Fix xcb 32bit pix_fmts: There is no screen transparency.

libavdevice/xcbgrab.c

@@ -455,11 +455,11 @@ static int pixfmt_from_pixmap_format(AVFormatContext *s, int depth,
             switch (depth) {
             case 32:
                 if (fmt->bits_per_pixel == 32)
-                    *pix_fmt = AV_PIX_FMT_ARGB;
+                    *pix_fmt = AV_PIX_FMT_0RGB;
                 break;
             case 24:
                 if (fmt->bits_per_pixel == 32)
-                    *pix_fmt = AV_PIX_FMT_RGB32;
+                    *pix_fmt = AV_PIX_FMT_0RGB32;
                 else if (fmt->bits_per_pixel == 24)
                     *pix_fmt = AV_PIX_FMT_RGB24;
                 break;