Change rc undershoot/overshoot semantics
This patch changes the rc_undershoot_pct and rc_overshoot_pct controls
to set the "aggressiveness" of rate adaptation, by limiting the
amount of difference between the target buffer level and the actual
buffer level which is applied to the target frame rate for this frame.
This patch was initially provided by arosenberg at logitech.com as
an attachment to issue #270. It was modified to separate these controls
from the other unrelated modifications in that patch, as well as to
use the pre-existing variables rather than introducing new ones.
Change-Id: Id542e3f5667dd92d857d5eabf29878f2fd730a62
diff --git a/vp8/encoder/ratectrl.c b/vp8/encoder/ratectrl.c
index 9821d29..767b271 100644
--- a/vp8/encoder/ratectrl.c
+++ b/vp8/encoder/ratectrl.c
@@ -817,11 +817,6 @@
}
}
- // Set a reduced data rate target for our initial Q calculation.
- // This should help to save bits during earier sections.
- if ((cpi->oxcf.under_shoot_pct > 0) && (cpi->oxcf.under_shoot_pct <= 100))
- cpi->this_frame_target = (cpi->this_frame_target * cpi->oxcf.under_shoot_pct) / 100;
-
// Sanity check that the total sum of adjustments is not above the maximum allowed
// That is that having allowed for KF and GF penalties we have not pushed the
// current interframe target to low. If the adjustment we apply here is not capable of recovering
@@ -858,11 +853,6 @@
percent_low =
(cpi->oxcf.optimal_buffer_level - cpi->buffer_level) /
one_percent_bits;
-
- if (percent_low > 100)
- percent_low = 100;
- else if (percent_low < 0)
- percent_low = 0;
}
// Are we overshooting the long term clip data rate...
else if (cpi->bits_off_target < 0)
@@ -870,16 +860,16 @@
// Adjust per frame data target downwards to compensate.
percent_low = (int)(100 * -cpi->bits_off_target /
(cpi->total_byte_count * 8));
-
- if (percent_low > 100)
- percent_low = 100;
- else if (percent_low < 0)
- percent_low = 0;
}
+ if (percent_low > cpi->oxcf.under_shoot_pct)
+ percent_low = cpi->oxcf.under_shoot_pct;
+ else if (percent_low < 0)
+ percent_low = 0;
+
// lower the target bandwidth for this frame.
- cpi->this_frame_target =
- (cpi->this_frame_target * (100 - (percent_low / 2))) / 100;
+ cpi->this_frame_target -= (cpi->this_frame_target * percent_low)
+ / 200;
// Are we using allowing control of active_worst_allowed_q
// according to buffer level.
@@ -950,20 +940,29 @@
}
else
{
- int percent_high;
+ int percent_high = 0;
- if (cpi->bits_off_target > cpi->oxcf.optimal_buffer_level)
+ if ((cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER)
+ && (cpi->buffer_level > cpi->oxcf.optimal_buffer_level))
{
- percent_high = (int)(100 * (cpi->bits_off_target - cpi->oxcf.optimal_buffer_level) / (cpi->total_byte_count * 8));
-
- if (percent_high > 100)
- percent_high = 100;
- else if (percent_high < 0)
- percent_high = 0;
-
- cpi->this_frame_target = (cpi->this_frame_target * (100 + (percent_high / 2))) / 100;
-
+ percent_high = (cpi->buffer_level
+ - cpi->oxcf.optimal_buffer_level)
+ / one_percent_bits;
}
+ else if (cpi->bits_off_target > cpi->oxcf.optimal_buffer_level)
+ {
+ percent_high = (int)((100 * cpi->bits_off_target)
+ / (cpi->total_byte_count * 8));
+ }
+
+ if (percent_high > cpi->oxcf.over_shoot_pct)
+ percent_high = cpi->oxcf.over_shoot_pct;
+ else if (percent_high < 0)
+ percent_high = 0;
+
+ cpi->this_frame_target += (cpi->this_frame_target *
+ percent_high) / 200;
+
// Are we allowing control of active_worst_allowed_q according to bufferl level.
if (cpi->auto_worst_q)
