When configuring the output stream quality settings on your encoder there is an advanced setting called 'Reserve idle stream bandwidth':
This setting is only available on encoders that support multiple output EdgeVis streams.
New in Version 8.6 - New default setting
Older encoder firmware set this default to disabled.
Encoders that use 8.6 and above (including those upgraded from an earlier version) will now enable this setting by default.
Behaviour when 'enabled'
The encoder will take the 'maximum streaming bandwidth' and divide it by the number of output video streams - and allocate that amount of bandwidth to each individual output video stream. Each individual output stream will never exceed this amount, regardless of how many streams are being viewed by end users.
For example:
An EVVR4 has four output video streams enabled and is configured with a maximum streaming bandwidth of 2 mbit/s.
Reserve idle stream bandwidth is enabled.
The encoder will allocate 500 kbit/s to each output video stream (2 mbit/s / 4 output streams).
Regardless of how many output video streams are being viewed, none of them will exceed 500 kbit/s.
Behaviour when 'disabled'
The encoder will take the 'maximum streaming bandwidth', and divide it by the number of output video streams that are currently being viewed - this is the amount of bandwidth that will be allocated to the video streams being viewed. Should a user start to view an additional unused video stream (or stop viewing a current stream) then the calculation is updated to reflect the current number of output video streams being used.
For example:
An EVVR4 has four output video streams enabled and is configured with a maximum streaming bandwidth of 2 mbit/s.
Reserve idle stream bandwidth is disabled, and no one is viewing any of the video streams.
A user starts to view one of the output video streams - the encoder will allocate all 2 mbit/s to this individual stream.
The user then starts to view an additional output video stream on the encoder - the encoder will then allocate 1 mbit/s to both streams being viewed.
The user then starts to view the remaining two output video streams on the encoder (so all four are now being viewed) - the encoder will then allocate all 500 kbit/s to all streams being viewed.
The user stops viewing all streams except the original single output stream - the encoder will reallocate 2 mbit/s to this single stream again.
Which setting should I use?
We normally recommend keeping this setting enabled. This ensures predictability, especially when you have large numbers of output video streams.
If you have between four and eight video streams and a high maximum streaming bandwidth (e.g. 4-8 mbit/s) you do not want a single output stream consuming the entire bandwidth allocation - especially for cost reasons.
When to disable the setting?
There are scenarios where it can be useful to disable it. For example:
You are using a small number of output streams, where one stream is used the majority of the time (and the others are used occasionally). Disabling this setting allows you to get the maximum quality out of your primary stream, with the ability to support viewing the secondary streams when necessary (at the expense of sharing the available bandwidth between the primary and secondary streams for short periods).