Presto Preservation Technologies for European Broadcast Archives

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Presto - Preservation Technologies forEuropean
Broadcast Archives

• Work Package 4
• Status Report

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Test bed architecture
Key link 4.2
Key link 4.4
Key link 4.3
Key link 4.1
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WP4 workplan
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Presto - Preservation Technologies forEuropean
Broadcast Archives

• key link 4.1
• QUALITY MONITOR

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Audio Quality Monitor

• Algorithms developed for
• computations of signal features
• silence detection
• bandwidth computation
• click detection

• Algorithm under construction
• channel phase correlation

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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

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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.

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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 (Fsample
  freq.)

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Click Detection

• The audio signal is modeled with autoregressive
  (AR) or
• all pole model
• According to AR model, the observed data xt,
  corrupted
• by clicks, is filtered using prediction error
  filter
• In this way the detection signal is
• The coefficients ai are estimated by the Maximum
  Entropy Method.

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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)

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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

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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.

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Presto - Preservation Technologies forEuropean
Broadcast Archives

• key link 4.3
• PLAYBACK DEVICE IMPROVEMENTS

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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

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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

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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
• THDN curves are significantly different
• Stagetec shows extended dynamic range, close to
  theoretical values

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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

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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
  THDN 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

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Presto - Preservation Technologies forEuropean
Broadcast Archives

• key link 4.4
• LOSSLESS COMPRESSION

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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
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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
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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

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Presto ProjectWP4 - AUDIO DIGITISATION

• Market survey - Main software features

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Presto ProjectWP4 - AUDIO DIGITISATION

• Test Material
• Source 33 RPM vinyl
• Status sufficient/good
• Material 7 item selection from classic, jazz,
  rockpop records
• Total duration about 107 minutes

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Presto ProjectWP4 - AUDIO DIGITISATION

• Test Material
• Two level test
• step 1 broadcast quality _at_ 24 bit / 48kHz
• step 2 CD quality _at_ 16 / bit 48kHz

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Presto ProjectWP4 - AUDIO DIGITISATION

• Compression Ratio

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Presto ProjectWP4 - AUDIO DIGITISATION

• Compression Time Ratio (n1)

n1 means n times faster than realtime
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Presto ProjectWP4 - AUDIO DIGITISATION

• Hardware Platform
• Pentium III _at_ 1 GHz
• 256 Mbyte RAM (DDR 266 MHz)
• OS Windows 2000