JPS5561171A - Tone code system for facsimile signal - Google Patents

Abstract

PURPOSE: To perform coding enabling the transmission of high speed and high quality for video information including tone information, by performing run length coding for black and white level, using tone coding for intermediate level, and performing coding through insertion of transit code at the boundary of video code train.

CONSTITUTION: To the white video element W being continuous code on time axis, the make up code Wm for white run and terminating code Wt for white run are produced, and succeedingly, when transistion is made from white to black via the two video elements having tone, the black transition code 11 of black is inserted to tone and the tone level code is kept for 4-bit two video elements and finally, the black return code 0000 is kept from the tone to black. In this case, at reception side, the black code is generated next to Wt without fail to constitute black following mode. In the video information, the zero run code 11 succeeded to the terminating code can be discriminated as transit code, this is detected and the succeeding code train is decoded into tone code by sectioning it by 4-bit. Simultaneously, the return code 0000 from tone to black is monitored and when it is detected, the code train succeeded is black MH code, then it is returned to the tracking mode of black run.

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