Abstract:
Video streaming over the Internet and
packet-based wireless networks is sensitive to packet loss,
which can severely damage the quality of the received
video. To protect the transmitted video data against packet
loss, application-layer forward error correction (FEC)
is commonly used. Typically, for a given source block,
the channel code rate is fixed in advance according to
an estimation of the packet loss rate. However, since
network conditions are difficult to predict, determining the
right amount of redundancy introduced by the channel
encoder is not obvious. To address this problem, we
consider a general framework where the sender applies
rateless erasure coding to every source block and keeps
on transmitting the encoded symbols until it receives an
acknowledgment from the receiver indicating that the
block was decoded successfully. Within this framework,
we design transmission strategies that aim at minimizing
the expected bandwidth usage while ensuring successful
decoding subject to an upper bound on the packet loss
rate. In real simulations over the Internet, our solution
outperformed standard FEC and hybrid ARQ approaches.
For the QCIF Foreman sequence compressed with the
H.264 video coder, the gain in average peak signal to noise
ratio over the best previous scheme exceeded 3.5 decibels
at 90 kilobits per second.
