mirrors/gstreamer
mirrors/gstreamer
1
1
Fork 0
mirror of https://gitlab.freedesktop.org/gstreamer/gstreamer.git synced 2024-12-23 08:46:40 +00:00
Code Issues 1 Projects Releases Wiki Activity

docs/design/part-qos.txt: Fix indexes in formulas to make more sense.

Browse source 
Original commit message from CVS:
* docs/design/part-qos.txt:
Fix indexes in formulas to make more sense.
This commit is contained in:
Wim Taymans 2006-05-16 13:31:32 +00:00
parent 6af1d4c999
commit 090f3f4adc
2 changed files with 21 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
ChangeLog
View file

@ -1,3 +1,8 @@
2006-05-16 Wim Taymans <wim@fluendo.com>
* docs/design/part-qos.txt:
Fix indexes in formulas to make more sense.
2006-05-15 Wim Taymans <wim@fluendo.com>
* libs/gst/base/gstbasesink.c: (gst_base_sink_get_position):

32
docs/design/part-qos.txt
View file

@ -89,7 +89,7 @@ the upstream element is given as:
For values 0.0 < DR1 <= 1.0 the upstream element is producing faster than
real-time. If DR1 is exactly 1.0, the element is running at a perfect speed.
Values DR1 > 1.0 means that the upstream element cannot produce buffers of
Values DR1 > 1.0 mean that the upstream element cannot produce buffers of
duration D1 in real-time. It is exactly DR1 that tells the amount of speedup
we require from upstream to regain real-time performance.
@ -125,38 +125,38 @@ This will effectively result in frame drops.
The element can even do a better estimation of the next valid timestamp it
should output.
Indeed, given the element generate a buffer with timestamp B1 that arrived
in time in the sink but then received a QoS message stating B2 arrived J2
too late. This means generating B2 took (B2 - J2) - B1 = T1 - T0 = PT1, as
given in (3). Given the buffer B2 had a duration D2 and assuming that
generating a new buffer B3 will take the same amount of processing time,
a better estimation for B3 would then be:
Indeed, given the element generated a buffer with timestamp B0 that arrived
in time in the sink but then received a QoS message stating B1 arrived J1
too late. This means generating B1 took (B1 - J1) - B0 = T1 - T0 = PT1, as
given in (3). Given the buffer B1 had a duration D1 and assuming that
generating a new buffer B2 will take the same amount of processing time,
a better estimation for B2 would then be:
B3 = T1 + D3 * DR2
B2 = T1 + D2 * DR1
expanding gives:
B3 = (B2 - J2) + D3 * (B2 - J2 - B1)
B2 = (B1 - J1) + D2 * (B1 - J1 - B0)
--------------
D2
D1
assuming the durations of the frames are equal and thus D2 = D3:
assuming the durations of the frames are equal and thus D1 = D2:
B3 = (B2 - J2) + (B2 - J2 - B1)
B2 = (B1 - J1) + (B1 - J1 - B0)
B3 = 2 * (B2 - J2) - B1
B2 = 2 * (B1 - J1) - B0
also:
B1 = B2 - D2
B0 = B1 - D1
so:
B3 = 2 * (B2 - J2) - (B2 - D2)
B2 = 2 * (B1 - J1) - (B1 - D1)
Which yields a more accurate prediction for the next buffer given as:
B3 = B2 - 2 * J2 + D2 (5)
B2 = B1 - 2 * J1 + D1 (5)
Long term correction