VoIP(voice over intemet protocol) has made great progress in Communication area in recent years.But a biggest pity is that the voice quality of VOIP can't satisfy users as traditional phone via PSTN does.In this p...VoIP(voice over intemet protocol) has made great progress in Communication area in recent years.But a biggest pity is that the voice quality of VOIP can't satisfy users as traditional phone via PSTN does.In this pa- per,the author analysis the reason and bring out some methods to improve the voice quality of VOIP that are utili- ring the bandwidth effectively to reduce delay;minishing the jitter to reduce packet lose and bit error;eliminating the echo.As the emphases,the author pointed out the specialty ...展开更多
In order to optionally regulate embedding capacity and embedding transparency according to user's requirements in voice-over-IP(VoIP) steganography,a dynamic matrix encoding strategy(DMES) was presented.Differing ...In order to optionally regulate embedding capacity and embedding transparency according to user's requirements in voice-over-IP(VoIP) steganography,a dynamic matrix encoding strategy(DMES) was presented.Differing from the traditional matrix encoding strategy,DMES dynamically chose the size of each message group in a given set of adoptable message sizes.The appearance possibilities of all adoptable sizes were set in accordance with the desired embedding performance(embedding rate or bit-change rate).Accordingly,a searching algorithm that could provide an optimal combination of appearance possibilities was proposed.Furthermore,the roulette wheel algorithm was employed to determine the size of each message group according to the optimal combination of appearance possibilities.The effectiveness of DMES was evaluated in StegVoIP,which is a typical covert communication system based on VoIP.The experimental results demonstrate that DMES can adjust embedding capacity and embedding transparency effectively and flexibly,and achieve the desired embedding performance in any case.For the desired embedding rate,the average errors are not more than 0.000 8,and the standard deviations are not more than 0.002 0;for the desired bit-change rate,the average errors are not more than 0.001 4,and the standard deviations are not more than 0.002 6.展开更多
近年来分组化技术在IP网络上传输实时音频数据进行语音通讯的VoIP技术获得了快速的发展。阐述了VoIP的基本原理,详细说明了如何具体运用微软公司提供的SDK中的WaveIn和WaveOut函数族以及WinSocket函数族实现一个具有实用价值的PC to PC...近年来分组化技术在IP网络上传输实时音频数据进行语音通讯的VoIP技术获得了快速的发展。阐述了VoIP的基本原理,详细说明了如何具体运用微软公司提供的SDK中的WaveIn和WaveOut函数族以及WinSocket函数族实现一个具有实用价值的PC to PC环境下的VoIP应用程序。展开更多
文摘VoIP(voice over intemet protocol) has made great progress in Communication area in recent years.But a biggest pity is that the voice quality of VOIP can't satisfy users as traditional phone via PSTN does.In this pa- per,the author analysis the reason and bring out some methods to improve the voice quality of VOIP that are utili- ring the bandwidth effectively to reduce delay;minishing the jitter to reduce packet lose and bit error;eliminating the echo.As the emphases,the author pointed out the specialty ...
基金Project(2009AA01A402) supported by the National High-Tech Research and Development Program of ChinaProject(NCET-06-0650) supported by Program for New Century Excellent Talents in University Project(IRT-0725) supported by Program for Changjiang Scholars and Innovative Research Team in Chinese University
文摘In order to optionally regulate embedding capacity and embedding transparency according to user's requirements in voice-over-IP(VoIP) steganography,a dynamic matrix encoding strategy(DMES) was presented.Differing from the traditional matrix encoding strategy,DMES dynamically chose the size of each message group in a given set of adoptable message sizes.The appearance possibilities of all adoptable sizes were set in accordance with the desired embedding performance(embedding rate or bit-change rate).Accordingly,a searching algorithm that could provide an optimal combination of appearance possibilities was proposed.Furthermore,the roulette wheel algorithm was employed to determine the size of each message group according to the optimal combination of appearance possibilities.The effectiveness of DMES was evaluated in StegVoIP,which is a typical covert communication system based on VoIP.The experimental results demonstrate that DMES can adjust embedding capacity and embedding transparency effectively and flexibly,and achieve the desired embedding performance in any case.For the desired embedding rate,the average errors are not more than 0.000 8,and the standard deviations are not more than 0.002 0;for the desired bit-change rate,the average errors are not more than 0.001 4,and the standard deviations are not more than 0.002 6.
