/* * This file is part of Libav. * * Libav 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. * * Libav 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 Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * null video source */ #include <stdio.h> #include "libavutil/avstring.h"#include "libavutil/eval.h"#include "libavutil/internal.h"#include "libavutil/mathematics.h"#include "libavutil/opt.h"#include "libavutil/parseutils.h"#include "avfilter.h"#include "formats.h"#include "internal.h" static const char *const var_names[] = {    "E",    "PHI",    "PI",    "AVTB",   /* default timebase 1/AV_TIME_BASE */    NULL}; enum var_name {    VAR_E,    VAR_PHI,    VAR_PI,    VAR_AVTB,    VAR_VARS_NB}; typedef struct NullContext {    const AVClass *class;    int w, h;    char *tb_expr;    double var_values[VAR_VARS_NB];} NullContext; static int config_props(AVFilterLink *outlink){    AVFilterContext *ctx = outlink->src;    NullContext *priv = ctx->priv;    AVRational tb;    int ret;    double res;     priv->var_values[VAR_E]    = M_E;    priv->var_values[VAR_PHI]  = M_PHI;    priv->var_values[VAR_PI]   = M_PI;    priv->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);     if ((ret = av_expr_parse_and_eval(&res, priv->tb_expr, var_names, priv->var_values,                                      NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {        av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);        return ret;    }    tb = av_d2q(res, INT_MAX);    if (tb.num <= 0 || tb.den <= 0) {        av_log(ctx, AV_LOG_ERROR,               "Invalid non-positive value for the timebase %d/%d.\n",               tb.num, tb.den);        return AVERROR(EINVAL);    }     outlink->w = priv->w;    outlink->h = priv->h;    outlink->time_base = tb;     av_log(outlink->src, AV_LOG_VERBOSE, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,           tb.num, tb.den);     return 0;} static int request_frame(AVFilterLink *link){    return -1;} #define OFFSET(x) offsetof(NullContext, x)#define FLAGS AV_OPT_FLAG_VIDEO_PARAMstatic const AVOption options[] = {    { "width",    NULL, OFFSET(w),       AV_OPT_TYPE_INT,    { .i64 = 352    }, 1, INT_MAX, FLAGS },    { "height",   NULL, OFFSET(h),       AV_OPT_TYPE_INT,    { .i64 = 288    }, 1, INT_MAX, FLAGS },    { "timebase", NULL, OFFSET(tb_expr), AV_OPT_TYPE_STRING, { .str = "AVTB" }, 0, 0,      FLAGS },    { NULL },}; static const AVClass nullsrc_class = {    .class_name = "nullsrc",    .item_name  = av_default_item_name,    .option     = options,    .version    = LIBAVUTIL_VERSION_INT,}; static const AVFilterPad avfilter_vsrc_nullsrc_outputs[] = {    {        .name          = "default",        .type          = AVMEDIA_TYPE_VIDEO,        .config_props  = config_props,        .request_frame = request_frame,    },    { NULL }}; AVFilter ff_vsrc_nullsrc = {    .name        = "nullsrc",    .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),     .priv_size = sizeof(NullContext),    .priv_class = &nullsrc_class,     .inputs    = NULL,     .outputs   = avfilter_vsrc_nullsrc_outputs,};