Adtec digital EN-20 (version 2.03.06) Manual - Manual (Page 39)

How TMR is Configured
The EN-20 is sold with an optional integrated QAM modulator. TMR is affected differently when
the modulator is installed. Below outlines the differences.
When the QAM modulator is present the TMR (Transport Stream Mux Rate) is controlled
by the modulator’s clock.
When in Annex B mode, the rates listed below will be configured and can not be changed.
Annex B QAM 256 the TMR is set to 38.810671 bps.
Annex B QAM 64 the TMR will be set to 26.970186 bps.
When in Annex A mode, the symbol rates are adjustable and that in turn affects the configured
TMR. The higher the symbol rate, the higher the data rate.
When the QAM modulator is not present, TMR can be configured via the webUI or from
the front panel Services Menu / TS Mux Rate (bit/s). The maximum TMR is 80 Mbps.
How Video Rates are Configured
Video rates can be configured manually or automatically. The factory default is to automatically
set the video rate based on TMR. This option is referred to as VAF (Video Autofill). VAF
determines what the TMR is. It reserves 3.5% for null packets. It detects the video input
resolution for each channel. It automatically calculates the required headroom for audio pids. It
sets the video bit rate for each channel accordingly to maximise available bandwidth.
SD encode bitrate = 1.00 to 15.00 Mbps
HD encode bit rate = 7.00 to 60.00 Mbps
Example:
TMR is set to 40 Mbps.
Channel 1 has a SD 720x480i source.
Channel 2 has a HD 1920x1080i source.
15.00 Mbps will be allocated to channel 1 because the source is standard definition. 19.10Mbps
will be allocated to channel 2 (this is the available band with after VAFs calculation)
If VAF is set to off the video rate can be manually adjusted for each channel. If you configure a
channel at a video rate that would cause a egress overflow the VAF logic will constrain the
misconfiguration and reconfigure the video rate for both channels.
Example:
TMR is set to 40 Mbps.
Both channels have a HD1920x1080i source.
Both channels audio = 256 kbps
Video fill is set to off.