1 files changed, 328 insertions, 110 deletions

diff --git a/libavcodec/gifdec.c b/libavcodec/gifdec.c
index cdb7f23fd4..78c8900628 100644
--- a/libavcodec/gifdec.c
+++ b/libavcodec/gifdec.c
@@ -2,122 +2,255 @@
  * GIF decoder
  * Copyright (c) 2003 Fabrice Bellard
  * Copyright (c) 2006 Baptiste Coudurier
+ * Copyright (c) 2012 Vitaliy E Sugrobov
  *
- * This file is part of Libav.
+ * This file is part of FFmpeg.
  *
- * Libav is free software; you can redistribute it and/or
+ * 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.
  *
- * Libav is distributed in the hope that it will be useful,
+ * 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 Libav; if not, write to the Free Software
+ * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
 #include "avcodec.h"
 #include "bytestream.h"
 #include "internal.h"
 #include "lzw.h"
+#include "gif.h"
 
-#define GCE_DISPOSAL_NONE       0
-#define GCE_DISPOSAL_INPLACE    1
-#define GCE_DISPOSAL_BACKGROUND 2
-#define GCE_DISPOSAL_RESTORE    3
+/* This value is intentionally set to "transparent white" color.
+ * It is much better to have white background instead of black
+ * when gif image converted to format which not support transparency.
+ */
+#define GIF_TRANSPARENT_COLOR    0x00ffffff
 
 typedef struct GifState {
+    const AVClass *class;
+    AVFrame *frame;
     int screen_width;
     int screen_height;
+    int has_global_palette;
     int bits_per_pixel;
+    uint32_t bg_color;
     int background_color_index;
     int transparent_color_index;
     int color_resolution;
-    uint32_t *image_palette;
+    /* intermediate buffer for storing color indices
+     * obtained from lzw-encoded data stream */
+    uint8_t *idx_line;
+    int idx_line_size;
 
     /* after the frame is displayed, the disposal method is used */
+    int gce_prev_disposal;
     int gce_disposal;
-    /* delay during which the frame is shown */
-    int gce_delay;
+    /* rectangle describing area that must be disposed */
+    int gce_l, gce_t, gce_w, gce_h;
+    /* depending on disposal method we store either part of the image
+     * drawn on the canvas or background color that
+     * should be used upon disposal */
+    uint32_t * stored_img;
+    int stored_img_size;
+    int stored_bg_color;
 
-    /* LZW compatible decoder */
     GetByteContext gb;
     LZWState *lzw;
 
     /* aux buffers */
-    uint8_t global_palette[256 * 3];
-    uint8_t local_palette[256 * 3];
+    uint32_t global_palette[256];
+    uint32_t local_palette[256];
 
-  AVCodecContext* avctx;
+    AVCodecContext *avctx;
+    int keyframe;
+    int keyframe_ok;
+    int trans_color;    /**< color value that is used instead of transparent color */
 } GifState;
 
-static const uint8_t gif87a_sig[6] = "GIF87a";
-static const uint8_t gif89a_sig[6] = "GIF89a";
+static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
+{
+    int i;
+
+    for (i = 0; i < nb; i++, pal++)
+        *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
+}
+
+static void gif_fill(AVFrame *picture, uint32_t color)
+{
+    uint32_t *p = (uint32_t *)picture->data[0];
+    uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;
+
+    for (; p < p_end; p++)
+        *p = color;
+}
+
+static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
+{
+    const int linesize = picture->linesize[0] / sizeof(uint32_t);
+    const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;
+    const uint32_t *pr, *pb = py + h * linesize;
+    uint32_t *px;
+
+    for (; py < pb; py += linesize) {
+        px = (uint32_t *)py + l;
+        pr = px + w;
+
+        for (; px < pr; px++)
+            *px = color;
+    }
+}
+
+static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
+                              int linesize, int l, int t, int w, int h)
+{
+    const int y_start = t * linesize;
+    const uint32_t *src_px,
+                   *src_py = src + y_start,
+                   *dst_py = dst + y_start;
+    const uint32_t *src_pb = src_py + h * linesize;
+    uint32_t *dst_px;
+
+    for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
+        src_px = src_py + l;
+        dst_px = (uint32_t *)dst_py + l;
+
+        memcpy(dst_px, src_px, w * sizeof(uint32_t));
+    }
+}
 
 static int gif_read_image(GifState *s, AVFrame *frame)
 {
     int left, top, width, height, bits_per_pixel, code_size, flags;
-    int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;
-    uint8_t *ptr, *spal, *palette, *ptr1;
-
-    left   = bytestream2_get_le16(&s->gb);
-    top    = bytestream2_get_le16(&s->gb);
-    width  = bytestream2_get_le16(&s->gb);
-    height = bytestream2_get_le16(&s->gb);
-    flags  = bytestream2_get_byte(&s->gb);
+    int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size;
+    uint32_t *ptr, *pal, *px, *pr, *ptr1;
+    int ret;
+    uint8_t *idx;
+
+    /* At least 9 bytes of Image Descriptor. */
+    if (bytestream2_get_bytes_left(&s->gb) < 9)
+        return AVERROR_INVALIDDATA;
+
+    left   = bytestream2_get_le16u(&s->gb);
+    top    = bytestream2_get_le16u(&s->gb);
+    width  = bytestream2_get_le16u(&s->gb);
+    height = bytestream2_get_le16u(&s->gb);
+    flags  = bytestream2_get_byteu(&s->gb);
     is_interleaved = flags & 0x40;
     has_local_palette = flags & 0x80;
     bits_per_pixel = (flags & 0x07) + 1;
 
-    av_dlog(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
+    av_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);
 
     if (has_local_palette) {
-        bytestream2_get_buffer(&s->gb, s->local_palette, 3 * (1 << bits_per_pixel));
-        palette = s->local_palette;
+        pal_size = 1 << bits_per_pixel;
+
+        if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
+            return AVERROR_INVALIDDATA;
+
+        gif_read_palette(s, s->local_palette, pal_size);
+        pal = s->local_palette;
     } else {
-        palette = s->global_palette;
-        bits_per_pixel = s->bits_per_pixel;
+        if (!s->has_global_palette) {
+            av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        pal = s->global_palette;
+    }
+
+    if (s->keyframe) {
+        if (s->transparent_color_index == -1 && s->has_global_palette) {
+            /* transparency wasn't set before the first frame, fill with background color */
+            gif_fill(frame, s->bg_color);
+        } else {
+            /* otherwise fill with transparent color.
+             * this is necessary since by default picture filled with 0x80808080. */
+            gif_fill(frame, s->trans_color);
+        }
     }
 
     /* verify that all the image is inside the screen dimensions */
     if (left + width > s->screen_width ||
-        top + height > s->screen_height ||
-        !width || !height) {
+        top + height > s->screen_height) {
+        av_log(s->avctx, AV_LOG_ERROR, "image is outside the screen dimensions.\n");
+        return AVERROR_INVALIDDATA;
+    }
+    if (width <= 0 || height <= 0) {
         av_log(s->avctx, AV_LOG_ERROR, "Invalid image dimensions.\n");
         return AVERROR_INVALIDDATA;
     }
 
-    /* build the palette */
-    n = (1 << bits_per_pixel);
-    spal = palette;
-    for(i = 0; i < n; i++) {
-        s->image_palette[i] = (0xffu << 24) | AV_RB24(spal);
-        spal += 3;
+    /* process disposal method */
+    if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {
+        gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
+    } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
+        gif_copy_img_rect(s->stored_img, (uint32_t *)frame->data[0],
+            frame->linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
     }
-    for(; i < 256; i++)
-        s->image_palette[i] = (0xffu << 24);
-    /* handle transparency */
-    if (s->transparent_color_index >= 0)
-        s->image_palette[s->transparent_color_index] = 0;
+
+    s->gce_prev_disposal = s->gce_disposal;
+
+    if (s->gce_disposal != GCE_DISPOSAL_NONE) {
+        s->gce_l = left;  s->gce_t = top;
+        s->gce_w = width; s->gce_h = height;
+
+        if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {
+            if (s->transparent_color_index >= 0)
+                s->stored_bg_color = s->trans_color;
+            else
+                s->stored_bg_color = s->bg_color;
+        } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
+            av_fast_malloc(&s->stored_img, &s->stored_img_size, frame->linesize[0] * frame->height);
+            if (!s->stored_img)
+                return AVERROR(ENOMEM);
+
+            gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,
+                frame->linesize[0] / sizeof(uint32_t), left, top, width, height);
+        }
+    }
+
+    /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
+    if (bytestream2_get_bytes_left(&s->gb) < 2)
+        return AVERROR_INVALIDDATA;
 
     /* now get the image data */
-    code_size = bytestream2_get_byte(&s->gb);
-    ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
-                       bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF);
+    code_size = bytestream2_get_byteu(&s->gb);
+    if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
+                                  bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {
+        av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
+        return ret;
+    }
 
     /* read all the image */
-    linesize = frame->linesize[0];
-    ptr1 = frame->data[0] + top * linesize + left;
+    linesize = frame->linesize[0] / sizeof(uint32_t);
+    ptr1 = (uint32_t *)frame->data[0] + top * linesize + left;
     ptr = ptr1;
     pass = 0;
     y1 = 0;
     for (y = 0; y < height; y++) {
-        ff_lzw_decode(s->lzw, ptr, width);
+        int count = ff_lzw_decode(s->lzw, s->idx_line, width);
+        if (count != width) {
+            if (count)
+                av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");
+            goto decode_tail;
+        }
+
+        pr = ptr + width;
+
+        for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
+            if (*idx != s->transparent_color_index)
+                *px = pal[*idx];
+        }
+
         if (is_interleaved) {
             switch(pass) {
             default:
@@ -149,53 +282,76 @@ static int gif_read_image(GifState *s, AVFrame *frame)
             ptr += linesize;
         }
     }
+
+ decode_tail:
     /* read the garbage data until end marker is found */
     ff_lzw_decode_tail(s->lzw);
 
-    bytestream2_skip(&s->gb, ff_lzw_size_read(s->lzw));
+    /* Graphic Control Extension's scope is single frame.
+     * Remove its influence. */
+    s->transparent_color_index = -1;
+    s->gce_disposal = GCE_DISPOSAL_NONE;
+
     return 0;
 }
 
 static int gif_read_extension(GifState *s)
 {
-    int ext_code, ext_len, i, gce_flags, gce_transparent_index;
+    int ext_code, ext_len, gce_flags, gce_transparent_index;
+
+    /* There must be at least 2 bytes:
+     * 1 for extension label and 1 for extension length. */
+    if (bytestream2_get_bytes_left(&s->gb) < 2)
+        return AVERROR_INVALIDDATA;
 
-    /* extension */
-    ext_code = bytestream2_get_byte(&s->gb);
-    ext_len  = bytestream2_get_byte(&s->gb);
+    ext_code = bytestream2_get_byteu(&s->gb);
+    ext_len  = bytestream2_get_byteu(&s->gb);
 
-    av_dlog(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
+    av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
 
     switch(ext_code) {
-    case 0xf9:
+    case GIF_GCE_EXT_LABEL:
         if (ext_len != 4)
             goto discard_ext;
-        s->transparent_color_index = -1;
-        gce_flags    = bytestream2_get_byte(&s->gb);
-        s->gce_delay = bytestream2_get_le16(&s->gb);
-        gce_transparent_index = bytestream2_get_byte(&s->gb);
+
+        /* We need at least 5 bytes more: 4 is for extension body
+         * and 1 for next block size. */
+        if (bytestream2_get_bytes_left(&s->gb) < 5)
+            return AVERROR_INVALIDDATA;
+
+        gce_flags    = bytestream2_get_byteu(&s->gb);
+        bytestream2_skipu(&s->gb, 2);    // delay during which the frame is shown
+        gce_transparent_index = bytestream2_get_byteu(&s->gb);
         if (gce_flags & 0x01)
             s->transparent_color_index = gce_transparent_index;
         else
             s->transparent_color_index = -1;
         s->gce_disposal = (gce_flags >> 2) & 0x7;
 
-        av_dlog(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
-               gce_flags, s->gce_delay,
+        av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
+               gce_flags,
                s->transparent_color_index, s->gce_disposal);
 
-        ext_len = bytestream2_get_byte(&s->gb);
+        if (s->gce_disposal > 3) {
+            s->gce_disposal = GCE_DISPOSAL_NONE;
+            av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
+        }
+
+        ext_len = bytestream2_get_byteu(&s->gb);
         break;
     }
 
     /* NOTE: many extension blocks can come after */
  discard_ext:
-    while (ext_len != 0) {
-        for (i = 0; i < ext_len; i++)
-            bytestream2_get_byte(&s->gb);
-        ext_len = bytestream2_get_byte(&s->gb);
+    while (ext_len) {
+        /* There must be at least ext_len bytes and 1 for next block size byte. */
+        if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
+            return AVERROR_INVALIDDATA;
 
-        av_dlog(s->avctx, "gif: ext_len1=%d\n", ext_len);
+        bytestream2_skipu(&s->gb, ext_len);
+        ext_len = bytestream2_get_byteu(&s->gb);
+
+        av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
     }
     return 0;
 }
@@ -204,44 +360,48 @@ static int gif_read_header1(GifState *s)
 {
     uint8_t sig[6];
     int v, n;
-    int has_global_palette;
+    int background_color_index;
 
     if (bytestream2_get_bytes_left(&s->gb) < 13)
         return AVERROR_INVALIDDATA;
 
     /* read gif signature */
-    bytestream2_get_buffer(&s->gb, sig, 6);
-    if (memcmp(sig, gif87a_sig, 6) != 0 &&
-        memcmp(sig, gif89a_sig, 6) != 0)
+    bytestream2_get_bufferu(&s->gb, sig, 6);
+    if (memcmp(sig, gif87a_sig, 6) &&
+        memcmp(sig, gif89a_sig, 6))
         return AVERROR_INVALIDDATA;
 
     /* read screen header */
     s->transparent_color_index = -1;
-    s->screen_width  = bytestream2_get_le16(&s->gb);
-    s->screen_height = bytestream2_get_le16(&s->gb);
-    if(   (unsigned)s->screen_width  > 32767
-       || (unsigned)s->screen_height > 32767){
-        av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
-        return AVERROR_INVALIDDATA;
-    }
+    s->screen_width  = bytestream2_get_le16u(&s->gb);
+    s->screen_height = bytestream2_get_le16u(&s->gb);
 
-    v = bytestream2_get_byte(&s->gb);
+    v = bytestream2_get_byteu(&s->gb);
     s->color_resolution = ((v & 0x70) >> 4) + 1;
-    has_global_palette = (v & 0x80);
+    s->has_global_palette = (v & 0x80);
     s->bits_per_pixel = (v & 0x07) + 1;
-    s->background_color_index = bytestream2_get_byte(&s->gb);
-    bytestream2_get_byte(&s->gb);                /* ignored */
+    background_color_index = bytestream2_get_byteu(&s->gb);
+    n = bytestream2_get_byteu(&s->gb);
+    if (n) {
+        s->avctx->sample_aspect_ratio.num = n + 15;
+        s->avctx->sample_aspect_ratio.den = 64;
+    }
 
-    av_dlog(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
+    av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
            s->screen_width, s->screen_height, s->bits_per_pixel,
-           has_global_palette);
+           s->has_global_palette);
 
-    if (has_global_palette) {
+    if (s->has_global_palette) {
+        s->background_color_index = background_color_index;
         n = 1 << s->bits_per_pixel;
         if (bytestream2_get_bytes_left(&s->gb) < n * 3)
             return AVERROR_INVALIDDATA;
-        bytestream2_get_buffer(&s->gb, s->global_palette, n * 3);
-    }
+
+        gif_read_palette(s, s->global_palette, n);
+        s->bg_color = s->global_palette[s->background_color_index];
+    } else
+        s->background_color_index = -1;
+
     return 0;
 }
 
@@ -251,23 +411,24 @@ static int gif_parse_next_image(GifState *s, AVFrame *frame)
         int code = bytestream2_get_byte(&s->gb);
         int ret;
 
-        av_dlog(s->avctx, "gif: code=%02x '%c'\n", code, code);
+        av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
 
         switch (code) {
-        case ',':
+        case GIF_IMAGE_SEPARATOR:
             return gif_read_image(s, frame);
-        case '!':
+        case GIF_EXTENSION_INTRODUCER:
             if ((ret = gif_read_extension(s)) < 0)
                 return ret;
             break;
-        case ';':
+        case GIF_TRAILER:
             /* end of image */
+            return AVERROR_EOF;
         default:
-            /* error or erroneous EOF */
+            /* erroneous block label */
             return AVERROR_INVALIDDATA;
         }
     }
-    return AVERROR_INVALIDDATA;
+    return AVERROR_EOF;
 }
 
 static av_cold int gif_decode_init(AVCodecContext *avctx)
@@ -276,38 +437,74 @@ static av_cold int gif_decode_init(AVCodecContext *avctx)
 
     s->avctx = avctx;
 
+    avctx->pix_fmt = AV_PIX_FMT_RGB32;
+    s->frame = av_frame_alloc();
+    if (!s->frame)
+        return AVERROR(ENOMEM);
     ff_lzw_decode_open(&s->lzw);
     return 0;
 }
 
-static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
-                            AVPacket *avpkt)
+static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
 {
-    const uint8_t *buf = avpkt->data;
-    int buf_size = avpkt->size;
     GifState *s = avctx->priv_data;
-    AVFrame *picture = data;
     int ret;
 
-    bytestream2_init(&s->gb, buf, buf_size);
-    if ((ret = gif_read_header1(s)) < 0)
-        return ret;
+    bytestream2_init(&s->gb, avpkt->data, avpkt->size);
 
-    avctx->pix_fmt = AV_PIX_FMT_PAL8;
+    s->frame->pts     = avpkt->pts;
+    s->frame->pkt_pts = avpkt->pts;
+    s->frame->pkt_dts = avpkt->dts;
+    av_frame_set_pkt_duration(s->frame, avpkt->duration);
 
-    if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
-        return ret;
+    if (avpkt->size >= 6) {
+        s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
+                      memcmp(avpkt->data, gif89a_sig, 6) == 0;
+    } else {
+        s->keyframe = 0;
+    }
 
-    if ((ret = ff_get_buffer(avctx, picture, 0)) < 0) {
-        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
-        return ret;
+    if (s->keyframe) {
+        s->keyframe_ok = 0;
+        s->gce_prev_disposal = GCE_DISPOSAL_NONE;
+        if ((ret = gif_read_header1(s)) < 0)
+            return ret;
+
+        if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
+            return ret;
+
+        av_frame_unref(s->frame);
+        if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)
+            return ret;
+
+        av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
+        if (!s->idx_line)
+            return AVERROR(ENOMEM);
+
+        s->frame->pict_type = AV_PICTURE_TYPE_I;
+        s->frame->key_frame = 1;
+        s->keyframe_ok = 1;
+    } else {
+        if (!s->keyframe_ok) {
+            av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        if ((ret = ff_reget_buffer(avctx, s->frame)) < 0)
+            return ret;
+
+        s->frame->pict_type = AV_PICTURE_TYPE_P;
+        s->frame->key_frame = 0;
     }
-    s->image_palette = (uint32_t *)picture->data[1];
-    ret = gif_parse_next_image(s, picture);
+
+    ret = gif_parse_next_image(s, s->frame);
     if (ret < 0)
         return ret;
 
+    if ((ret = av_frame_ref(data, s->frame)) < 0)
+        return ret;
     *got_frame = 1;
+
     return bytestream2_tell(&s->gb);
 }
 
@@ -316,9 +513,29 @@ static av_cold int gif_decode_close(AVCodecContext *avctx)
     GifState *s = avctx->priv_data;
 
     ff_lzw_decode_close(&s->lzw);
+    av_frame_free(&s->frame);
+    av_freep(&s->idx_line);
+    av_freep(&s->stored_img);
+
     return 0;
 }
 
+static const AVOption options[] = {
+    { "trans_color", "color value (ARGB) that is used instead of transparent color",
+      offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
+      {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
+      AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },
+    { NULL },
+};
+
+static const AVClass decoder_class = {
+    .class_name = "gif decoder",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+    .category   = AV_CLASS_CATEGORY_DECODER,
+};
+
 AVCodec ff_gif_decoder = {
     .name           = "gif",
     .long_name      = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
@@ -329,4 +546,5 @@ AVCodec ff_gif_decoder = {
     .close          = gif_decode_close,
     .decode         = gif_decode_frame,
     .capabilities   = CODEC_CAP_DR1,
+    .priv_class     = &decoder_class,
 };