A method for determining whether digital content downloaded from a content server to a content buffer can be accessed for playback from the content buffer at a predetermined bit rate without causing a buffer under-run, the method comprising: determining that one or more units of digital content in a file of digital content still have to be downloaded and buffered for playback; estimating a download time of a first unit of digital content based on the size of the first unit of digital content and an available download bandwidth, wherein a first encoded sequence is included in a plurality of encoded sequences stored in the file of digital content and each encoded sequence corresponds to a different bit rate at which digital content in the content buffer can be accessed for playback, whereby the size of the first unit of digital content depends on the first encoded sequence included in the file of digital content from which the first unit of digital content is downloaded; computing a new value of an amount of playback time currently stored in the content buffer by subtracting the estimated download time from a current value of the amount of playback time currently stored in the content buffer; determining whether the new value of the amount of playback time currently stored in the content buffer is less than or equal to zero, indicating that a buffer under-run will occur; indicating that downloading the first unit of digital content from the first encoded sequence is feasible, if a buffer under-run will not occur, or indicating that downloading the first unit of digital content from the first encoded sequence is not feasible if a buffer under-run will occur; wherein the step of computing a new value of an amount of playback time further comprises the step of updating the time associated with playing back all of the digital content stored in the content buffer to account for the first unit of digital content being downloaded from the first encoded sequence to the content buffer, and wherein the steps of estimating a download time, computing a time associated with playing back, determining whether the computed time is less than or equal to zero, and indicating whether downloading is feasible or not feasible are repeated for a second unit of digital content, and wherein the second unit of digital content is downloaded from either the first encoded sequence or another encoded sequence included in the file of digital content. determining that one or more units of digital content in a file of digital content still have to be downloaded and buffered for playback; estimating a download time of a first unit of digital content based on the size of the first unit of digital content and an available download bandwidth, wherein a first encoded sequence is included in a plurality of encoded sequences stored in the file of digital content and each encoded sequence corresponds to a different bit rate at which digital content in the content buffer can be accessed for playback, whereby the size of the first unit of digital content depends on the first encoded sequence included in the file of digital content from which the first unit of digital content is downloaded; computing a new value of an amount of playback time currently stored in the content buffer by subtracting the estimated download time from a current value of the amount of playback time currently stored in the content buffer; determining whether the new value of the amount of playback time currently stored in the content buffer is less than or equal to zero, indicating that a buffer under-run will occur; indicating that downloading the first unit of digital content from the first encoded sequence is feasible, if a buffer under-run will not occur, or indicating that downloading the first unit of digital content from the first encoded sequence is not feasible if a buffer under-run will occur; wherein the step of computing a new value of an amount of playback time further comprises the step of updating the time associated with playing back all of the digital content stored in the content buffer to account for the first unit of digital content being downloaded from the first encoded sequence to the content buffer, and wherein the steps of estimating a download time, computing a time associated with playing back, determining whether the computed time is less than or equal to zero, and indicating whether downloading is feasible or not feasible are repeated for a second unit of digital content, and wherein the second unit of digital content is downloaded from either the first encoded sequence or another encoded sequence included in the file of digital content.