From b530c0ef4eac10ec01c84fcef96e63a501950c1f Mon Sep 17 00:00:00 2001
From: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date: Wed, 10 Feb 2021 16:37:01 -0500
Subject: [PATCH] v4l2src: Calculate framerate from DV timings

And use this framerate in our preference. Note that we also flush
the probed caps as it seems that the format enumeration may change
when a new source change event get triggered.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/870>
---
 sys/v4l2/gstv4l2src.c | 27 ++++++++++++++++++++++++---
 sys/v4l2/v4l2_calls.c |  2 +-
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/sys/v4l2/gstv4l2src.c b/sys/v4l2/gstv4l2src.c
index e2aa918d54..f3e28b1e3d 100644
--- a/sys/v4l2/gstv4l2src.c
+++ b/sys/v4l2/gstv4l2src.c
@@ -493,19 +493,39 @@ gst_v4l2src_query_preferred_dv_timings (GstV4l2Src * v4l2src,
 {
   GstV4l2Object *obj = v4l2src->v4l2object;
   struct v4l2_dv_timings dv_timings = { 0, };
+  const struct v4l2_bt_timings *bt = &dv_timings.bt;
+  gint tot_width, tot_height;
+  gint gcd;
 
   if (!gst_v4l2_query_dv_timings (obj, &dv_timings))
     return FALSE;
 
-  pref->width = dv_timings.bt.width;
-  pref->height = dv_timings.bt.height;
-  /* FIXME calculate frame rate */
+  pref->width = bt->width;
+  pref->height = bt->height;
+
+  tot_height = bt->height +
+      bt->vfrontporch + bt->vsync + bt->vbackporch +
+      bt->il_vfrontporch + bt->il_vsync + bt->il_vbackporch;
+  tot_width = bt->width + bt->hfrontporch + bt->hsync + bt->hbackporch;
+
+  pref->fps_n = bt->pixelclock;
+  pref->fps_d = tot_width * tot_height;
+
+  if (bt->interlaced)
+    pref->fps_d /= 2;
+
+  gcd = gst_util_greatest_common_divisor (pref->fps_n, pref->fps_d);
+  pref->fps_n /= gcd;
+  pref->fps_d /= gcd;
 
   /* If are are not streaming (e.g. we received source-change event), lock the
    * new timing immediatly so that TRY_FMT can properly work */
   if (!obj->pool || !GST_V4L2_BUFFER_POOL_IS_STREAMING (obj->pool))
     gst_v4l2_set_dv_timings (obj, &dv_timings);
 
+  GST_INFO_OBJECT (v4l2src, "Using DV Timings: %i x %i (%i/%i fps)",
+      pref->width, pref->height, pref->fps_n, pref->fps_d);
+
   return TRUE;
 }
 
@@ -922,6 +942,7 @@ gst_v4l2src_create (GstPushSrc * src, GstBuffer ** buf)
          * streamoff in order to allow locking a new DV_TIMING which will
          * influence the output of TRY_FMT */
         gst_v4l2src_stop (GST_BASE_SRC (src));
+        gst_caps_replace (&obj->probed_caps, NULL);
 
         /* Force renegotiation */
         v4l2src->renegotiation_adjust = v4l2src->offset + 1;
diff --git a/sys/v4l2/v4l2_calls.c b/sys/v4l2/v4l2_calls.c
index 2dada91151..b6b51af224 100644
--- a/sys/v4l2/v4l2_calls.c
+++ b/sys/v4l2/v4l2_calls.c
@@ -1352,7 +1352,7 @@ gst_v4l2_query_dv_timings (GstV4l2Object * v4l2object,
     return FALSE;
   }
 
-  GST_INFO_OBJECT (v4l2object->dbg_obj, "Detected DV Timings (%i x %i)",
+  GST_DEBUG_OBJECT (v4l2object->dbg_obj, "Detected DV Timings (%i x %i)",
       timings->bt.width, timings->bt.height);
 
   return TRUE;