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WebP muxer: support a packet containing animated WebP.

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This is the 1st patch in preparation for using WebPAnimEncoder API for encoding
and muxing WebP images.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Urvang Joshi 2015-05-19 17:39:54 -07:00 committed by Michael Niedermayer
parent 1c6ede3360
commit 6b56fcbd10
1 changed files with 62 additions and 13 deletions
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75
libavformat/webpenc.c
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@ -29,6 +29,8 @@ typedef struct WebpContext{
int frame_count;
AVPacket last_pkt;
int loop;
int wrote_webp_header;
int using_webp_anim_encoder;
} WebpContext;
static int webp_write_header(AVFormatContext *s)
@ -46,8 +48,29 @@ static int webp_write_header(AVFormatContext *s)
}
avpriv_set_pts_info(st, 24, 1, 1000);
avio_write(s->pb, "RIFF\0\0\0\0WEBP", 12);
return 0;
}
static int is_animated_webp_packet(AVPacket *pkt)
{
if (pkt->size) {
int skip = 0;
unsigned flags = 0;
if (pkt->size < 4)
return 0;
if (AV_RL32(pkt->data) == AV_RL32("RIFF"))
skip = 12;
if (pkt->size < skip + 4)
return 0;
if (AV_RL32(pkt->data + skip) == AV_RL32("VP8X")) {
flags |= pkt->data[skip + 4 + 4];
}
if (flags & 2) // ANIMATION_FLAG is on
return 1;
}
return 0;
}
@ -61,15 +84,25 @@ static int flush(AVFormatContext *s, int trailer, int64_t pts)
unsigned flags = 0;
int vp8x = 0;
if (w->last_pkt.size < 4)
return 0;
if (AV_RL32(w->last_pkt.data) == AV_RL32("RIFF"))
skip = 12;
if (w->last_pkt.size < skip + 4)
return 0; // Safe to do this as a valid WebP bitstream is >=30 bytes.
if (AV_RL32(w->last_pkt.data + skip) == AV_RL32("VP8X")) {
flags |= w->last_pkt.data[skip + 4 + 4];
vp8x = 1;
skip += AV_RL32(w->last_pkt.data + skip + 4) + 8;
}
w->frame_count ++;
if (!w->wrote_webp_header) {
avio_write(s->pb, "RIFF\0\0\0\0WEBP", 12);
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.
}
if (w->frame_count == 1) {
if (!trailer) {
@ -116,12 +149,18 @@ static int flush(AVFormatContext *s, int trailer, int64_t pts)
static int webp_write_packet(AVFormatContext *s, AVPacket *pkt)
{
WebpContext *w = s->priv_data;
int ret;
w->using_webp_anim_encoder |= is_animated_webp_packet(pkt);
if ((ret = flush(s, 0, pkt->pts)) < 0)
return ret;
av_copy_packet(&w->last_pkt, pkt);
if (w->using_webp_anim_encoder) {
avio_write(s->pb, pkt->data, pkt->size);
w->wrote_webp_header = 1; // for good measure
} else {
int ret;
if ((ret = flush(s, 0, pkt->pts)) < 0)
return ret;
av_copy_packet(&w->last_pkt, pkt);
}
++w->frame_count;
return 0;
}
@ -129,14 +168,24 @@ static int webp_write_packet(AVFormatContext *s, AVPacket *pkt)
static int webp_write_trailer(AVFormatContext *s)
{
unsigned filesize;
int ret;
WebpContext *w = s->priv_data;
if ((ret = flush(s, 1, AV_NOPTS_VALUE)) < 0)
return ret;
if (w->using_webp_anim_encoder) {
if ((w->frame_count > 1) && w->loop) { // Write loop count.
avio_seek(s->pb, 42, SEEK_SET);
avio_wl16(s->pb, w->loop);
}
} else {
int ret;
if ((ret = flush(s, 1, AV_NOPTS_VALUE)) < 0)
return ret;
filesize = avio_tell(s->pb);
avio_seek(s->pb, 4, SEEK_SET);
avio_wl32(s->pb, filesize - 8);
filesize = avio_tell(s->pb);
avio_seek(s->pb, 4, SEEK_SET);
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);
}
return 0;
}