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Communicating with the UiO Bitfield Gateway

The Bitfield codecs used by UiO are variable bit rate and can easily generate data rates the V3.0b of the codec controller cannot run at. It is therefore important to ensure that the bitfield gateway is set to a maximum data rate of around the chosen clock rate of the GPT/BT codec.

The current versions of the Bitfield card being used have a bug which means that they cannot properly decode H261 quantisers of less than 4. The GPT and BT codecs normally choose the quantisers dynamically, and thus sometimes use quantisers that cause image corruption on the image the bitfield codec has decoded. To avoid this, it's suggested that the quantiser be fixed to 8 when transmitting to a bitfield codec. See Appendix 1 for details of how to do this.