Presto - Preservation Technologies for
European Broadcast Archives
Work Package 4
Status Report
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Test bed architecture
Key link 4.2
Player control interface
Tape/Vynil
Player
XML (House keeping data)
Key link 4.4
Key link 4.3
Acquisition
&
Player Control
A/D
Converter
BWF
Lossless
Compression
XML
24 bit@48 KHz
BWF
Quality Control
(process monitor)
XML
Quality Control
(acquisition monitor)
Mp3/BWF
BWF
MP3 encoder
BWF
Key link 4.1
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WP4 workplan
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Presto - Preservation Technologies for
European 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:

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channel phase correlation
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 1,.
Then, the bandwidth can be estimated as (F=sample 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 x[t], 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 for
European 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
THD+N 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 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
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Presto - Preservation Technologies for
European Broadcast Archives
key link 4.4:
LOSSLESS COMPRESSION
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Presto Project
WP4 - AUDIO DIGITISATION
 key link: Lossless Compression Tecnology (LCT)
 With Lossless Compression Tecnology is possible to
reduce the storage necessary for the digitized
material
24bit - 48kHz
linear
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24bit - 48kHz
compressed
Presto Project
WP4 - AUDIO DIGITISATION
 Any Lossless Compression Module (LCM) can be
considered as a trasparent layer for the applications
accessing the archive storage area
LCM codec
Digital archive
BWF format
in
BWF format
out
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24bit/48kHz
compressed
Presto Project
WP4 - 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 Project
WP4 - AUDIO DIGITISATION
 Market survey - Main software features
Product
FLAC
LPAC
Monkey's Audio
PkZip
RKAU
WavPack
Version
1.0
1.31
3.92b
4.00
1.07
3.9
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Source available OS support
yes
any
no
Win/Linux
no
windows only
no
any
no
windows only
no
windows only
Presto Project
WP4 - 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
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Presto Project
WP4 - AUDIO DIGITISATION
 Test Material
 Two level test:
 step 1: broadcast quality @ 24 bit / 48kHz
 step 2: CD quality @ 16 / bit 48kHz
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Presto Project
WP4 - AUDIO DIGITISATION
%
 Compression Ratio
100,0
90,0
80,0
70,0
60,0
50,0
40,0
30,0
20,0
10,0
0,0
FLAC
LPAC
Monkey's Audio
PkZip
RKAU
WavPack
original
24 bit
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16bit
Presto Project
WP4 - AUDIO DIGITISATION
 Compression Time Ratio (n:1)
40
35
FLAC
30
LPAC
n:1
25
Monkey's Audio
20
PkZip
15
RKAU
10
WavPack
5
0
24 bit
16bit
n:1 means n times faster than realtime
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Presto Project
WP4 - AUDIO DIGITISATION
 Hardware Platform
 Pentium III @ 1 GHz
 256 Mbyte RAM (DDR 266 MHz)
 OS Windows 2000
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