This patch should allow to play an image sequence in backwards
direction, without needing to apply a reverse filter.
ffmpeg -i sequence%05d.png forward.mkv
ffmpeg -reverse 1 -i sequence%05d.png backward.mkv
Signed-off-by: Sergio Acereda <sergio.acer...@gmail.com>
---
libavformat/img2.h | 1 +
libavformat/img2dec.c | 34 ++++++++++++++++++++++++----------
2 files changed, 25 insertions(+), 10 deletions(-)
diff --git a/libavformat/img2.h b/libavformat/img2.h
index 5fd8ff77fc..3d01c00537 100644
--- a/libavformat/img2.h
+++ b/libavformat/img2.h
@@ -59,6 +59,7 @@ typedef struct VideoDemuxData {
#endif
int start_number;
int start_number_range;
+ int reverse;
int frame_size;
int ts_from_file;
int export_path_metadata; /**< enabled when set to 1. */
diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
index 8608252d83..7b85e01aca 100644
--- a/libavformat/img2dec.c
+++ b/libavformat/img2dec.c
@@ -105,10 +105,12 @@ static int is_glob(const char *path)
* @param plast_index pointer to index updated with the last number
in the range
* @param path path which has to be matched by the image files
in the range
* @param start_index minimum accepted value for the first index in
the range
+ * @param start_index_range range for looking at the first sequence number
+ * @param reverse play backwards
* @return -1 if no image file could be found
*/
static int find_image_range(AVIOContext *pb, int *pfirst_index, int
*plast_index,
- const char *path, int start_index, int
start_index_range)
+ const char *path, int start_index, int
start_index_range, int reverse)
{
char buf[1024];
int range, last_index, range1, first_index;
@@ -152,8 +154,13 @@ static int find_image_range(AVIOContext *pb, int
*pfirst_index, int *plast_index
break;
last_index += range;
}
- *pfirst_index = first_index;
- *plast_index = last_index;
+ if (reverse) {
+ *pfirst_index = last_index;
+ *plast_index = first_index;
+ } else {
+ *pfirst_index = first_index;
+ *plast_index = last_index;
+ }
return 0;
fail:
@@ -274,7 +281,7 @@ int ff_img_read_header(AVFormatContext *s1)
}
if ((s->pattern_type == PT_GLOB_SEQUENCE && !s->use_glob) ||
s->pattern_type == PT_SEQUENCE) {
if (find_image_range(s1->pb, &first_index, &last_index,
s->path,
- s->start_number,
s->start_number_range) < 0) {
+ s->start_number,
s->start_number_range, s->reverse) < 0) {
av_log(s1, AV_LOG_ERROR,
"Could find no file with path '%s' and index in
the range %d-%d\n",
s->path, s->start_number, s->start_number +
s->start_number_range - 1);
@@ -307,7 +314,7 @@ int ff_img_read_header(AVFormatContext *s1)
/* compute duration */
if (!s->ts_from_file) {
st->start_time = 0;
- st->duration = last_index - first_index + 1;
+ st->duration = abs(last_index - first_index) + 1;
}
}
@@ -413,11 +420,12 @@ int ff_img_read_packet(AVFormatContext *s1,
AVPacket *pkt)
AVCodecParameters *par = s1->streams[0]->codecpar;
if (!s->is_pipe) {
+ int bad = s->reverse? (s->img_number < s->img_last) :
(s->img_number > s->img_last);
/* loop over input */
- if (s->loop && s->img_number > s->img_last) {
+ if (s->loop && bad) {
s->img_number = s->img_first;
}
- if (s->img_number > s->img_last)
+ if (bad)
return AVERROR_EOF;
if (s->pattern_type == PT_NONE) {
av_strlcpy(filename_bytes, s->path, sizeof(filename_bytes));
@@ -554,8 +562,9 @@ int ff_img_read_packet(AVFormatContext *s1, AVPacket
*pkt)
}
goto fail;
} else {
+ int step = s->reverse? -1 : 1;
s->img_count++;
- s->img_number++;
+ s->img_number += step;
s->pts++;
return 0;
}
@@ -594,9 +603,13 @@ static int img_read_seek(AVFormatContext *s, int
stream_index, int64_t timestamp
return 0;
}
- if (timestamp < 0 || !s1->loop && timestamp > s1->img_last -
s1->img_first)
+ int bad = s1->reverse? (timestamp < s1->img_last) : (timestamp >
s1->img_last);
+ if (timestamp < 0 || !s1->loop && bad)
return -1;
- s1->img_number = timestamp%(s1->img_last - s1->img_first + 1) +
s1->img_first;
+ int dir = s1->reverse? -1 : 1;
+ int span = 1 + dir * (s1->img_last - s1->img_first);
+ int rel = timestamp % span;
+ s1->img_number = s1->img_first + dir * rel;
s1->pts = timestamp;
return 0;
}
@@ -619,6 +632,7 @@ const AVOption ff_img_options[] = {
{ "none", "disable pattern matching", 0,
AV_OPT_TYPE_CONST, {.i64=PT_NONE }, INT_MIN, INT_MAX, DEC,
"pattern_type" },
{ "start_number", "set first number in the sequence",
OFFSET(start_number), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN,
INT_MAX, DEC },
{ "start_number_range", "set range for looking at the first
sequence number", OFFSET(start_number_range), AV_OPT_TYPE_INT, {.i64 =
5}, 1, INT_MAX, DEC },
+ { "reverse", "reverse direction",
OFFSET(reverse), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 1, DEC },
{ "ts_from_file", "set frame timestamp from file's one",
OFFSET(ts_from_file), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 2,
DEC, "ts_type" },
{ "none", "none", 0, AV_OPT_TYPE_CONST, {.i64
= 0 }, 0, 2, DEC, "ts_type" },
{ "sec", "second precision", 0, AV_OPT_TYPE_CONST, {.i64
= 1 }, 0, 2, DEC, "ts_type" },
--
2.34.0
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