avdevice/dshow: list_devices: show media type(s) per device

the list_devices option of dshow didn't indicate whether a specific
device provides audio or video output. This patch iterates through all
media formats of all pins exposed by the device to see what types it
provides for capture, and prints this to the console for each device.
Importantly, this now allows to find devices that provide both audio and
video, and devices that provide neither.

Signed-off-by: Diederick Niehorster <dcnieho@gmail.com>
Reviewed-by: Roger Pack <rogerdpack2@gmail.com>

libavdevice/dshow.c

@@ -197,6 +197,80 @@ fail:
     return;
 }
 
+static void
+dshow_get_device_media_types(AVFormatContext *avctx, enum dshowDeviceType devtype,
+                                         enum dshowSourceFilterType sourcetype, IBaseFilter *device_filter,
+                                         enum AVMediaType **media_types, int *nb_media_types)
+{
+    struct dshow_ctx *ctx = avctx->priv_data;
+    IEnumPins *pins = 0;
+    IPin *pin;
+    int has_audio = 0, has_video = 0;
+
+    if (IBaseFilter_EnumPins(device_filter, &pins) != S_OK)
+        return;
+
+    while (IEnumPins_Next(pins, 1, &pin, NULL) == S_OK) {
+        IKsPropertySet *p = NULL;
+        PIN_INFO info = { 0 };
+        GUID category;
+        DWORD r2;
+        IEnumMediaTypes *types = NULL;
+        AM_MEDIA_TYPE *type;
+
+        if (IPin_QueryPinInfo(pin, &info) != S_OK)
+            goto next;
+        IBaseFilter_Release(info.pFilter);
+
+        if (info.dir != PINDIR_OUTPUT)
+            goto next;
+        if (IPin_QueryInterface(pin, &IID_IKsPropertySet, (void **) &p) != S_OK)
+            goto next;
+        if (IKsPropertySet_Get(p, &AMPROPSETID_Pin, AMPROPERTY_PIN_CATEGORY,
+                               NULL, 0, &category, sizeof(GUID), &r2) != S_OK)
+            goto next;
+        if (!IsEqualGUID(&category, &PIN_CATEGORY_CAPTURE))
+            goto next;
+
+        if (IPin_EnumMediaTypes(pin, &types) != S_OK)
+            goto next;
+
+        // enumerate media types exposed by pin
+        // NB: don't know if a pin can expose both audio and video, check 'm all to be safe
+        IEnumMediaTypes_Reset(types);
+        while (IEnumMediaTypes_Next(types, 1, &type, NULL) == S_OK) {
+            if (IsEqualGUID(&type->majortype, &MEDIATYPE_Video)) {
+                has_video = 1;
+            } else if (IsEqualGUID(&type->majortype, &MEDIATYPE_Audio)) {
+                has_audio = 1;
+            }
+            CoTaskMemFree(type);
+        }
+
+    next:
+        if (types)
+            IEnumMediaTypes_Release(types);
+        if (p)
+            IKsPropertySet_Release(p);
+        if (pin)
+            IPin_Release(pin);
+    }
+
+    IEnumPins_Release(pins);
+
+    if (has_audio || has_video) {
+        int nb_types = has_audio + has_video;
+        *media_types = av_malloc_array(nb_types, sizeof(enum AVMediaType));
+        if (*media_types) {
+            if (has_audio)
+                (*media_types)[0] = AVMEDIA_TYPE_AUDIO;
+            if (has_video)
+                (*media_types)[0 + has_audio] = AVMEDIA_TYPE_VIDEO;
+            *nb_media_types = nb_types;
+        }
+    }
+}
+
 /**
  * Cycle through available devices using the device enumerator devenum,
  * retrieve the device with type specified by devtype and return the
@@ -242,6 +316,8 @@ dshow_cycle_devices(AVFormatContext *avctx, ICreateDevEnum *devenum,
         LPOLESTR olestr = NULL;
         LPMALLOC co_malloc = NULL;
         AVDeviceInfo *device = NULL;
+        enum AVMediaType *media_types = NULL;
+        int nb_media_types = 0;
         int i;
 
         r = CoGetMalloc(1, &co_malloc);
@@ -286,6 +362,12 @@ dshow_cycle_devices(AVFormatContext *avctx, ICreateDevEnum *devenum,
                 // success, loop will end now
             }
         } else {
+            // get media types exposed by pins of device
+            if (IMoniker_BindToObject(m, 0, 0, &IID_IBaseFilter, (void* ) &device_filter) == S_OK) {
+                dshow_get_device_media_types(avctx, devtype, sourcetype, device_filter, &media_types, &nb_media_types);
+                IBaseFilter_Release(device_filter);
+                device_filter = NULL;
+            }
             if (device_list) {
                 device = av_mallocz(sizeof(AVDeviceInfo));
                 if (!device)
@@ -308,12 +390,25 @@ dshow_cycle_devices(AVFormatContext *avctx, ICreateDevEnum *devenum,
                 device = NULL;  // copied into array, make sure not freed below
             }
             else {
-                av_log(avctx, AV_LOG_INFO, " \"%s\"\n", friendly_name);
-                av_log(avctx, AV_LOG_INFO, "    Alternative name \"%s\"\n", unique_name);
+                av_log(avctx, AV_LOG_INFO, "\"%s\"", friendly_name);
+                if (nb_media_types > 0) {
+                    const char* media_type = av_get_media_type_string(media_types[0]);
+                    av_log(avctx, AV_LOG_INFO, " (%s", media_type ? media_type : "unknown");
+                    for (int i = 1; i < nb_media_types; ++i) {
+                        media_type = av_get_media_type_string(media_types[i]);
+                        av_log(avctx, AV_LOG_INFO, ", %s", media_type ? media_type : "unknown");
+                    }
+                    av_log(avctx, AV_LOG_INFO, ")");
+                } else {
+                    av_log(avctx, AV_LOG_INFO, " (none)");
+                }
+                av_log(avctx, AV_LOG_INFO, "\n");
+                av_log(avctx, AV_LOG_INFO, "  Alternative name \"%s\"\n", unique_name);
             }
         }
 
-fail:
+    fail:
+        av_freep(&media_types);
         if (device) {
             av_freep(&device->device_name);
             av_freep(&device->device_description);
@@ -1186,9 +1281,7 @@ static int dshow_read_header(AVFormatContext *avctx)
     }
 
     if (ctx->list_devices) {
-        av_log(avctx, AV_LOG_INFO, "DirectShow video devices (some may be both video and audio devices)\n");
         dshow_cycle_devices(avctx, devenum, VideoDevice, VideoSourceDevice, NULL, NULL, NULL);
-        av_log(avctx, AV_LOG_INFO, "DirectShow audio devices\n");
         dshow_cycle_devices(avctx, devenum, AudioDevice, AudioSourceDevice, NULL, NULL, NULL);
         ret = AVERROR_EXIT;
         goto error;