mozilla-central/third_party/libwebrtc/modules/rtp_rtcp/test/testFec
Name Description Size
average_residual_loss_xor_codes.h 3280
test_fec.cc Test application for core FEC algorithm. Calls encoding and decoding functions in ForwardErrorCorrection directly. 19273
test_packet_masks_metrics.cc The purpose of this test is to compute metrics to characterize the properties and efficiency of the packets masks used in the generic XOR FEC code. The metrics measure the efficiency (recovery potential or residual loss) of the FEC code, under various statistical loss models for the packet/symbol loss events. Various constraints on the behavior of these metrics are verified, and compared to the reference RS (Reed-Solomon) code. This serves in some way as a basic check/benchmark for the packet masks. By an FEC code, we mean an erasure packet/symbol code, characterized by: (1) The code size parameters (k,m), where k = number of source/media packets, and m = number of FEC packets, (2) The code type: XOR or RS. In the case of XOR, the residual loss is determined via the set of packet masks (generator matrix). In the case of RS, the residual loss is determined directly from the MDS (maximum distance separable) property of RS. Currently two classes of packets masks are available (random type and bursty type), so three codes are considered below: RS, XOR-random, and XOR-bursty. The bursty class is defined up to k=12, so (k=12,m=12) is largest code size considered in this test. The XOR codes are defined via the RFC 5109 and correspond to the class of LDGM (low density generator matrix) codes, which is a subset of the LDPC (low density parity check) codes. Future implementation will consider extending our XOR codes to include LDPC codes, which explicitly include protection of FEC packets. The type of packet/symbol loss models considered in this test are: (1) Random loss: Bernoulli process, characterized by the average loss rate. (2) Bursty loss: Markov chain (Gilbert-Elliot model), characterized by two parameters: average loss rate and average burst length. 48020