ffmpeg: support dump bit stream filter options.

Support dump bit stream filter option in ffmpeg -h full and
ffmpeg -h bsf=FooBar.
Signed-off-by: Jun Zhao <mypopydev@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

fftools/cmdutils.c

@@ -1897,6 +1897,21 @@ static void show_help_filter(const char *name)
 }
 #endif
 
+static void show_help_bsf(const char *name)
+{
+    const AVBitStreamFilter *bsf = av_bsf_get_by_name(name);
+
+    if (!bsf) {
+        av_log(NULL, AV_LOG_ERROR, "Unknown bit stream filter '%s'.\n", name);
+        return;
+    }
+
+    printf("Bit stream filter %s\n", bsf->name);
+    if (bsf->priv_class)
+        show_help_children(bsf->priv_class, AV_OPT_FLAG_BSF_PARAM);
+    printf("\n");
+}
+
 int show_help(void *optctx, const char *opt, const char *arg)
 {
     char *topic, *par;
@@ -1923,6 +1938,8 @@ int show_help(void *optctx, const char *opt, const char *arg)
     } else if (!strcmp(topic, "filter")) {
         show_help_filter(par);
 #endif
+    } else if (!strcmp(topic, "bsf")) {
+        show_help_bsf(par);
     } else {
         show_help_default(topic, par);
     }

fftools/ffmpeg_opt.c

@@ -3114,7 +3114,7 @@ void show_help_default(const char *opt, const char *arg)
            "    -h      -- print basic options\n"
            "    -h long -- print more options\n"
            "    -h full -- print all options (including all format and codec specific options, very long)\n"
-           "    -h type=name -- print all options for the named decoder/encoder/demuxer/muxer/filter\n"
+           "    -h type=name -- print all options for the named decoder/encoder/demuxer/muxer/filter/bsf\n"
            "    See man %s for detailed description of the options.\n"
            "\n", program_name);
 
@@ -3159,6 +3159,7 @@ void show_help_default(const char *opt, const char *arg)
 #endif
         show_help_children(swr_get_class(), AV_OPT_FLAG_AUDIO_PARAM);
         show_help_children(avfilter_get_class(), AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM);
+        show_help_children(av_bsf_get_class(), AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_BSF_PARAM);
     }
 }