According to one aspect of the present invention there is provided a method of transmitting an encoded sequence over a network to a terminal, comprising: storing a plurality of encoded versions of the same sequence, wherein each version comprises a plurality of discrete portions of data and each version corresponds to a respective different degree of compression; transmitting a current one of said versions; ascertaining the data rate permitted by the network; ascertaining the state of a receiving buffer at the terminal; for at least one candidate version, computing in respect of at least one discrete portion thereof as yet unsent the maximum value of a timing error that would occur were any number of portions starting with that portion to be sent at the currently ascertained permitted rate; comparing the determined maximum error values with the ascertained buffer state; selecting one of said versions for transmission, in dependence on the results of said comparisons; and transmitting the selected version.
In another aspect, the invention provides a method of transmitting an encoded sequence over a network to a terminal, comprising: storing a plurality of encoded versions of the same sequence, wherein each version comprises a plurality of discrete portions of data and each version corresponds to a respective different degree of compression; for each version and for each of a plurality of nominal transmitting rates, computing in respect of at least one discrete portion thereof the maximum value of a timing error that would occur were any number of portions starting with that portion to be sent at the respective nominal rate; storing said maximum error values; transmitting a current one of said versions; ascertaining the data rate permitted by the network; ascertaining the state of a receiving buffer at the terminal; for at least one candidate version, using the ascertained permitted data rate and the stored maximum error values to estimate a respective maximum error value corresponding to said ascertained permitted data rate; comparing the estimated maximum error values with the ascertained buffer state; selecting one of said versions for transmission, in dependence on the results of said comparisons; and transmitting the selected version.
Further aspects of the invention are set out in the claims