Free dac software for linux

Image::MetaData::JPEG::Structures is a Perl module that describes the structure of a JPEG file; it is an appendix to the main manual page of the Image::MetaData::JPEG module, which the reader should refer to for further details and the general scope.

THE STRUCTURE OF JPEG PICTURES

The JPEG (Joint Photographic Experts Group) ISO standard is a lossy image compression mechanism developed before 1990, designed for compressing colour or gray-scale photo-realistic images (it performs poorly on line-art drawings). The JPEG mechanism is designed to exploit known limitations of the human eye, in particular the fact that colour changes are perceived less accurately than changes in brightness.

Note that although the "baseline" JPEG format is patent-free, there are patents associated with some optional features, namely arithmetic coding and hierarchical storage. For this reason, these optional features are never used on the Web (good job, patent fans ...). JPEG refers only to a class of compression algorithms, not to a specific file format. In order to produce files with embedded JPEG streams, a number of file format (semi-)standards have been adapted or devised, some of which are listed in the format section. The structure of a well formed JPEG file can be described by the following pseudo production rules (for sake of simplicity, some additional constraints between tables and SOF segments are neglected).

JPEG --> (SOI)(misc)*(image)?(EOI)
(image) --> (hierarch.)|(non-hier.)
(hierarch.) --> (DHP)(frame)+
(frame) --> (misc)*(EXP)?(non-hier.)
(non-hier.) --> (SOF)(scan)+
(scan) --> (misc)*(SOS)(data)*(ECS)(DNL)?
(data) --> (ECS)(RST)
(misc) --> (DQT)|(DHT)|(DAC)|(DRI)|(COM)|(APP)

(SOI) = Start Of Image
(EOI) = End Of Image
(SOF) = Start Of Frame header (10 types)
(SOS) = Start Of Scan header
(ECS) = Entropy Coded Segment (row data, not a real segment)
(DNL) = Define Number of Lines segment
(DHP) = Define Hierarchical P??? segment
(EXP) = EXPansion segment
(RST) = ReSTart segment (8 types)
(DQT) = Define Quantisation Table
(DHT) = Define Huffman coding Table
(DAC) = Define Arithmetic coding Table
(DRI) = Define Restart Interval
(COM) = COMment segment
(APP) = APPlication segment

This package does not check that a JPEG file is really correct; it accepts a looser syntax, were segments and ECS blocks are just contiguous (basically, because it does not need to display the image!). All meta-data information is concentrated in the (COM*) and (APP) Segments, exception made for some records in the (SOF*) segment (e.g. image dimensions).

Reference: B< "Digital compression and coding of continuous-tone still
images: requirements and guidelines", CCITT recommend. T.81, 1992,
The International Telegraph and Telephone Consultative Committee,
standard ISO/IEC IS 10918-1 or ITU-T Recommendation T.81 >.
Also: B< "The JPEG still picture compression standard", G.K.Wallace,
1991, IEEE Transactions on Consumer Electronics >.

active acoustic vibration control tool is a set of basic tools for monitoring and modulating audio noise.

The tools aim toward a set of codes and algorithms for monitoring noise signal and modulation and reducing them using active noise control priciples.

Active noise control and soundproofing is a relativly recent development (first researched around 30 years ago), and has been in constant development for many and varied situations and applications.

The basic concept of active noise control is the aplication of equal and opposite force to cancel out vibration.

The project attempts to provide a starting point and library for experimentation into various methods of digital signal processing for active noise reduction and soundproofing.

Noise cancellation has been used in many environments currently active control is best used in constant vibrations with lower frequencys.

The principle is of controlling the noise level by adding an equal and opposite sound to the noise in the environment. The basic principle may be simple but the actual effectivness depends on many environmental factors.

Generally simplistic out of phase sound wave is used which works to some extent and requires little processing (a simple XOR with -1) this will tend to leave a large number of artifacts as the amplitude of higher frequency components (above i->o delay time) rises.

i->o processing delay
e transducer efficiency
p sound propagation characteristics
r reflections

The project aims to provide a framework for many dsp architectures, dac/adc chips, transducers and monitors.

Create tools for acoustic calibration and data logging hardware
To simplify implementation of active noise and vibration control systems.
To provide an open source standard for use within the industry and education.
To encourage hardware producers to distribute standard interface descriptions for their hardware
Enable low cost development of systems using COTS consumer hardware for noise and vibration control.

XymMS is an XMMS input plugin capable of playing Sega Genesis GYM files by
rendering DAC, FM, and PSG signals through emulation of the YM2612 and SN76496 sound chips found in the video game console. (CYM files will be supported in the beta release.)

GYM files are created by various emulators such as DGen and Megasis. XymMS supports ZLib compression and decompression, and other various settings for output quality, etc. You can compress and decompress files along with updating ID tags using the File Info window.

The emulation backend is courtesy the M.A.M.E. project. XymMS is based on code and ideas from the YMAMP and MSP Open Source projects.