Looks like software decoding of NTSC has a long (but sporadic) history. This 2002 PDF was linked in a 2005 archived
discuss-gnuradio discussion.
http://www.stanford.edu/class/ee392j...met_report.pdf
Quote:
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The first 2 stages of preparing the analog signal and converting it to digital are done by hardware and will be discussed in section 2. The samples out of the ADC are digital quantized form of the 1D signal. To extract the valid video data, in stage 3, the timing information is used and the data is organized in a field matrices. Each raw in the matrix represents the active video of one horizontal line. This stage is discussed in section 3. For easier processing of the chrominance and luminance separation, the data is resampled to four times the sub-carrier frequency. Y/C separation is the most challenging part of composite video processing. In section 5 we discuss the different methods for implementing Y/C separation. In the next stage the color information is being demodulated from the sub-carrier as discussed in section 7. To display the information on a progressive display such as a PC monitor, interlace to progressive conversion as well as YUV to RGB conversions are performed. These two stages are discussed in sections 8 and 9.
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