@section thumbnail
Select the most representative frame in a given sequence of consecutive frames.
-It accepts as argument the frames batch size to analyze (default @var{N}=100);
-in a set of @var{N} frames, the filter will pick one of them, and then handle
-the next batch of @var{N} frames until the end.
+The filter accepts parameters as a list of @var{key}=@var{value}
+pairs, separated by ":". If the key of the first options is omitted,
+the arguments are interpreted according to the syntax
+thumbnail[=@var{n}].
+
+@table @option
+@item n
+Set the frames batch size to analyze; in a set of @var{n} frames, the filter
+will pick one of them, and then handle the next batch of @var{n} frames until
+the end. Default is @code{100}.
+@end table
-Since the filter keeps track of the whole frames sequence, a bigger @var{N}
+Since the filter keeps track of the whole frames sequence, a bigger @var{n}
value will result in a higher memory usage, so a high value is not recommended.
-The following example extract one picture each 50 frames:
+@subsection Examples
+
+@itemize
+@item
+Extract one picture each 50 frames:
@example
thumbnail=50
@end example
+@item
Complete example of a thumbnail creation with @command{ffmpeg}:
@example
ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
@end example
+@end itemize
@section tile
* @see http://notbrainsurgery.livejournal.com/29773.html
*/
+#include "libavutil/opt.h"
#include "avfilter.h"
#include "internal.h"
};
typedef struct {
+ const AVClass *class;
int n; ///< current frame
int n_frames; ///< number of frames for analysis
struct thumb_frame *frames; ///< the n_frames frames
AVRational tb; ///< copy of the input timebase to ease access
} ThumbContext;
+#define OFFSET(x) offsetof(ThumbContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption thumbnail_options[] = {
+ { "n", "set the frames batch size", OFFSET(n_frames), AV_OPT_TYPE_INT, {.i64=100}, 2, INT_MAX, FLAGS },
+ { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(thumbnail);
+
static av_cold int init(AVFilterContext *ctx, const char *args)
{
ThumbContext *thumb = ctx->priv;
- if (!args) {
- thumb->n_frames = 100;
- } else {
- int n = sscanf(args, "%d", &thumb->n_frames);
- if (n != 1 || thumb->n_frames < 2) {
- thumb->n_frames = 0;
- av_log(ctx, AV_LOG_ERROR,
- "Invalid number of frames specified (minimum is 2).\n");
- return AVERROR(EINVAL);
- }
- }
thumb->frames = av_calloc(thumb->n_frames, sizeof(*thumb->frames));
if (!thumb->frames) {
av_log(ctx, AV_LOG_ERROR,
{ NULL }
};
+static const char *const shorthand[] = { "n", NULL };
+
AVFilter avfilter_vf_thumbnail = {
.name = "thumbnail",
.description = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."),
.query_formats = query_formats,
.inputs = thumbnail_inputs,
.outputs = thumbnail_outputs,
+ .priv_class = &thumbnail_class,
+ .shorthand = shorthand,
};