基于dsp的語音信號(hào)采集與回放系統(tǒng)的設(shè)計(jì)開題報(bào)告-文庫吧資料
2025-03-31 12:42本頁面
【正文】 der the following scenario: An ethernet cable is tapped for voice packets and the VoIP recorder intercepts the packets before they have been buffered. As a result, the packets pulled off the network are misaligned and predictably, the audio quality is poor. To pensate for this, hardware ponents used for VoIP call recording properly time the buffering of ining packets.Packet FilteringIn a conventional circuitbased telephone network, the line is used to transmit only voice data. On an IP network many types of packets data, voice and media are present on the same ethernet cable. Packet filtering is the selective passing or blocking of packets as they pass through a network interface. Packet filtering is used by VoIP recording systems to isolate voice related packets from data and media packets.Many earlystage VoIP recorders rely on host resources for packet filtering. This is a viable solution on networks with light traffic. However, this system is not scalable and quickly reaches limitation when the system density grows beyond 100 ports. The better solution is a logging system that uses hardware ponents capable of packet filtering. This system would no longer be limited by host resources and would provide a scalable solution for either low to high density environments.Voice CODECSAn important consideration in the design any logging system is its ability to encode/decode numerous pression schemes. Like all recording environments, the type of CODEC used for media transport is controlled by the network. As a result, when selecting hardware ponents for call recording, application developers prefer products that support multiple CODECs. This is crucial when tapping a VoIP network. When call setup is negotiated between two Call Agents, the media format is also negotiated. As a result, the type of media format used can change from call to call on one network. Unlike circuitbased recording systems, a VoIP recorder must have the ability to determine the type of media format on a per call basis. This is acplished by decoding the packet’s header, where the media format is identified. In today’s VoIP market, the formats , , or are prevalent on most VoIP networks and must be supported by the recording hardware.The type of media format used for recording is driven by the business needs of the customer. As an application developer, you may be asked to design one system that maximizes storage capabilities and then another system that requires webenabled playback. The best bet is a versatile hardware ponent capable of encoding a variety of media formats. Specifically, ponents that offer both low bit rate CODECS and .wav header support.SignalingAll call recording applications rely on hardware ponents to interpret call
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