Description
TD-Expert – is a system for forensic audio investigation – a set of professional instruments for audio editing detection.
TD-Expert is a set of special tools designed to detect audio modification during forensic study when the audio recording stands as evidence in a criminal case: audio stream authentication, revealing changes in the sequence of events or their content, speech enhancement, identification of the audio recording device.
TD-Expert is developed together with forensic experts and practitioners during real case studies and uses seven main approaches to audio authenticity:
- investigation of the audio recording device memory;
- file header and file structure analysis;
- time domain signal analysis;
- frequency domain signal analysis;
- psychoacoustic codecs traces investigation;
- inter-stream analysis (synchronization of the video and audio sequence of the video recording);
- audio device identification.
Device's storage examination
device's storage examination reveals the features of the data sequences formation. This allows to establish whether the audio evidence was recorded using this device or copied to the storage device from an external source.
File Header Examination
includes a detailed analysis of the file header and file structure verifying its compliance with the file format and recording format standards. The frame allocation map reveals the order of frames (and its violations). Metadata analysis reveals signs of editing using specialized software tools.
Time domain signal analysis
Consists of instruments focused on samples sequence analysis: histogram of samples, samples levelogram, distribution center behavior, repeating samples automatic search, automatic search of identical signal fragments (“copy-paste” detector), signal derivative.
Frequency domain signal analysis
is represented with methods focused on frequency characteristics of the recorded signal: momentum and average spectrum, dynamic spectrogram with view normalization, dynamic cepstrogram (autocorrelation), frequency range analysis, re-sampling traces detection, usage of filters traces investigation, narrowband signals (technical harmonics) energy and phase continuity detection.
Electrical Network Frequency analysis allows to establish exact date and time of the recording and its continuity.
Psychoacoustic codecs traces investigation
allows to detect parameters of codec by the signal properties (MP3, WMA, AAC, OGG) including positioning of codec frames in the signal without information from the file header. Periodicity of frames sequence confirms audio signal continuity. The method allows to detect previous coding traces and compare evidence and test recordings features.
Interstream Analysis
includes the research of synchronization between audio and video stream of the evidence. Comparison of video and audio signals behavior reveals traces of editing and manipulation, complementing each other.
Video/Audio Recording Device Identification
includes the recording device analog and digital features analysis by evidence and test video recording comparison. Every approach listed above provides its own contribution into recording device identification: FAT analysis, file header and structure analysis, histogram of samples and DC Offset analysis. The unique functionality implemented in TD-Expert allows the user to extract and analyze audio recording editing traces and to export the results to the expert's report.
Functionality
Basic:
- Audio signal playback with adjustable speed and simultaneous video stream playback;
- Different signal representations: waveform and energy, dynamic spectrogram, cepstrally smoothed spectrogram, LPC spectrogram, dynamic cepstrogram;
- Intuitive signal navigation interface with segmentation and marking features;
- Signals synchronization;
- Case files navigation;
- Audio files batch processing;
- System results export (image and textual).
Special:
- Analysis of media storage media with FAT16 and FAT32 file systems;
- Extraction of specific features of data allocation in the device’s memory;
- Unique file features and properties extraction;
- File structure analysis;
- File format and recording format Standards compliance, service fields fill control;
- Interpretation of data sequences as different variables types;
- Extracting specific codec information (including date and time recording settings);
- Metadata analysis;
- Frame allocation map, being a unique tool for analysis of the data placement in the file structure;
- Extraction Histogram of samples;
- Asymmetry, smoothing calculation;
- Histogram of samples autocorrelation analysis
- Maximum and minimum samples values automatic extraction;
- Levelogram signal representation;
- DC Offset extractor;
- Repeating samples automatic search;
- Signal derivative analysis;
- Identical signal fragments automatic detection (“copy-paste” search);
- Matching energy patterns detector;
- Average spectrum calculation;
- Spectra ratio calculation;
- Narrowband harmonics energy continuity approval (for any frequency value);
- Narrowband harmonics phase continuity approval (for any frequency value);
- MDCT-spectrum calculation
- MP3 codec traces extraction with frame allocation over the signal;
- WMA codec traces extraction with frame allocation over the signal;
- AAC codec traces extraction with frame allocation over the signal;
- OGG codec traces extraction with frame allocation over the signal;
- Codec discontinuity detection
- Histogram of codec frame shift calculation
- MP3, WMA, AAC, OGG codec sampling rate detection and storing.
- Codec Re-sampling detection.
Supported file formats
All audio files formats and majority of video files formats supported and converted: 3gp, aac, ac3, amr, ape, asf, au, avi, avm, avs, cda, dat, divx, dts, flac, flv, m4a, mkv, mka, mov, mp2, mp3, mp4, mpa, mpc, mpeg, mpg, mts, nsv, ofr, ogg, ogm, ppk, ra, rm, rmvb, tp, ts, tta, vdr, vob, voc, wav, wma, wmv, wsd.
Majority of video formats supported. Audio track extraction and simultaneous audio and video playback.
Advantages
- Unique technologies for forensic audio examination;
- Audio continuity verification;
- Automatic search of identical signal fragments (“copy-paste” detector);
- Establishing traces of last and previous coding;
- Recording device identification;
- Export of results in textual and graphical form for the expert’s reporting.
License
The software is protected
by USB dongle;
Installation on multiple workstations is allowed;
The license
is lifetime.
Phone/Fax: +7 (495) 679-19-28
Moscow, st. 5th Kozhukhovskaya, 22, bldg. 1, 15A
E-mail: info@ot-contact.com
