Differences

This shows you the differences between two versions of the page.

--- wiki:statmux_priorities [2016/12/09 09:06] – walkeradmin
+++ wiki:statmux_priorities [2016/12/09 09:19] – walkeradmin
@@ Line 8: / Line 8: @@
 \\
 \\
+----
 ==== Context ====
 \\
@@ Line 16: / Line 18: @@
 \\
 \\
+----
 ==== Specifications ====
-\\
 \\
 In this first version, the priority will be set only by mpeg4.cfg by specifying for each channel the prioritized level (1 or 0), using  the following line:
@@ Line 28: / Line 31: @@
 \\
 \\
-{{:wiki:statmuxpriorities01.png?300|}}
+{{:wiki:statmuxpriorities01.png?500|}}
+\\
+\\
+To set a priority to this channel:
+\\
+\\
+<color red>Service1.Profile 1-1.vid0.statmuxPriority=1</color>
+\\
+\\
+By default, all channels will set to un-prioritized.
+\\
+\\
+The expected behaviour is that a prioritized channel will have a better average objective video quality than without being prioritized. It could be checked by comparing in the same pool the same channel with and without priority.
+\\
+\\
+The improved VQ will be achieved by allocating more bitrate to prioritized channels compared to others. However, a prioritized channel could have in particular cases, a lower bitrate and so a lower VQ compared to non-prioritized channel.
+\\
+\\
+The maximal increase of bitrate, i.e. by comparing a channel bitrate with a VERY HIGH PRIORITY and the same channel with a normal priority, could be changed by mpeg4.cfg using the following parameter:
+\\
+\\
+<color red>statmux.m_smxPriorityRateFactor=0.5.</color>
+\\
+\\
+The default value is 0.2. The overridden value is clipped between 0.05 and 1.
+\\
+\\
+----
+==== 3	Priorities design ====
+\\
+Five priority levels have been planned. However, in the current state, only two priorities are used (VERY_HIGH and NORMAL):
+\\
+  * 	SMX_PRIORITY_VERY_HIGH		= 5
+  * 	SMX_PRIORITY_HIGH		= 4
+  * 	SMX_PRIORITY_NORMAL		= 3
+  * 	SMX_PRIORITY_LOW		= 2
+  * 	SMX_PRIORITY_VERY_LOW		= 1
+\\
+\\
+According to the maximal increase of bitrate  , priorities factor are:
+\\
+\\
+{{:wiki:statmuxpriorities02.png?500|}}
+\\
+\\
+Once the priority factor is computed, the statmux algorithm weights the complexity (STC) with each priority in order to balance the channel bit rate. Priorities are computed each time a channel is added or removed from the pool.
+\\
+\\
+----
+==== 4	Priorities and distortion control ====
+\\
+The distortion control aims at weighting channel’s complexity according to their MSE. Bigger the channel’s MSE, bigger the distortion factor is. Factors are computed every four statmux iterations (around twice a second). Factors are clipped between 0.5 and 2.
+\\
+\\
+However, when priorities are enabled, the distortion control could in some cases nullify the priority.  Indeed, as distortion factors can inferior to 1, it could nullify the impact of prioritizing a channel.
+To avoid such cases, factors are clipped according to the channel’s complexity:
+\\
+  * 	1.00 < F < 2.0 with a very high priority
+  * 	0.75 < F < 2.0 with a high complexity
+  * 	0.50 < F < 2.0 with a normal priority
+  * 	0.50 < F < 1.5 with a low priority
+  * 	0.50 < F < 1.0 with a very low complexity.
+\\
 \\