Multichannel Audio Based On Ip Real-time Transmission Technology Research

Currently, the LAN transport high-quality compressed digital audio standard including AES, MADI, the A-Net, the EtherSound and CobraNet-enabled and so on, AES, MADI and A-Net and other agreements are at the physical layer transmission technology in the OSI network reference model, physical layer transmission technology are proprietary point-to-point connection, does not involve the network.Ethersound and CobraNet protocol are on the data link layer transmission technology, technology patents, and is only suitable for LAN. this thesis launched a real-time transmission of IP-based multi-channel digital audio technology, the network layer for the digital audio signal and not compressed real-time transmission.The most network applicaes IEEE1588protocol which gets software timestamp at the application layer,synchronization accuracy is not high,Through hardware-assisted manner, the use of timestamps with the precision of the hardware support functions of the IEEE1588Precision Time Protocol (PTP) Ethernet transceiver chip DP83640network underlying physical layer, has a very high accuracy. The system is designed for real-time transmission of uncompressed multi-channel professional digital audio signal based on the IP layer. The clock synchronization signal transmits using the IEEE1588Precision Time Protocol (PTP) to achieve precise clock synchronization. Data audio streaming uses RTP/RTCP Real-time Transport Protocol, the introduction of the LWIP protocol stack is to meet the requirements of embedded systems.Hardware platform is set up by the DSP chip TMS320DM642of TI’s TMS6000series and integrated with the PTP hardware support Ethernet transceiver chip DP83640. This thesis research on the transmission of real-time on the IP network layer for multi-channel audio signals, there is roughly the following modules:digital audio network is mainly composed of digital audio processing module, TMS320DM642peripheral driver configuration module, RTP Real-time Transport Protocol and RTCP Real-time transmission protocol control module, the precise IEEE1588clock synchronization module and PHY chip DP83640network control module. digital audio is convered by A/D converter from the external, digital audio processor as the master device processes the I2S audio signal input, it is packaged as a standard IP packet and transmitted through the network control module on the network layer, while sending clock information packet, the transmission correction of the clock information is highly synchronized so that from the device with the master clock, which the DP83640network control module is responsible for acquisition hardware timestamps. Meantime, the slave device from the network layer receives the package audio packets and passes to the digital audio processor, the I2S digital audio signal is output,then through the D/A converter to get the output.