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avformat/webpenc: Write correct size for single images when unseekable

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The earlier code writes the file and then tries to patch up
the size later. This is avoidable for the common case of
a single image because one can know the complete size
in advance and write it.

Fixes ticket #4609.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2023-11-03 16:54:24 +01:00
parent 8283db7fb0
commit b021bc4a47
1 changed files with 41 additions and 27 deletions
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68
libavformat/webpenc.c
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@ -21,6 +21,7 @@
#include "libavutil/intreadwrite.h"
#include "libavutil/opt.h"
#include "libavcodec/bytestream.h"
#include "avformat.h"
#include "internal.h"
#include "mux.h"
@ -76,11 +77,16 @@ static int is_animated_webp_packet(AVPacket *pkt)
return 0;
}
/**
* Returns 1 if it has written a RIFF header with a correct length field
*/
static int flush(AVFormatContext *s, int trailer, int64_t pts)
{
WebpContext *w = s->priv_data;
AVStream *st = s->streams[0];
int skip = 0;
uint8_t buf[12 /* RIFF+WEBP */ + 18 /* VP8X */ +
14 /* ANIM */ + 24 /* ANMF */], *bufp = buf;
int writing_webp_header = 0, skip = 0;
unsigned flags = 0;
int vp8x = 0;
@ -97,7 +103,10 @@ static int flush(AVFormatContext *s, int trailer, int64_t pts)
}
if (!w->wrote_webp_header) {
avio_write(s->pb, "RIFF\0\0\0\0WEBP", 12);
bytestream_put_le32(&bufp, MKTAG('R', 'I', 'F', 'F'));
bytestream_put_le32(&bufp, 0); /* Size to be patched later */
bytestream_put_le32(&bufp, MKTAG('W', 'E', 'B', 'P'));
writing_webp_header = 1;
w->wrote_webp_header = 1;
if (w->frame_count > 1) // first non-empty packet
w->frame_count = 1; // so we don't count previous empty packets.
@ -110,38 +119,41 @@ static int flush(AVFormatContext *s, int trailer, int64_t pts)
}
if (vp8x) {
avio_write(s->pb, "VP8X", 4);
avio_wl32(s->pb, 10);
avio_w8(s->pb, flags);
avio_wl24(s->pb, 0);
avio_wl24(s->pb, st->codecpar->width - 1);
avio_wl24(s->pb, st->codecpar->height - 1);
bytestream_put_le32(&bufp, MKTAG('V', 'P', '8', 'X'));
bytestream_put_le32(&bufp, 10);
bytestream_put_byte(&bufp, flags);
bytestream_put_le24(&bufp, 0);
bytestream_put_le24(&bufp, st->codecpar->width - 1);
bytestream_put_le24(&bufp, st->codecpar->height - 1);
}
if (!trailer) {
avio_write(s->pb, "ANIM", 4);
avio_wl32(s->pb, 6);
avio_wl32(s->pb, 0xFFFFFFFF);
avio_wl16(s->pb, w->loop);
bytestream_put_le32(&bufp, MKTAG('A', 'N', 'I', 'M'));
bytestream_put_le32(&bufp, 6);
bytestream_put_le32(&bufp, 0xFFFFFFFF);
bytestream_put_le16(&bufp, w->loop);
}
}
if (w->frame_count > trailer) {
avio_write(s->pb, "ANMF", 4);
avio_wl32(s->pb, 16 + w->last_pkt->size - skip);
avio_wl24(s->pb, 0);
avio_wl24(s->pb, 0);
avio_wl24(s->pb, st->codecpar->width - 1);
avio_wl24(s->pb, st->codecpar->height - 1);
bytestream_put_le32(&bufp, MKTAG('A', 'N', 'M', 'F'));
bytestream_put_le32(&bufp, 16 + w->last_pkt->size - skip);
bytestream_put_le24(&bufp, 0);
bytestream_put_le24(&bufp, 0);
bytestream_put_le24(&bufp, st->codecpar->width - 1);
bytestream_put_le24(&bufp, st->codecpar->height - 1);
if (w->last_pkt->pts != AV_NOPTS_VALUE && pts != AV_NOPTS_VALUE) {
avio_wl24(s->pb, pts - w->last_pkt->pts);
bytestream_put_le24(&bufp, pts - w->last_pkt->pts);
} else
avio_wl24(s->pb, w->last_pkt->duration);
avio_w8(s->pb, 0);
bytestream_put_le24(&bufp, w->last_pkt->duration);
bytestream_put_byte(&bufp, 0);
}
if (trailer && writing_webp_header)
AV_WL32(buf + 4, bufp - (buf + 8) + w->last_pkt->size - skip);
avio_write(s->pb, buf, bufp - buf);
avio_write(s->pb, w->last_pkt->data + skip, w->last_pkt->size - skip);
av_packet_unref(w->last_pkt);
return 0;
return trailer && writing_webp_header;
}
static int webp_write_packet(AVFormatContext *s, AVPacket *pkt)
@ -185,11 +197,13 @@ static int webp_write_trailer(AVFormatContext *s)
if ((ret = flush(s, 1, AV_NOPTS_VALUE)) < 0)
return ret;
filesize = avio_tell(s->pb);
if (avio_seek(s->pb, 4, SEEK_SET) == 4) {
avio_wl32(s->pb, filesize - 8);
// Note: without the following, avio only writes 8 bytes to the file.
avio_seek(s->pb, filesize, SEEK_SET);
if (!ret) {
filesize = avio_tell(s->pb);
if (avio_seek(s->pb, 4, SEEK_SET) == 4) {
avio_wl32(s->pb, filesize - 8);
// Note: without the following, avio only writes 8 bytes to the file.
avio_seek(s->pb, filesize, SEEK_SET);
}
}
}