[FFmpeg-devel] [PATCH] avcodec/libwebpdec: Add libwebp WebP decoder.

[Peter Xia <aattyy@gmail.com>]

Adds support of decoding animated webp.

Signed-off-by: Peter Xia <aattyy@gmail.com>
---
 Changelog                 |   1 +
 configure                 |   4 +-
 doc/general_contents.texi |   2 +-
 libavcodec/Makefile       |   1 +
 libavcodec/allcodecs.c    |   3 +-
 libavcodec/libwebpdec.c   | 200 ++++++++++++++++++++++++++++++++++++++
 libavcodec/version.h      |   2 +-
 7 files changed, 209 insertions(+), 4 deletions(-)
 create mode 100644 libavcodec/libwebpdec.c

diff --git a/Changelog b/Changelog
index a03a79d17a..4635e16c05 100644
--- a/Changelog
+++ b/Changelog
@@ -12,6 +12,7 @@ version <next>:
 - Animated JPEG XL encoding (via libjxl)
 - VVC in Matroska
 - CENC AV1 support in MP4 muxer
+- Animated WebP decoding
 
 version 7.1:
 - Raw Captions with Time (RCWT) closed caption demuxer
diff --git a/configure b/configure
index 4559962a4a..28a532641b 100755
--- a/configure
+++ b/configure
@@ -3611,6 +3611,7 @@ libvpx_vp9_encoder_deps="libvpx"
 libvvenc_encoder_deps="libvvenc"
 libwebp_encoder_deps="libwebp"
 libwebp_anim_encoder_deps="libwebp"
+libwebp_decoder_deps="libwebp"
 libx262_encoder_deps="libx262"
 libx264_encoder_deps="libx264"
 libx264_encoder_select="atsc_a53 golomb"
@@ -7081,7 +7082,8 @@ enabled libvpx            && {
 enabled libvvenc          && require_pkg_config libvvenc "libvvenc >= 1.6.1" "vvenc/vvenc.h" vvenc_get_version
 enabled libwebp           && {
     enabled libwebp_encoder      && require_pkg_config libwebp "libwebp >= 0.2.0" webp/encode.h WebPGetEncoderVersion
-    enabled libwebp_anim_encoder && check_pkg_config libwebp_anim_encoder "libwebpmux >= 0.4.0" webp/mux.h WebPAnimEncoderOptionsInit; }
+    enabled libwebp_anim_encoder && check_pkg_config libwebp_anim_encoder "libwebpmux >= 0.4.0" webp/mux.h WebPAnimEncoderOptionsInit
+    enabled libwebp_decoder      && check_pkg_config libwebp_decoder "libwebpdemux >= 1.5.0" webp/demux.h WebPAnimDecoderOptionsInitInternal; }
 enabled libx264           && require_pkg_config libx264 x264 "stdint.h x264.h" x264_encoder_encode &&
                              require_cpp_condition libx264 x264.h "X264_BUILD >= 155" && {
                              [ "$toolchain" != "msvc" ] ||
diff --git a/doc/general_contents.texi b/doc/general_contents.texi
index 5faf89815b..4f10c3e34a 100644
--- a/doc/general_contents.texi
+++ b/doc/general_contents.texi
@@ -857,7 +857,7 @@ following image formats are supported:
 @item WBMP         @tab X @tab X
     @tab Wireless Application Protocol Bitmap image format
 @item WebP         @tab E @tab X
-    @tab WebP image format, encoding supported through external library libwebp
+    @tab WebP image format, supported through external library libwebp
 @item XBM  @tab X @tab X
     @tab X BitMap image format
 @item XFace @tab X @tab X
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index b24201b1af..c9637a2114 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1179,6 +1179,7 @@ OBJS-$(CONFIG_LIBVPX_VP9_ENCODER)         += libvpxenc.o
 OBJS-$(CONFIG_LIBVVENC_ENCODER)           += libvvenc.o
 OBJS-$(CONFIG_LIBWEBP_ENCODER)            += libwebpenc_common.o libwebpenc.o
 OBJS-$(CONFIG_LIBWEBP_ANIM_ENCODER)       += libwebpenc_common.o libwebpenc_animencoder.o
+OBJS-$(CONFIG_LIBWEBP_DECODER)            += libwebpdec.o
 OBJS-$(CONFIG_LIBX262_ENCODER)            += libx264.o
 OBJS-$(CONFIG_LIBX264_ENCODER)            += libx264.o
 OBJS-$(CONFIG_LIBX265_ENCODER)            += libx265.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index f10519617e..5f8f682111 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -810,8 +810,9 @@ extern FFCodec ff_libvpx_vp9_encoder;
 extern const FFCodec ff_libvpx_vp9_decoder;
 extern const FFCodec ff_libvvenc_encoder;
 /* preferred over libwebp */
-extern const FFCodec ff_libwebp_anim_encoder;
 extern const FFCodec ff_libwebp_encoder;
+extern const FFCodec ff_libwebp_anim_encoder;
+extern const FFCodec ff_libwebp_decoder;
 extern const FFCodec ff_libx262_encoder;
 extern const FFCodec ff_libx264_encoder;
 extern const FFCodec ff_libx264rgb_encoder;
diff --git a/libavcodec/libwebpdec.c b/libavcodec/libwebpdec.c
new file mode 100644
index 0000000000..9ec3b60709
--- /dev/null
+++ b/libavcodec/libwebpdec.c
@@ -0,0 +1,200 @@
+/*
+ * LibWebP decoder
+ * Copyright (c) 2025 Peter Xia
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * LibWebP decoder
+ */
+
+#include "decode.h"
+#include "codec_internal.h"
+#include "libavutil/avutil.h"
+#include "libavutil/opt.h"
+#include "libavformat/avformat.h"
+#include "libavformat/avio.h"
+
+#include <webp/demux.h>
+#include <webp/decode.h>
+
+typedef struct AnimatedWebPContext
+{
+    const AVClass *class;
+    WebPAnimDecoderOptions dec_options;
+    WebPAnimDecoder *dec;
+    AVBufferRef *file_content;
+    WebPData webp_data; // references |file_content|
+    uint32_t loop_to_send;
+    uint32_t loop_sent;
+
+    // --- Options ---
+    int ignore_loop;
+} AnimatedWebPContext;
+
+// Initialize the decoder context
+static av_cold int decode_libwebp_init(AVCodecContext *avctx)
+{
+    AnimatedWebPContext *s = avctx->priv_data;
+
+    if (!WebPAnimDecoderOptionsInit(&s->dec_options))
+    {
+        av_log(avctx, AV_LOG_DEBUG, "Cannot initialize WebPAnimDecoderOptions\n");
+        return AVERROR(ENOMEM);
+    }
+    s->dec_options.color_mode = MODE_RGBA;
+    s->dec_options.use_threads = 1;
+    s->file_content = NULL;
+    s->loop_sent = 0;
+
+    avctx->pix_fmt = AV_PIX_FMT_RGBA;
+    avctx->pkt_timebase = av_make_q(1, 1000);
+    avctx->framerate = av_make_q(1, 0);
+
+    av_log(avctx, AV_LOG_DEBUG, "Animated WebP decoder initialized.\n");
+    return 0; // Success
+}
+
+// Decode one frame of the animated WebP
+// This function will be called multiple times by FFmpeg.
+// The first call receives the AVPacket with the full WebP file.
+// Subsequent calls receive empty AVPacket until all frames are decoded.
+static int decode_libwebp_frame(AVCodecContext *avctx, AVFrame *p,
+                                int *got_frame, AVPacket *avpkt)
+{
+    av_log(avctx, AV_LOG_INFO, "decode_libwebp_frame()\n");
+
+    WebPAnimInfo anim_info;
+    uint8_t *frame_rgba;
+    int timestamp_ms;
+
+    AnimatedWebPContext *s = avctx->priv_data;
+    int ret = avpkt->size;
+
+    // Initialization Phase (First Call)
+    // |avpkt| contains the entire file.
+    if (!s->dec)
+    {
+        if (!avpkt || avpkt->size <= 0)
+        {
+            // Should not happen on the first call, but check anyway.
+            av_log(avctx, AV_LOG_ERROR, "No input data provided on first call.\n");
+            return AVERROR(EINVAL);
+        }
+
+        // Store entire WebP file in memory.
+        s->file_content = av_buffer_ref(avpkt->buf);
+        s->webp_data.bytes = s->file_content->data;
+        s->webp_data.size = s->file_content->size;
+
+        s->dec = WebPAnimDecoderNew(&s->webp_data, &s->dec_options);
+        if (!s->dec)
+        {
+            av_log(avctx, AV_LOG_ERROR, "Error creating WebPAnimDecoder.\n");
+            av_buffer_unref(&s->file_content);
+            return AVERROR(ENOMEM);
+        }
+
+        WebPAnimDecoderGetInfo(s->dec, &anim_info);
+
+        s->loop_to_send = s->ignore_loop ? 1 : anim_info.loop_count;
+        avctx->width = anim_info.canvas_width;
+        avctx->coded_width = anim_info.canvas_width;
+        avctx->height = anim_info.canvas_height;
+        avctx->coded_height = anim_info.canvas_height;
+        avctx->framerate = av_make_q(1, 0);
+    }
+
+    if (!WebPAnimDecoderHasMoreFrames(s->dec))
+    {
+        s->loop_sent++;
+        WebPAnimDecoderReset(s->dec);
+    }
+
+    if (s->loop_sent >= s->loop_to_send)
+    {
+        av_log(avctx, AV_LOG_DEBUG, "End of animated WebP stream.\n");
+        return AVERROR_EOF;
+    }
+
+
+    if (!WebPAnimDecoderGetNext(s->dec, &frame_rgba, &timestamp_ms))
+    {
+        av_log(avctx, AV_LOG_ERROR, "Error getting next frame from WebPAnimDecoder.\n");
+        return AVERROR(EINVAL);
+    }
+
+    ret = ff_get_buffer(avctx, p, 0);
+    if (ret)
+    {
+        av_log(avctx, AV_LOG_ERROR, "Failed to allocated buffer.\n");
+        return AVERROR(ENOMEM);
+    }
+
+    p->width = avctx->width;
+    p->height = avctx->height;
+    p->format = AV_PIX_FMT_RGBA;
+    p->pts = timestamp_ms;
+    p->pkt_dts = 0;
+    p->pict_type = AV_PICTURE_TYPE_I;
+
+    memcpy(p->data[0], frame_rgba, p->width * p->height * 4);
+
+    *got_frame = 1;
+    return ret;
+}
+
+static av_cold int decode_libwebp_close(AVCodecContext *avctx)
+{
+    AnimatedWebPContext *s = avctx->priv_data;
+    av_buffer_unref(&s->file_content);
+    if (s->dec)
+    {
+        WebPAnimDecoderDelete(s->dec);
+        s->dec = NULL;
+    }
+    return 0;
+}
+
+static const AVOption options[] = {
+    {"ignore_loop", "ignore loop setting (netscape extension)", offsetof(AnimatedWebPContext, ignore_loop), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, AV_OPT_FLAG_DECODING_PARAM},
+    {NULL}};
+
+static const AVClass libwebp_decoder_class = {
+    .class_name = "libwebp_decoder",
+    .item_name = av_default_item_name,
+    .option = options,
+    .version = LIBAVUTIL_VERSION_INT,
+    .category = AV_CLASS_CATEGORY_DECODER,
+};
+
+// Define the AVCodec structure for FFmpeg
+const FFCodec ff_libwebp_decoder = {
+    .p.name         = "libwebp",
+    CODEC_LONG_NAME("libwebp image/animation decoder"),
+    .p.type         = AVMEDIA_TYPE_VIDEO,
+    .p.id           = AV_CODEC_ID_WEBP,
+    .p.priv_class   = &libwebp_decoder_class,
+    .priv_data_size = sizeof(AnimatedWebPContext),
+    .p.wrapper_name = "libwebp",
+    .init           = decode_libwebp_init,
+    FF_CODEC_DECODE_CB(decode_libwebp_frame),
+    .close          = decode_libwebp_close,
+    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
+};
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 8c3d476003..5957009457 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR   0
+#define LIBAVCODEC_VERSION_MINOR   1
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
-- 
2.39.5 (Apple Git-154)

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