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

[Peter Xia <aattyy@gmail.com>]

Hi Leon, 

Thanks for the feedback! I’ve send a v2 of this patch.

Peter

> On Apr 3, 2025, at 12:11 AM, Leon Grutters <gruttersleonbot2@gmail.com> wrote:
> 
> On 4/1/25 12:29 PM, Peter Xia 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))
>> +    {
> Braces for if-statements should be on the same line as the if-statement
>> +        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.
> These comments should probably be in Javadoc format
>> +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;
> This gives a -Wdeclaration-after-statement warning
> (though that wouldn't matter if
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/AS8P250MB07446AE8C7CDDD1AC795DD568FA22@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM/
> is merged)
>> +    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}};
> This closing brace should be on its line
>> +
>> +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
> This patch doesn't apply anymore because of a merge conflict
> in this file since 839b419
> (of course that's not your fault, but just a heads up!)
>> @@ -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, \
> 
> 
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