try to guess the codec for imag2pipe too

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@3674 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/utils.c

@@ -138,7 +138,7 @@ enum CodecID av_guess_codec(AVOutputFormat *fmt, const char *short_name,
     if(type == CODEC_TYPE_VIDEO){
         enum CodecID codec_id= CODEC_ID_NONE;
 
-        if(!strcmp(fmt->name, "image2")){
+        if(!strcmp(fmt->name, "image2") || !strcmp(fmt->name, "image2pipe")){
             codec_id= av_guess_image2_codec(filename);
         }
         if(codec_id == CODEC_ID_NONE)