@@ -405,6 +405,16 @@ The description of the accepted options follows.

 @table @option

+@item duration, d

+Set the minimum duration of the sourced audio. See the function

+@code{av_parse_time()} for the accepted format.

+Note that the resulting duration may be greater than the specified

+duration, as the generated audio is always cut at the end of a

+complete frame.

+

+If not specified, or the expressed duration is negative, the audio is

+supposed to be generated forever.

+

 @item nb_samples, n

 Set the number of samples per channel per each output frame,

 default to 1024.

@@ -28,6 +28,7 @@

 #include "libavutil/avstring.h"

 #include "libavutil/eval.h"

 #include "libavutil/opt.h"

+#include "libavutil/parseutils.h"

 #include "avfilter.h"

 #include "internal.h"

@@ -55,6 +56,8 @@ typedef struct {

     AVExpr *expr[8];

     char *expr_str[8];

     int nb_samples;             ///< number of samples per requested frame

+    char *duration_str;         ///< total duration of the generated audio

+    double duration;

     uint64_t n;

     double var_values[VAR_VARS_NB];

 } EvalContext;

@@ -66,6 +69,8 @@ static const AVOption eval_options[]= {

     { "n",           "set the number of samples per requested frame", OFFSET(nb_samples),      AV_OPT_TYPE_INT,    {.dbl = 1024},    0,        INT_MAX },

     { "sample_rate", "set the sample rate",                           OFFSET(sample_rate_str), AV_OPT_TYPE_STRING, {.str = "44100"}, CHAR_MIN, CHAR_MAX },

     { "s",           "set the sample rate",                           OFFSET(sample_rate_str), AV_OPT_TYPE_STRING, {.str = "44100"}, CHAR_MIN, CHAR_MAX },

+    { "duration",    "set audio duration", OFFSET(duration_str), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0 },

+    { "d",           "set audio duration", OFFSET(duration_str), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0 },

 {NULL},

 };

@@ -127,6 +132,16 @@ static int init(AVFilterContext *ctx, const char *args, void *opaque)

     if ((ret = ff_parse_sample_rate(&eval->sample_rate, eval->sample_rate_str, ctx)))

         goto end;

+

+    eval->duration = -1;

+    if (eval->duration_str) {

+        int64_t us = -1;

+        if ((ret = av_parse_time(&us, eval->duration_str, 1)) < 0) {

+            av_log(ctx, AV_LOG_ERROR, "Invalid duration: '%s'\n", eval->duration_str);

+            goto end;

+        }

+        eval->duration = (double)us / 1000000;

+    }

     eval->n = 0;

 end:

@@ -143,6 +158,7 @@ static void uninit(AVFilterContext *ctx)

         av_expr_free(eval->expr[i]);

         eval->expr[i] = NULL;

     }

+    av_freep(&eval->duration_str);

     av_freep(&eval->sample_rate_str);

 }

@@ -159,7 +175,8 @@ static int config_props(AVFilterLink *outlink)

     av_get_channel_layout_string(buf, sizeof(buf), 0, eval->chlayout);

     av_log(outlink->src, AV_LOG_INFO,

-           "sample_rate:%d chlayout:%s\n", eval->sample_rate, buf);

+           "sample_rate:%d chlayout:%s duration:%f\n",

+           eval->sample_rate, buf, eval->duration);

     return 0;

 }

@@ -183,6 +200,10 @@ static int request_frame(AVFilterLink *outlink)

     EvalContext *eval = outlink->src->priv;

     AVFilterBufferRef *samplesref;

     int i, j;

+    double t = eval->var_values[VAR_N] * (double)1/eval->sample_rate;

+

+    if (eval->duration >= 0 && t > eval->duration)

+        return AVERROR_EOF;

     samplesref = avfilter_get_audio_buffer(outlink, AV_PERM_WRITE, eval->nb_samples);

@@ -30,7 +30,7 @@

 #define LIBAVFILTER_VERSION_MAJOR  2

 #define LIBAVFILTER_VERSION_MINOR 50

-#define LIBAVFILTER_VERSION_MICRO  0

+#define LIBAVFILTER_VERSION_MICRO  1

 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

                                                LIBAVFILTER_VERSION_MINOR, \