Adaptive Time-Frequency Resolution for Analysis and Processing of Audio - PowerPoint PPT Presentation

slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Adaptive Time-Frequency Resolution for Analysis and Processing of Audio PowerPoint Presentation
Download Presentation
Adaptive Time-Frequency Resolution for Analysis and Processing of Audio

play fullscreen
1 / 18
Adaptive Time-Frequency Resolution for Analysis and Processing of Audio
223 Views
Download Presentation
grizelda
Download Presentation

Adaptive Time-Frequency Resolution for Analysis and Processing of Audio

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

    1. Adaptive Time-Frequency Resolution for Analysis and Processing of Audio

    2. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 2/15 Short-Time Fourier Transform Most commonly used transform for audio: Spectral analysis Noise reduction (spectral subtraction algorithms) Time-variable filters and other effects Very fast implementation for large number of bands via FFT Good energy compaction for many musical signals Many oscillations in basis functions ? ringing (Gibbs phenomenon) Uniform frequency resolution ? inadequate resolution at lows

    3. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 3/15 Filter banks

    4. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 4/15 Suggested approach Imitation of time-frequency resolution of human hearing Adaptation of resolution to local signal features

    5. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 5/15 Spectrograms Problems: Most perceptually meaningful energy is concentrated in the narrow band below 4 kHz ? cant see useful details Time/frequency resolution trade-off

    6. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 6/15 Spectrograms Problems: Poor frequency resolution at low frequencies ? cant separate bass harmonics from bass drum Time/frequency resolution trade-off

    7. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 7/15 Spectrograms Problems: Poor time resolution at transients ? time-smearing of drums

    8. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 8/15 Spectrograms Simple solution: combine spectrograms with different resolutions Take bass from spectrogram with good freq. resolution Take treble from spectrogram with good time resolution

    9. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 9/15 Spectrograms Simple solution: Combine spectrograms with different resolutions: take bass from spectrogram with good frequency resolution, take treble from spectrogram with good time resolution

    10. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 10/15 Spectrograms Better approach: select best resolution for each time-frequency neighborhood Criteria? Better frequency resolution at bass (reflects a-priori psychoacoustical knowledge) Maximal energy compaction (to minimize spectral smearing in both time and frequency)

    11. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 11/15 Spectrograms Calculation of energy compaction (energy smearing in the given block for all given resolutions)

    12. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 12/15 Spectrograms Benefits: Sharper bass drum hits and other transients, even in mid-frequency range Sharper guitar harmonics in high frequencies

    13. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 13/15 Spectrograms

    14. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 14/15 Spectrograms

    15. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 15/15 Processing framework General framework for multi-resolution processing Perform processing with several different resolutions Adaptively combine (mix) results in time-frequency space Mixing is controlled by a-priori knowledge of psychoacoustics and analysis of local signal features (e.g. transience)

    16. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 16/15 Noise reduction Spectral subtraction algorithm modifications Better frequency resolution at low frequencies (according to the human hearing resolution) Better temporal resolution near signal transients (for reduction of Gibbs phenomenon)

    17. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 17/15 Noise reduction Results of single-resolution and multi-resolution algorithms

    18. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 18/15 Noise reduction Results of single-resolution and multi-resolution algorithms

    19. A. Lukin, J. Todd Adaptive Time-Frequency Resolution 19/15 Your questions