[FFmpeg-devel] [PATCH 1/2] avcodec: add gif parser
Paul B Mahol
onemda at gmail.com
Sun Dec 9 13:16:21 EET 2018
Signed-off-by: Paul B Mahol <onemda at gmail.com>
---
libavcodec/Makefile | 1 +
libavcodec/gif_parser.c | 188 ++++++++++++++++++++++++++++++++++++++++
libavcodec/parsers.c | 1 +
3 files changed, 190 insertions(+)
create mode 100644 libavcodec/gif_parser.c
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 5feadac729..d53b8ff330 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1026,6 +1026,7 @@ OBJS-$(CONFIG_DVDSUB_PARSER) += dvdsub_parser.o
OBJS-$(CONFIG_FLAC_PARSER) += flac_parser.o flacdata.o flac.o \
vorbis_data.o
OBJS-$(CONFIG_G729_PARSER) += g729_parser.o
+OBJS-$(CONFIG_GIF_PARSER) += gif_parser.o
OBJS-$(CONFIG_GSM_PARSER) += gsm_parser.o
OBJS-$(CONFIG_H261_PARSER) += h261_parser.o
OBJS-$(CONFIG_H263_PARSER) += h263_parser.o
diff --git a/libavcodec/gif_parser.c b/libavcodec/gif_parser.c
new file mode 100644
index 0000000000..9d31dc7e48
--- /dev/null
+++ b/libavcodec/gif_parser.c
@@ -0,0 +1,188 @@
+/*
+ * GIF parser
+ * Copyright (c) 2018 Paul B Mahol
+ *
+ * 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
+ * GIF parser
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/bswap.h"
+#include "libavutil/common.h"
+
+#include "gif.h"
+#include "parser.h"
+
+typedef enum GIFParseStates {
+ GIF_HEADER = 1,
+ GIF_EXTENSION,
+ GIF_EXTENSION_BLOCK,
+ GIF_IMAGE,
+ GIF_IMAGE_BLOCK,
+} gif_states;
+
+typedef struct GIFParseContext {
+ ParseContext pc;
+ unsigned found_sig;
+ int found_start;
+ int found_end;
+ int index;
+ int state;
+ int gct_flag;
+ int gct_size;
+ int block_size;
+ int etype;
+ int delay;
+} GIFParseContext;
+
+static int gif_find_frame_end(GIFParseContext *g, const uint8_t *buf,
+ int buf_size, void *logctx)
+{
+ int index, next = END_NOT_FOUND;
+
+ for (index = 0; index < buf_size; index++) {
+ if (!g->state) {
+ if (!memcmp(buf + index, gif87a_sig, 6) ||
+ !memcmp(buf + index, gif89a_sig, 6)) {
+ g->state = GIF_HEADER;
+ g->found_sig++;
+ } else if (buf[index] == GIF_EXTENSION_INTRODUCER) {
+ g->state = GIF_EXTENSION;
+ g->found_start = 1;
+ } else if (buf[index] == GIF_IMAGE_SEPARATOR) {
+ g->state = GIF_IMAGE;
+ } else if (buf[index] == GIF_TRAILER) {
+ g->state = 0;
+ g->found_end = 1;
+ g->found_sig = 0;
+ } else {
+ av_assert0(0);
+ }
+ }
+
+ if (g->state == GIF_HEADER) {
+ if (g->index == 10) {
+ g->gct_flag = !!(buf[index] & 0x80);
+ g->gct_size = 3 * (1 << ((buf[index] & 0x07) + 1));
+ }
+ if (g->index >= 12 + g->gct_flag * g->gct_size) {
+ g->state = 0;
+ g->index = 0;
+ g->gct_flag = 0;
+ g->gct_size = 0;
+ continue;
+ }
+ g->index++;
+ } else if (g->state == GIF_EXTENSION) {
+ if (g->found_start && g->found_end && g->found_sig) {
+ next = index;
+ g->found_start = 0;
+ g->found_end = 0;
+ g->index = 0;
+ g->gct_flag = 0;
+ g->gct_size = 0;
+ g->state = 0;
+ break;
+ }
+ if (g->index == 1) {
+ g->etype = buf[index];
+ }
+ if (g->index >= 2) {
+ g->block_size = buf[index];
+ g->index = 0;
+ g->state = GIF_EXTENSION_BLOCK;
+ continue;
+ }
+ g->index++;
+ } else if (g->state == GIF_IMAGE_BLOCK) {
+ if (!g->index)
+ g->block_size = buf[index];
+ if (g->index >= g->block_size) {
+ g->index = 0;
+ if (!g->block_size) {
+ g->state = 0;
+ g->found_end = 1;
+ }
+ continue;
+ }
+ g->index++;
+ } else if (g->state == GIF_EXTENSION_BLOCK) {
+ if (g->etype == GIF_GCE_EXT_LABEL) {
+ if (g->index == 0)
+ g->delay = 0;
+ if (g->index >= 1 && g->index <= 2) {
+ g->delay |= buf[index] << (8 * (g->index - 1));
+ }
+ }
+ if (g->index >= g->block_size) {
+ g->block_size = buf[index];
+ g->index = 0;
+ if (!g->block_size)
+ g->state = 0;
+ continue;
+ }
+ g->index++;
+ } else if (g->state == GIF_IMAGE) {
+ if (g->index == 8) {
+ g->gct_flag = !!(buf[index] & 0x80);
+ g->gct_size = 3 * (1 << ((buf[index] & 0x07) + 1));
+ }
+ if (g->index >= 10 + g->gct_flag * g->gct_size) {
+ g->state = GIF_IMAGE_BLOCK;
+ g->index = 0;
+ g->gct_flag = 0;
+ g->gct_size = 0;
+ continue;
+ }
+ g->index++;
+ }
+ }
+
+ return next;
+}
+
+static int gif_parse(AVCodecParserContext *s, AVCodecContext *avctx,
+ const uint8_t **poutbuf, int *poutbuf_size,
+ const uint8_t *buf, int buf_size)
+{
+ GIFParseContext *g = s->priv_data;
+ int next;
+
+ next = gif_find_frame_end(g, buf, buf_size, avctx);
+ if (ff_combine_frame(&g->pc, next, &buf, &buf_size) < 0) {
+ *poutbuf = NULL;
+ *poutbuf_size = 0;
+ return buf_size;
+ }
+
+ s->duration = g->delay;
+
+ *poutbuf = buf;
+ *poutbuf_size = buf_size;
+ return next;
+}
+
+AVCodecParser ff_gif_parser = {
+ .codec_ids = { AV_CODEC_ID_GIF },
+ .priv_data_size = sizeof(GIFParseContext),
+ .parser_parse = gif_parse,
+ .parser_close = ff_parse_close,
+};
diff --git a/libavcodec/parsers.c b/libavcodec/parsers.c
index f01cad4c84..eca95787ae 100644
--- a/libavcodec/parsers.c
+++ b/libavcodec/parsers.c
@@ -41,6 +41,7 @@ extern AVCodecParser ff_dvdsub_parser;
extern AVCodecParser ff_dvd_nav_parser;
extern AVCodecParser ff_flac_parser;
extern AVCodecParser ff_g729_parser;
+extern AVCodecParser ff_gif_parser;
extern AVCodecParser ff_gsm_parser;
extern AVCodecParser ff_h261_parser;
extern AVCodecParser ff_h263_parser;
--
2.17.1
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