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avformat/gifdec: switch to using gif parser

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Update fate test, more correct as last packet is not truncated.
This commit is contained in:
Paul B Mahol 2023-05-20 14:13:27 +02:00
parent e7cadd0ee5
commit c6b6356635
3 changed files with 74 additions and 190 deletions
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11
libavcodec/gifdec.c
View File

@ -472,10 +472,6 @@ static int gif_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
bytestream2_init(&s->gb, avpkt->data, avpkt->size);
s->frame->pts = avpkt->pts;
s->frame->pkt_dts = avpkt->dts;
s->frame->duration = avpkt->duration;
if (avpkt->size >= 6) {
s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
memcmp(avpkt->data, gif89a_sig, 6) == 0;
@ -522,6 +518,13 @@ static int gif_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
if ((ret = av_frame_ref(rframe, s->frame)) < 0)
return ret;
if (s->keyframe) {
rframe->pict_type = AV_PICTURE_TYPE_I;
rframe->flags |= AV_FRAME_FLAG_KEY;
} else {
rframe->pict_type = AV_PICTURE_TYPE_P;
rframe->flags &= ~AV_FRAME_FLAG_KEY;
}
*got_frame = 1;
return bytestream2_tell(&s->gb);

251
libavformat/gifdec.c
View File

@ -28,9 +28,12 @@
#include "libavutil/bprint.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/opt.h"
#include "avio_internal.h"
#include "internal.h"
#include "libavcodec/gif.h"
#define GIF_PACKET_SIZE 1024
typedef struct GIFDemuxContext {
const AVClass *class;
/**
@ -53,9 +56,6 @@ typedef struct GIFDemuxContext {
int total_iter;
int iter_count;
int ignore_loop;
int nb_frames;
int last_duration;
} GIFDemuxContext;
/**
@ -84,8 +84,8 @@ static int gif_probe(const AVProbeData *p)
static int resync(AVIOContext *pb)
{
int i;
for (i = 0; i < 6; i++) {
ffio_ensure_seekback(pb, 13);
for (int i = 0; i < 6; i++) {
int b = avio_r8(pb);
if (b != gif87a_sig[i] && b != gif89a_sig[i])
i = -(b != 'G');
@ -113,11 +113,12 @@ static int gif_read_header(AVFormatContext *s)
AVIOContext *pb = s->pb;
AVStream *st;
int type, width, height, ret, n, flags;
int64_t nb_frames = 0, duration = 0;
int64_t nb_frames = 0, duration = 0, pos;
if ((ret = resync(pb)) < 0)
return ret;
pos = avio_tell(pb);
gdc->delay = gdc->default_delay;
width = avio_rl16(pb);
height = avio_rl16(pb);
@ -132,6 +133,9 @@ static int gif_read_header(AVFormatContext *s)
if (!st)
return AVERROR(ENOMEM);
if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
goto skip;
if (flags & 0x80)
avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1)));
@ -158,15 +162,37 @@ static int gif_read_header(AVFormatContext *s)
avio_skip(pb, 1);
delay = avio_rl16(pb);
if (delay < gdc->min_delay)
delay = gdc->default_delay;
delay = FFMIN(delay, gdc->max_delay);
delay = delay ? delay : gdc->default_delay;
duration += delay;
avio_skip(pb, 1);
} else {
avio_skip(pb, block_size);
}
gif_skip_subblocks(pb);
} else if (subtype == GIF_APP_EXT_LABEL) {
uint8_t data[256];
int sb_size;
sb_size = avio_r8(pb);
ret = avio_read(pb, data, sb_size);
if (ret < 0 || !sb_size)
break;
if (sb_size == strlen(NETSCAPE_EXT_STR)) {
sb_size = avio_r8(pb);
ret = avio_read(pb, data, sb_size);
if (ret < 0 || !sb_size)
break;
if (sb_size == 3 && data[0] == 1) {
gdc->total_iter = AV_RL16(data+1);
av_log(s, AV_LOG_DEBUG, "Loop count is %d\n", gdc->total_iter);
if (gdc->total_iter == 0)
gdc->total_iter = -1;
}
}
gif_skip_subblocks(pb);
} else {
gif_skip_subblocks(pb);
}
@ -183,80 +209,30 @@ static int gif_read_header(AVFormatContext *s)
}
}
skip:
/* jump to start because gif decoder needs header data too */
if (avio_seek(pb, pos - 6, SEEK_SET) != pos - 6)
return AVERROR(EIO);
/* GIF format operates with time in "hundredths of second",
* therefore timebase is 1/100 */
avpriv_set_pts_info(st, 64, 1, 100);
ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL_RAW;
st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
st->codecpar->codec_id = AV_CODEC_ID_GIF;
st->codecpar->width = width;
st->codecpar->height = height;
if (nb_frames > 1) {
av_reduce(&st->avg_frame_rate.num, &st->avg_frame_rate.den,
100, duration / nb_frames, INT_MAX);
} else if (duration) {
st->avg_frame_rate = (AVRational) { 100, duration };
}
st->start_time = 0;
st->duration = duration;
st->nb_frames = nb_frames;
if (n) {
st->codecpar->sample_aspect_ratio.num = n + 15;
st->codecpar->sample_aspect_ratio.den = 64;
}
/* jump to start because gif decoder needs header data too */
if (avio_seek(pb, 0, SEEK_SET) != 0)
return AVERROR(EIO);
return 0;
}
static int gif_read_ext(AVFormatContext *s)
{
GIFDemuxContext *gdc = s->priv_data;
AVIOContext *pb = s->pb;
int sb_size, ext_label = avio_r8(pb);
int ret;
if (ext_label == GIF_GCE_EXT_LABEL) {
if ((sb_size = avio_r8(pb)) < 4) {
av_log(s, AV_LOG_FATAL, "Graphic Control Extension block's size less than 4.\n");
return AVERROR_INVALIDDATA;
}
/* skip packed fields */
if ((ret = avio_skip(pb, 1)) < 0)
return ret;
gdc->delay = avio_rl16(pb);
if (gdc->delay < gdc->min_delay)
gdc->delay = gdc->default_delay;
gdc->delay = FFMIN(gdc->delay, gdc->max_delay);
/* skip the rest of the Graphic Control Extension block */
if ((ret = avio_skip(pb, sb_size - 3)) < 0 )
return ret;
} else if (ext_label == GIF_APP_EXT_LABEL) {
uint8_t data[256];
sb_size = avio_r8(pb);
ret = avio_read(pb, data, sb_size);
if (ret < 0 || !sb_size)
return ret;
if (sb_size == strlen(NETSCAPE_EXT_STR)) {
sb_size = avio_r8(pb);
ret = avio_read(pb, data, sb_size);
if (ret < 0 || !sb_size)
return ret;
if (sb_size == 3 && data[0] == 1) {
gdc->total_iter = AV_RL16(data+1);
av_log(s, AV_LOG_DEBUG, "Loop count is %d\n", gdc->total_iter);
if (gdc->total_iter == 0)
gdc->total_iter = -1;
}
}
}
if ((ret = gif_skip_subblocks(pb)) < 0)
return ret;
if (n)
st->codecpar->sample_aspect_ratio = av_make_q(n + 15, 64);
return 0;
}
@ -265,121 +241,25 @@ static int gif_read_packet(AVFormatContext *s, AVPacket *pkt)
{
GIFDemuxContext *gdc = s->priv_data;
AVIOContext *pb = s->pb;
int packed_fields, block_label, ct_size,
keyframe, frame_parsed = 0, ret;
int64_t frame_start = avio_tell(pb), frame_end;
unsigned char buf[6];
int ret;
if ((ret = avio_read(pb, buf, 6)) == 6) {
keyframe = memcmp(buf, gif87a_sig, 6) == 0 ||
memcmp(buf, gif89a_sig, 6) == 0;
} else if (ret < 0) {
if ((pb->seekable & AVIO_SEEKABLE_NORMAL) &&
!gdc->ignore_loop && avio_feof(pb) &&
(gdc->total_iter < 0 || (++gdc->iter_count < gdc->total_iter))) {
avio_seek(pb, 0, SEEK_SET);
}
if ((ret = av_new_packet(pkt, GIF_PACKET_SIZE)) < 0)
return ret;
} else {
keyframe = 0;
}
if (keyframe) {
parse_keyframe:
/* skip 2 bytes of width and 2 of height */
if ((ret = avio_skip(pb, 4)) < 0)
return ret;
packed_fields = avio_r8(pb);
/* skip 1 byte of Background Color Index and 1 byte of Pixel Aspect Ratio */
if ((ret = avio_skip(pb, 2)) < 0)
return ret;
/* global color table presence */
if (packed_fields & 0x80) {
ct_size = 3 * (1 << ((packed_fields & 0x07) + 1));
if ((ret = avio_skip(pb, ct_size)) < 0)
return ret;
}
} else {
avio_seek(pb, -ret, SEEK_CUR);
ret = AVERROR_EOF;
}
while (GIF_TRAILER != (block_label = avio_r8(pb)) && !avio_feof(pb)) {
if (block_label == GIF_EXTENSION_INTRODUCER) {
if ((ret = gif_read_ext (s)) < 0 )
goto resync;
} else if (block_label == GIF_IMAGE_SEPARATOR) {
/* skip to last byte of Image Descriptor header */
if ((ret = avio_skip(pb, 8)) < 0)
return ret;
packed_fields = avio_r8(pb);
/* local color table presence */
if (packed_fields & 0x80) {
ct_size = 3 * (1 << ((packed_fields & 0x07) + 1));
if ((ret = avio_skip(pb, ct_size)) < 0)
return ret;
}
/* read LZW Minimum Code Size */
if (avio_r8(pb) < 1) {
av_log(s, AV_LOG_ERROR, "lzw minimum code size must be >= 1\n");
goto resync;
}
if ((ret = gif_skip_subblocks(pb)) < 0)
goto resync;
frame_end = avio_tell(pb);
if (avio_seek(pb, frame_start, SEEK_SET) != frame_start)
return AVERROR(EIO);
ret = av_get_packet(pb, pkt, frame_end - frame_start);
if (ret < 0)
return ret;
if (keyframe)
pkt->flags |= AV_PKT_FLAG_KEY;
pkt->stream_index = 0;
pkt->duration = gdc->delay;
gdc->nb_frames ++;
gdc->last_duration = pkt->duration;
/* Graphic Control Extension's scope is single frame.
* Remove its influence. */
gdc->delay = gdc->default_delay;
frame_parsed = 1;
break;
} else {
av_log(s, AV_LOG_ERROR, "invalid block label\n");
resync:
if (!keyframe)
avio_seek(pb, frame_start, SEEK_SET);
if ((ret = resync(pb)) < 0)
return ret;
frame_start = avio_tell(pb) - 6;
keyframe = 1;
goto parse_keyframe;
}
}
if ((ret >= 0 && !frame_parsed) || ret == AVERROR_EOF) {
if (gdc->nb_frames == 1) {
s->streams[0]->r_frame_rate = (AVRational) {100, gdc->last_duration};
}
/* This might happen when there is no image block
* between extension blocks and GIF_TRAILER or EOF */
if (!gdc->ignore_loop && (block_label == GIF_TRAILER || avio_feof(pb))
&& (gdc->total_iter < 0 || ++gdc->iter_count < gdc->total_iter))
return avio_seek(pb, 0, SEEK_SET);
return AVERROR_EOF;
} else
pkt->pos = avio_tell(pb);
pkt->stream_index = 0;
ret = avio_read_partial(pb, pkt->data, GIF_PACKET_SIZE);
if (ret < 0) {
av_packet_unref(pkt);
return ret;
}
av_shrink_packet(pkt, ret);
return ret;
}
static const AVOption options[] = {
@ -405,6 +285,7 @@ const AVInputFormat ff_gif_demuxer = {
.read_probe = gif_probe,
.read_header = gif_read_header,
.read_packet = gif_read_packet,
.flags = AVFMT_GENERIC_INDEX,
.flags = AVFMT_GENERIC_INDEX | AVFMT_NOTIMESTAMPS,
.extensions = "gif",
.priv_class = &demuxer_class,
};

2
tests/ref/fate/gif-demux
View File

@ -38,4 +38,4 @@
0, 74, 74, 2, 4633, 0x8f64fda7, F=0x0
0, 76, 76, 2, 4700, 0x45f40805, F=0x0
0, 78, 78, 2, 5117, 0x4eb4c5fb, F=0x0
0, 80, 80, 2, 5370, 0xb10c6910, F=0x0
0, 80, 80, 2, 5371, 0x1a66694b, F=0x0