arr/scripts/make-probe-fixtures.sh

#!/usr/bin/env bash
# Regenerate the ffprobe fixture clips in crates/arr-probe/tests/fixtures.
#
# The clips are committed (a few KB each, DESIGN.md §12) so the test suite
# never needs ffmpeg. This script exists to document how they were made and to
# rebuild them if the set ever needs to change.
#
# The two Dolby Vision clips cannot be encoded directly: x265 refuses to write
# a DV stream without an RPU file. Instead a real HEVC clip is produced and the
# `dvcC`/`dvvC` configuration box is spliced into its sample entry, which is
# exactly what ffprobe reads to report `dv_profile`.

set -euo pipefail

root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
out="$root/crates/arr-probe/tests/fixtures"
work="$(mktemp -d)"
trap 'rm -rf "$work"' EXIT

mkdir -p "$out"

# 1080p feature: three audio tracks covering all three §5.2 signals, plus two
# subtitle tracks. Three seconds, so the runtime sanity check has something to
# compare against.
printf '1\n00:00:00,000 --> 00:00:01,000\nhello\n\n' > "$work/en.srt"
printf '1\n00:00:00,000 --> 00:00:01,000\nolá\n\n' > "$work/pt.srt"

ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "color=c=black:s=1920x1080:r=24:d=3" \
    -f lavfi -i "sine=frequency=440:duration=3" \
    -f lavfi -i "sine=frequency=660:duration=3" \
    -f lavfi -i "sine=frequency=880:duration=3" \
    -i "$work/en.srt" -i "$work/pt.srt" \
    -map 0:v -map 1:a -map 2:a -map 3:a -map 4:s -map 5:s \
    -c:v libx264 -preset ultrafast -crf 51 -pix_fmt yuv420p \
    -c:a aac -b:a 8k -c:s srt \
    -metadata:s:a:0 language=eng -metadata:s:a:0 title="English" \
    -metadata:s:a:1 language=por -metadata:s:a:1 title="Português (Brasil)" \
    -metadata:s:a:1 handler_name="Portuguese (Brazil)" \
    -metadata:s:a:2 language=pt-PT \
    -metadata:s:s:0 language=eng -metadata:s:s:1 language=por \
    "$out/movie-1080p.mkv"

# The extras reel trap: larger on disk than the feature (noise compresses
# badly) but a third of its runtime.
ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "nullsrc=s=640x360:r=12:d=1,geq=random(1)*255:128:128" \
    -an -c:v libx264 -preset ultrafast -crf 51 -pix_fmt yuv420p \
    "$out/extras-360p.mkv"

# HDR10: bt2020 primaries and the PQ transfer, which is all ffprobe reports.
ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "color=c=black:s=3840x2160:r=24:d=1" -an \
    -vf "format=yuv420p10le,setparams=color_primaries=bt2020:color_trc=smpte2084:colorspace=bt2020nc" \
    -c:v libx265 -preset ultrafast -crf 51 \
    "$out/hdr10-2160p.mkv"

# HLG and SDR both use HEVC here so transfer function, rather than codec bit
# depth, is what distinguishes their probe results.
ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "color=c=black:s=1280x720:r=24:d=1" -an \
    -vf "format=yuv420p10le,setparams=color_primaries=bt2020:color_trc=arib-std-b67:colorspace=bt2020nc" \
    -c:v libx265 -preset ultrafast -crf 51 \
    "$out/hlg-720p.mkv"

ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "color=c=black:s=1280x720:r=24:d=1" -an \
    -vf "format=yuv420p10le" \
    -c:v libx265 -preset ultrafast -crf 51 \
    "$out/sdr-10bit-hevc-720p.mkv"

# HEVC base layer for the two Dolby Vision clips.
ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "color=c=black:s=1280x720:r=24:d=1" -an \
    -vf "format=yuv420p10le,setparams=color_primaries=bt2020:color_trc=smpte2084:colorspace=bt2020nc" \
    -c:v libx265 -preset ultrafast -crf 51 -tag:v hvc1 \
    "$work/base.mp4"

cat > "$work/dovi.py" <<'PY'
"""Splice a DolbyVisionConfigurationBox into an MP4 HEVC sample entry."""

import struct
import sys

CONTAINERS = {"moov", "trak", "mdia", "minf", "stbl", "stsd"}


def children(buf, start, end):
    boxes = []
    off = start
    while off + 8 <= end:
        size = struct.unpack(">I", buf[off : off + 4])[0]
        if size == 0:
            size = end - off
        boxes.append((off, size, buf[off + 4 : off + 8].decode("latin1")))
        off += size
    return boxes


def first_child_offset(off, kind):
    # stsd carries a version/flags word and an entry count before its children.
    return off + (16 if kind == "stsd" else 8)


def find(buf, start, end, path):
    for off, size, kind in children(buf, start, end):
        if kind != path[0]:
            continue
        if len(path) == 1:
            return off, size
        return find(buf, first_child_offset(off, kind), off + size, path[1:])
    return None


def configuration(profile, compatibility_id, level=6):
    bits = (profile & 0x7F) << 41
    bits |= (level & 0x3F) << 35
    bits |= 1 << 34  # rpu_present_flag
    bits |= 1 << 32  # bl_present_flag
    bits |= (compatibility_id & 0xF) << 28
    return bytes([1, 0]) + bits.to_bytes(6, "big") + bytes(16)


def grow_ancestors(buf, target, growth):
    def walk(start, end):
        for off, size, kind in children(buf, start, end):
            if not off <= target < off + size:
                continue
            struct.pack_into(">I", buf, off, size + growth)
            if kind in CONTAINERS:
                walk(first_child_offset(off, kind), off + size)
            return

    walk(0, len(buf))


def main(source, destination, profile, compatibility_id):
    buf = bytearray(open(source, "rb").read())
    entry = find(buf, 0, len(buf), ["moov", "trak", "mdia", "minf", "stbl", "stsd", "hvc1"])
    if entry is None:
        sys.exit("no hvc1 sample entry")
    off, size = entry

    payload = configuration(profile, compatibility_id)
    kind = b"dvvC" if profile == 5 else b"dvcC"
    box = struct.pack(">I", 8 + len(payload)) + kind + payload

    buf[off + 4 : off + 8] = b"dvh1"
    buf[off + size : off + size] = box
    grow_ancestors(buf, off, len(box))
    open(destination, "wb").write(bytes(buf))


if __name__ == "__main__":
    main(sys.argv[1], sys.argv[2], int(sys.argv[3]), int(sys.argv[4]))
PY

python3 "$work/dovi.py" "$work/base.mp4" "$out/dv-profile5.mp4" 5 0
python3 "$work/dovi.py" "$work/base.mp4" "$out/dv-profile8-1.mp4" 8 1

# An audio file with embedded artwork. ffprobe reports the cover as a video
# stream, so this is what stops a soundtrack passing for a feature.
ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "color=c=red:s=64x64:d=1" -frames:v 1 "$work/cover.jpg"
ffmpeg -hide_banner -loglevel error -y \
    -f lavfi -i "sine=frequency=440:duration=2" -i "$work/cover.jpg" \
    -map 0:a -map 1:v -c:a aac -b:a 8k -c:v mjpeg -disposition:v attached_pic \
    "$out/audio-with-cover.m4a"

# Not media at all: the thing a multi-file torrent is full of.
printf 'Release notes. Not a video file.\n' > "$out/notes.nfo"

ls -l "$out"