Libav 0.7.1
libavfilter/vsrc_nullsrc.c
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00001 /*
00002  * This file is part of Libav.
00003  *
00004  * Libav is free software; you can redistribute it and/or
00005  * modify it under the terms of the GNU Lesser General Public
00006  * License as published by the Free Software Foundation; either
00007  * version 2.1 of the License, or (at your option) any later version.
00008  *
00009  * Libav is distributed in the hope that it will be useful,
00010  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012  * Lesser General Public License for more details.
00013  *
00014  * You should have received a copy of the GNU Lesser General Public
00015  * License along with Libav; if not, write to the Free Software
00016  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00017  */
00018 
00024 #include "libavutil/avstring.h"
00025 #include "libavutil/eval.h"
00026 #include "libavutil/parseutils.h"
00027 #include "avfilter.h"
00028 
00029 static const char *var_names[] = {
00030     "E",
00031     "PHI",
00032     "PI",
00033     "AVTB",   /* default timebase 1/AV_TIME_BASE */
00034     NULL
00035 };
00036 
00037 enum var_name {
00038     VAR_E,
00039     VAR_PHI,
00040     VAR_PI,
00041     VAR_AVTB,
00042     VAR_VARS_NB
00043 };
00044 
00045 typedef struct {
00046     int w, h;
00047     char tb_expr[256];
00048     double var_values[VAR_VARS_NB];
00049 } NullContext;
00050 
00051 static int init(AVFilterContext *ctx, const char *args, void *opaque)
00052 {
00053     NullContext *priv = ctx->priv;
00054 
00055     priv->w = 352;
00056     priv->h = 288;
00057     av_strlcpy(priv->tb_expr, "AVTB", sizeof(priv->tb_expr));
00058 
00059     if (args)
00060         sscanf(args, "%d:%d:%255[^:]", &priv->w, &priv->h, priv->tb_expr);
00061 
00062     if (priv->w <= 0 || priv->h <= 0) {
00063         av_log(ctx, AV_LOG_ERROR, "Non-positive size values are not acceptable.\n");
00064         return AVERROR(EINVAL);
00065     }
00066 
00067     return 0;
00068 }
00069 
00070 static int config_props(AVFilterLink *outlink)
00071 {
00072     AVFilterContext *ctx = outlink->src;
00073     NullContext *priv = ctx->priv;
00074     AVRational tb;
00075     int ret;
00076     double res;
00077 
00078     priv->var_values[VAR_E]    = M_E;
00079     priv->var_values[VAR_PHI]  = M_PHI;
00080     priv->var_values[VAR_PI]   = M_PI;
00081     priv->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);
00082 
00083     if ((ret = av_expr_parse_and_eval(&res, priv->tb_expr, var_names, priv->var_values,
00084                                       NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {
00085         av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);
00086         return ret;
00087     }
00088     tb = av_d2q(res, INT_MAX);
00089     if (tb.num <= 0 || tb.den <= 0) {
00090         av_log(ctx, AV_LOG_ERROR,
00091                "Invalid non-positive value for the timebase %d/%d.\n",
00092                tb.num, tb.den);
00093         return AVERROR(EINVAL);
00094     }
00095 
00096     outlink->w = priv->w;
00097     outlink->h = priv->h;
00098     outlink->time_base = tb;
00099 
00100     av_log(outlink->src, AV_LOG_INFO, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,
00101            tb.num, tb.den);
00102 
00103     return 0;
00104 }
00105 
00106 static int request_frame(AVFilterLink *link)
00107 {
00108     return -1;
00109 }
00110 
00111 AVFilter avfilter_vsrc_nullsrc = {
00112     .name        = "nullsrc",
00113     .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),
00114 
00115     .init       = init,
00116     .priv_size = sizeof(NullContext),
00117 
00118     .inputs    = (AVFilterPad[]) {{ .name = NULL}},
00119 
00120     .outputs   = (AVFilterPad[]) {
00121         {
00122             .name            = "default",
00123             .type            = AVMEDIA_TYPE_VIDEO,
00124             .config_props    = config_props,
00125             .request_frame   = request_frame,
00126         },
00127         { .name = NULL}
00128     },
00129 };