Shredpix - Encode COFDMTV

*Shredpix* converts images to COFDMTV encoded audio signals and is based on open-source software.

COFDMTV is based on COFDM (coded orthogonal frequency-division multiplexing) technology:
• 160 ms long OFDM symbols
• 6.25 Hz per sub-carrier
• 1/8 guard interval
• differentially encoded PSK (phase-shift keying) modulation
• systematic polar codes for forward error correction

Following modes are supported:

Using SPC(64800, 43072):
Mode 6: 8PSK, 2700 Hz BW and about 10 seconds long
Mode 7: 8PSK, 2500 Hz BW and about 11 seconds long
Mode 8: QPSK, 2500 Hz BW and about 16 seconds long
Mode 9: QPSK, 2250 Hz BW and about 18 seconds long

Using SPC(64512, 43072):
Mode 10: 8PSK, 3200 Hz BW and about 9 seconds long
Mode 11: 8PSK, 2400 Hz BW and about 11 seconds long
Mode 12: QPSK, 2400 Hz BW and about 16 seconds long
Mode 13: QPSK, 1600 Hz BW and about 24 seconds long

Payload must be smaller or equal to 5380 bytes.
JPEG, PNG and WebP image formats are supported.
Width and height are limited to between 16 and 1024 pixels.