Simulation of an audio system

Simulate an audio system composed of:

• a producer;

• a transport mechanism;

• a consumer.

The producer takes an audio file, chuncks it in packets, and put them in an input FIFO fifoIn. One packet every FRAME_INTERVAL.

The transport takes one packet out of the input FIFO fifoIn every TRANSPORT_INTERVAL and puts them in the output FIFO fifoOut. The transport simulates a Bluetooth LE link layer (ACL connection). Packets are successfully received with a given probability that follow a certain probability distribution. This is to simulate the propagation channel. Successfully received packets are stored in the output FIFO fifoOut. The radio also has a FIFO that holds packets ready to be transmitted or retransmitted.

The consumer takes one packet out of the output FIFO fifoOut every FRAME_INTERVAL and store them in an output wav file.

Producer, consumer and transport are implemented using Python threads that run in realtime.

This simulator can be used to evaluate:

• the effect of packet losses

• the effect of buffer overflow/underflow due to different "clocks" in the producer, transport and consumer. Overflows result in packets in the FIFO being overwritten; underflows result in "silence" (0s) being put in the FIFO instead of the missing packet.

• effect of different FIFO sizes

The Bluetooth LE link layer simulator uses infinite retransmissions or finite retransmissions.

TODO

• ASRC to compensate unsynchronized clocks. The consumer can estimate the period of the producer clock by counting how many packets are received in a certain period of time, and comparing with how many packets should have been theoretically been received if the producer clock period was exact.

• Visualize results, e.g., using PulseView.

• Realistic channel model.

• Instead of saving the results in an output files, the consumer reproduces the audio in realitime (e.g., using PyAudio)

• Try some Packet Loss Conceilment (PLC) algorithms to cope with packet losses.