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Presto - Preservation Technologies for European Broadcast Archives

Presto - Preservation Technologies for European Broadcast Archives. Work Package 4 Status Report. Test bed architecture. Key link 4.2. Key link 4.4. Key link 4.3. Key link 4.1. WP4 workplan. Presto - Preservation Technologies for European Broadcast Archives. key link 4.1:

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Presto - Preservation Technologies for European Broadcast Archives

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  1. Presto - Preservation Technologies forEuropean Broadcast Archives Work Package 4 Status Report

  2. Test bed architecture Key link 4.2 Key link 4.4 Key link 4.3 Key link 4.1

  3. WP4 workplan

  4. Presto - Preservation Technologies forEuropean Broadcast Archives key link 4.1: QUALITY MONITOR

  5. Algorithm under construction: channel phase correlation AudioQuality Monitor Algorithms developed for: • computations of signal features • silence detection • bandwidth computation • click detection

  6. Signal Features • power: estimated through the mean square amplitude • peak level: maximum sample value • dynamic: difference between maximum and minimum sample values • presence of DC: estimated through the mean of sample values

  7. Silence Detection Robust detection of silence can be based on the comparison of values of the following parameters with properly set thresholds: • absolute energy • ratio between local and average energy • sample variance • sample maximum For light computation, only sample variance is used.

  8. Bandwidth Computation The power spectral density of a function s(t), sampled at N points to produce FFT values c0-cN-1, can be estimated by the sum squared amplitude (SSA): Let k the index such that: that is, k is the index that split the total power in . Then, the bandwidth can be estimated as (F=sample freq.):

  9. Click Detection The audio signal is modeled with autoregressive (AR) or all pole model: According to AR model, the observed data x[t], corrupted by clicks, is filtered using prediction error filter: In this way the detection signal is: The coefficientsai are estimated by the Maximum Entropy Method.

  10. Integration into Elettra System • process monitor (on-line): all the processing functions are integrated through a library into the Elettra system: • input: buffer of data samples (size configurable) • output: log file + interface with visual tools • acquisition monitor (off-line): it is an executable program: • input: BWF file (audio 48KHz, 24bit, stereo) • output: XML file (quality analysis)

  11. Exploitation (1) As stated in the Key Links System Specification Document, ITC-irst will release two sets of libraries: • Video Quality Control • Audio Quality Control compiled for Linux OS, and documentation. The packages can be exploited in the following ways: • within and beyond Presto, by all the project partners for demos of Presto results • beyond Presto, even for commercial purposes after an agreement with ITC-irst

  12. Exploitation (2) Usually, ITC-irst does not release source codes exploited for commercial purposes, neither guarantees heavy support. More relaxed conditions are applied if exploitation regards demos and research. However, we decide case by case, and all the aspects of the agreement are defined during the negotiation.

  13. Presto - Preservation Technologies forEuropean Broadcast Archives key link 4.3: PLAYBACK DEVICE IMPROVEMENTS

  14. Turntable improvement • Double arm for 78 RPM • Two different pickups can be used at the same time: • E.g. conical vs. elliptical stylus or .0040” vs. .0028” stylus • Both output can be captured and compared in the digital domain with the aid of Quality Control • Commercial solutions are disappearing from the market • Start/stop automation for 33 RPM • Automatic synchronisation between reproduction and capturing equipment under software control • No commercial solutions available

  15. Activities carried out so far • Interface control document available • Command set: start, stop, status • Physical layer: RS232 • Basic turntable components selected • Plate, motor, electronics: Technics 1200 • Tonearm: SME 309/312. Up to 2 arms per turntable • First prototype mechanical design completed • Turntable base and arm fixing block • Arm lift device • Stop detector • Physical realization is under way

  16. A/D conversion technology selection (1) • Stagetec Reference Master 24 bit quad converter tested against Apogee PSX-100 24 bit Sigma/Delta conversion unit • Extensive set of objective measurements have been carried out • THD+N curves are significantly different • Stagetec shows extended dynamic range, close to theoretical values

  17. A/D conversion technology selection (2) • Subjective tests (expert panel listening) • Test materials: • Live recording of the RAI orchestra • Recording of vynil records (33 and 78 RPM) at nominal level • Recording of vynil records at low level (30 dB below nominal) • Test set up • The listening was performed with both loudspeakers (Genelec S30c and 1038A and Dynaudio) and with headphones (Stax Lambda Pro with diffuse field eq) using Apogee PSX-100 24 bit D/A converter for all the materials • Low level materials were played after rescaling at nominal level • 5 expert listeners took part in the evaluation

  18. A/D conversion technology selection (3) • Preliminary results • The listeners were hardly able to detect any difference on nominal level recorded materials • Altought this could be due to the insufficient resolution of the D/A converter, it seems that THD+N values lower then -100 dB are scarcely perceptible during normal listening • The extended dynamic range of Stagetec was clearly perceivable on low level recorded materials • Further tests will be performed by applying restoration techniques (denoise, declick) to vynil recorded materials

  19. Presto - Preservation Technologies forEuropean Broadcast Archives key link 4.4: LOSSLESS COMPRESSION

  20. Presto ProjectWP4 - AUDIO DIGITISATION • key link: Lossless Compression Tecnology (LCT) • With Lossless Compression Tecnology is possible to reduce the storage necessary for the digitized material Storage requirement reduction 24bit - 48kHz linear 24bit - 48kHz compressed

  21. Presto ProjectWP4 - AUDIO DIGITISATION • Any Lossless Compression Module (LCM) can be considered as a trasparent layer for the applications accessing the archive storage area Digital archive LCM codec BWF format 24bit/48kHz compressed in BWF format out

  22. Presto ProjectWP4 - AUDIO DIGITISATION • Software requirement: • Integration in an acquisition automatic process (command line version, etc..) • algorithm robustness • Public source code / Open Project • Platform independence • Encoding/decoding faster than real time • Partial file decoding

  23. Presto ProjectWP4 - AUDIO DIGITISATION • Market survey - Main software features

  24. Presto ProjectWP4 - AUDIO DIGITISATION • Test Material • Source: 33 RPM vinyl • Status: sufficient/good • Material: 7 item selection from classic, jazz, rock&pop records • Total duration: about 107 minutes

  25. Presto ProjectWP4 - AUDIO DIGITISATION • Test Material • Two level test: • step 1: broadcast quality @ 24 bit / 48kHz • step 2: CD quality @ 16 / bit 48kHz

  26. Presto ProjectWP4 - AUDIO DIGITISATION • Compression Ratio

  27. Presto ProjectWP4 - AUDIO DIGITISATION • Compression Time Ratio (n:1) n:1 means n times faster than realtime

  28. Presto ProjectWP4 - AUDIO DIGITISATION • Hardware Platform • Pentium III @ 1 GHz • 256 Mbyte RAM (DDR 266 MHz) • OS Windows 2000

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