Video Streaming: An FEC-Based Novel Approach Jianfei Cai, Chang Wen Chen Electrical and Computer Engineering, Canadian Conference on

Outline Introduction Characteristics of Video Streaming Packetization and Channel Coding Source Coding and Channel Coding Description of the proposed system Pre-interleaving Experimental Result

Introduction Problems of Internet video streaming packet loss Packet delay Because of the bandwidth constraint, the video data are necessarily compressed for efficient transmission Compressed video data become very sensitive to transport error

Introduction (cont.) Due to the time constraint for video streaming, it is considered more beneficial to use FEC coding schemes than to use retransmission schemes Video streaming over packet-switching network: Packet loss: can be viewed as bursty errors with known length and positions. Video transmission in wireless channels: The errors tend to occur in bursts

FEC with Interleaving Conventional design of FEC-based video transmission HEADER FEC Channel Coding a network packet

FEC with Interleaving (cont.) The interleaving is able to re-distribute the burst errors to many channel coding blocks so that the bursty errors will become approximately random error patterns When there are residual errors remaining after the channel coding, the errors will be re- distributed to many channel coded blocks

FEC with Interleaving (cont.) HEADER FEC A Channel Block a network packet Lost!

FEC with Interleaving (cont.) HEADER FEC A Channel Block a network packet Lost!! FEC is useless

Conventional Video Streaming Channel Coder (N, K) Compressed Video Bitstream Interleaver Wireline & Wireless Network

Packetization and Channel Coding FEC is applied in channel coding to protect the compressed video bitstream In the case of direct packetization, the loss of a packet may severely damage a channel coding block Orthogonal packetization is often employed to re- distribute the errors due to each lost packet to many channel blocks, so that each channel block would contain few errors that can be corrected.

Source Coding and Channel Coding Many video communication studies show that the source decoder is more effective in handling bursty errors than the random errors. Some source codec such as MPEG-4 provides several error-resilient tools Resynchronization markers Data partitions Reversible VLC

System structure Compressed Video Bitstream CRC Interleaver Channel Coder Wireline & Wireless Networks Video Signal Video Source Decoder CRC Check & Post-processing Deinterleaver Channel Decoder

Pre-Interleaving Header FEC A Channel Block A Network Packet Error Control Frame

Pre-Interleaving (cont.) With pre-interleaving, the direction of the interleaving becomes the same as the direction of the original video data stream To limit the error propagation, an EC frame contains only a multiple of the smallest independent unit Data Partition

Experimental Result 150 frames of “Foreman” in QCIF format Packet size 47 byte Reed-Solomon code with the channel block size N =128

Experimental Result (cont.)