@@ -4,6 +4,15 @@
 
 ### Features
 
+- `Image.encodeAVIF({ quality, alphaQuality, subsampling, effort })` encodes AVIFs: an AV1 encoder of its own (still
+  pictures, intra coding) whose syntax mirrors the dav1d based decoder, so dav1d decodes its files to exactly the
+  encoder's reconstruction. It chooses partitions (64x64 to 8x8), the 13 intra modes, chroma from luma and the transform
+  types by rate and distortion, quantizes the coefficients by rate and distortion, and picks the loop filter level and
+  up to 8 CDEF strengths (per 64x64 block) by the filtered image. On photos its files are within a few percent of
+  libaom's (avifenc's default speed) at the same PSNR, but encoding takes about 15 times as long. `quality` (0-100,
+  default 60) maps to the quantizer like avifenc's -q; 100 is lossless (RGB, identity matrix). Transparency is a
+  monochrome alpha image, lossless by default (`alphaQuality`). `subsampling`: '4:4:4' (default) or '4:2:0'. `effort`
+  (0-2, default 1): how many modes and partitions are tried.
 - `Image.encodeJXL()` encodes lossless JPEG XLs: ported from libjxl's fast lossless encoder, the codestream is byte for
   byte what `cjxl -e 1` writes on CPUs with AVX2 or NEON (libjxl's output depends on the CPU: it works in chunks of 16
   pixels there, of 8 without SIMD, of 32 with AVX-512). Images of at most 511 colors besides black get a palette,
 
@@ -67,6 +67,7 @@ deno add jsr:@matmen/imagescript     # Deno (npm:imagescript works too)
   , [JPEGs](https://imagescript.matmen.dev/classes/Image.html#encodejpeg)
   , lossless and lossy [WebPs](https://imagescript.matmen.dev/classes/Image.html#encodewebp) (lossy ones byte for
   byte like libwebp's cwebp)
+  , [AVIFs](https://imagescript.matmen.dev/classes/Image.html#encodeavif) (lossy and lossless, with alpha)
   , lossless [JPEG XLs](https://imagescript.matmen.dev/classes/Image.html#encodejxl) (byte for byte like libjxl's
   `cjxl -e 1`)
   , [BMPs](https://imagescript.matmen.dev/classes/Image.html#encodebmp)
@@ -129,7 +130,7 @@ the text shaping is ported from [HarfBuzz](https://github.com/harfbuzz/harfbuzz)
 [dav1d](https://code.videolan.org/videolan/dav1d), AVIFs are converted to RGB like
 [libavif](https://github.com/AOMediaCodec/libavif) does, the JPEG XL decoder is ported from
 [jxl-oxide](https://github.com/tirr-c/jxl-oxide) and [libjxl](https://github.com/libjxl/libjxl), the JPEG XL encoder
-from libjxl's fast lossless encoder.
+from libjxl's fast lossless encoder, the AV1 encoder mirrors the decoder and uses libaom's symbol encoder.
 See [THIRD_PARTY_NOTICES.md](THIRD_PARTY_NOTICES.md) for their licenses.
 
 ---
 
@@ -13,7 +13,8 @@ following projects, under their own licenses. Each derived file says so in its h
 | [RFC 9649](https://www.rfc-editor.org/rfc/rfc9649) (WebP Image Format) | `src/codecs/vp8l.ts` (lossless bitstream, short distance code table), `src/codecs/webp.ts` (container) | BSD-3-Clause (Revised BSD) |
 | [RFC 6386](https://www.rfc-editor.org/rfc/rfc6386) (VP8 Data Format and Decoding Guide, with the libvpx reference decoder) | `src/codecs/vp8-tables.ts` (probability and quantizer tables), `src/codecs/vp8.ts` (decoding procedures) | BSD-3-Clause |
 | [libwebp](https://chromium.googlesource.com/webm/libwebp) | `src/codecs/vp8.ts` (YUV to RGB conversion, "fancy" chroma upsampling), `src/codecs/webp.ts` (animation frame blending), `src/codecs/vp8-enc.ts`, `src/codecs/vp8-enc-dsp.ts` (the lossy encoder: RGB to YUV conversion, analysis, segments, rate-distortion optimized mode decisions, quantization, token probabilities, bitstream, alpha filtering), `src/codecs/vp8-enc-tables.ts` (its tables, generated from libwebp by `scripts/vp8-enc-tables.py`) | BSD-3-Clause |
-| [dav1d](https://code.videolan.org/videolan/dav1d) by VideoLAN, the dav1d authors and Two Orioles | `src/codecs/av1/*` (the AV1 decoder: bitstream parsing, symbol decoding, prediction, inverse transforms, loop filters, film grain; the tables in `src/codecs/av1/data.ts`, generated from dav1d by `scripts/av1-tables.c`) | BSD-2-Clause |
+| [dav1d](https://code.videolan.org/videolan/dav1d) by VideoLAN, the dav1d authors and Two Orioles | `src/codecs/av1/*` (the AV1 decoder, and the encoder's syntax, contexts and reconstruction mirrored from it: bitstream parsing, symbol decoding, prediction, inverse transforms, loop filters, film grain; the tables in `src/codecs/av1/data.ts`, generated from dav1d by `scripts/av1-tables.c`) | BSD-2-Clause |
+| [libaom](https://aomedia.googlesource.com/aom/) by the Alliance for Open Media | `src/codecs/av1/msac-enc.ts` (the symbol encoder), `src/codecs/av1/fdct.ts` (the forward Walsh-Hadamard transform), `src/codecs/av1/encode.ts` (the loop filter level from the quantizer), `src/codecs/avif-enc.ts` (the quantizer to qindex table) | BSD-2-Clause |
 | [libavif](https://github.com/AOMediaCodec/libavif) by Joe Drago | `src/codecs/avif.ts` (YUV to RGB conversion with bilinear chroma upsampling, alpha range expansion and unpremultiplication) | BSD-2-Clause |
 | [jxl-oxide](https://github.com/tirr-c/jxl-oxide) by Wonwoo Choi | `src/codecs/jxl/*` (the JPEG XL decoder: bit reader, header and frame header fields, entropy decoding, VarDCT, dequantization matrices, transforms, restoration filters, upsampling, the parsing of patches, splines and noise) | MIT (or Apache-2.0) |
 | [libjxl](https://github.com/libjxl/libjxl) by the JPEG XL Project Authors | `src/codecs/jxl/modular.ts` (Modular decoding: MA trees, predictors, the self-correcting predictor, transforms), `src/codecs/jxl/frame.ts` (the sections of frames, the order of the rendering stages, reference frames), `src/codecs/jxl/blend.ts`, `src/codecs/jxl/color.ts` (XYB to RGB), `src/codecs/jxl/features.ts` (rendering patches, splines and noise), `src/codecs/jxl/fast-lossless.ts` (the lossless encoder: palette detection, YCoCg, the gradient predictor, prefix codes, runs as LZ77, the headers) | BSD-3-Clause |
@@ -188,6 +189,41 @@ ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ```
 
+## libaom
+
+The AV1 encoder's symbol encoder and forward Walsh-Hadamard transform are ported from libaom, the AV1 reference
+implementation, as are its guess of the loop filter level and the quantizer table of the quality. AV1 is covered by the
+[Alliance for Open Media Patent License 1.0](https://aomedia.org/license/patent-license/).
+
+```
+Copyright (c) 2016, Alliance for Open Media. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in
+   the documentation and/or other materials provided with the
+   distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+```
+
 ## libavif
 
 The conversion of decoded AVIFs to RGB reproduces libavif's reference conversion (in floating point, with bilinear