DOC-USR-00XX-0X
___________________________________________________________________________________________
Z3 Technology, LLC
♦
100 N 8
th
ST, STE 250
♦
Lincoln, NE 68508-1369 USA
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+1.402.323.0702
23
6.8
Tuning for Latency
For latency, the key parameters to work with are Maximum Delay and Number of B-frames.
Maximum Delay defines the number of milliseconds of buffering the encoder has to work with. The
higher this value, the more buffer it has to work with and the more time it has to “smooth things out”
for challenging content. However, a higher value also causes latency to increase accordingly. To minimize
latency, this value should be set to the lowest possible value. The lowest value Z3 recommends is 100.
Note that lowering this value will also cause quality to degrade for challenging content (because the
encoder has fewer bits “over time” to work with). The tradeoff between latency and quality through this
parameter is left up to the user.
B-frames improve the quality of the picture, but they also increase the latency by 1 frame time. To
minimize latency, B-frames should be disabled (done by setting “Number of B-frames” to 0).
In general, streaming using RTP will result in lower latency than streaming using TS.
Figure 21 shows the suggested values for Maximum Delay and Number of B-frames for three common use
cases:
Maximum Delay
# of B-frames
Case 1: Highest Quality, Highest Latency
3000
2
Case 2: Good Quality, Standard Latency
2000
1
Case 3: Normal Quality, Lowest Latency
100
0
Figure 21 Tuning for Latency
If streaming to VLC, latency can be reduced on the decode side by adjusting the network caching
value. By default, this is set to 1000ms. You can lower this to as low as 200ms. To do this, go to the
following:
VLC
→
Tools
→
Preferences
→
Show Settings (ALL)
→
Input / Codecs
→
Network caching (ms)
