Testing.md

A1800 Codec Testing

Test Input: test_input.wav

5-second synthetic WAV file for codec round-trip testing.

Format: 16 kHz, mono, 16-bit PCM (80,000 samples, 250 frames)

Segments

Time (s)	Frames	Content	Amplitude	Purpose
0–1	0–49	440 Hz sine	8000	Basic mid-frequency tone
1–2	50–99	1 kHz sine	12000	Higher frequency, higher energy
2–3	100–149	200 + 800 + 2000 Hz mix	4000 each	Exercises multiple subbands
3–4	150–199	Chirp sweep 100 Hz to 4 kHz	10000	Sweeps across subbands
4–5	200–249	600 Hz decaying to silence	10000→0	Amplitude transition

Generation

python3 -c "
import struct, math, wave

sr = 16000
n = sr * 5
samples = []

for i in range(n):
    t = i / sr
    if t < 1.0:
        s = 8000.0 * math.sin(2 * math.pi * 440 * t)
    elif t < 2.0:
        s = 12000.0 * math.sin(2 * math.pi * 1000 * t)
    elif t < 3.0:
        s = (4000.0 * math.sin(2 * math.pi * 200 * t)
           + 4000.0 * math.sin(2 * math.pi * 800 * t)
           + 4000.0 * math.sin(2 * math.pi * 2000 * t))
    elif t < 4.0:
        frac = t - 3.0
        freq = 100.0 + 3900.0 * frac
        phase = 2 * math.pi * (100.0 * frac + 0.5 * 3900.0 * frac * frac)
        s = 10000.0 * math.sin(phase)
    else:
        frac = t - 4.0
        env = max(0.0, 1.0 - frac)
        s = 10000.0 * env * math.sin(2 * math.pi * 600 * t)
    samples.append(max(-32768, min(32767, int(round(s)))))

with wave.open('test_data/test_input.wav', 'w') as w:
    w.setnchannels(1)
    w.setsampwidth(2)
    w.setframerate(sr)
    w.writeframes(struct.pack('<' + 'h' * len(samples), *samples))
"

Usage

Encode and decode at a given bitrate:

cargo run -- encode test_data/test_input.wav test.a18 --bitrate 16000
cargo run -- decode test.a18 test_output.wav

Compare input and output in an audio editor or with a spectral analysis tool to evaluate codec quality.