一种改进的MP3被动篡改定位检测算法

随着多媒体处理技术和录音设备的发展,录音资料作为客观证据越来越多地出现在法院庭审和案件侦察中.录音证据若成为判决依据,必须确保未被剪接或者伪造.音频真实性鉴定的一个重要方向即为信号的篡改定位检测.MP3是目前应用最为广泛的数字压缩录音格式.在亚马逊网站上所销售的数字录音设备中,销量排名前20位的设备大部分支持MP3格式,并且其中有一部分仅支持MP3格式.目前大多数的智能手机,其默认的录音文件格式也为MP3格式,因此MP3的真实性和完整性检测受到广泛关注.文章针对现有基于帧偏移特性的MP3篡改定位检测算法所存在的误判率高的问题,提出一种改进的MP3被动篡改定位检测算法.观察发现,现有检测算法的误判常出现于含有静音段较多的样本中,文中改进算法利用静音检测技术,通过设定阈值排除静音帧的干扰,降低了误检率;同时算法采用平移窗进行偏移量的提取,避免了单帧提取偏移量不稳定的问题.实验结果表明,改进算法能更准确地定位删除、插入、替换、拼接这四类篡改点的位置.与现有算法相比,误检率明显降低.

An Improved Method of MP3 Passive Forgery Detection

With the development of multimedia technology and recording equipments, recording material as objective evidence increasingly appears in court trail and investigation. If the recording material becomes a judgment, it must ensure that the evidence has not been spliced or forged. In audio forensics, tamper localization is an important part of signal interpolation detection. MP3 is the most widely used digital compressed audio format currently. In Amazon.com, recording devices of top 20 sales mostly support MP3 format and a portion only support MP3 format. The default recording format of most smart mobile phones is MP3. Thus, the authenticity and the integrity of MP3 receive more widespread concern. In this paper, to solve the problem of high false positive rate of the existing method using frame offset, an improved passive algorithm in locating MP3 forgeries is proposed. Observed that the misjudgment of the existing detection algorithms often appear in samples containing more silent segments. In order to eliminate the effect of silent segments on extracting offsets, this paper uses silence detection technology to set a threshold value. Meanwhile, in order to avoid instability in extracting one frame offset, this paper uses moving window to extract. The experiment result shows, the improved method can locate deletion, insertion, substitution and splicing forgeries accurately and reduce the false positive rate largely compared with the existing method.