AN1090 STMicroelectronics, AN1090 Datasheet

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AN1090

Manufacturer Part Number
AN1090
Description
STA013 MPEG 2.5 LAYER III (MP3) SOURCE DECODER
Manufacturer
STMicroelectronics
Datasheet
MPEG 2.5 LAYER III TECHNICAL INTRODUCTION
An Overview
Since 1988 MPEG group has been working on the standardisation of high-quality low-bitrate audio cod-
ing techniques. Two standards have been completed: MPEG 1 (coding of mono and stereo signals at
sampling rates of 32, 44.1, and 48 KHz) and MPEG 2 (backward-compatible coding of 5+1 multichannel
sound signals and low-bitrate coding of mono and stereo at sampling rates of 16, 22.05, 24 KHz).
A non standardized evolution of MPEG 2 has been developed by industry, called MPEG 2.5.
It is practically the extension to the sampling rates 8, 11.025, and 12 KHz, of the current MPEG 2 stand-
ard.
The basic idea behind perceptual coding, the general audio coding theory implemented by MPEG, is to
hide the quantisation noise below the signal-dependent tresholds of hearing. In this view, the most im-
portant question in perceptual coding is: "how much noise can be introduced to the signal without being
audible?". The most prominent feature in psychoacoustics is masking in the frequency domain. A fainter
signal is completely masked by a masker that is louder and has a similar frequency content.
The overall processing chain of an MPEG encoder can summarised in the following four steps:
March 1999
This Application Note helps the user to work with STA013 Evaluation Board, installing the PC Soft-
ware Driver, understanding how STA013 MPEG 2.5 Layer III Source Decoder works, and explaining
how to control the device functions.
The document is composed by 5 main points:
- MPEG 2.5 Layer III Technical Introduction
- STA013 Device Description
- STA013 Evaluation Board Description
- STA013 PC Software Driver Description
- General Information on STA013 Evaluation Environment
A filter bank is used to decompose the input signal into subsampled spectral components (time to
frequency domain). Together with the corresponding filter bank in the decoder it forms an analysis-
synthesis system.
Using either the time-domain input signal or the output of the analysis filter bank, an estimate of the
actual (time-dependent) masked threshold is computed using rules known from psychoacoustic.
This is called the perceptual encoding system.
The spectral components are quantized and coded with the aim of keeping the noise, which is intro-
duced by quantizing, below the masking treshold. Depending on the algorithm, this step is done in
different ways, from simple block companding to analysis-by-synthesis system using additional
noiseless compression.
A bitstream formatter is used to assemble the bitstream, which typically consists of the quantized
and coded spectral coefficients and some side information, such as bit allocation information.
®
STA013 MPEG 2.5 LAYER III SOURCE DECODER
APPLICATION NOTE
by Ruggero DE LUCA
AN1090
1/17

Related parts for AN1090

AN1090 Summary of contents

Page 1

... A bitstream formatter is used to assemble the bitstream, which typically consists of the quantized and coded spectral coefficients and some side information, such as bit allocation information. March 1999 AN1090 APPLICATION NOTE by Ruggero DE LUCA 1/17 ...

Page 2

... AN1090 APPLICATION NOTE The Layers Recognizing a variety of application needs, the concept of a generic coding system was envisaged. De- pending on the application, one of the three layers of the coding system with increasing complexity and performances is chosen. In all the three layers the input PCM audio signal is converted from the time into a time-frequency domain ...

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... Huffman to Time & Decoder Transform Error Check Side Info Decoding Main Layer III Decoder Diagram Clocks Serial Output Generation Audio Buffer System Interface Digital Audio Effects Stereophonic Digital Audio Signal AN1090 APPLICATION NOTE Reconstruction Filterbank Digital Digital Tone Volume Control Control 3/17 ...

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... AN1090 APPLICATION NOTE The JP3 connection point no connected to pin no STA013 and is the I2C Serial Data line (SDA). The STA013 I2C interface is used to: Figure 3. STA013EVB Functional Diagram I2C CONNECTOR JP3 MPEG 2.5 LAYER III DECODER RESET CLK/DATA INPUT CONNECTOR J6 Bootstrap the device by downloading the appropriate configuration file. This is done to program STA013 working with one of the three possible cristal frequencies, to select the appropriate output data format depending on the DAC used in the other application ...

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... TP OUT1 IN1 AVCC C25 100 F R17 1K VCC IN1 TDA2822D IN2+ OUT2 R18 C26 100 F 1K GND IN2 DESCRIPTION AN1090 APPLICATION NOTE VDD R6 8.2K C10 4.7 F RESET C9 SW1 26 10nF SMD TP GND 27 SCANEN 25 FILT 19 C7 VDD 4.7nF 23 VDD 470pF GND ...

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... AN1090 APPLICATION NOTE STA013 MASTER CLOCK The STA013 can use three different Master Clock frequencies, each one obtained by an external crystal oscillator X1. The user can even evaluate these three different input frequencies by connecting a func- tion generator to J3-SMB connector. On STA013EVB the mounted crystal is a standard SMD SXA Packaged commercial one. ...

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... Figure 6. 1134-137.7 PC INTERFACE BOARD (not in scale) AN1090 APPLICATION NOTE 7/17 ...

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... AN1090 APPLICATION NOTE Figure 7. PC Interface Schematic. 8/17 ...

Page 9

... Panel Functions. By pressing this button the Panel will show the status of all the displayed registers used to write the current I Panel Functions. By pressing this button the software will update the status of all the displayed registers. AN1090 APPLICATION NOTE 2 C registers register. C registers status, corresponding to the ...

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... AN1090 APPLICATION NOTE Registers Button Status Button Run Button . Firmware Button HW Reset . 10/17 this function allow the read and/or the write op- eration on all the STA013 registers. To write the registers the user has to update the register set- ting before pressing the write button. ...

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... Tone Button Header Button AN1090 APPLICATION NOTE by selecting this function, the user opens a window describing the ideal frequency response of the Tone Control function. The window is updated when the Tone Control pa- rameters are modified by the users. by pressing this button the STA013SDR displays all ...

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... AN1090 APPLICATION NOTE Ancillary Button PLL Button 12/17 this function allow the user to read the Ancillary Data coded in the MPEG stream. The Ancillary Data are displayed as ASCII characters. by pressing this button, all the PLL configuration register become visible and can be read or writ- ...

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... PCM Button Init Button AN1090 APPLICATION NOTE this button, if selected, opens a window to read or change the PCM audio interface configura- tion. by pressing this button the user download the initialisation file to bootstrap the STA013 on the application board. The initialisation file must be called sta013.ini and must be placed ...

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... AN1090 APPLICATION NOTE STA013 PC TRANSMISSION SOFTWARE DRIVER DESCRIPTION The STA013EVB is provided with the PC Software Transmission Driver (STA013TXD), allowing the user to send the MPEG bitstream to the device. The STA013TXD is a Win 3xx/Win95 software and can be installed by the user on a standard PC (see Installation Procedure Section) STA013TXD Panel The STA013TXD user interface is composed by a graphical panel ...

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... The STA013TXD can handle data rates up to 128Kbit/sec. PC Parallel Port Pinout for STA013TXD STA013 DATA REQUEST (from STA013EVB J6 D98AU977A AN1090 APPLICATION NOTE STA013 SERIAL DATA (to STA013EVB J6) STA013 SERIAL CLOCK (to STA013EVB J6 ...

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... AN1090 APPLICATION NOTE GENERAL INFORMATION ON STA013 EVALUATION ENVIRONMENT The STA013 Evaluation toolkit is composed by a set of components, as follows: STA013EVB STA013TXD STA013SDR PC Interface Board All the kit components are provided with flat cables to connect the different units. Evaluation Environment PC 1: STA013SDR PC 2: STA013TXD ...

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... STMicroelectronics – Printed in Italy – All Rights Reserved Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. STMicroelectronics GROUP OF COMPANIES http://www.st.com AN1090 APPLICATION NOTE 17/17 ...

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