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MrCloudy2andClaude Opus 5.5
53a0d959fe
VP8 WebM showed black video: there was no VP8 decoder. New L0 crate filmcraft-vp8, implemented from RFC 6386 sections 1-19 (tables extracted from the RFC text, nothing from the attached reference decoder): every coding tool, versions 0-3, hidden altref frames, size changes. Bit-exact with libvpx on 62 libvpx VP8 test vectors, real-world FATE samples and generated fixtures; never panics on corrupted input. Wired into codecs for Matroska / WebM (V_VP8, including the alpha layer of transparent WebM) and MP4 (vp08). VP8 colour is BT.601 (RFC 6386 9.2). A hidden altref frame is a WebM block of its own with the time of the frame that follows it: the VP8 time lookup now moves on to that shown frame instead of repeating the previous one. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
85 lines
3.5 KiB
Python
85 lines
3.5 KiB
Python
#!/usr/bin/env python3
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"""Extract the VP8 constant tables from the text of RFC 6386 ("VP8 Data Format and Decoding Guide").
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Usage:
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curl -L -o rfc6386.txt https://www.rfc-editor.org/rfc/rfc6386.txt
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python3 extract_tables.py rfc6386.txt > ../src/spec_tables.rs
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Only sections 1-19 (the format description) are read: the text is cut at section 20 ("Attachment
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One: Reference Decoder Source Code"), so nothing comes from the reference decoder. Every table is
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emitted flat (row-major, as printed) with its element count checked against the declared dimensions.
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"""
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import re
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import sys
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text = open(sys.argv[1], encoding="utf-8").read()
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cut = text.find("\n20. Attachment One")
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if cut < 0:
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sys.exit("section 20 not found")
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text = text[:cut]
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# page breaks: footer / header lines and form feeds
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text = "\n".join(l for l in text.split("\n") if not l.startswith("Bankoski") and not l.startswith("RFC 6386 ") and "\f" not in l)
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def table(name, count, occurrence=-1):
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"""Integers of the table `name ... = { ... }` (by default the last definition in the text)."""
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found = []
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# a definition: `name [dim] [dim] ... = {` (uses of the table never have `= {` after the brackets)
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for m in re.finditer(r"\b%s\s*(?:\[[^\]\n]*\]\s*)+=\s*\{" % re.escape(name), text):
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brace = m.end() - 1
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depth = 0
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i = brace
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while True:
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ch = text[i]
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if ch == "{":
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depth += 1
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elif ch == "}":
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depth -= 1
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if depth == 0:
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break
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i += 1
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body = re.sub(r"/\*.*?\*/", "", text[brace:i], flags=re.S)
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body = re.sub(r"//[^\n]*", "", body)
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found.append([int(v) for v in re.findall(r"-?\d+", body)])
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if not found:
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sys.exit("table %s not found" % name)
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vals = found[occurrence]
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if len(vals) != count:
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sys.exit("table %s: %d values, expected %d" % (name, len(vals), count))
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return vals
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TABLES = [
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# (spec name, rust name, rust type, count)
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("coeff_update_probs", "COEFF_UPDATE_PROBS", "u8", 4 * 8 * 3 * 11),
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("default_coeff_probs", "DEFAULT_COEFF_PROBS", "u8", 4 * 8 * 3 * 11),
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("kf_bmode_prob", "KF_BMODE_PROBS", "u8", 10 * 10 * 9),
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("dc_qlookup", "DC_QLOOKUP", "u16", 128),
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("ac_qlookup", "AC_QLOOKUP", "u16", 128),
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("vp8_mode_contexts", "MODE_CONTEXTS", "u8", 6 * 4),
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("sub_mv_ref_prob", "SUB_MV_REF_PROBS", "u8", 5 * 3),
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("vp8_mv_update_probs", "MV_UPDATE_PROBS", "u8", 2 * 19),
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("default_mv_context", "DEFAULT_MV_PROBS", "u8", 2 * 19),
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("bmode_prob", "BMODE_PROBS", "u8", 9),
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("coeff_bands", "COEFF_BANDS", "u8", 16),
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("kf_ymode_prob", "KF_YMODE_PROBS", "u8", 4),
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("kf_uv_mode_prob", "KF_UV_MODE_PROBS", "u8", 3),
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("ymode_prob", "YMODE_PROBS", "u8", 4),
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("uv_mode_prob", "UV_MODE_PROBS", "u8", 3),
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("mvpartition_probs", "MVPARTITION_PROBS", "u8", 3),
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("BilinearFilters", "BILINEAR_FILTERS", "i32", 8 * 6),
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("filters", "SIXTAP_FILTERS", "i32", 8 * 6),
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]
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print("// Generated by tools/extract_tables.py from the text of RFC 6386 (sections 1-19). Do not edit.")
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print("// Every table is flat, row-major, in the order the specification prints it.")
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print()
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for spec, rust, ty, count in TABLES:
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vals = table(spec, count)
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print("/// `%s` (RFC 6386), %d entries." % (spec, count))
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print("pub const %s: [%s; %d] = [" % (rust, ty, count))
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for i in range(0, count, 16):
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print(" " + ", ".join(str(v) for v in vals[i:i + 16]) + ",")
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print("];")
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print()
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