skills/creative/ascii-video/references/inputs.md
See also: architecture.md · effects.md · scenes.md · shaders.md · optimization.md · troubleshooting.md
tmp = tempfile.mktemp(suffix=".wav")
subprocess.run(["ffmpeg", "-y", "-i", input_path, "-ac", "1", "-ar", "22050",
"-sample_fmt", "s16", tmp], capture_output=True, check=True)
with wave.open(tmp) as wf:
sr = wf.getframerate()
raw = wf.readframes(wf.getnframes())
samples = np.frombuffer(raw, dtype=np.int16).astype(np.float32) / 32768.0
hop = sr // fps # samples per frame
win = hop * 2 # analysis window (2x hop for overlap)
window = np.hanning(win)
freqs = rfftfreq(win, 1.0 / sr)
bands = {
"sub": (freqs >= 20) & (freqs < 80),
"bass": (freqs >= 80) & (freqs < 250),
"lomid": (freqs >= 250) & (freqs < 500),
"mid": (freqs >= 500) & (freqs < 2000),
"himid": (freqs >= 2000)& (freqs < 6000),
"hi": (freqs >= 6000),
}
For each frame: extract chunk, apply window, FFT, compute band energies.
| Feature | Formula | Controls |
|---|---|---|
rms | sqrt(mean(chunk²)) | Overall loudness/energy |
sub..hi | sqrt(mean(band_magnitudes²)) | Per-band energy |
centroid | sum(freq*mag) / sum(mag) | Brightness/timbre |
flatness | geomean(mag) / mean(mag) | Noise vs tone |
flux | sum(max(0, mag - prev_mag)) | Transient strength |
sub_r..hi_r | band / sum(all_bands) | Spectral shape (volume-independent) |
cent_d | abs(gradient(centroid)) | Timbral change rate |
beat | Flux peak detection | Binary beat onset |
bdecay | Exponential decay from beats | Smooth beat pulse (0→1→0) |
Band ratios are critical — they decouple spectral shape from volume, so a quiet bass section and a loud bass section both read as "bassy" rather than just "loud" vs "quiet".
EMA prevents visual jitter:
def ema(arr, alpha):
out = np.empty_like(arr); out[0] = arr[0]
for i in range(1, len(arr)):
out[i] = alpha * arr[i] + (1 - alpha) * out[i-1]
return out
# Slow-moving features (alpha=0.12): centroid, flatness, band ratios, cent_d
# Fast-moving features (alpha=0.3): rms, flux, raw bands
flux_smooth = np.convolve(flux, np.ones(5)/5, mode="same")
peaks, _ = signal.find_peaks(flux_smooth, height=0.15, distance=fps//5, prominence=0.05)
beat = np.zeros(n_frames)
bdecay = np.zeros(n_frames, dtype=np.float32)
for p in peaks:
beat[p] = 1.0
for d in range(fps // 2):
if p + d < n_frames:
bdecay[p + d] = max(bdecay[p + d], math.exp(-d * 2.5 / (fps // 2)))
bdecay gives smooth 0→1→0 pulse per beat, decaying over ~0.5s. Use for flash/glitch/mirror triggers.
After computing all frames, normalize each feature to 0-1:
for k in features:
a = features[k]
lo, hi = a.min(), a.max()
features[k] = (a - lo) / (hi - lo + 1e-10)
# Method 1: ffmpeg pipe (memory efficient)
cmd = ["ffmpeg", "-i", input_video, "-f", "rawvideo", "-pix_fmt", "rgb24",
"-s", f"{target_w}x{target_h}", "-r", str(fps), "-"]
pipe = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
frame_size = target_w * target_h * 3
for fi in range(n_frames):
raw = pipe.stdout.read(frame_size)
if len(raw) < frame_size: break
frame = np.frombuffer(raw, dtype=np.uint8).reshape(target_h, target_w, 3)
# process frame...
# Method 2: OpenCV (if available)
cap = cv2.VideoCapture(input_video)
Convert video pixels to ASCII characters based on brightness:
def frame_to_ascii(frame_rgb, grid, pal=PAL_DEFAULT):
"""Convert video frame to character + color arrays."""
rows, cols = grid.rows, grid.cols
# Resize frame to grid dimensions
small = np.array(Image.fromarray(frame_rgb).resize((cols, rows), Image.LANCZOS))
# Luminance
lum = (0.299 * small[:,:,0] + 0.587 * small[:,:,1] + 0.114 * small[:,:,2]) / 255.0
# Map to chars
chars = val2char(lum, lum > 0.02, pal)
# Colors: use source pixel colors, scaled by luminance for visibility
colors = np.clip(small * np.clip(lum[:,:,None] * 1.5 + 0.3, 0.3, 1), 0, 255).astype(np.uint8)
return chars, colors
Use edge detection for more detail in contour regions:
def frame_to_ascii_edges(frame_rgb, grid, pal=PAL_DEFAULT, edge_pal=PAL_BOX):
gray = np.mean(frame_rgb, axis=2)
small_gray = resize(gray, (grid.rows, grid.cols))
lum = small_gray / 255.0
# Sobel edge detection
gx = np.abs(small_gray[:, 2:] - small_gray[:, :-2])
gy = np.abs(small_gray[2:, :] - small_gray[:-2, :])
edge = np.zeros_like(small_gray)
edge[:, 1:-1] += gx; edge[1:-1, :] += gy
edge = np.clip(edge / edge.max(), 0, 1)
# Edge regions get box drawing chars, flat regions get brightness chars
is_edge = edge > 0.15
chars = val2char(lum, lum > 0.02, pal)
edge_chars = val2char(edge, is_edge, edge_pal)
chars[is_edge] = edge_chars[is_edge]
return chars, colors
Detect pixel changes between frames for motion-reactive effects:
prev_frame = None
def compute_motion(frame):
global prev_frame
if prev_frame is None:
prev_frame = frame.astype(np.float32)
return np.zeros(frame.shape[:2])
diff = np.abs(frame.astype(np.float32) - prev_frame).mean(axis=2)
prev_frame = frame.astype(np.float32) * 0.7 + prev_frame * 0.3 # smoothed
return np.clip(diff / 30.0, 0, 1) # normalized motion map
Use motion map to drive particle emission, glitch intensity, or character density.
Per-frame features analogous to audio features, for driving effects:
def analyze_video_frame(frame_rgb):
gray = np.mean(frame_rgb, axis=2)
return {
"brightness": gray.mean() / 255.0,
"contrast": gray.std() / 128.0,
"edge_density": compute_edge_density(gray),
"motion": compute_motion(frame_rgb).mean(),
"dominant_hue": compute_dominant_hue(frame_rgb),
"color_variance": compute_color_variance(frame_rgb),
}
Same as single video frame conversion. For animated sequences:
import glob
frames = sorted(glob.glob("frames/*.png"))
for fi, path in enumerate(frames):
img = np.array(Image.open(path).resize((VW, VH)))
chars, colors = frame_to_ascii(img, grid, pal)
Use an image as a background texture that effects modulate:
def load_texture(path, grid):
img = np.array(Image.open(path).resize((grid.cols, grid.rows)))
lum = np.mean(img, axis=2) / 255.0
return lum, img # luminance for char mapping, RGB for colors
import re
def parse_srt(path):
"""Returns [(start_sec, end_sec, text), ...]"""
entries = []
with open(path) as f:
content = f.read()
blocks = content.strip().split("\n\n")
for block in blocks:
lines = block.strip().split("\n")
if len(lines) >= 3:
times = lines[1]
m = re.match(r"(\d+):(\d+):(\d+),(\d+) --> (\d+):(\d+):(\d+),(\d+)", times)
if m:
g = [int(x) for x in m.groups()]
start = g[0]*3600 + g[1]*60 + g[2] + g[3]/1000
end = g[4]*3600 + g[5]*60 + g[6] + g[7]/1000
text = " ".join(lines[2:])
entries.append((start, end, text))
return entries
def lyrics_typewriter(ch, co, text, row, col, t, t_start, t_end, color):
"""Reveal characters progressively over time window."""
progress = np.clip((t - t_start) / (t_end - t_start), 0, 1)
n_visible = int(len(text) * progress)
stamp(ch, co, text[:n_visible], row, col, color)
For pure generative ASCII art, the "features" dict is synthesized from time:
def synthetic_features(t, bpm=120):
"""Generate audio-like features from time alone."""
beat_period = 60.0 / bpm
beat_phase = (t % beat_period) / beat_period
return {
"rms": 0.5 + 0.3 * math.sin(t * 0.5),
"bass": 0.5 + 0.4 * math.sin(t * 2 * math.pi / beat_period),
"sub": 0.3 + 0.3 * math.sin(t * 0.8),
"mid": 0.4 + 0.3 * math.sin(t * 1.3),
"hi": 0.3 + 0.2 * math.sin(t * 2.1),
"cent": 0.5 + 0.2 * math.sin(t * 0.3),
"flat": 0.4,
"flux": 0.3 + 0.2 * math.sin(t * 3),
"beat": 1.0 if beat_phase < 0.05 else 0.0,
"bdecay": max(0, 1.0 - beat_phase * 4),
# ratios
"sub_r": 0.2, "bass_r": 0.25, "lomid_r": 0.15,
"mid_r": 0.2, "himid_r": 0.12, "hi_r": 0.08,
"cent_d": 0.1,
}
For narrated videos (testimonials, quotes, storytelling), generate speech audio per segment and mix with background music.
import requests, time, os
def generate_tts(text, voice_id, api_key, output_path, model="eleven_multilingual_v2"):
"""Generate TTS audio via ElevenLabs API. Streams response to disk."""
# Skip if already generated (idempotent re-runs)
if os.path.exists(output_path) and os.path.getsize(output_path) > 1000:
return
url = f"https://api.elevenlabs.io/v1/text-to-speech/{voice_id}"
headers = {"xi-api-key": api_key, "Content-Type": "application/json"}
data = {
"text": text,
"model_id": model,
"voice_settings": {
"stability": 0.65,
"similarity_boost": 0.80,
"style": 0.15,
"use_speaker_boost": True,
},
}
resp = requests.post(url, json=data, headers=headers, stream=True)
resp.raise_for_status()
with open(output_path, "wb") as f:
for chunk in resp.iter_content(chunk_size=4096):
f.write(chunk)
time.sleep(0.3) # rate limit: avoid 429s on batch generation
Voice settings notes:
stability 0.65 gives natural variation without drift. Lower (0.3-0.5) for more expressive reads, higher (0.7-0.9) for monotone/narration.similarity_boost 0.80 keeps it close to the voice profile. Lower for more generic sound.style 0.15 adds slight stylistic variation. Keep low (0-0.2) for straightforward reads.use_speaker_boost True improves clarity at the cost of slightly more processing time.ElevenLabs has ~20 built-in voices. Use multiple voices for variety across quotes. Reference pool:
VOICE_POOL = [
("JBFqnCBsd6RMkjVDRZzb", "George"),
("nPczCjzI2devNBz1zQrb", "Brian"),
("pqHfZKP75CvOlQylNhV4", "Bill"),
("CwhRBWXzGAHq8TQ4Fs17", "Roger"),
("cjVigY5qzO86Huf0OWal", "Eric"),
("onwK4e9ZLuTAKqWW03F9", "Daniel"),
("IKne3meq5aSn9XLyUdCD", "Charlie"),
("iP95p4xoKVk53GoZ742B", "Chris"),
("bIHbv24MWmeRgasZH58o", "Will"),
("TX3LPaxmHKxFdv7VOQHJ", "Liam"),
("SAz9YHcvj6GT2YYXdXww", "River"),
("EXAVITQu4vr4xnSDxMaL", "Sarah"),
("Xb7hH8MSUJpSbSDYk0k2", "Alice"),
("pFZP5JQG7iQjIQuC4Bku", "Lily"),
("XrExE9yKIg1WjnnlVkGX", "Matilda"),
("FGY2WhTYpPnrIDTdsKH5", "Laura"),
("SOYHLrjzK2X1ezoPC6cr", "Harry"),
("hpp4J3VqNfWAUOO0d1Us", "Bella"),
("N2lVS1w4EtoT3dr4eOWO", "Callum"),
("cgSgspJ2msm6clMCkdW9", "Jessica"),
("pNInz6obpgDQGcFmaJgB", "Adam"),
]
Shuffle deterministically so re-runs produce the same voice mapping:
import random as _rng
def assign_voices(n_quotes, voice_pool, seed=42):
"""Assign a different voice to each quote, cycling if needed."""
r = _rng.Random(seed)
ids = [v[0] for v in voice_pool]
r.shuffle(ids)
return [ids[i % len(ids)] for i in range(n_quotes)]
TTS text must be separate from display text. The display text has line breaks for visual layout; the TTS text is a flat sentence with phonetic fixes.
Common fixes:
# Display text: line breaks control visual layout
QUOTES = [
("It can do far more than the Claws,\nand you don't need to buy a Mac Mini.\nNous Research has a winner here.", "Brian Roemmele"),
]
# TTS text: flat, phonetically corrected for speech
QUOTES_TTS = [
"It can do far more than the Claws, and you don't need to buy a Mac Mini. Noose Research has a winner here.",
]
# Keep both arrays in sync -- same indices
def build_tts_track(tts_clips, target_duration, intro_pad=5.0, outro_pad=4.0):
"""Concatenate TTS clips with calculated gaps, pad to target duration.
Returns:
timing: list of (start_time, end_time, quote_index) tuples
"""
sr = 22050
# Convert MP3s to WAV for duration and sample-level concatenation
durations = []
for clip in tts_clips:
wav = clip.replace(".mp3", ".wav")
subprocess.run(
["ffmpeg", "-y", "-i", clip, "-ac", "1", "-ar", str(sr),
"-sample_fmt", "s16", wav],
capture_output=True, check=True)
result = subprocess.run(
["ffprobe", "-v", "error", "-show_entries", "format=duration",
"-of", "csv=p=0", wav],
capture_output=True, text=True)
durations.append(float(result.stdout.strip()))
# Calculate gap to fill target duration
total_speech = sum(durations)
n_gaps = len(tts_clips) - 1
remaining = target_duration - total_speech - intro_pad - outro_pad
gap = max(1.0, remaining / max(1, n_gaps))
# Build timing and concatenate samples
timing = []
t = intro_pad
all_audio = [np.zeros(int(sr * intro_pad), dtype=np.int16)]
for i, dur in enumerate(durations):
wav = tts_clips[i].replace(".mp3", ".wav")
with wave.open(wav) as wf:
samples = np.frombuffer(wf.readframes(wf.getnframes()), dtype=np.int16)
timing.append((t, t + dur, i))
all_audio.append(samples)
t += dur
if i < len(tts_clips) - 1:
all_audio.append(np.zeros(int(sr * gap), dtype=np.int16))
t += gap
all_audio.append(np.zeros(int(sr * outro_pad), dtype=np.int16))
# Pad or trim to exactly target_duration
full = np.concatenate(all_audio)
target_samples = int(sr * target_duration)
if len(full) < target_samples:
full = np.pad(full, (0, target_samples - len(full)))
else:
full = full[:target_samples]
# Write concatenated TTS track
with wave.open("tts_full.wav", "w") as wf:
wf.setnchannels(1)
wf.setsampwidth(2)
wf.setframerate(sr)
wf.writeframes(full.tobytes())
return timing
Mix TTS (center) with background music (wide stereo, low volume). The filter chain:
extrastereodef mix_audio(tts_path, bgm_path, output_path, bgm_volume=0.15):
"""Mix TTS centered with BGM panned wide stereo."""
filter_complex = (
# TTS: mono -> stereo center
"[0:a]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=mono,"
"pan=stereo|c0=c0|c1=c0[tts];"
# BGM: normalize loudness, reduce volume, widen stereo
f"[1:a]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo,"
f"loudnorm=I=-16:TP=-1.5:LRA=11,"
f"volume={bgm_volume},"
f"extrastereo=m=2.5[bgm];"
# Mix with smooth dropout at end
"[tts][bgm]amix=inputs=2:duration=longest:dropout_transition=3,"
"aformat=sample_fmts=s16:sample_rates=44100:channel_layouts=stereo[out]"
)
cmd = [
"ffmpeg", "-y",
"-i", tts_path,
"-i", bgm_path,
"-filter_complex", filter_complex,
"-map", "[out]", output_path,
]
subprocess.run(cmd, capture_output=True, check=True)
Cycle through visual presets per quote for variety. Each preset defines a background effect, color scheme, and text color:
QUOTE_STYLES = [
{"hue": 0.08, "accent": 0.7, "bg": "spiral", "text_rgb": (255, 220, 140)}, # warm gold
{"hue": 0.55, "accent": 0.6, "bg": "rings", "text_rgb": (180, 220, 255)}, # cool blue
{"hue": 0.75, "accent": 0.7, "bg": "wave", "text_rgb": (220, 180, 255)}, # purple
{"hue": 0.35, "accent": 0.6, "bg": "matrix", "text_rgb": (140, 255, 180)}, # green
{"hue": 0.95, "accent": 0.8, "bg": "fire", "text_rgb": (255, 180, 160)}, # red/coral
{"hue": 0.12, "accent": 0.5, "bg": "interference", "text_rgb": (255, 240, 200)}, # amber
{"hue": 0.60, "accent": 0.7, "bg": "tunnel", "text_rgb": (160, 210, 255)}, # cyan
{"hue": 0.45, "accent": 0.6, "bg": "aurora", "text_rgb": (180, 255, 220)}, # teal
]
style = QUOTE_STYLES[quote_index % len(QUOTE_STYLES)]
This guarantees no two adjacent quotes share the same look, even without randomness.
Display quote text character-by-character synced to speech progress. Recently revealed characters are brighter, creating a "just typed" glow:
def render_typewriter(ch, co, lines, block_start, cols, progress, total_chars, text_rgb, t):
"""Overlay typewriter text onto character/color grids.
progress: 0.0 (nothing visible) to 1.0 (all text visible)."""
chars_visible = int(total_chars * min(1.0, progress * 1.2)) # slight overshoot for snappy feel
tr, tg, tb = text_rgb
char_count = 0
for li, line in enumerate(lines):
row = block_start + li
col = (cols - len(line)) // 2
for ci, c in enumerate(line):
if char_count < chars_visible:
age = chars_visible - char_count
bri_factor = min(1.0, 0.5 + 0.5 / (1 + age * 0.015)) # newer = brighter
hue_shift = math.sin(char_count * 0.3 + t * 2) * 0.05
stamp(ch, co, c, row, col + ci,
(int(min(255, tr * bri_factor * (1.0 + hue_shift))),
int(min(255, tg * bri_factor)),
int(min(255, tb * bri_factor * (1.0 - hue_shift)))))
char_count += 1
# Blinking cursor at insertion point
if progress < 1.0 and int(t * 3) % 2 == 0:
# Find cursor position (char_count == chars_visible)
cc = 0
for li, line in enumerate(lines):
for ci, c in enumerate(line):
if cc == chars_visible:
stamp(ch, co, "\u258c", block_start + li,
(cols - len(line)) // 2 + ci, (255, 220, 100))
return
cc += 1
Run the standard audio analysis (FFT, beat detection) on the final mixed track so visual effects react to both TTS and music:
# Analyze mixed_final.wav (not individual tracks)
features = analyze_audio("mixed_final.wav", fps=24)
Visuals pulse with both the music beats and the speech energy.
After rendering, verify that visual beat markers align with actual audio beats. Drift accumulates from frame timing errors, ffmpeg concat boundaries, and rounding in fi / fps.
def extract_beat_timestamps(features, fps, threshold=0.5):
"""Extract timestamps where beat feature exceeds threshold."""
beat = features["beat"]
timestamps = []
for fi in range(len(beat)):
if beat[fi] > threshold:
timestamps.append(fi / fps)
return timestamps
def extract_visual_beat_timestamps(video_path, fps, brightness_jump=30):
"""Detect visual beats by brightness jumps between consecutive frames.
Returns timestamps where mean brightness increases by more than threshold."""
import subprocess
cmd = ["ffmpeg", "-i", video_path, "-f", "rawvideo", "-pix_fmt", "gray", "-"]
proc = subprocess.run(cmd, capture_output=True)
frames = np.frombuffer(proc.stdout, dtype=np.uint8)
# Infer frame dimensions from total byte count
n_pixels = len(frames)
# For 1080p: 1920*1080 pixels per frame
# Auto-detect from video metadata is more robust:
probe = subprocess.run(
["ffprobe", "-v", "error", "-select_streams", "v:0",
"-show_entries", "stream=width,height",
"-of", "csv=p=0", video_path],
capture_output=True, text=True)
w, h = map(int, probe.stdout.strip().split(","))
ppf = w * h # pixels per frame
n_frames = n_pixels // ppf
frames = frames[:n_frames * ppf].reshape(n_frames, ppf)
means = frames.mean(axis=1)
timestamps = []
for i in range(1, len(means)):
if means[i] - means[i-1] > brightness_jump:
timestamps.append(i / fps)
return timestamps
def sync_report(audio_beats, visual_beats, tolerance_ms=50):
"""Compare audio beat timestamps to visual beat timestamps.
Args:
audio_beats: list of timestamps (seconds) from audio analysis
visual_beats: list of timestamps (seconds) from video brightness analysis
tolerance_ms: max acceptable drift in milliseconds
Returns:
dict with matched/unmatched/drift statistics
"""
tolerance = tolerance_ms / 1000.0
matched = []
unmatched_audio = []
unmatched_visual = list(visual_beats)
for at in audio_beats:
best_match = None
best_delta = float("inf")
for vt in unmatched_visual:
delta = abs(at - vt)
if delta < best_delta:
best_delta = delta
best_match = vt
if best_match is not None and best_delta < tolerance:
matched.append({"audio": at, "visual": best_match, "drift_ms": best_delta * 1000})
unmatched_visual.remove(best_match)
else:
unmatched_audio.append(at)
drifts = [m["drift_ms"] for m in matched]
return {
"matched": len(matched),
"unmatched_audio": len(unmatched_audio),
"unmatched_visual": len(unmatched_visual),
"total_audio_beats": len(audio_beats),
"total_visual_beats": len(visual_beats),
"mean_drift_ms": np.mean(drifts) if drifts else 0,
"max_drift_ms": np.max(drifts) if drifts else 0,
"p95_drift_ms": np.percentile(drifts, 95) if len(drifts) > 1 else 0,
}
# Usage:
audio_beats = extract_beat_timestamps(features, fps=24)
visual_beats = extract_visual_beat_timestamps("output.mp4", fps=24)
report = sync_report(audio_beats, visual_beats)
print(f"Matched: {report['matched']}/{report['total_audio_beats']} beats")
print(f"Mean drift: {report['mean_drift_ms']:.1f}ms, Max: {report['max_drift_ms']:.1f}ms")
# Target: mean drift < 20ms, max drift < 42ms (1 frame at 24fps)
| Symptom | Cause | Fix |
|---|---|---|
| Consistent late visual beats | ffmpeg concat adds frames at boundaries | Use -vsync cfr flag; pad segments to exact frame count |
| Drift increases over time | Floating-point accumulation in t = fi / fps | Use integer frame counter, compute t fresh each frame |
| Random missed beats | Beat threshold too high / feature smoothing too aggressive | Lower threshold; reduce EMA alpha for beat feature |
| Beats land on wrong frame | Off-by-one in frame indexing | Verify: frame 0 = t=0, frame 1 = t=1/fps (not t=0) |