Add pipeline code

_pipeline/assemble.py

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+"""Assembly with ffmpeg: wav pieces + chimes + pauses -> one MP3 per script file, to ACX levels.
+1. Speech track: head, pieces, chimes, pauses (digital silence), tail.
+2. Room tone: quiet noise (fixed seed) as long as the speech track, mixed underneath everywhere, so there is no digital silence.
+3. Gain on the speech track so the finished mix lands on the RMS target; a limiter holds the peak ceiling.
+4. MP3, CBR, 44.1 kHz, mono."""
+import json
+import math
+import os
+import shutil
+import tempfile
+
+import audiomeasure as am
+import settings
+import voice
+
+FMT = ["-ar", "{sr}", "-ac", "{ch}", "-c:a", "pcm_f32le"]
+
+
+def fmt(a):
+    return [x.format(sr=a["sample_rate"], ch=a["channels"]) for x in FMT]
+
+
+def make_silence(a, seconds, path):
+    am.ffmpeg(["-f", "lavfi", "-i", "anullsrc=r=%d:cl=%s" % (a["sample_rate"], "mono" if a["channels"] == 1 else "stereo"),
+               "-t", "%.3f" % seconds] + fmt(a) + [path])
+
+
+def make_room_tone(a, seconds, path):
+    """Very quiet noise (ACX wants room tone, not digital silence). Fixed seed, so output is repeatable."""
+    amp = 10 ** (a["room_tone_db"] / 20) * math.sqrt(3)      # uniform white noise: RMS = amplitude / sqrt(3)
+    am.ffmpeg(["-f", "lavfi", "-i", "anoisesrc=d=%.3f:c=white:r=%d:a=%.6f:seed=1" % (seconds, a["sample_rate"], amp)] + fmt(a) + [path])
+
+
+def make_chime(a, level_db, path):
+    """A soft sine tone with a smooth rise and fall (sin^2 envelope), peak at level_db."""
+    amp = 10 ** (level_db / 20)
+    dur = a["chime_s"]
+    expr = "%.6f*sin(2*PI*%g*t)*pow(sin(PI*t/%g),2)" % (amp, a["chime_hz"], dur)
+    am.ffmpeg(["-f", "lavfi", "-i", "aevalsrc='%s':s=%d:d=%g" % (expr, a["sample_rate"], dur)] + fmt(a) + [path])
+
+
+def concat(paths, out, tmp):
+    lst = os.path.join(tmp, "list_%s.txt" % os.path.basename(out))
+    with open(lst, "w") as f:
+        for p in paths:
+            f.write("file '%s'\n" % p.replace("'", "'\\''"))
+    am.ffmpeg(["-f", "concat", "-safe", "0", "-i", lst, "-c", "copy", out])
+
+
+def build_speech(a, items, chime_db, tmp, tag):
+    """Speech track. chime_db None leaves the cue slots silent (used to find the gain before the chime is made)."""
+    cache = {}
+
+    def silence(seconds):
+        key = "sil%.3f" % seconds
+        if key not in cache:
+            cache[key] = os.path.join(tmp, key + ".wav")
+            make_silence(a, seconds, cache[key])
+        return cache[key]
+
+    parts = [silence(a["head_room_tone_s"])]
+    for n, it in enumerate(items):
+        if "cue" in it:
+            if chime_db is None:
+                parts.append(silence(a["chime_s"]))
+            else:
+                if "chime" not in cache:
+                    cache["chime"] = os.path.join(tmp, "chime_%s.wav" % tag)
+                    make_chime(a, chime_db, cache["chime"])
+                parts.append(cache["chime"])
+        else:
+            p = os.path.join(tmp, "p%05d.wav" % n)
+            if not os.path.exists(p):
+                am.ffmpeg(["-i", it["wav"]] + fmt(a) + [p])
+            parts.append(p)
+        if n < len(items) - 1:
+            parts.append(silence(it["gap_after_s"]))
+    parts.append(silence(a["tail_room_tone_s"]))
+    out = os.path.join(tmp, "speech_%s.wav" % tag)
+    concat(parts, out, tmp)
+    return out
+
+
+def mix(a, speech, gain, noise, out):
+    limit = 10 ** (a["peak_ceiling_db"] / 20)
+    am.ffmpeg(["-i", speech, "-i", noise, "-filter_complex",
+               "[0:a]volume=%.3fdB,alimiter=limit=%.5f:level=0[s];[s][1:a]amix=inputs=2:normalize=0:duration=first" % (gain, limit)]
+              + fmt(a) + [out])
+
+
+def set_level(a, speech, tmp):
+    """Find the gain that puts the finished mix on the RMS target. Returns (mix path, gain dB)."""
+    noise = os.path.join(tmp, "noise.wav")
+    make_room_tone(a, float(am.probe(speech)["duration"]), noise)
+    rms, _ = am.overall(speech)
+    gain = a["target_rms_db"] - rms
+    for i in range(3):
+        out = os.path.join(tmp, "mix_%d.wav" % i)
+        mix(a, speech, gain, noise, out)
+        got, _ = am.overall(out)
+        if abs(got - a["target_rms_db"]) <= 0.3:
+            break
+        gain += a["target_rms_db"] - got
+    return out, gain, noise
+
+
+def assemble_items(cfg, items, out_mp3):
+    """items as written by voice.py. Writes out_mp3. Returns the gain applied to speech in dB."""
+    a = dict(cfg["audio"])
+    work = settings.resolve(cfg, "work_dir")
+    os.makedirs(work, exist_ok=True)
+    tmp = tempfile.mkdtemp(prefix="asm_", dir=work)
+    try:
+        speech = build_speech(a, items, None, tmp, "measure")
+        final, gain, noise = set_level(a, speech, tmp)
+        if any("cue" in it for it in items):
+            # build again with the chime in; it is made so it lands at chime_db after the gain
+            speech = build_speech(a, items, a["chime_db"] - gain, tmp, "final")
+            final = os.path.join(tmp, "final.wav")
+            mix(a, speech, gain, noise, final)
+        os.makedirs(os.path.dirname(out_mp3), exist_ok=True)
+        am.ffmpeg(["-i", final, "-c:a", "libmp3lame", "-b:a", a["mp3_bitrate"], "-ar", str(a["sample_rate"]), "-ac", str(a["channels"]), out_mp3])
+        return gain
+    finally:
+        shutil.rmtree(tmp, ignore_errors=True)
+
+
+def run(cfg, book_dir, only=None):
+    import bookio
+    book = bookio.read_book(book_dir)
+    out_dir = settings.audio_dir(cfg, book_dir)
+    for name in book["audio_files"]:
+        if only and name != only:
+            continue
+        with open(os.path.join(voice.work_dir_for(cfg, book_dir, name), "manifest.json"), encoding="utf-8") as f:
+            items = json.load(f)
+        gain = assemble_items(cfg, items, os.path.join(out_dir, name + ".mp3"))
+        print("%s.mp3 written (speech gain %.1f dB)" % (name, gain))