scope.py

#!/usr/bin/env python
import numpy as np
import cv2
import sys
import scipy.io.wavfile
import scipy.signal

# Needs to be a regular wav file, not wavex
# Also, assuming PCM, 2 channels, 16-bit
fs, data = scipy.io.wavfile.read(sys.argv[1], 'rb')

dimension = 800

print "data shape:", data.shape

if False:
    ratio = int(fs / 48000)
    new_fs = fs / ratio
    print "fs was", fs, "decimating to", new_fs
    fs = new_fs
    data = scipy.signal.decimate(data, ratio, axis=0)

print "data shape:", data.shape

# create an empty dimension x dimension bgr image
vis = np.zeros((dimension, dimension, 3), np.uint8)


def sample_to_xy(in_sample_pair):
    # bias towards the middle of the image
    # we use 65600 instead of 65536 so we don't go off the edge.
    x = int((32768 - in_sample_pair[0]) * (dimension / 65600.0))
    y = int((32768 - in_sample_pair[1]) * (dimension / 65600.0))
    return (x, y)

framerate = 20

fourcc = cv2.VideoWriter_fourcc(*'XVID')
vwobj = cv2.VideoWriter(sys.argv[2], fourcc, framerate, (dimension, dimension))

sample_cnt = 0

samples_per_frame = int(fs / framerate)

total_samples = data.shape[0]

print "Starting loop, ", total_samples, " total samples"
print samples_per_frame, "samples per frame"

old_point = (0, 0)

for sample_pair in data:
    point = sample_to_xy(sample_pair)
    # Draw a green line segment from old_point to point
    cv2.line(vis, old_point, point, (0, 255, 0))
    old_point = point
    if (sample_cnt % 1000) == 0:
        print sample_cnt, " samples so far"
    if (sample_cnt % samples_per_frame) == 0:
        cv2.imshow("foo", vis)
        cv2.waitKey(1)
        print "Frame out, ", sample_cnt, " samples so far"
    vwobj.write(vis)
    vis *= 0.5
    sample_cnt += 1