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

[Peter Xia <aattyy@gmail.com>]

Can anyone take a look at this? This is my first patch so not entirely sure about the process.

Thanks,
Peter

> On Apr 1, 2025, at 3:29 AM, Peter Xia <aattyy@gmail.com> wrote:
> 
> 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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