From 7c5f1171ff553accc588bd00500bf03b8a5de517 Mon Sep 17 00:00:00 2001
From: Jeffy Chen <jeffy.chen@rock-chips.com>
Date: Wed, 6 Nov 2019 15:07:44 +0800
Subject: [PATCH 04/12] v4l2: Support preferred formats

Set env "GST_V4L2_PREFERRED_FOURCC" to specify preferred formats, for
example:
export GST_V4L2SRC_PREFERRED_FOURCC=YU12:NV12

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
---
 sys/v4l2/gstv4l2object.c | 17 +++++++++++++++++
 sys/v4l2/gstv4l2src.c    | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index 032fd69..19ae751 100644
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -25,6 +25,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/ioctl.h>
@@ -1142,6 +1143,22 @@ gst_v4l2_object_format_get_rank (const struct v4l2_fmtdesc *fmt)
       break;
   }
 
+  {
+    const char *buf = g_getenv ("GST_V4L2_PREFERRED_FOURCC");
+    int max_rank = YUV_BASE_RANK * 2;
+
+    while (buf) {
+      if (buf[0] == ':')
+        buf++;
+
+      if (!strncmp (buf, (char *) &fourcc, 4))
+        rank = max_rank;
+
+      buf = strchr (buf, ':');
+      max_rank--;
+    }
+  }
+
   /* All ranks are below 1<<15 so a shift by 15
    * will a) make all non-emulated formats larger
    * than emulated and b) will not overflow
diff --git a/sys/v4l2/gstv4l2src.c b/sys/v4l2/gstv4l2src.c
index e33b71e..4cc4cdf 100644
--- a/sys/v4l2/gstv4l2src.c
+++ b/sys/v4l2/gstv4l2src.c
@@ -438,6 +438,38 @@ gst_v4l2_src_parse_fixed_struct (GstStructure * s,
     gst_structure_get_fraction (s, "framerate", fps_n, fps_d);
 }
 
+static gint
+gst_v4l2src_get_format_loss (GstStructure * s)
+{
+  GstVideoFormat format;
+  const gchar *buf = g_getenv ("GST_V4L2_PREFERRED_FOURCC");
+  guint32 fourcc, loss;
+
+  if (!buf)
+    return 0;
+
+  format =
+      gst_video_format_from_string (gst_structure_get_string (s, "format"));
+  if (format == GST_VIDEO_FORMAT_UNKNOWN)
+    return 0;
+
+  fourcc = gst_video_format_to_fourcc (format);
+
+  loss = 0;
+  while (buf) {
+    if (buf[0] == ':')
+      buf++;
+
+    if (!strncmp (buf, (char *) &fourcc, 4))
+      return loss;
+
+    buf = strchr (buf, ':');
+    loss++;
+  }
+
+  return loss;
+}
+
 /* TODO Consider framerate */
 static gint
 gst_v4l2src_fixed_caps_compare (GstCaps * caps_a, GstCaps * caps_b,
@@ -490,6 +522,11 @@ gst_v4l2src_fixed_caps_compare (GstCaps * caps_a, GstCaps * caps_b,
   if (bh == pref->height)
     bd -= 1;
 
+  if (ad == bd) {
+    ad = gst_v4l2src_get_format_loss (a);
+    bd = gst_v4l2src_get_format_loss (b);
+  }
+
   /* If the choices are equivalent, maintain the order */
   if (ad == bd)
     ret = 1;
-- 
2.20.1