CSI Digital xCoder, User Manual

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Stream Group Settings: Stream Groups define common settings optimized for client device video
capabilities. Preset values such as Apple devices, PCs, etc are available to be chosen. More than one
stream group can be used for each input channel.
For example, one stream group could be “iPad” and the second stream group “ipod”. Each of these
stream groups would then be optimized for these device types including the H.264 profile support.
For each stream group, 1 to 4 streams can be created with different video parameters. This is to support
the dynamic streaming protocols of Flash, Apple, and Silverlight.
Stream parameter options:
•
Stream: You can enable each stream within a stream group with the check box next to each
Stream N name.
•
Audio Only: Audio only stream can be defined by selecting the check box audio only. This is only
supported by Apple HLS.
•
Video Resolution: Video resolution presets (common resolutions used on the internet) or a
customer defined video resolution can be created.
•
Horizontal/Vertical Resolution: Custom horizontal and vertical resolutions are available to be
defined
•
Frame Rate: Each stream group can have a different frame rate based on the incoming rate.
xCoder can also change the frame rate per stream, however most multistream protocols, servers,
and end devices do not support this mode
. It is recommended to keep the frame rate of all
streams in a stream group to be the same.
•
CBR or VBR Mode: VBR mode is more bandwidth efficient. Depending on the specific content
and settings, the VBR mode can provide 20-30% more efficient bitstreams. To put another way,
20-30% less bandwidth is needed to distribute the content.
•
Mux Target (kbps): This is the Total bitrate (audio + video+ mux overhead) setting for the stream.
o
For CBR mode, this is the birate for the TS stream.
o
For VBR, this is the target rate, but the rate will vary up to the VBR Max parameter.
o
Be careful to include some overhead bit rate. Mux overhead varies but 30 Kbps is a good
rule of thumb. For example, if you want 500 Kbps video rate, and your audio rate is set
to 64 Kbps, then set the total bitrate to 600 Kbps, and video rate will be close to 500
Kbps.
•
VBR Max: This is the max total bitrate for the stream for VBR mode. CBR mode ignores this
parameter
•
Audio Bitrate (kbps): Audio bitrate is defined from the Output section (previous tab). All streams
are forced to use the same audio bit rate for audio quality reasons during stream switching.
•
Image Overlay: The image overlay can be enabled or disabled per stream.
The Video bitrate is calculated internal to xCoder based on the total bitrate and audio bitrate.