 Any of the above can be made variable bit rate by changing the bit rate switch. Video Bandwidth Cost and Value For video coding the mandatory H263 codec supports a QCIF frame size of 176 by 144 pixels or sub-QCIF 128 by 96 pixels at up to 15 frames per second. MPEG4 is similar. Both map to a maximum 64-kb channel. In 3G Handset and Network Design we suggested users might be prepared to pay extra for better quality images and video. Image and video quality is usually already degraded as a result of compression with the loss of quality being determined as a Q factor. In J-PEG (image encoding), 8 X 8 pixel blocks are transformed in the frequency domain and expressed as digital coefficients. A Q factor of 100 means that pixel blocks need to be identical to be coded as 'the same'. A Q factor of 50 means that pixel blocks can be quite different from one another, but the differences are ignored by the encoder. The result is a reduction in image 'verity' - the image resembles the original but has incurred loss of information. In digital cameras, 90 equates to fine camera mode, a Q factor of 70 equates to standard camera mode. These compression standards have been developed generally to maximise storage band- width. You can store more Q70 pictures in your camera than Q90 pictures. However, choice of Q also has a significant impact on transmission bandwidth. An image with a Q of 90 (a 172-kbyte file) would take just over 40 seconds to send on a 33 kbps (uncoded) channel. The same picture with a Q of 5 would be 12 kb and could be sent in under 3 seconds. The delivery cost has been reduced by an order of magnitude. The question is how much value has been from the picture. The question also arises as to who sizes the image and decides on its original quality, the user, the application, the user's device or the network. Similar issues arise with video encoding excepting that in addition to the resolution, colour depth and Q comprehended by J-PEG, we have to add in frame rate. Perceptions of quality will, however, be quite sub