lavd/fbdev_dec: use default device when not provided

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>

libavdevice/fbdev_dec.c

@@ -68,6 +68,7 @@ static av_cold int fbdev_read_header(AVFormatContext *avctx)
     AVStream *st = NULL;
     enum AVPixelFormat pix_fmt;
     int ret, flags = O_RDONLY;
+    const char* device;
 
     if (!(st = avformat_new_stream(avctx, NULL)))
         return AVERROR(ENOMEM);
@@ -77,11 +78,16 @@ static av_cold int fbdev_read_header(AVFormatContext *avctx)
     if (avctx->flags & AVFMT_FLAG_NONBLOCK)
         flags |= O_NONBLOCK;
 
-    if ((fbdev->fd = avpriv_open(avctx->filename, flags)) == -1) {
+    if (avctx->filename[0])
+        device = avctx->filename;
+    else
+        device = ff_fbdev_default_device();
+
+    if ((fbdev->fd = avpriv_open(device, flags)) == -1) {
         ret = AVERROR(errno);
         av_log(avctx, AV_LOG_ERROR,
                "Could not open framebuffer device '%s': %s\n",
-               avctx->filename, av_err2str(ret));
+               device, av_err2str(ret));
         return ret;
     }