1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
From fd3e16faa494e47b00cf1374bb4ac1f463b0fc48 Mon Sep 17 00:00:00 2001
From: Don Darling <ddarling@ti.com>
Date: Thu, 14 Oct 2010 11:19:04 -0500
Subject: [PATCH 16/17] v4l2src: add feature to artifically lower framerate by dropping frames.
Some capture devices do not let you set the framerate. In these cases, even
if you specify a frame rate of 30/1, you may still get 60/1. With this change,
if you specify 30/1 and the framerate is really 60/1, every other capture
frame will be dropped and only half of them will be pushed downstream to
simulate 30fps.
The implementation is generic enough to handle any framerate. It automatically
calculates how many and how often frames need to be dropped.
Unfortuately, there is no way to query the "default" fps that will be used
on platforms that do not support setting the frame rate, and target-specific
code must be introduced to make this work. Initially, this feature will only
kick-in for DM6467 and DM6467T.
---
sys/v4l2/gstv4l2object.c | 4 +++
sys/v4l2/gstv4l2object.h | 5 +++
sys/v4l2/gstv4l2src.c | 15 ++++++++++
sys/v4l2/v4l2src_calls.c | 66 +++++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 89 insertions(+), 1 deletions(-)
diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index e63a762..fdcd0d1 100644
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -377,6 +377,10 @@ gst_v4l2_object_new (GstElement * element,
v4l2object->davinci_previewer_fd = -1;
#endif
+ v4l2object->pushed_frame_count_1000x = 0UL;
+ v4l2object->push_rate_1000x = 0UL;
+ v4l2object->next_pushed_frame_1000x = 0UL;
+
return v4l2object;
}
diff --git a/sys/v4l2/gstv4l2object.h b/sys/v4l2/gstv4l2object.h
index 640f948..d4eb8a8 100644
--- a/sys/v4l2/gstv4l2object.h
+++ b/sys/v4l2/gstv4l2object.h
@@ -98,6 +98,11 @@ struct _GstV4l2Object {
gint davinci_previewer_fd;
#endif
+ /* how many capture frames to drop for each frame pushed */
+ guint32 pushed_frame_count_1000x;
+ guint32 push_rate_1000x;
+ guint32 next_pushed_frame_1000x;
+
/* the video buffer (mmap()'ed) */
guint8 **buffer;
diff --git a/sys/v4l2/gstv4l2src.c b/sys/v4l2/gstv4l2src.c
index 9c4c5c3..dd6c65c 100644
--- a/sys/v4l2/gstv4l2src.c
+++ b/sys/v4l2/gstv4l2src.c
@@ -919,6 +919,21 @@ again:
if (G_UNLIKELY (ret != GST_FLOW_OK))
goto done;
+ /* Skip frames if needed to artificially lower the frame rate */
+ if (v4l2src->v4l2object->push_rate_1000x > 0) {
+ if (v4l2src->v4l2object->pushed_frame_count_1000x <
+ v4l2src->v4l2object->next_pushed_frame_1000x) {
+ gst_buffer_unref (temp);
+ goto again;
+ } else {
+ v4l2src->v4l2object->next_pushed_frame_1000x =
+ v4l2src->v4l2object->next_pushed_frame_1000x -
+ v4l2src->v4l2object->pushed_frame_count_1000x +
+ v4l2src->v4l2object->push_rate_1000x;
+ v4l2src->v4l2object->pushed_frame_count_1000x = 0;
+ }
+ }
+
if (v4l2src->frame_byte_size > 0) {
size = GST_BUFFER_SIZE (temp);
diff --git a/sys/v4l2/v4l2src_calls.c b/sys/v4l2/v4l2src_calls.c
index b069920..a9853fd 100644
--- a/sys/v4l2/v4l2src_calls.c
+++ b/sys/v4l2/v4l2src_calls.c
@@ -90,6 +90,25 @@ queue_failed:
}
}
+/* Greatest common divisor */
+static guint32
+gst_v4l2src_gcd(guint32 a, guint32 b)
+{
+ guint32 r;
+
+ if (a < b) {
+ guint32 t = a;
+ a = b;
+ b = t;
+ }
+ while ((r = a % b) != 0) {
+ a = b;
+ b = r;
+ }
+ return b;
+}
+
+
/******************************************************
* gst_v4l2src_grab_frame ():
* grab a frame for capturing
@@ -135,8 +154,10 @@ gst_v4l2src_grab_frame (GstV4l2Src * v4l2src, GstBuffer ** buf)
}
pool_buffer = GST_BUFFER (gst_v4l2_buffer_pool_dqbuf (pool));
- if (pool_buffer)
+ if (pool_buffer) {
+ v4l2src->v4l2object->pushed_frame_count_1000x += 1000;
break;
+ }
GST_WARNING_OBJECT (pool->v4l2elem, "trials=%d", trials);
@@ -248,6 +269,8 @@ gst_v4l2src_set_capture (GstV4l2Src * v4l2src, guint32 pixelformat,
goto done;
}
+ /* We can't trust the frame rate reported by DM6467[T] driver */
+ #if !defined(Platform_dm6467) && !defined(Platform_dm6467t)
/* Note: V4L2 provides the frame interval, we have the frame rate */
if (fractions_are_equal (stream.parm.capture.timeperframe.numerator,
stream.parm.capture.timeperframe.denominator, fps_d, fps_n)) {
@@ -256,11 +279,52 @@ gst_v4l2src_set_capture (GstV4l2Src * v4l2src, guint32 pixelformat,
v4l2src->fps_d = fps_d;
goto done;
}
+ #endif
/* We want to change the frame rate, so check whether we can. Some cheap USB
* cameras don't have the capability */
if ((stream.parm.capture.capability & V4L2_CAP_TIMEPERFRAME) == 0) {
+ guint default_n = 0;
+ guint default_d = 0;
+
GST_DEBUG_OBJECT (v4l2src, "Not setting framerate (not supported)");
+
+ /* If we know the default framerate for this device, we can throw away
+ * frames to artifically lower the framerate to the one desired. */
+ #if defined(Platform_dm6467) || defined(Platform_dm6467t)
+ {
+ const guint component_input_id = 1;
+ gint current_input_id;
+
+ gst_v4l2_get_input(v4l2src->v4l2object, ¤t_input_id);
+ if (current_input_id == component_input_id) {
+ default_n = 60;
+ default_d = 1;
+ }
+ }
+ #endif
+
+ if (default_n > 0) {
+ guint32 div_n = default_n * fps_d;
+ guint32 div_d = default_d * fps_n;
+ guint32 div_gcd = gst_v4l2src_gcd(div_n, div_d);
+ guint32 push_rate_1000x;
+
+ div_n /= div_gcd;
+ div_d /= div_gcd;
+
+ push_rate_1000x = (div_n * 1000) / div_d;
+
+ /* For every push_rate frames captured, push 1 downstream */
+ if (push_rate_1000x > 1000) {
+ GST_LOG_OBJECT (v4l2src, "A frame rate of %u/%u will be simulated "
+ "by only pushing 1 of every %2.4lf captured frames downstream",
+ fps_n, fps_d, push_rate_1000x / ((gdouble)1000));
+ v4l2src->v4l2object->push_rate_1000x = push_rate_1000x;
+ v4l2src->v4l2object->next_pushed_frame_1000x = push_rate_1000x;
+ }
+ }
+
goto done;
}
--
1.7.1
|
