int max_bits;
// For CBR we need to also consider buffer fullness.
- // If we are running below the optimal level then we need to gradually tighten up on max_bits.
if (cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER)
{
- double buffer_fullness_ratio = (double)cpi->buffer_level / DOUBLE_DIVIDE_CHECK((double)cpi->oxcf.optimal_buffer_level);
+ max_bits = 2 * cpi->av_per_frame_bandwidth;
+ max_bits -= cpi->buffered_av_per_frame_bandwidth;
+ max_bits *= ((double)cpi->oxcf.two_pass_vbrmax_section / 100.0);
+ }
+ // VBR
+ else
+ {
+ // For VBR base this on the bits and frames left plus the two_pass_vbrmax_section rate passed in by the user
+ max_bits = (int)(((double)cpi->twopass.bits_left / (cpi->twopass.total_stats->count - (double)cpi->common.current_video_frame)) * ((double)cpi->oxcf.two_pass_vbrmax_section / 100.0));
+ }
+
+ // Trap case where we are out of bits
+ if (max_bits < 0)
+ max_bits = 0;
- // For CBR base this on the target average bits per frame plus the maximum sedction rate passed in by the user
- max_bits = (int)(cpi->av_per_frame_bandwidth * ((double)cpi->oxcf.two_pass_vbrmax_section / 100.0));
+ return max_bits;
+}
- // If our buffer is below the optimum level
- if (buffer_fullness_ratio < 1.0)
- {
- // The lower of max_bits / 4 or cpi->av_per_frame_bandwidth / 4.
- int min_max_bits = ((cpi->av_per_frame_bandwidth >> 2) < (max_bits >> 2)) ? cpi->av_per_frame_bandwidth >> 2 : max_bits >> 2;
- max_bits = (int)(max_bits * buffer_fullness_ratio);
+static int gf_group_max_bits(VP8_COMP *cpi)
+{
+ // Max allocation for a golden frame group
+ int max_bits;
- if (max_bits < min_max_bits)
- max_bits = min_max_bits; // Lowest value we will set ... which should allow the buffer to refil.
+ // For CBR we need to also consider buffer fullness.
+ if (cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER)
+ {
+ max_bits = cpi->av_per_frame_bandwidth * cpi->baseline_gf_interval;
+ if (max_bits > cpi->oxcf.optimal_buffer_level)
+ {
+ max_bits -= cpi->oxcf.optimal_buffer_level;
+ max_bits += cpi->buffer_level;
}
+ else
+ {
+ max_bits -= (cpi->buffered_av_per_frame_bandwidth
+ - cpi->av_per_frame_bandwidth)
+ * cpi->baseline_gf_interval;
+ }
+
+ max_bits *= ((double)cpi->oxcf.two_pass_vbrmax_section / 100.0);
}
- // VBR
else
{
// For VBR base this on the bits and frames left plus the two_pass_vbrmax_section rate passed in by the user
max_bits = (int)(((double)cpi->twopass.bits_left / (cpi->twopass.total_stats->count - (double)cpi->common.current_video_frame)) * ((double)cpi->oxcf.two_pass_vbrmax_section / 100.0));
+ max_bits *= cpi->baseline_gf_interval;
}
+
// Trap case where we are out of bits
if (max_bits < 0)
max_bits = 0;
double abs_mv_in_out_accumulator = 0.0;
double mod_err_per_mb_accumulator = 0.0;
- int max_bits = frame_max_bits(cpi); // Max for a single frame
+ int max_group_bits;
unsigned int allow_alt_ref =
cpi->oxcf.play_alternate && cpi->oxcf.lag_in_frames;
// Clip cpi->twopass.gf_group_bits based on user supplied data rate
// variability limit (cpi->oxcf.two_pass_vbrmax_section)
- if (cpi->twopass.gf_group_bits > max_bits * cpi->baseline_gf_interval)
- cpi->twopass.gf_group_bits = max_bits * cpi->baseline_gf_interval;
+ max_group_bits = gf_group_max_bits(cpi);
+ if (cpi->twopass.gf_group_bits > max_group_bits)
+ cpi->twopass.gf_group_bits = max_group_bits;
// Reset the file position
reset_fpf_position(cpi, start_pos);
}
}
- // Apply an additional limit for CBR
- if (cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER)
- {
- if (cpi->twopass.gf_bits > (cpi->buffer_level >> 1))
- cpi->twopass.gf_bits = cpi->buffer_level >> 1;
- }
-
// Dont allow a negative value for gf_bits
if (gf_bits < 0)
gf_bits = 0;
cpi->rolling_actual_bits = cpi->av_per_frame_bandwidth;
cpi->long_rolling_target_bits = cpi->av_per_frame_bandwidth;
cpi->long_rolling_actual_bits = cpi->av_per_frame_bandwidth;
+ cpi->buffered_av_per_frame_bandwidth = cpi->av_per_frame_bandwidth;
cpi->total_actual_bits = 0;
cpi->total_target_vs_actual = 0;
break;
}
- if (cpi->pass == 0)
+ if (cpi->pass == 0 && cpi->oxcf.end_usage != USAGE_STREAM_FROM_SERVER)
cpi->auto_worst_q = 1;
cpi->oxcf.worst_allowed_q = q_trans[oxcf->worst_allowed_q];
}
+
+static void update_buffer_level(VP8_COMP *cpi)
+{
+ long long tmp;
+
+ /* Update the buffered average bitrate.
+ *
+ * The buffered average bitrate tracks the bitrate over the buffer
+ * window. Here we simulate taking a frame of average size out
+ * of the buffer, and putting in the new frame just encoded.
+ * It is calculated accordingly:
+ *
+ * A = Average Bits Per Frame In The Buffer
+ * P = New Frame Size
+ * N = Number of bits in the buffer
+ *
+ * We recalculate the average as so:
+ * (N-A)*A + A*P A * (N - A + P)
+ * A' = ------------- = ---------------
+ * N N
+ *
+ * This is modeled after a the standard algorithm for a moving
+ * average with fixed weighting (eg A' = ((N-1)*A + 1*P) / N). This makes
+ * the step response nonlinear but consistent with expected behavior --
+ * when A is large, the model adapts more quickly, since there are
+ * fewer frames in the buffer and conversely when A is small there
+ * will be more frames in the buffer so the average will adapt
+ * slowly.
+ *
+ * TODO(jkoleszar): This may give poor step response in some situations,
+ * for example motion following a long static section. It might be
+ * worth experimenting more with weighting by av_per_frame_bandwidth
+ * rather than buffered_av_per_frame_bandwidth or using a more accurate
+ * algorithm to get faster response. Current testing showed worse results
+ * with that setting though.
+ *
+ */
+
+ /* Guard against buffered_av_per_frame_bandwidth falling to 0. Should
+ * never happen, but without this check, it would be irrecoverable.
+ */
+ if(cpi->buffered_av_per_frame_bandwidth == 0)
+ cpi->buffered_av_per_frame_bandwidth = 1;
+
+ tmp = cpi->oxcf.maximum_buffer_size
+ - cpi->buffered_av_per_frame_bandwidth
+ + cpi->projected_frame_size;
+ tmp *= cpi->buffered_av_per_frame_bandwidth;
+ cpi->buffered_av_per_frame_bandwidth = tmp
+ / cpi->oxcf.maximum_buffer_size;
+
+ if(cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER)
+ {
+ /* In CBR mode, buffer level is synthesized from the buffered
+ * average per-frame bandwidth to get the response characteristics
+ * of that model, rather than using the unbounded (wrt buffer size)
+ * bits_off_target. ie, the long term average bitrate doesn't
+ * matter in CBR mode. If the clip is consistently undershooting
+ * because it is very static, for example, you don't want to blow
+ * your short term bitrate budget trying to the the long term spend
+ * up to the target when you hit a motion section.
+ *
+ * Instead, the ratio of buffered_av_per_frame_bandwidth to the
+ * target av_per_frame_bandwidth is taken, scaled by
+ * maximum_buffer_size and centered around optimal_buffer_level,
+ * which presents the expected behavior of buffer_level for the other
+ * parts of the rate control code which handle the targeting.
+ *
+ * Note that this only happens after the starting_buffer_level
+ * has passed, to give the model a chance to stabilize.
+ */
+ if(cpi->total_actual_bits > cpi->oxcf.starting_buffer_level)
+ {
+ tmp = (long long)cpi->buffered_av_per_frame_bandwidth
+ * cpi->oxcf.maximum_buffer_size
+ / cpi->av_per_frame_bandwidth;
+ cpi->buffer_level = cpi->oxcf.maximum_buffer_size
+ - tmp
+ + cpi->oxcf.optimal_buffer_level;
+ }
+ else
+ cpi->buffer_level = cpi->oxcf.optimal_buffer_level;
+
+ /* Accumulate recent overshoot error.
+ *
+ * If this frame is larger than the target, then accumulate
+ * that error to apply as a damping factor later. Only care about
+ * recent overshoot, so this value decays by (N-P)/N
+ */
+ if(cpi->total_actual_bits > cpi->oxcf.starting_buffer_level)
+ {
+ long long decayed_overshoot;
+
+ decayed_overshoot = cpi->accumulated_overshoot;
+ decayed_overshoot *= (cpi->oxcf.maximum_buffer_size
+ - cpi->projected_frame_size);
+ decayed_overshoot /= cpi->oxcf.maximum_buffer_size;
+ cpi->accumulated_overshoot = decayed_overshoot;
+
+ cpi->accumulated_overshoot +=
+ (cpi->projected_frame_size > cpi->av_per_frame_bandwidth)
+ ? cpi->projected_frame_size - cpi->av_per_frame_bandwidth
+ : 0;
+ }
+ }
+ else
+ cpi->buffer_level = cpi->bits_off_target;
+}
+
+
static void encode_frame_to_data_rate
(
VP8_COMP *cpi,
// For CBR if the buffer reaches its maximum level then we can no longer
// save up bits for later frames so we might as well use them up
// on the current frame.
- if ((cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER) &&
+ if (cpi->pass == 2
+ && (cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER) &&
(cpi->buffer_level >= cpi->oxcf.optimal_buffer_level) && cpi->buffered_mode)
{
int Adjustment = cpi->active_worst_quality / 4; // Max adjustment is 1/4
}
else
{
+ if(cpi->pass != 2)
+ Q = cpi->auto_worst_q?
+ cpi->active_worst_quality:cpi->avg_frame_qindex;
+
cpi->active_best_quality = inter_minq[Q];
// For the constant/constrained quality mode we dont want
(cpi->active_worst_quality < cpi->worst_quality) &&
(cpi->projected_frame_size > frame_over_shoot_limit))
{
- int over_size_percent = ((cpi->projected_frame_size - frame_over_shoot_limit) * 100) / frame_over_shoot_limit;
+ /* step down active_worst_quality such that the corresponding
+ * active_best_quality will be equal to the current
+ * active_worst_quality + 1. Once the limit on active_best_quality
+ * is reached, active_worst_quality will equal worst_quality.
+ */
+ int i;
- // If so is there any scope for relaxing it
- while ((cpi->active_worst_quality < cpi->worst_quality) && (over_size_percent > 0))
- {
- cpi->active_worst_quality++;
- top_index = cpi->active_worst_quality;
- over_size_percent = (int)(over_size_percent * 0.96); // Assume 1 qstep = about 4% on frame size.
- }
+ for(i=cpi->active_worst_quality; i<cpi->worst_quality; i++)
+ if(inter_minq[i] >= cpi->active_worst_quality + 1)
+ break;
+ cpi->active_worst_quality = i;
// If we have updated the active max Q do not call vp8_update_rate_correction_factors() this loop.
active_worst_qchanged = TRUE;
// Update the buffer level variable.
// Non-viewable frames are a special case and are treated as pure overhead.
- if ( !cm->show_frame )
- cpi->bits_off_target -= cpi->projected_frame_size;
- else
- cpi->bits_off_target += cpi->av_per_frame_bandwidth - cpi->projected_frame_size;
+ if ( cm->show_frame )
+ cpi->bits_off_target += cpi->av_per_frame_bandwidth;
+ cpi->bits_off_target -= cpi->projected_frame_size;
// Rolling monitors of whether we are over or underspending used to help regulate min and Max Q in two pass.
cpi->rolling_target_bits = ((cpi->rolling_target_bits * 3) + cpi->this_frame_target + 2) / 4;
// Debug stats
cpi->total_target_vs_actual += (cpi->this_frame_target - cpi->projected_frame_size);
- cpi->buffer_level = cpi->bits_off_target;
+ update_buffer_level(cpi);
// Update bits left to the kf and gf groups to account for overshoot or undershoot on these frames
if (cm->frame_type == KEY_FRAME)
projects / libvpx / commitdiff