An Efficient Packetization Scheme for Bluetooth Video Transmission

The Bluetooth wireless link is likely to be the last hop in the delivery of an encoded streamed video clip. This paper shows that it is preferable to optimally map arriving IP packets onto Bluetooth packets than preserve the stream’s internal synchronization structure. Video quality improves and latency reduces, even when there is cross traffic on the piconet. Introduction: For efficient transport across an IEEE 802.15.1 (Bluetooth) wireless link [1], the slice structure of an MPEG-2 encoded video stream must be mapped onto the Bluetooth (B/T) packet structure. In the widely-deployed MPEG-2 codec, a slice consists of up to one row of macroblocks but unlike an MPEG-1 slice should not extend beyond one row. The main reason for defining slices is to prevent channel error propagation by means of synchronization markers. Assuming a slice arrives at a B/T base station encapsulated in an IP packet then it must be formed into a B/T packet, the maximum sizes of which are quantized by the B/T channel time-slot structure. This Letter demonstrates that allowing a slice to be split between two B/T packets, dynamic packetization, brings significant advantages when the receiver’s buffer size is limited. The advantages occur in terms of reduced overall delay and packet loss through buffer overflow, and improved peak signal-to-noise ratio (PSNR). The dynamic packetization scheme achieved higher received video quality, despite the potential loss of synchronization at the decoder due to the arrival of packets bearing partial slices. Only in conditions of very low SNR will dynamic packetization possibly lose its attraction, in which case static slice allocation schemes may be considered. The results have implications for other codecs.