DYNAMIC BIT RATE ADAPTATION OVER BANDWIDTH VARYING CONNECTION

摘要

Audio and video streams of a media file are transcoded just-in-time by keeping the transcoding process synchronized to a wall clock. The transcoding is initially configured slightly faster than real-time. The transcoded frames are pushed from the transcoder through a variable bandwidth connection as soon as they are transcoded. Transcoding is then monitored periodically to assess the bandwidth that was available during the transmission of a transcoded buffer. Two time intervals are measured: a buffer interval which is the difference in the transcoded buffer timestamps of the previous two transmissions, and a clock interval corresponding to the real time transmission time of the last transcoded buffer. If a significant difference is observed, the transcoder bit rate is adjusted by a factor that is derived from that difference.

主权项

1. A method for encoding a media file or part thereof for transmission in real time over a varying bandwidth link to a mobile unit, comprising:
employing at least one processor of a transcoder for: (i) encoding one or more fragments of the media file into transcoded media fragments to form a stream fragment; (ii) sending the stream fragment to a transmission buffer of the transcoder; (iii) determining an estimated transmit time of a previously formed stream fragment, the estimated transmit time being a time interval required for said previously formed stream fragment to be conveyed from the transmission buffer and consumed by the varying bandwidth link; (iv) determining an estimated display time of said stream fragment; and (v) adjusting a current encoding rate of the transcoded media fragments as a function of the estimated transmit time and the estimated display time.