Show per-codec options on FFmpeg commandline help.

Originally committed as revision 25927 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -3883,6 +3883,8 @@ static void show_usage(void)
 
 static void show_help(void)
 {
+    AVCodec *c;
+
     av_log_set_callback(log_callback_help);
     show_usage();
     show_help_options(options, "Main options:\n",
@@ -3911,6 +3913,16 @@ static void show_help(void)
     printf("\n");
     av_opt_show2(avcodec_opts[0], NULL, AV_OPT_FLAG_ENCODING_PARAM|AV_OPT_FLAG_DECODING_PARAM, 0);
     printf("\n");
+
+    /* individual codec options */
+    c = NULL;
+    while ((c = av_codec_next(c))) {
+        if (c->priv_class) {
+            av_opt_show2(&c->priv_class, NULL, AV_OPT_FLAG_ENCODING_PARAM|AV_OPT_FLAG_DECODING_PARAM, 0);
+            printf("\n");
+        }
+    }
+
     av_opt_show2(avformat_opts, NULL, AV_OPT_FLAG_ENCODING_PARAM|AV_OPT_FLAG_DECODING_PARAM, 0);
     printf("\n");
     av_opt_show2(sws_opts, NULL, AV_OPT_FLAG_ENCODING_PARAM|AV_OPT_FLAG_DECODING_PARAM, 0);