avdevice/dshow: Don't skip audio devices if no video device is present

The search of the current DirectShow device list has been customized so
that audio devices are always found even if no video device is connected.

Signed-off-by: Jens Frederich <jens.frederich@vector.com>
Reviewed-by: Roger Pack <rogerdpack2@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavdevice/dshow.c

@@ -645,7 +645,7 @@ static int dshow_get_device_list(AVFormatContext *avctx, AVDeviceInfoList *devic
     }
 
     ret = dshow_cycle_devices(avctx, devenum, VideoDevice, VideoSourceDevice, NULL, NULL, &device_list);
-    if (ret < S_OK)
+    if (ret < S_OK && ret != AVERROR(EIO))
         goto error;
     ret = dshow_cycle_devices(avctx, devenum, AudioDevice, AudioSourceDevice, NULL, NULL, &device_list);