/* * 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 "libavutil/avstring.h"#include "libavutil/eval.h"#include "libavutil/mathematics.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 {    int w, h;    char tb_expr[256];    double var_values[VAR_VARS_NB];} NullContext; static int init(AVFilterContext *ctx, const char *args, void *opaque){    NullContext *priv = ctx->priv;     priv->w = 352;    priv->h = 288;    av_strlcpy(priv->tb_expr, "AVTB", sizeof(priv->tb_expr));     if (args)        sscanf(args, "%d:%d:%255[^:]", &priv->w, &priv->h, priv->tb_expr);     if (priv->w <= 0 || priv->h <= 0) {        av_log(ctx, AV_LOG_ERROR, "Non-positive size values are not acceptable.\n");        return AVERROR(EINVAL);    }     return 0;} 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_INFO, "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;} AVFilter avfilter_vsrc_nullsrc = {    .name        = "nullsrc",    .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),     .init       = init,    .priv_size = sizeof(NullContext),     .inputs    = (AVFilterPad[]) {{ .name = NULL}},     .outputs   = (AVFilterPad[]) {        {            .name            = "default",            .type            = AVMEDIA_TYPE_VIDEO,            .config_props    = config_props,            .request_frame   = request_frame,        },        { .name = NULL}    },};