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Improved KF insertion after fades to still.

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This code extends what was previously done for GFs, to pick
cases where insertion of a key frame after a fade (or other
transition or complex motion)  followed by a still section, will
be beneficial and will reduce the number of forced key frames.

Change-Id: If8bca00457f0d5f83dc3318a587f61c17d90f135
This commit is contained in:
Paul Wilkins 2011-03-07 15:11:09 +00:00
parent 3fae3283e6
commit 9fc8cb39aa
1 changed files with 86 additions and 71 deletions
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157
vp8/encoder/firstpass.c
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@ -1341,7 +1341,7 @@ void vp8_end_second_pass(VP8_COMP *cpi)
// This function gives and estimate of how badly we believe
// the predicition quality is decaying from frame to frame.
double gf_prediction_decay_rate(VP8_COMP *cpi, FIRSTPASS_STATS *next_frame)
double get_prediction_decay_rate(VP8_COMP *cpi, FIRSTPASS_STATS *next_frame)
{
double prediction_decay_rate;
double motion_decay;
@ -1375,6 +1375,51 @@ double gf_prediction_decay_rate(VP8_COMP *cpi, FIRSTPASS_STATS *next_frame)
return prediction_decay_rate;
}
// Funtion to test for a condition where a complex transition is followe
// by a static section. For example in slide shows where there is a fade
// between slides. This is to help with more optimal kf and gf positioning.
BOOL detect_transition_to_still(
VP8_COMP *cpi,
int frame_interval,
int still_interval,
double loop_decay_rate,
double decay_accumulator )
{
BOOL trans_to_still = FALSE;
// Break clause to detect very still sections after motion
// For example a staic image after a fade or other transition
// instead of a clean scene cut.
if ( (frame_interval > MIN_GF_INTERVAL) &&
(loop_decay_rate >= 0.999) &&
(decay_accumulator < 0.9) )
{
int j;
FIRSTPASS_STATS * position = cpi->stats_in;
FIRSTPASS_STATS tmp_next_frame;
double decay_rate;
// Look ahead a few frames to see if static condition
// persists...
for ( j = 0; j < still_interval; j++ )
{
if (EOF == vp8_input_stats(cpi, &tmp_next_frame))
break;
decay_rate = get_prediction_decay_rate(cpi, &tmp_next_frame);
if ( decay_rate < 0.999 )
break;
}
// Reset file position
reset_fpf_position(cpi, position);
// Only if it does do we signal a transition to still
if ( j == still_interval )
trans_to_still = TRUE;
}
return trans_to_still;
}
// Analyse and define a gf/arf group .
static void define_gf_group(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
@ -1528,7 +1573,7 @@ static void define_gf_group(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
if (r > GF_RMAX)
r = GF_RMAX;
loop_decay_rate = gf_prediction_decay_rate(cpi, &next_frame);
loop_decay_rate = get_prediction_decay_rate(cpi, &next_frame);
// Cumulative effect of decay
decay_accumulator = decay_accumulator * loop_decay_rate;
@ -1537,48 +1582,13 @@ static void define_gf_group(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
boost_score += (decay_accumulator * r);
// Break clause to detect very still sections after motion
// For example a staic image after a fade or other transition
// instead of a clean key frame.
if ( (i > MIN_GF_INTERVAL) &&
(loop_decay_rate >= 0.999) &&
(decay_accumulator < 0.9) )
// For example a staic image after a fade or other transition.
if ( detect_transition_to_still( cpi, i, 5,
loop_decay_rate, decay_accumulator ) )
{
int j;
FIRSTPASS_STATS * position = cpi->stats_in;
FIRSTPASS_STATS tmp_next_frame;
double decay_rate;
// Look ahead a few frames to see if static condition
// persists...
for ( j = 0; j < 4; j++ )
{
if (EOF == vp8_input_stats(cpi, &tmp_next_frame))
break;
decay_rate = gf_prediction_decay_rate(cpi, &tmp_next_frame);
if ( decay_rate < 0.999 )
break;
}
reset_fpf_position(cpi, position); // Reset file position
// Force GF not alt ref
if ( j == 4 )
{
if (0)
{
FILE *f = fopen("fadegf.stt", "a");
fprintf(f, " %8d %8d %10.4f %10.4f %10.4f\n",
cpi->common.current_video_frame+i, i,
loop_decay_rate, decay_accumulator,
boost_score );
fclose(f);
}
allow_alt_ref = FALSE;
boost_score = old_boost_score;
break;
}
allow_alt_ref = FALSE;
boost_score = old_boost_score;
break;
}
// Break out conditions.
@ -2363,13 +2373,13 @@ static BOOL test_candidate_kf(VP8_COMP *cpi, FIRSTPASS_STATS *last_frame, FIRST
}
void vp8_find_next_key_frame(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
{
int i;
int i,j;
FIRSTPASS_STATS last_frame;
FIRSTPASS_STATS first_frame;
FIRSTPASS_STATS next_frame;
FIRSTPASS_STATS *start_position;
double decay_accumulator = 0;
double decay_accumulator = 1.0;
double boost_score = 0;
double old_boost_score = 0.0;
double loop_decay_rate;
@ -2379,6 +2389,7 @@ void vp8_find_next_key_frame(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
double kf_group_intra_err = 0.0;
double kf_group_coded_err = 0.0;
double two_pass_min_rate = (double)(cpi->oxcf.target_bandwidth * cpi->oxcf.two_pass_vbrmin_section / 100);
double recent_loop_decay[8] = {1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0};
vpx_memset(&next_frame, 0, sizeof(next_frame)); // assure clean
@ -2407,6 +2418,7 @@ void vp8_find_next_key_frame(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
kf_mod_err = calculate_modified_err(cpi, this_frame);
// find the next keyframe
i = 0;
while (cpi->stats_in < cpi->stats_in_end)
{
// Accumulate kf group error
@ -2425,9 +2437,34 @@ void vp8_find_next_key_frame(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
if (cpi->oxcf.auto_key
&& lookup_next_frame_stats(cpi, &next_frame) != EOF)
{
// Normal scene cut check
if (test_candidate_kf(cpi, &last_frame, this_frame, &next_frame))
break;
// How fast is prediction quality decaying
loop_decay_rate = get_prediction_decay_rate(cpi, &next_frame);
// We want to know something about the recent past... rather than
// as used elsewhere where we are concened with decay in prediction
// quality since the last GF or KF.
recent_loop_decay[i%8] = loop_decay_rate;
decay_accumulator = 1.0;
for (j = 0; j < 8; j++)
{
decay_accumulator = decay_accumulator * recent_loop_decay[j];
}
// Special check for transition or high motion followed by a
// to a static scene.
if ( detect_transition_to_still( cpi, i,
(cpi->key_frame_frequency-i),
loop_decay_rate,
decay_accumulator ) )
{
break;
}
// Step on to the next frame
cpi->frames_to_key ++;
@ -2437,6 +2474,8 @@ void vp8_find_next_key_frame(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
break;
} else
cpi->frames_to_key ++;
i++;
}
// If there is a max kf interval set by the user we must obey it.
@ -2588,32 +2627,8 @@ void vp8_find_next_key_frame(VP8_COMP *cpi, FIRSTPASS_STATS *this_frame)
if (r > RMAX)
r = RMAX;
// Adjust loop decay rate
//if ( next_frame.pcnt_inter < loop_decay_rate )
loop_decay_rate = next_frame.pcnt_inter;
// High % motion -> somewhat higher decay rate
motion_pct = next_frame.pcnt_motion;
motion_decay = (1.0 - (motion_pct / 20.0));
if (motion_decay < loop_decay_rate)
loop_decay_rate = motion_decay;
// Adjustment to decay rate based on speed of motion
{
double this_mv_rabs;
double this_mv_cabs;
double distance_factor;
this_mv_rabs = fabs(next_frame.mvr_abs * motion_pct);
this_mv_cabs = fabs(next_frame.mvc_abs * motion_pct);
distance_factor = sqrt((this_mv_rabs * this_mv_rabs) +
(this_mv_cabs * this_mv_cabs)) / 250.0;
distance_factor = ((distance_factor > 1.0)
? 0.0 : (1.0 - distance_factor));
if (distance_factor < loop_decay_rate)
loop_decay_rate = distance_factor;
}
// How fast is prediction quality decaying
loop_decay_rate = get_prediction_decay_rate(cpi, &next_frame);
decay_accumulator = decay_accumulator * loop_decay_rate;
decay_accumulator = decay_accumulator < 0.1 ? 0.1 : decay_accumulator;