abuffer=44100:1:3:1
@end example
+@section aevalsrc
+
+Generate an audio signal specified by an expression.
+
+This source accepts in input one or more expressions (one for each
+channel), which are evaluated and used to generate a corresponding
+audio signal.
+
+It accepts the syntax: @var{exprs}[::@var{options}].
+@var{exprs} is a list of expressions separated by ":", one for each
+separate channel. The output channel layout depends on the number of
+provided expressions, up to 8 channels are supported.
+
+@var{options} is an optional sequence of @var{key}=@var{value} pairs,
+separated by ":".
+
+The description of the accepted options follows.
+
+@table @option
+
+@item nb_samples, n
+Set the number of samples per channel per each output frame,
+default to 1024.
+
+@item sample_rate, s
+Specify the sample rate, default to 44100.
+@end table
+
+Each expression in @var{exprs} can contain the following constants:
+
+@table @option
+@item n
+number of the evaluated sample, starting from 0
+
+@item t
+time of the evaluated sample expressed in seconds, starting from 0
+
+@item s
+sample rate
+
+@end table
+
+@subsection Examples
+
+@itemize
+
+@item
+Generate silence:
+@example
+aevalsrc=0
+@end example
+
+@item
+
+Generate a sin signal with frequence of 440 Hz, set sample rate to
+8000 Hz:
+@example
+aevalsrc="sin(440*2*PI*t)::s=8000"
+@end example
+
+@item
+Generate white noise:
+@example
+aevalsrc="-2+random(0)"
+@end example
+
+@item
+Generate an amplitude modulated signal:
+@example
+aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
+@end example
+
+@item
+Generate 2.5 Hz binaural beats on a 360 Hz carrier:
+@example
+aevalsrc=0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)
+@end example
+
+@end itemize
+
@section amovie
Read an audio stream from a movie container.
--- /dev/null
+/*
+ * Copyright (c) 2011 Stefano Sabatini
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * eval audio source
+ */
+
+#include "libavutil/audioconvert.h"
+#include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
+#include "libavutil/eval.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "internal.h"
+
+static const char *var_names[] = {
+ "n", ///< number of frame
+ "t", ///< timestamp expressed in seconds
+ "s", ///< sample rate
+ NULL
+};
+
+enum var_name {
+ VAR_N,
+ VAR_T,
+ VAR_S,
+ VAR_VARS_NB
+};
+
+typedef struct {
+ const AVClass *class;
+ char *sample_rate_str;
+ int sample_rate;
+ int64_t chlayout;
+ int nb_channels;
+ int64_t pts;
+ AVExpr *expr[8];
+ char *expr_str[8];
+ int nb_samples; ///< number of samples per requested frame
+ uint64_t n;
+ double var_values[VAR_VARS_NB];
+} EvalContext;
+
+#define OFFSET(x) offsetof(EvalContext, x)
+
+static const AVOption eval_options[]= {
+ { "nb_samples", "set the number of samples per requested frame", OFFSET(nb_samples), FF_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX },
+ { "n", "set the number of samples per requested frame", OFFSET(nb_samples), FF_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX },
+ { "sample_rate", "set the sample rate", OFFSET(sample_rate_str), FF_OPT_TYPE_STRING, {.str = "44100"}, 0, INT_MAX },
+ { "s", "set the sample rate", OFFSET(sample_rate_str), FF_OPT_TYPE_STRING, {.str = "44100"}, 0, INT_MAX },
+{NULL},
+};
+
+static const char *eval_get_name(void *ctx)
+{
+ return "aevalsrc";
+}
+
+static const AVClass eval_class = {
+ "AEvalSrcContext",
+ eval_get_name,
+ eval_options
+};
+
+static int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+ EvalContext *eval = ctx->priv;
+ char *args1 = av_strdup(args);
+ char *expr, *buf, *bufptr;
+ int ret, i;
+
+ eval->class = &eval_class;
+ av_opt_set_defaults(eval);
+
+ /* parse expressions */
+ buf = args1;
+ i = 0;
+ while (expr = strtok_r(buf, ":", &bufptr)) {
+ if (i >= 8) {
+ av_log(ctx, AV_LOG_ERROR,
+ "More than 8 expressions provided, unsupported.\n");
+ ret = AVERROR(EINVAL);
+ return ret;
+ }
+ ret = av_expr_parse(&eval->expr[i], expr, var_names,
+ NULL, NULL, NULL, NULL, 0, ctx);
+ if (ret < 0)
+ goto end;
+ i++;
+ if (bufptr && *bufptr == ':') { /* found last expression */
+ bufptr++;
+ break;
+ }
+ buf = NULL;
+ }
+
+ /* guess channel layout from nb expressions/channels */
+ eval->nb_channels = i;
+ eval->chlayout = av_get_default_channel_layout(eval->nb_channels);
+ if (!eval->chlayout) {
+ av_log(ctx, AV_LOG_ERROR, "Invalid number of channels '%d' provided\n",
+ eval->nb_channels);
+ ret = AVERROR(EINVAL);
+ goto end;
+ }
+
+ if (bufptr && (ret = av_set_options_string(eval, bufptr, "=", ":")) < 0)
+ goto end;
+
+ if ((ret = ff_parse_sample_rate(&eval->sample_rate, eval->sample_rate_str, ctx)))
+ goto end;
+ eval->n = 0;
+
+end:
+ av_free(args1);
+ return ret;
+}
+
+static void uninit(AVFilterContext *ctx)
+{
+ EvalContext *eval = ctx->priv;
+ int i;
+
+ for (i = 0; i < 8; i++) {
+ av_expr_free(eval->expr[i]);
+ eval->expr[i] = NULL;
+ }
+ av_freep(&eval->sample_rate_str);
+}
+
+static int config_props(AVFilterLink *outlink)
+{
+ EvalContext *eval = outlink->src->priv;
+ char buf[128];
+
+ outlink->time_base = (AVRational){1, eval->sample_rate};
+ outlink->sample_rate = eval->sample_rate;
+
+ eval->var_values[VAR_S] = eval->sample_rate;
+
+ 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);
+
+ return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+ EvalContext *eval = ctx->priv;
+ enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_DBL, AV_SAMPLE_FMT_NONE };
+ int64_t chlayouts[] = { eval->chlayout, -1 };
+ int packing_fmts[] = { AVFILTER_PLANAR, -1 };
+
+ avfilter_set_common_sample_formats (ctx, avfilter_make_format_list(sample_fmts));
+ avfilter_set_common_channel_layouts(ctx, avfilter_make_format64_list(chlayouts));
+ avfilter_set_common_packing_formats(ctx, avfilter_make_format_list(packing_fmts));
+
+ return 0;
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+ EvalContext *eval = outlink->src->priv;
+ AVFilterBufferRef *samplesref;
+ int i, j;
+
+ samplesref = avfilter_get_audio_buffer(outlink, AV_PERM_WRITE, eval->nb_samples);
+
+ /* evaluate expression for each single sample and for each channel */
+ for (i = 0; i < eval->nb_samples; i++, eval->n++) {
+ eval->var_values[VAR_N] = eval->n;
+ eval->var_values[VAR_T] = eval->var_values[VAR_N] * (double)1/eval->sample_rate;
+
+ for (j = 0; j < eval->nb_channels; j++) {
+ *((double *) samplesref->data[j] + i) =
+ av_expr_eval(eval->expr[j], eval->var_values, NULL);
+ }
+ }
+
+ samplesref->pts = eval->pts;
+ samplesref->pos = -1;
+ samplesref->audio->sample_rate = eval->sample_rate;
+ eval->pts += eval->nb_samples;
+
+ avfilter_filter_samples(outlink, samplesref);
+
+ return 0;
+}
+
+AVFilter avfilter_asrc_aevalsrc = {
+ .name = "aevalsrc",
+ .description = NULL_IF_CONFIG_SMALL("Generate an audio signal generated by an expression."),
+
+ .query_formats = query_formats,
+ .init = init,
+ .uninit = uninit,
+ .priv_size = sizeof(EvalContext),
+
+ .inputs = (AVFilterPad[]) {{ .name = NULL}},
+
+ .outputs = (AVFilterPad[]) {{ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ .config_props = config_props,
+ .request_frame = request_frame, },
+ { .name = NULL}},
+};
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