ntsc-parser.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
import struct
import sys
import wave
import numpy as np
import matplotlib.pyplot as plt

def read_samples(wave_file, nb_frames):
    frame_data = wave_file.readframes(nb_frames)
    if frame_data:
        sample_width = wave_file.getsampwidth()
        nb_samples = len(frame_data) // sample_width
        format = {1: '%db', 2: '<%dh', 4: '<%dl'}[sample_width] \
            % nb_samples
        return struct.unpack(format, frame_data)
    else:
        return ()
      
if __name__ == '__main__':
    buffer_size = 16324
    norm_value = 2147
    input_wave_file = wave.open('data.wav', 'rb')
    nb_frames = input_wave_file.getnframes()
    sync_cnt = 0
    hsync_cnt = 0
    vsync_cnt = 0
    line_signal = []
    smp_cnt = 0
    img_cnt = 0
    image = np.zeros((241, 385))
    for frame_window in range(nb_frames // buffer_size + 1):
        samples = read_samples(input_wave_file, buffer_size)
        if samples:
            for sample in samples:
                if sample < -10000:
                    sync_cnt += 1
                else:
                    if sync_cnt > 300:
                        vsync_cnt += 1
                        if vsync_cnt == 1:
                            print ('Found VSYNC ', hsync_cnt)
                        if vsync_cnt == 3:
                            plt.imsave('decode' + format(img_cnt, '05d') + '.png'
                                    , image, cmap='binary')
                            image = np.zeros((241, 385))
                            vsync_cnt = 0
                            img_cnt += 1
                        hsync_cnt = 0
                        sync_cnt = 0
                    elif sync_cnt > 20:
                        #print ('Found HSYNC ', smp_cnt)
                        if smp_cnt > 0:
                            hsync_cnt += 1
                        vsync_cnt = 0
                        sync_cnt = 0
                        smp_cnt = 0
                    else:
                        if sample > 2000:
                            image[hsync_cnt][smp_cnt] = sample
                            smp_cnt += 1
                        sync_cnt = 0