual 
        // framerate, unless it's higher than the specified peak framerate. 
        double source_fps = (double)pv->input_vrate / pv->input_vrate_base;
        double peak_fps = (double)pv->vrate / pv->vrate_base;
        sprintf( info->human_readable_desc, 
                "frame rate: %.3f fps -> peak rate limited to %.3f fps",
                source_fps , peak_fps );
    }
    else
    {
        // Constant framerate. Signal the framerate we are using.
        double source_fps = (double)pv->input_vrate / pv->input_vrate_base;
        double constant_fps = (double)pv->vrate / pv->vrate_base;
        sprintf( info->human_readable_desc, 
                "frame rate: %.3f fps -> constant %.3f fps",
                source_fps , constant_fps );
    }

    return 0;
}

static void hb_vfr_close( hb_filter_object_t * filter )
{
    hb_filter_private_t * pv = filter->private_data;

    if( !pv )
        return;

    if ( pv->cfr )
    {
        hb_log("render: %d frames output, %d dropped and %d duped for CFR/PFR",
               pv->count_frames, pv->drops, pv->dups );
    }

    if( pv->job )
    {
        hb_interjob_t * interjob = hb_interjob_get( pv->job->h );
        
        /* Preserve dropped frame count for more accurate 
         * framerates in 2nd passes. 
         */
        interjob->out_frame_count = pv->count_frames;
        interjob->total_time = pv->out_last_stop;
    }

    hb_log("render: lost time: %"PRId64" (%i frames)", 
           pv->total_lost_time, pv->dropped_frames);
    hb_log("render: gained time: %"PRId64" (%i frames) (%"PRId64" not accounted for)", 
           pv->total_gained_time, pv->extended_frames, 
           pv->total_lost_time - pv->total_gained_time);

    if (pv->dropped_frames)
    {
        hb_log("render: average dropped frame duration: %"PRId64, 
               (pv->total_lost_time / pv->dropped_frames) );
    }

    if( pv->delay_queue )
    {
        hb_fifo_close( &pv->delay_queue );
    }

    /* Cleanup render work structure */
    free( pv );
    filter->private_data = NULL;
}

static int hb_vfr_work( hb_filter_object_t * filter,
                        hb_buffer_t ** buf_in,
                        hb_buffer_t ** buf_out )
{
    hb_filter_private_t * pv = filter->private_data;
    hb_buffer_t * in = *buf_in;
    hb_buffer_t * out = NULL;

    *buf_in = NULL;
    *buf_out = NULL;
    if( in->size <= 0 )
    {
        hb_buffer_t *head = NULL, *tail = NULL, *next;
        int counter = 2;

        /* If the input buffer is end of stream, send out an empty one
         * to the next stage as well. To avoid losing the contents of
         * the delay queue connect the buffers in the delay queue in 
         * the correct order, and add the end of stream buffer to the
         * end.
         */     
        while( ( next = hb_fifo_get( pv->delay_queue ) ) != NULL )
        {
            
            /* We can't use the given time stamps. Previous frames
               might already have been extended, throwing off the
               raw values fed to render.c. Instead, their
               stop and start times are stored in arrays.
               The 4th cached frame will be the to use.
               If it needed its duration extended to make up
               lost time, it will have happened above. */
            next->s.start = pv->last_start[counter];
            next->s.stop = pv->last_stop[counter--];
            
            adjust_frame_rate( pv, &next );

            if( next )
            {
                if( !head && !tail )
                {
                    head = tail = next;
                } else {
                    tail->next = next;
                    tail = next;
                }
            }
        }
        if( tail )
        {
            tail->next = in;
            *buf_out = head;
        } else {
            *buf_out = in;
        }     
        return HB_FILTER_DONE;
    }

    // If there is a gap between the last stop and the current start
    // then frame(s) were dropped.
    if ( in->s.start > pv->last_stop[0] )
    {
        /* We need to compensate for the time lost by dropping frame(s).
           Spread its duration out in quarters, because usually dropped frames
           maintain a 1-out-of-5 pattern and this spreads it out amongst 
           the remaining ones.  Store these in the lost_time array, which
           has 4 slots in it.  Because not every frame duration divides 
           evenly by 4, and we can't lose the remainder, we have to go 
           through an awkward process to preserve it in the 4th array index. 
        */
        uint64_t temp_duration = in->s.start - pv->last_stop[0];
        pv->lost_time[0] += (temp_duration / 4);
        pv->lost_time[1] += (temp_duration / 4);
        pv->lost_time[2] += (temp_duration / 4);
        pv->lost_time[3] += ( temp_duration - 3 * (temp_duration / 4) );

        pv->total_lost_time += temp_duration;
    }

    /* Cache frame start and stop times, so we can renumber
       time stamps if dropping frames for VFR.              */
    int i;
    for( i = 3; i >= 1; i-- )
    {
        pv->last_start[i] = pv->last_start[i-1];
        pv->last_stop[i] = pv->last_stop[i-1];
    }

    /* In order to make sure we have continuous time stamps, store
       the current frame's duration as starting when the last one stopped. */
    pv->last_start[0] = pv->last_stop[1];
    pv->last_stop[0] = pv->last_start[0] + (in->s.stop - in->s.start);

    hb_fifo_push( pv->delay_queue, in );

    /*
     * Keep the last three frames in our queue, this ensures that we have 
     * the last two always in there should we need to rewrite the 
     * durations on them.
     */

    if( hb_fifo_size( pv->delay_queue ) >= 4 )
    {
        out = hb_fifo_get( pv->delay_queue );
    }

    if( out )
    {
        /* The current frame exists. That means it hasn't been dropped by a 
         * filter. We may edit its duration if needed. 
         */
        if( pv->lost_time[3] > 0 )
        {
            int time_shift = 0;

            for( i = 3; i >= 0; i-- )
            {
                /*
                 * A frame's been dropped earlier by VFR detelecine.
                 * Gotta make up the lost time. This will also
                 * slow down the video.
                 * The dropped frame's has to be accounted for, so
                 * divvy it up amongst the 4 frames left behind.
                 * This is what the delay_queue is for;
                 * telecined sequences start 2 frames before
                 * the dropped frame, so to slow down the right
                 * ones you need a 2 frame delay between
                 * reading input and writing output.
                 */

                /* We want to extend the outputted frame's duration by the value
                  stored in the 4th slot of the lost_time array. Because we need
                  to adjust all the values in the array so they're contiguous,
                  extend the duration inside the array first, before applying
                  it to the current frame buffer. */
                pv->last_start[i] += time_shift;
                pv->last_stop[i] += pv->lost_time[i] + time_shift;

                /* Log how much time has been added back in to the video. */
                pv->total_gained_time += pv->lost_time[i];
                time_shift += pv->lost_time[i];

                pv->lost_time[i] = 0;

                /* Log how many frames have had their durations extended. */
                pv->extended_frames++;
            }
        }

        /* We can't use the given time stamps. Previous frames
           might already have been extended, throwing off the
           raw values fed to render.c. Instead, their
           stop and start times are stored in arrays.
           The 4th cached frame will be the to use.
           If it needed its duration extended to make up
           lost time, it will have happened above. */
        out->s.start = pv->last_start[3];
        out->s.stop = pv->last_stop[3];

        adjust_frame_rate( pv, &out );
    }

    *buf_out = out;
    return HB_FILTER_OK;
}