ffmpeg: Fix regression where various fields where not initialized leading to segfaults

Bug introduced by:
commit f12f40b31a
Author: Anton Khirnov <anton@khirnov.net>
Date:   Tue Aug 30 04:05:20 2011 +0200

    ffmpeg: get rid of new* options.

    They are confusing, irregular and redundant -- -map already contains all
    the information.  Stream maps can now be parsed in opt_output_file().

    Add a more user-friendly default behavior in case no maps are present.

    Breaks -programid for now, but it never worked properly anyway. A better
    solution will be written soon.

ffmpeg.c

@@ -3681,6 +3681,7 @@ static void opt_output_file(void *optctx, const char *filename)
 
     if (!strcmp(file_oformat->name, "ffm") &&
         av_strstart(filename, "http:", NULL)) {
+        int j;
         /* special case for files sent to ffserver: we get the stream
            parameters from ffserver */
         int err = read_ffserver_streams(o, oc, filename);
@@ -3688,6 +3689,18 @@ static void opt_output_file(void *optctx, const char *filename)
             print_error(filename, err);
             exit_program(1);
         }
+        for(j = nb_output_streams - oc->nb_streams; j < nb_output_streams; j++) {
+            ost = &output_streams[j];
+            for (i = 0; i < nb_input_streams; i++) {
+                ist = &input_streams[i];
+                if(ist->st->codec->codec_type == ost->st->codec->codec_type){
+                    ost->sync_ist= ist;
+                    ost->source_index= i;
+                    ist->discard = 0;
+                    break;
+                }
+            }
+        }
     } else if (!o->nb_stream_maps) {
         /* pick the "best" stream of each type */
 #define NEW_STREAM(type, index)\