Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1994-06-24
1996-12-24
Rogers, Scott A.
Facsimile and static presentation processing
Facsimile
Recording apparatus
3582612, 3582621, 341109, 341178, 341179, H04N 1419, G08C 1912
Patent
active
055877974
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention concerns a process for encoding and transmitting information, for instance text, images, data and speech. The examples given concern mainly telefax and colour television.
STATE OF THE ART
For telefax it should also be possible to encode and transmit photographs and documents with different levels of grey. For this a range of values scanned for the pixels (picture elements) are distributed for example into 16 levels and encoded according to the dither principle into 16 black/white pixels arranged in squares. In this 16 white pixels correspond to the grey value 1 and 16 black pixels to the grey value 16. For each grey value, thus also voltage value, the pixels are distributed in more or less dense samples of white and black pixels. For the eye this appears always as light or dark grey tones. The transmission of these squares takes time and is not simple. A transmission through current is then often made with the help of a phase difference or amplitude/phase difference modulation.
Colour photographs and pictures, also those from the still-video system from Canon are often encoded and transmitted as with colour television e.g. PAL. In the NTSC system this leads to significant colour faults, which can only be corrected with much effort in the PAL system. Furthermore, in all the systems there are faults known as cross luminance and cross colour. This type of coding and transmission also requires delay elements to adapt the transit times.
SUMMARY OF THE INVENTION
The objective of the invention is to create such a coding and transmission of the information in which the transmission time is shortened, and/or the bandwidth is reduced. For the transmission of colours the known faults must be avoided. This is achieved for example in grey telefax transmission in that the conversion according to the dither process is only made at the receiver end. Furthermore, for instance in run length coding, the same code words of similar lines, e.g. only one code word for white, are combined with the same or with different synchronously placed code words in a sequence. This is carried out as follows, that before or after the multiple code word or line the number of repeated code words or lines is indicated. The same can of course be carried out on the coding of speech, colour or others. The colours may be also coded in appropriate manner by means of chromatic components and transmitted for example on a QAM basis. The chromatic components can be transmitted for example per image one after the other or the corresponding position values or CPM values can be exchanged on 2 coding sequences for transmission. In this case it is an advantage to make a code multiplexing of several information channels. A combination code of phase shifted in leading phase position, trailing phase position, identical phase position (as a reference phase position) and optionally a code made of a different number of periods linked with an amplitude code is especially effective. The amplitude level is thereby foreseen as redundant or quasi-level for the unambiguous identification of definite code combinations.
The combination code of the phase, number of periods and amplitudes can only be made with an alternating current. The phase position is determined and by the duration of the sums of the alternating current period durations. The number or frequency of the alternating current periods is such that it is an even numbered multiple of the duration of the phase position. The amplitudes of the periods are then the amplitude levels.
SHORT DESCRIPTION OF THE FIGURES
FIG. 1, 2--Coding of grey tones in telefax
FIG. 3--Principle of the dither process
FIG. 4--Basic circuit diagram of a telefax apparatus
FIG. 5, 6--Use of a run length code for white and black
FIG. 7--Quadrature modulated transmission of step signals on 2 channels
FIG. 8, 12--Quadrature amplitude modulation with vector diagram
FIG. 9--Code multiplex combination of channels
FIG. 10--Basic circuit diagram for the generation of phase/amplitude levels
FIG. 11--R
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Nguyen Madeleine Anh-Vinh
Rogers Scott A.
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