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Wait for a frame to become available before capturing it

Browse source 
Use GstPoll to wait for the fd of the video device to become readable before
trying to capture a frame. This speeds up stopping v4l2src a lot as it no
longer has to wait for the next frame, especially when capturing with low
framerates or when the video device just never generates a frame (which seems a
common issue for uvcvideo devices)

Fixes bug #563574.
This commit is contained in:
Sjoerd Simons 2009-03-01 19:55:26 +01:00 committed by Sebastian Dröge
parent 7087da96dc
commit b6755a7000
5 changed files with 95 additions and 2 deletions
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4
sys/v4l2/gstv4l2object.c
View file

@ -270,6 +270,7 @@ gst_v4l2_object_new (GstElement * element,
v4l2object->update_fps_func = update_fps_func;
v4l2object->video_fd = -1;
v4l2object->poll = gst_poll_new (TRUE);
v4l2object->buffer = NULL;
v4l2object->videodev = g_strdup (DEFAULT_PROP_DEVICE);
@ -290,6 +291,9 @@ gst_v4l2_object_destroy (GstV4l2Object * v4l2object)
if (v4l2object->videodev)
g_free (v4l2object->videodev);
if (v4l2object->poll)
gst_poll_free (v4l2object->poll);
if (v4l2object->channel)
g_free (v4l2object->channel);

1
sys/v4l2/gstv4l2object.h
View file

@ -71,6 +71,7 @@ struct _GstV4l2Object {
/* the video-device's file descriptor */
gint video_fd;
GstPoll * poll;
/* the video buffer (mmap()'ed) */
guint8 **buffer;

53
sys/v4l2/gstv4l2src.c
View file

@ -240,6 +240,10 @@ static void gst_v4l2src_finalize (GstV4l2Src * v4l2src);
/* basesrc methods */
static gboolean gst_v4l2src_start (GstBaseSrc * src);
static gboolean gst_v4l2src_unlock (GstBaseSrc * src);
static gboolean gst_v4l2src_unlock_stop (GstBaseSrc * src);
static gboolean gst_v4l2src_stop (GstBaseSrc * src);
static gboolean gst_v4l2src_set_caps (GstBaseSrc * src, GstCaps * caps);
@ -312,6 +316,8 @@ gst_v4l2src_class_init (GstV4l2SrcClass * klass)
basesrc_class->get_caps = GST_DEBUG_FUNCPTR (gst_v4l2src_get_caps);
basesrc_class->set_caps = GST_DEBUG_FUNCPTR (gst_v4l2src_set_caps);
basesrc_class->start = GST_DEBUG_FUNCPTR (gst_v4l2src_start);
basesrc_class->unlock = GST_DEBUG_FUNCPTR (gst_v4l2src_unlock);
basesrc_class->unlock_stop = GST_DEBUG_FUNCPTR (gst_v4l2src_unlock_stop);
basesrc_class->stop = GST_DEBUG_FUNCPTR (gst_v4l2src_stop);
basesrc_class->query = GST_DEBUG_FUNCPTR (gst_v4l2src_query);
basesrc_class->fixate = GST_DEBUG_FUNCPTR (gst_v4l2src_fixate);
@ -1175,6 +1181,29 @@ gst_v4l2src_start (GstBaseSrc * src)
return TRUE;
}
static gboolean
gst_v4l2src_unlock (GstBaseSrc * src)
{
GstV4l2Src *v4l2src = GST_V4L2SRC (src);
GST_LOG_OBJECT (src, "Flushing");
gst_poll_set_flushing (v4l2src->v4l2object->poll, TRUE);
return TRUE;
}
static gboolean
gst_v4l2src_unlock_stop (GstBaseSrc * src)
{
GstV4l2Src *v4l2src = GST_V4L2SRC (src);
GST_LOG_OBJECT (src, "No longer flushing");
gst_poll_set_flushing (v4l2src->v4l2object->poll, FALSE);
return TRUE;
}
static gboolean
gst_v4l2src_stop (GstBaseSrc * src)
{
@ -1203,6 +1232,7 @@ static GstFlowReturn
gst_v4l2src_get_read (GstV4l2Src * v4l2src, GstBuffer ** buf)
{
gint amount;
gint ret;
gint buffersize;
@ -1211,6 +1241,18 @@ gst_v4l2src_get_read (GstV4l2Src * v4l2src, GstBuffer ** buf)
*buf = gst_buffer_new_and_alloc (buffersize);
do {
ret = gst_poll_wait (v4l2src->v4l2object->poll, GST_CLOCK_TIME_NONE);
if (G_UNLIKELY (ret < 0)) {
if (errno == EBUSY)
goto stopped;
#ifdef G_OS_WIN32
if (WSAGetLastError () != WSAEINTR)
goto select_error;
#else
if (errno != EAGAIN && errno != EINTR)
goto select_error;
#endif
}
amount =
v4l2_read (v4l2src->v4l2object->video_fd, GST_BUFFER_DATA (*buf),
buffersize);
@ -1270,6 +1312,17 @@ gst_v4l2src_get_read (GstV4l2Src * v4l2src, GstBuffer ** buf)
return GST_FLOW_OK;
/* ERRORS */
select_error:
{
GST_ELEMENT_ERROR (v4l2src, RESOURCE, READ, (NULL),
("select error %d: %s (%d)", ret, g_strerror (errno), errno));
return GST_FLOW_ERROR;
}
stopped:
{
GST_DEBUG ("stop called");
return GST_FLOW_WRONG_STATE;
}
read_error:
{
GST_ELEMENT_ERROR (v4l2src, RESOURCE, READ,

8
sys/v4l2/v4l2_calls.c
View file

@ -400,6 +400,7 @@ gst_v4l2_open (GstV4l2Object * v4l2object)
{
struct stat st;
int libv4l2_fd;
GstPollFD pollfd = GST_POLL_FD_INIT;
GST_DEBUG_OBJECT (v4l2object->element, "Trying to open device %s",
v4l2object->videodev);
@ -453,6 +454,10 @@ gst_v4l2_open (GstV4l2Object * v4l2object)
"Opened device '%s' (%s) successfully",
v4l2object->vcap.card, v4l2object->videodev);
pollfd.fd = v4l2object->video_fd;
gst_poll_add_fd (v4l2object->poll, &pollfd);
gst_poll_fd_ctl_read (v4l2object->poll, &pollfd, TRUE);
return TRUE;
/* ERRORS */
@ -508,6 +513,7 @@ error:
gboolean
gst_v4l2_close (GstV4l2Object * v4l2object)
{
GstPollFD pollfd = GST_POLL_FD_INIT;
GST_DEBUG_OBJECT (v4l2object->element, "Trying to close %s",
v4l2object->videodev);
@ -516,6 +522,8 @@ gst_v4l2_close (GstV4l2Object * v4l2object)
/* close device */
v4l2_close (v4l2object->video_fd);
pollfd.fd = v4l2object->video_fd;
gst_poll_remove_fd (v4l2object->poll, &pollfd);
v4l2object->video_fd = -1;
/* empty lists */

31
sys/v4l2/v4l2src_calls.c
View file

@ -976,7 +976,7 @@ default_frame_sizes:
/******************************************************
* gst_v4l2src_grab_frame ():
* grab a frame for capturing
* return value: GST_FLOW_OK or GST_FLOW_ERROR
* return value: GST_FLOW_OK, GST_FLOW_WRONG_STATE or GST_FLOW_ERROR
******************************************************/
GstFlowReturn
gst_v4l2src_grab_frame (GstV4l2Src * v4l2src, GstBuffer ** buf)
@ -987,12 +987,28 @@ gst_v4l2src_grab_frame (GstV4l2Src * v4l2src, GstBuffer ** buf)
GstBuffer *pool_buffer;
gboolean need_copy;
gint index;
gint ret;
memset (&buffer, 0x00, sizeof (buffer));
buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buffer.memory = V4L2_MEMORY_MMAP;
while (v4l2_ioctl (v4l2src->v4l2object->video_fd, VIDIOC_DQBUF, &buffer) < 0) {
for (;;) {
ret = gst_poll_wait (v4l2src->v4l2object->poll, GST_CLOCK_TIME_NONE);
if (G_UNLIKELY (ret < 0)) {
if (errno == EBUSY)
goto stopped;
#ifdef G_OS_WIN32
if (WSAGetLastError () != WSAEINTR)
goto select_error;
#else
if (errno != EAGAIN && errno != EINTR)
goto select_error;
#endif
}
if (v4l2_ioctl (v4l2src->v4l2object->video_fd, VIDIOC_DQBUF, &buffer) >= 0)
break;
GST_WARNING_OBJECT (v4l2src,
"problem grabbing frame %d (ix=%d), trials=%d, pool-ct=%d, buf.flags=%d",
@ -1135,6 +1151,17 @@ gst_v4l2src_grab_frame (GstV4l2Src * v4l2src, GstBuffer ** buf)
return GST_FLOW_OK;
/* ERRORS */
select_error:
{
GST_ELEMENT_ERROR (v4l2src, RESOURCE, READ, (NULL),
("select error %d: %s (%d)", ret, g_strerror (errno), errno));
return GST_FLOW_ERROR;
}
stopped:
{
GST_DEBUG ("stop called");
return GST_FLOW_WRONG_STATE;
}
einval:
{
GST_ELEMENT_ERROR (v4l2src, RESOURCE, FAILED,