sys/v4l2/: When probing the formats and sizes a camera supports, make sure the best ones (highest resolution, prefere...

Original commit message from CVS:
* sys/v4l2/gstv4l2src.c:
* sys/v4l2/v4l2src_calls.c:
When probing the formats and sizes a camera supports, make
sure the best ones (highest resolution, prefered format)
end up at the beginning of the probed caps and the less
desirable ones at the end.  This is important because the
order within the caps matters for things like fixation and
negotiation, ie. what format is chosen in the end.
With recent kernels, the current probing code will end up
querying the supported sizes from lowest resolution to
highest resolution, adding them to the probed caps in that
order, resulting to v4l2src fixating to the lowest possible
resolution if downstream does not express a size preference.
Also make up a somewhat random ranking of prefered output
formats for the same reason. Fixes #485828.

1 files changed, 109 insertions, 3 deletions

diff --git a/sys/v4l2/v4l2src_calls.c b/sys/v4l2/v4l2src_calls.c
index 0ed28a88..21022c8c 100644
--- a/sys/v4l2/v4l2src_calls.c
+++ b/sys/v4l2/v4l2src_calls.c
@@ -373,6 +373,97 @@ gst_v4l2_buffer_pool_destroy (GstV4l2BufferPool * pool)
   gst_mini_object_unref (GST_MINI_OBJECT (pool));
 }
 
+/* complete made up ranking, the values themselves are meaningless */
+#define YUV_BASE_RANK     1000
+#define JPEG_BASE_RANK     500
+#define DV_BASE_RANK       200
+#define RGB_BASE_RANK      100
+#define YUV_ODD_BASE_RANK   50
+#define RGB_ODD_BASE_RANK   25
+#define BAYER_BASE_RANK     15
+#define GREY_BASE_RANK       5
+
+static gint
+gst_v4l2src_format_get_rank (guint32 fourcc)
+{
+  switch (fourcc) {
+    case V4L2_PIX_FMT_MJPEG:
+      return JPEG_BASE_RANK;
+    case V4L2_PIX_FMT_JPEG:
+      return JPEG_BASE_RANK + 1;
+
+    case V4L2_PIX_FMT_RGB332:
+    case V4L2_PIX_FMT_RGB555:
+    case V4L2_PIX_FMT_RGB555X:
+    case V4L2_PIX_FMT_RGB565:
+    case V4L2_PIX_FMT_RGB565X:
+      return RGB_ODD_BASE_RANK;
+
+    case V4L2_PIX_FMT_RGB24:
+    case V4L2_PIX_FMT_BGR24:
+      return RGB_BASE_RANK - 1;
+
+    case V4L2_PIX_FMT_RGB32:
+    case V4L2_PIX_FMT_BGR32:
+      return RGB_BASE_RANK;
+
+    case V4L2_PIX_FMT_GREY:    /*  8  Greyscale     */
+      return GREY_BASE_RANK;
+
+    case V4L2_PIX_FMT_NV12:    /* 12  Y/CbCr 4:2:0  */
+    case V4L2_PIX_FMT_NV21:    /* 12  Y/CrCb 4:2:0  */
+    case V4L2_PIX_FMT_YYUV:    /* 16  YUV 4:2:2     */
+    case V4L2_PIX_FMT_HI240:   /*  8  8-bit color   */
+      return YUV_ODD_BASE_RANK;
+
+    case V4L2_PIX_FMT_YVU410:  /* YVU9,  9 bits per pixel */
+      return YUV_BASE_RANK + 3;
+    case V4L2_PIX_FMT_YUV410:  /* YUV9,  9 bits per pixel */
+      return YUV_BASE_RANK + 2;
+    case V4L2_PIX_FMT_YUV420:  /* I420, 12 bits per pixel */
+      return YUV_BASE_RANK + 7;
+    case V4L2_PIX_FMT_YUYV:    /* YUY2, 16 bits per pixel */
+      return YUV_BASE_RANK + 10;
+    case V4L2_PIX_FMT_YVU420:  /* YV12, 12 bits per pixel */
+      return YUV_BASE_RANK + 6;
+    case V4L2_PIX_FMT_UYVY:    /* UYVY, 16 bits per pixel */
+      return YUV_BASE_RANK + 9;
+    case V4L2_PIX_FMT_Y41P:    /* Y41P, 12 bits per pixel */
+      return YUV_BASE_RANK + 5;
+    case V4L2_PIX_FMT_YUV411P: /* Y41B, 12 bits per pixel */
+      return YUV_BASE_RANK + 4;
+    case V4L2_PIX_FMT_YUV422P: /* Y42B, 16 bits per pixel */
+      return YUV_BASE_RANK + 8;
+
+    case V4L2_PIX_FMT_DV:
+      return DV_BASE_RANK;
+
+    case V4L2_PIX_FMT_MPEG:    /* MPEG          */
+    case V4L2_PIX_FMT_WNVA:    /* Winnov hw compres */
+      return 0;
+
+    case V4L2_PIX_FMT_SBGGR8:
+      return BAYER_BASE_RANK;
+
+    default:
+      break;
+  }
+
+  return 0;
+}
+
+static gint
+gst_v4l2src_format_cmp_func (gconstpointer a, gconstpointer b)
+{
+  guint32 pf1 = ((struct v4l2_fmtdesc *) a)->pixelformat;
+  guint32 pf2 = ((struct v4l2_fmtdesc *) b)->pixelformat;
+
+  if (pf1 == pf2)
+    return 0;
+
+  return gst_v4l2src_format_get_rank (pf2) - gst_v4l2src_format_get_rank (pf1);
+}
+
 /******************************************************
  * gst_v4l2src_fill_format_list():
  *   create list of supported capture formats
@@ -407,9 +498,12 @@ gst_v4l2src_fill_format_list (GstV4l2Src * v4l2src)
     GST_LOG_OBJECT (v4l2src, "pixelformat: %" GST_FOURCC_FORMAT,
         GST_FOURCC_ARGS (format->pixelformat));
 
-    v4l2src->formats = g_slist_prepend (v4l2src->formats, format);
+    /* sort formats according to our preference;  we do this, because caps
+     * are probed in the order the formats are in the list, and the order of
+     * formats in the final probed caps matters for things like fixation */
+    v4l2src->formats = g_slist_insert_sorted (v4l2src->formats, format,
+        (GCompareFunc) gst_v4l2src_format_cmp_func);
   }
-  v4l2src->formats = g_slist_reverse (v4l2src->formats);
 
   GST_DEBUG_OBJECT (v4l2src, "got %d format(s)", n);
 
@@ -638,6 +732,7 @@ gst_v4l2src_probe_caps_for_format (GstV4l2Src * v4l2src, guint32 pixelformat,
 {
   GstCaps *ret;
   GstStructure *tmp;
+  GList *results = NULL;
 
 #ifdef VIDIOC_ENUM_FRAMESIZES
   gint fd = v4l2src->v4l2object->video_fd;
@@ -661,7 +756,7 @@ gst_v4l2src_probe_caps_for_format (GstV4l2Src * v4l2src, guint32 pixelformat,
       tmp = gst_v4l2src_probe_caps_for_format_and_size (v4l2src, pixelformat,
           w, h, template);
       if (tmp)
-        gst_caps_append_structure (ret, tmp);
+        results = g_list_prepend (results, tmp);
 
       size.index++;
     } while (ioctl (fd, VIDIOC_ENUM_FRAMESIZES, &size) >= 0);
@@ -697,6 +792,17 @@ gst_v4l2src_probe_caps_for_format (GstV4l2Src * v4l2src, guint32 pixelformat,
     goto unknown_type;
   }
 
+  /* we use an intermediary list to store the results of the probing because
+   * we probe from lowest resolution to highest resolution, but want the caps
+   * to contain the results in reverse order starting with the highest
+   * resolution, as order in caps matters for things like fixation.  However,
+   * there's no gst_caps_prepend_structure(), so we use the list as helper to
+   * reverse the order */
+  while (results != NULL) {
+    gst_caps_append_structure (ret, GST_STRUCTURE (results->data));
+    results = g_list_delete_link (results, results);
+  }
+
   return ret;
 
   /* ERRORS */