Stefano Sabatini:
> This is useful to simulate random jitter.
> ---
> Changelog | 1 +
> doc/filters.texi | 10 +++++++++-
> libavfilter/setpts.c | 39 +++++++++++++++++++++++++++++++++------
> 3 files changed, 43 insertions(+), 7 deletions(-)
>
> diff --git a/Changelog b/Changelog
> index 424bfc11af..ed01c53264 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -15,6 +15,7 @@ version <next>:
> - tiltandshift filter
> - qrencode filter and qrencodesrc source
> - quirc filter
> +- lavfi/setpts: introduce rand() function in expression
>
> version 6.1:
> - libaribcaption decoder
> diff --git a/doc/filters.texi b/doc/filters.texi
> index d1f95b9781..1d9a5d6c7d 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -30946,7 +30946,7 @@ The expression which is evaluated for each frame to
> construct its timestamp.
> @end table
>
> The expression is evaluated through the eval API and can contain the
> following
> -constants:
> +constants and functions:
>
> @table @option
> @item FRAME_RATE, FR
> @@ -31010,6 +31010,8 @@ The timebase of the input timestamps.
> @item T_CHANGE
> Time of the first frame after command was applied or time of the first frame
> if no commands.
>
> +@item rand(min, max)
> +a random number included between min and max
> @end table
>
> @subsection Examples
> @@ -31021,6 +31023,12 @@ Start counting PTS from zero
> setpts=PTS-STARTPTS
> @end example
>
> +@item
> +Apply a random jitter effect of +/-100 TB units:
> +@example
> +setpts=PTS+100rand(-100\,100)
> +@end example
> +
> @item
> Apply fast motion effect:
> @example
> diff --git a/libavfilter/setpts.c b/libavfilter/setpts.c
> index 88a8d6af86..0f24a900b3 100644
> --- a/libavfilter/setpts.c
> +++ b/libavfilter/setpts.c
> @@ -32,6 +32,8 @@
> #include "libavutil/internal.h"
> #include "libavutil/mathematics.h"
> #include "libavutil/opt.h"
> +#include "libavutil/lfg.h"
> +#include "libavutil/random_seed.h"
> #include "libavutil/time.h"
> #include "audio.h"
> #include "avfilter.h"
> @@ -101,18 +103,39 @@ typedef struct SetPTSContext {
> AVExpr *expr;
> double var_values[VAR_VARS_NB];
> enum AVMediaType type;
> + AVLFG lfg;
> } SetPTSContext;
>
> #define V(name_) \
> setpts->var_values[VAR_##name_]
>
> +static double drand(void *ctx, double min, double max)
> +{
> + SetPTSContext *setpts = ((AVFilterContext *)ctx)->priv;
> +
> + return min + (max-min) / UINT_MAX * av_lfg_get(&setpts->lfg);
> +}
> +
> +typedef double (*eval_func2)(void *, double a, double b);
> +
> +static const eval_func2 fun2[] = {
> + drand,
> + NULL
> +};
> +
> +static const char *const fun2_names[] = {
> + "rand"
> +};
> +
> static av_cold int init(AVFilterContext *ctx)
> {
> SetPTSContext *setpts = ctx->priv;
> int ret;
>
> + av_lfg_init(&setpts->lfg, av_get_random_seed());
> +
> if ((ret = av_expr_parse(&setpts->expr, setpts->expr_str,
> - var_names, NULL, NULL, NULL, NULL, 0, ctx)) <
> 0) {
> + var_names, NULL, NULL, fun2_names, fun2, 0,
> ctx)) < 0) {
> av_log(ctx, AV_LOG_ERROR, "Error while parsing expression '%s'\n",
> setpts->expr_str);
> return ret;
> }
> @@ -126,6 +149,7 @@ static av_cold int init(AVFilterContext *ctx)
> V(STARTPTS) = NAN;
> V(STARTT) = NAN;
> V(T_CHANGE) = NAN;
> +
> return 0;
> }
>
> @@ -159,8 +183,10 @@ static inline char *double2int64str(char *buf, double v)
> return buf;
> }
>
> -static double eval_pts(SetPTSContext *setpts, AVFilterLink *inlink, AVFrame
> *frame, int64_t pts)
> +static double eval_pts(AVFilterContext *ctx, AVFilterLink *inlink, AVFrame
> *frame, int64_t pts)
> {
> + SetPTSContext *setpts = ctx->priv;
> +
> if (isnan(V(STARTPTS))) {
> V(STARTPTS) = TS2D(pts);
> V(STARTT ) = TS2T(pts, inlink->time_base);
> @@ -186,17 +212,18 @@ FF_ENABLE_DEPRECATION_WARNINGS
> }
> }
>
> - return av_expr_eval(setpts->expr, setpts->var_values, NULL);
> + return av_expr_eval(setpts->expr, setpts->var_values, ctx);
> }
> #define d2istr(v) double2int64str((char[BUF_SIZE]){0}, v)
>
> static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
> {
> - SetPTSContext *setpts = inlink->dst->priv;
> + AVFilterContext *ctx = inlink->dst;
> + SetPTSContext *setpts = ctx->priv;
> int64_t in_pts = frame->pts;
> double d;
>
> - d = eval_pts(setpts, inlink, frame, frame->pts);
> + d = eval_pts(ctx, inlink, frame, frame->pts);
> frame->pts = D2TS(d);
>
> av_log(inlink->dst, AV_LOG_TRACE,
> @@ -250,7 +277,7 @@ static int activate(AVFilterContext *ctx)
> return filter_frame(inlink, in);
>
> if (ff_inlink_acknowledge_status(inlink, &status, &pts)) {
> - double d = eval_pts(setpts, inlink, NULL, pts);
> + double d = eval_pts(ctx, inlink, NULL, pts);
>
> av_log(ctx, AV_LOG_TRACE, "N:EOF PTS:%s T:%f -> PTS:%s T:%f\n",
> d2istr(V(PTS)), V(T), d2istr(d), TS2T(d, inlink->time_base));
Why is this added here and not in lavu/eval so that it is available with
all expressions?
- Andreas
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