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在iOS AAC编码中对零振幅样本填充的定量研究:跨设备的一致性和背景噪声的影响
1Colorado Springs, Colorado, USA.
Journal of forensic sciences
|August 20, 2025
概括
语音备忘录中的iOS高级音频编码 (AAC) 零填充显示了显著的变化,影响了法医音频流的散列. 背景噪声也会影响填充,因此需要适应数字证据的验证方法.
科学领域:
- 数字法医
- 音频工程
- 计算机科学
背景情况:
- 在高级音频编码 (AAC) 编码过程中,iOS应用程序会自动插入零振幅样本填充 (zero-padding).
- 这种填充可以改变解码的音频数据结构,可能会影响法医音频流的散列可靠性.
- 感知音频内容不受这种零填充的影响.
研究的目的:
- 在iOS设备和模型中对零填充一致性进行定量分析.
- 在AAC编码过程中检查背景噪声对零填充的影响.
- 提供适应性法医验证方法的基础.
主要方法:
- 分析了来自11个iPhone设备的100个M4A (AAC) 记录.
- 使用可控的高和低背景噪声条件.
- 使用MATLAB,Pydub和Py-audioread进行了预信号零填充测量.
主要成果:
- 在预信号填充中观察到显著的变化,超过了果记录的1024个样本的原始值 (中位数:2070.5个样本).
- 较高的背景噪声与预信号填充的减少有关.
- 信号前的填充测量在分析工具中一致,而信号后的填充显示了依赖于工具的变化.
结论:
- iOS AAC编码表现出不一致的零填充,具有挑战性的法医音频流散列.
- 背景噪声显著影响零填充,需要在法医分析中考虑.
- 这些发现支持适应性法医验证方法的开发,以提高数字证据的可靠性.
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