this adds video4linux2 source and element plugins. The division in v4l2* plugins is the same as for v4l1 - i.e. an el...

Original commit message from CVS:
this adds video4linux2 source and element plugins. The division in v4l2* plugins is the same as for v4l1 - i.e. an element, a src and a sink, but there won't be separate encoding plugins (like v4lmjpegsrc) - all functionality is (thanks to video4linux2) integrated in one plugin: v4l2src. v4l2sink is still to be done, that'll come later.

1 files changed, 863 insertions, 0 deletions

diff --git a/sys/v4l2/v4l2_calls.c b/sys/v4l2/v4l2_calls.c
new file mode 100644
index 00000000..c24d0e4d
--- /dev/null
+++ b/sys/v4l2/v4l2_calls.c
@@ -0,0 +1,863 @@
+/* G-Streamer generic V4L2 element - generic V4L2 calls handling
+ * Copyright (C) 2002 Ronald Bultje <rbultje@ronald.bitfreak.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <string.h>
+#include <errno.h>
+#include "v4l2_calls.h"
+
+#define DEBUG(format, args...) \
+	GST_DEBUG_ELEMENT(GST_CAT_PLUGIN_INFO, \
+		GST_ELEMENT(v4l2element), \
+		"V4L2: " format "\n", ##args)
+
+
+/******************************************************
+ * gst_v4l2_get_capabilities():
+ *   get the device's capturing capabilities
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+static gboolean
+gst_v4l2_get_capabilities (GstV4l2Element *v4l2element)
+{
+	DEBUG("getting capabilities");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_QUERYCAP, &(v4l2element->vcap)) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Error getting %s capabilities: %s",
+			v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_empty_lists() and gst_v4l2_fill_lists():
+ *   fill/empty the lists of enumerations
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+static gboolean
+gst_v4l2_fill_lists (GstV4l2Element *v4l2element)
+{
+	gint n;
+
+	DEBUG("getting enumerations");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	/* create enumeration lists - let's start with format enumeration */
+	for (n=0;;n++) {
+		struct v4l2_fmtdesc format, *fmtptr;
+		format.index = n;
+		if (ioctl(v4l2element->video_fd, VIDIOC_ENUM_PIXFMT, &format) < 0) {
+			if (errno == EINVAL)
+				break; /* end of enumeration */
+			else {
+				gst_element_error(GST_ELEMENT(v4l2element),
+					"Failed to get no. %d in pixelformat enumeration for %s: %s",
+					n, v4l2element->device, sys_errlist[errno]);
+				return FALSE;
+			}
+		}
+		fmtptr = g_malloc(sizeof(format));
+		memcpy(fmtptr, &format, sizeof(format));
+		v4l2element->formats = g_list_append(v4l2element->formats, fmtptr);
+	}
+
+	/* and now, the inputs */
+	for (n=0;;n++) {
+		struct v4l2_input input, *inpptr;
+		input.index = n;
+		if (ioctl(v4l2element->video_fd, VIDIOC_ENUMINPUT, &input) < 0) {
+			if (errno == EINVAL)
+				break; /* end of enumeration */
+			else {
+				gst_element_error(GST_ELEMENT(v4l2element),
+					"Failed to get no. %d in input enumeration for %s: %s",
+					n, v4l2element->device, sys_errlist[errno]);
+				return FALSE;
+			}
+		}
+		inpptr = g_malloc(sizeof(input));
+		memcpy(inpptr, &input, sizeof(input));
+		v4l2element->inputs = g_list_append(v4l2element->inputs, inpptr);
+	}
+
+	/* outputs */
+	for (n=0;;n++) {
+		struct v4l2_output output, *outptr;
+		output.index = n;
+		if (ioctl(v4l2element->video_fd, VIDIOC_ENUMOUTPUT, &output) < 0) {
+			if (errno == EINVAL)
+				break; /* end of enumeration */
+			else {
+				gst_element_error(GST_ELEMENT(v4l2element),
+					"Failed to get no. %d in output enumeration for %s: %s",
+					n, v4l2element->device, sys_errlist[errno]);
+				return FALSE;
+			}
+		}
+		outptr = g_malloc(sizeof(output));
+		memcpy(outptr, &output, sizeof(output));
+		v4l2element->outputs = g_list_append(v4l2element->outputs, outptr);
+	}
+
+	/* norms... */
+	for (n=0;;n++) {
+		struct v4l2_enumstd standard, *stdptr;
+		standard.index = n;
+		if (ioctl(v4l2element->video_fd, VIDIOC_ENUMSTD, &standard) < 0) {
+			if (errno == EINVAL)
+				break; /* end of enumeration */
+			else {
+				gst_element_error(GST_ELEMENT(v4l2element),
+					"Failed to get no. %d in norm enumeration for %s: %s",
+					n, v4l2element->device, sys_errlist[errno]);
+				return FALSE;
+			}
+		}
+		stdptr = g_malloc(sizeof(standard));
+		memcpy(stdptr, &standard, sizeof(standard));
+		v4l2element->norms = g_list_append(v4l2element->norms, stdptr);
+	}
+
+	/* and lastly, controls+menus (if appropriate) */
+	for (n=0;;n++) {
+		struct v4l2_queryctrl control, *ctrlptr;
+		GList *menus = NULL;
+		control.id = n;
+		if (ioctl(v4l2element->video_fd, VIDIOC_QUERYCTRL, &control) < 0) {
+			if (errno == EINVAL)
+				break; /* end of enumeration */
+			else {
+				gst_element_error(GST_ELEMENT(v4l2element),
+					"Failed to get no. %d in control enumeration for %s: %s",
+					n, v4l2element->device, sys_errlist[errno]);
+				return FALSE;
+			}
+		}
+		ctrlptr = g_malloc(sizeof(control));
+		memcpy(ctrlptr, &control, sizeof(control));
+		v4l2element->controls = g_list_append(v4l2element->controls, ctrlptr);
+		if (control.type == V4L2_CTRL_TYPE_MENU) {
+			struct v4l2_querymenu menu, *mptr;
+			int i;
+			menu.id = n;
+			for (i=0;;i++) {
+				menu.index = i;
+				if (ioctl(v4l2element->video_fd, VIDIOC_QUERYMENU, &menu) < 0) {
+					if (errno == EINVAL)
+						break; /* end of enumeration */
+					else {
+						gst_element_error(GST_ELEMENT(v4l2element),
+							"Failed to get no. %d in menu %d enumeration for %s: %s",
+							i, n, v4l2element->device, sys_errlist[errno]);
+						return FALSE;
+					}
+				}
+				mptr = g_malloc(sizeof(menu));
+				memcpy(mptr, &menu, sizeof(menu));
+				menus = g_list_append(menus, mptr);
+			}
+		}
+		v4l2element->menus = g_list_append(v4l2element->menus, menus);
+	}
+
+	return TRUE;
+}
+
+
+static void
+gst_v4l2_empty_lists (GstV4l2Element *v4l2element)
+{
+	DEBUG("deleting enumerations");
+
+	/* empty lists */
+	while (g_list_length(v4l2element->inputs) > 0) {
+		gpointer data = g_list_nth_data(v4l2element->inputs, 0);
+		v4l2element->inputs = g_list_remove(v4l2element->inputs, data);
+		g_free(data);
+	}
+	while (g_list_length(v4l2element->outputs) > 0) {
+		gpointer data = g_list_nth_data(v4l2element->outputs, 0);
+		v4l2element->outputs = g_list_remove(v4l2element->outputs, data);
+		g_free(data);
+	}
+	while (g_list_length(v4l2element->norms) > 0) {
+		gpointer data = g_list_nth_data(v4l2element->norms, 0);
+		v4l2element->norms = g_list_remove(v4l2element->norms, data);
+		g_free(data);
+	}
+	while (g_list_length(v4l2element->formats) > 0) {
+		gpointer data = g_list_nth_data(v4l2element->formats, 0);
+		v4l2element->formats = g_list_remove(v4l2element->formats, data);
+		g_free(data);
+	}
+	while (g_list_length(v4l2element->controls) > 0) {
+		gpointer data = g_list_nth_data(v4l2element->controls, 0);
+		v4l2element->controls = g_list_remove(v4l2element->controls, data);
+		g_free(data);
+	}
+	v4l2element->menus = g_list_remove_all(v4l2element->menus, NULL);
+	while (g_list_length(v4l2element->menus) > 0) {
+		GList *items = (GList *) g_list_nth_data(v4l2element->menus, 0);
+		v4l2element->inputs = g_list_remove(v4l2element->inputs, items);
+		while (g_list_length(items) > 0) {
+			gpointer data = g_list_nth_data(v4l2element->menus, 0);
+			items = g_list_remove(items, data);
+			g_free(data);
+		}
+	}
+}
+
+
+/******************************************************
+ * gst_v4l2_open():
+ *   open the video device (v4l2element->device)
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_open (GstV4l2Element *v4l2element)
+{
+	DEBUG("Trying to open device %s", v4l2element->device);
+	GST_V4L2_CHECK_NOT_OPEN(v4l2element);
+	GST_V4L2_CHECK_NOT_ACTIVE(v4l2element);
+
+	/* be sure we have a device */
+	if (!v4l2element->device)
+		v4l2element->device = g_strdup("/dev/video");
+
+	/* open the device */
+	v4l2element->video_fd = open(v4l2element->device, O_RDWR);
+	if (!GST_V4L2_IS_OPEN(v4l2element)) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to open device %s: %s",
+			v4l2element->device, sys_errlist[errno]);
+		goto error;
+	}
+
+	/* get capabilities */
+	if (!gst_v4l2_get_capabilities(v4l2element)) {
+		goto error;
+	}
+
+	/* and get the video window */
+	if (GST_V4L2_IS_OVERLAY(v4l2element)) {
+		if (ioctl(v4l2element->video_fd, VIDIOC_G_WIN, &(v4l2element->vwin)) < 0) {
+			gst_element_error(GST_ELEMENT(v4l2element),
+				"Failed to get video window properties of %s: %s",
+				v4l2element->device, sys_errlist[errno]);
+			goto error;
+		}
+	}
+
+	/* create enumerations */
+	if (!gst_v4l2_fill_lists(v4l2element))
+		goto error;
+
+	gst_info("Opened device '%s' (%s) successfully\n",
+		v4l2element->vcap.name, v4l2element->device);
+
+	return TRUE;
+
+error:
+	if (GST_V4L2_IS_OPEN(v4l2element)) {
+		/* close device */
+		close(v4l2element->video_fd);
+		v4l2element->video_fd = -1;
+	}
+	/* empty lists */
+	gst_v4l2_empty_lists(v4l2element);
+
+	return FALSE;
+}
+
+
+/******************************************************
+ * gst_v4l2_close():
+ *   close the video device (v4l2element->video_fd)
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_close (GstV4l2Element *v4l2element)
+{
+	DEBUG("Trying to close %s", v4l2element->device);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+	GST_V4L2_CHECK_NOT_ACTIVE(v4l2element);
+
+	/* close device */
+	close(v4l2element->video_fd);
+	v4l2element->video_fd = -1;
+
+	/* empty lists */
+	gst_v4l2_empty_lists(v4l2element);
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_get_norm()
+ *   Get the norm of the current device
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_get_norm (GstV4l2Element *v4l2element,
+                   gint           *norm)
+{
+	struct v4l2_standard standard;
+	gint n;
+
+	DEBUG("getting norm");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_STD, &standard) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to get the current norm for device %s: %s",
+			v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	/* try to find out what norm number this actually is */
+	for (n=0;n<g_list_length(v4l2element->norms);n++) {
+		struct v4l2_enumstd *stdptr = (struct v4l2_enumstd *) g_list_nth_data(v4l2element->norms, n);
+		if (!strcmp(stdptr->std.name, standard.name)) {
+			*norm = n;
+			return TRUE;
+		}
+	}
+
+	gst_element_error(GST_ELEMENT(v4l2element),
+		"Failed to find norm '%s' in our list of available norms for device %s",
+		standard.name, v4l2element->device);
+	return FALSE;
+}
+
+
+/******************************************************
+ * gst_v4l2_set_norm()
+ *   Set the norm of the current device
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_set_norm (GstV4l2Element *v4l2element,
+                   gint            norm)
+{
+	struct v4l2_enumstd *standard;
+
+	DEBUG("trying to set norm to %d", norm);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+	GST_V4L2_CHECK_NOT_ACTIVE(v4l2element);
+
+	if (norm < 0 || norm >= g_list_length(v4l2element->norms)) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Invalid norm number %d (%d-%d)",
+			norm, 0, g_list_length(v4l2element->norms));
+		return FALSE;
+	}
+
+	standard = (struct v4l2_enumstd *) g_list_nth_data(v4l2element->norms, norm);
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_S_STD, &standard->std) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to set norm '%s' (%d) for device %s: %s",
+			standard->std.name, norm, v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_get_norm_names()
+ *   Get the list of available norms
+ * return value: the list
+ ******************************************************/
+
+GList *
+gst_v4l2_get_norm_names (GstV4l2Element *v4l2element)
+{
+	GList *names = NULL;
+	gint n;
+
+	DEBUG("getting a list of norm names");
+
+	for (n=0;n<g_list_length(v4l2element->norms);n++) {
+		struct v4l2_enumstd *standard = (struct v4l2_enumstd *) g_list_nth_data(v4l2element->norms, n);
+		names = g_list_append(names, g_strdup(standard->std.name));
+	}
+
+	return names;
+}
+
+
+/******************************************************
+ * gst_v4l2_get_input()
+ *   Get the input of the current device
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_get_input (GstV4l2Element *v4l2element,
+                    gint           *input)
+{
+	gint n;
+
+	DEBUG("trying to get input");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_INPUT, &n) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to get current input on device %s: %s",
+			v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	*input = n;
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_set_input()
+ *   Set the input of the current device
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_set_input (GstV4l2Element *v4l2element,
+                    gint            input)
+{
+	DEBUG("trying to set input to %d", input);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+	GST_V4L2_CHECK_NOT_ACTIVE(v4l2element);
+
+	if (input < 0 || input >= g_list_length(v4l2element->inputs)) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Invalid input number %d (%d-%d)",
+			input, 0, g_list_length(v4l2element->inputs));
+		return FALSE;
+	}
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_S_INPUT, &input) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to set input %d on device %s: %s",
+			input, v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_get_input_names()
+ *   Get the list of available input channels
+ * return value: the list
+ ******************************************************/
+
+GList *
+gst_v4l2_get_input_names (GstV4l2Element *v4l2element)
+{
+	GList *names = NULL;
+	gint n;
+
+	DEBUG("getting a list of input names");
+
+	for (n=0;n<g_list_length(v4l2element->inputs);n++) {
+		struct v4l2_input *input = (struct v4l2_input *) g_list_nth_data(v4l2element->inputs, n);
+		names = g_list_append(names, g_strdup(input->name));
+	}
+
+	return names;
+}
+
+
+/******************************************************
+ * gst_v4l2_get_output()
+ *   Get the output of the current device
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_get_output (GstV4l2Element *v4l2element,
+                     gint           *output)
+{
+	gint n;
+
+	DEBUG("trying to get output");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_OUTPUT, &n) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to get current output on device %s: %s",
+			v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	*output = n;
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_set_output()
+ *   Set the output of the current device
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_set_output (GstV4l2Element *v4l2element,
+                     gint            output)
+{
+	DEBUG("trying to set output to %d", output);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+	GST_V4L2_CHECK_NOT_ACTIVE(v4l2element);
+
+	if (output < 0 || output >= g_list_length(v4l2element->outputs)) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Invalid output number %d (%d-%d)",
+			output, 0, g_list_length(v4l2element->outputs));
+		return FALSE;
+	}
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_S_OUTPUT, &output) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to set output %d on device %s: %s",
+			output, v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l2_get_output_names()
+ *   Get the list of available output channels
+ * return value: the list, or NULL on error
+ ******************************************************/
+
+GList *
+gst_v4l2_get_output_names (GstV4l2Element *v4l2element)
+{
+	GList *names = NULL;
+	gint n;
+
+	DEBUG("getting a list of output names");
+
+	for (n=0;n<g_list_length(v4l2element->outputs);n++) {
+		struct v4l2_output *output = (struct v4l2_output *) g_list_nth_data(v4l2element->outputs, n);
+		names = g_list_append(names, g_strdup(output->name));
+	}
+
+	return names;
+}
+
+
+/******************************************************
+ * gst_v4l_has_tuner():
+ *   Check whether the device has a tuner
+ * return value: TRUE if it has a tuner, else FALSE
+ ******************************************************/
+
+gboolean
+gst_v4l2_has_tuner (GstV4l2Element *v4l2element)
+{
+	gint input_num;
+	struct v4l2_input *input;
+
+	DEBUG("detecting whether device has a tuner");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (!gst_v4l2_get_input(v4l2element, &input_num))
+		return FALSE;
+
+	input = (struct v4l2_input *) g_list_nth_data(v4l2element->inputs, input_num);
+
+	return (input->type == V4L2_INPUT_TYPE_TUNER &&
+	        v4l2element->vcap.flags & V4L2_FLAG_TUNER);
+}
+
+
+/******************************************************
+ * gst_v4l_get_frequency():
+ *   get the current frequency
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_get_frequency (GstV4l2Element *v4l2element,
+                        gulong         *frequency)
+{
+	gint n;
+
+	DEBUG("getting current tuner frequency");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (!gst_v4l2_has_tuner(v4l2element))
+		return FALSE;
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_FREQ, &n) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to get current tuner frequency for device %s: %s",
+			v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	*frequency = n;
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l_set_frequency():
+ *   set frequency
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_set_frequency (GstV4l2Element *v4l2element,
+                        gulong          frequency)
+{
+	gint n = frequency;
+
+	DEBUG("setting current tuner frequency to %lu", frequency);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+	GST_V4L2_CHECK_NOT_ACTIVE(v4l2element);
+
+	if (!gst_v4l2_has_tuner(v4l2element))
+		return FALSE;
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_FREQ, &n) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to set tuner frequency to %lu for device %s: %s",
+			frequency, v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l_signal_strength():
+ *   get the strength of the signal on the current input
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_signal_strength (GstV4l2Element *v4l2element,
+                          gulong         *signal_strength)
+{
+	struct v4l2_tuner tuner;
+
+	DEBUG("trying to get signal strength");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_TUNER, &tuner) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to set signal strength for device %s: %s",
+			v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	*signal_strength = tuner.signal;
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l_has_audio():
+ *   Check whether the device has audio capabilities
+ * return value: TRUE if it has a tuner, else FALSE
+ ******************************************************/
+
+gboolean
+gst_v4l2_has_audio (GstV4l2Element *v4l2element)
+{
+	gint input_num;
+	struct v4l2_input *input;
+
+	DEBUG("detecting whether device has audio");
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (!gst_v4l2_get_input(v4l2element, &input_num))
+		return FALSE;
+
+	input = (struct v4l2_input *) g_list_nth_data(v4l2element->inputs, input_num);
+
+	return (input->capability & V4L2_INPUT_CAP_AUDIO);
+}
+
+
+/******************************************************
+ * gst_v4l_get_attributes():
+ *   get a list of attributes available on this device
+ * return value: the list
+ ******************************************************/
+
+GList *
+gst_v4l2_get_attributes	(GstV4l2Element *v4l2element)
+{
+	gint i;
+	GList *list = NULL;
+
+	DEBUG("getting a list of available attributes");
+
+	for (i=0;i<g_list_length(v4l2element->controls);i++) {
+		struct v4l2_queryctrl *control = (struct v4l2_queryctrl *) g_list_nth_data(v4l2element->controls, i);
+		GstV4l2Attribute* attribute = g_malloc(sizeof(GstV4l2Attribute));
+		attribute->name = g_strdup(control->name);
+		attribute->index = i;
+		attribute->list_items = NULL;
+		switch (control->type) {
+			case V4L2_CTRL_TYPE_INTEGER:
+				attribute->val_type = GST_V4L2_ATTRIBUTE_VALUE_TYPE_INT;
+				break;
+			case V4L2_CTRL_TYPE_BOOLEAN:
+				attribute->val_type = GST_V4L2_ATTRIBUTE_VALUE_TYPE_BOOLEAN;
+				break;
+			case V4L2_CTRL_TYPE_MENU: {
+				/* list items */
+				gint n;
+				GList *menus = (GList *) g_list_nth_data(v4l2element->menus, i);
+				for (n=0;n<g_list_length(menus);n++) {
+					struct v4l2_querymenu *menu = g_list_nth_data(menus, n);
+					attribute->list_items = g_list_append(attribute->list_items, g_strdup(menu->name));
+				}
+				attribute->val_type = GST_V4L2_ATTRIBUTE_VALUE_TYPE_LIST;
+				break; }
+			case V4L2_CTRL_TYPE_BUTTON:
+				attribute->val_type = GST_V4L2_ATTRIBUTE_VALUE_TYPE_BUTTON;
+				break;
+		}
+		switch (control->category) {
+			case V4L2_CTRL_CAT_VIDEO:
+				attribute->type = GST_V4L2_ATTRIBUTE_TYPE_VIDEO;
+				break;
+			case V4L2_CTRL_CAT_AUDIO:
+				attribute->type = GST_V4L2_ATTRIBUTE_TYPE_AUDIO;
+				break;
+			case V4L2_CTRL_CAT_EFFECT:
+				attribute->type = GST_V4L2_ATTRIBUTE_TYPE_EFFECT;
+				break;
+		}
+		gst_v4l2_get_attribute(v4l2element, i, &attribute->value);
+		attribute->min = control->minimum;
+		attribute->max = control->maximum;
+	}
+
+	return list;
+}
+
+
+/******************************************************
+ * gst_v4l_get_attribute():
+ *   try to get the value of one specific attribute
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_get_attribute	(GstV4l2Element *v4l2element,
+                         gint            attribute_num,
+                         gint           *value)
+{
+	struct v4l2_control control;
+
+	DEBUG("getting value of attribute %d", attribute_num);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (attribute_num < 0 || attribute_num >= g_list_length(v4l2element->controls)) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Invalid control ID %d", attribute_num);
+		return FALSE;
+	}
+
+	control.id = attribute_num;
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_G_CTRL, &control) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to get value for control %d on device %s: %s",
+			attribute_num, v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	*value = control.value;
+
+	return TRUE;
+}
+
+
+/******************************************************
+ * gst_v4l_set_attribute():
+ *   try to set the value of one specific attribute
+ * return value: TRUE on success, FALSE on error
+ ******************************************************/
+
+gboolean
+gst_v4l2_set_attribute	(GstV4l2Element *v4l2element,
+                         gint            attribute_num,
+                         gint            value)
+{
+	struct v4l2_control control;
+
+	DEBUG("setting value of attribute %d to %d", attribute_num, value);
+	GST_V4L2_CHECK_OPEN(v4l2element);
+
+	if (attribute_num < 0 || attribute_num >= g_list_length(v4l2element->controls)) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Invalid control ID %d", attribute_num);
+		return FALSE;
+	}
+
+	control.id = attribute_num;
+	control.value = value;
+
+	if (ioctl(v4l2element->video_fd, VIDIOC_S_CTRL, &control) < 0) {
+		gst_element_error(GST_ELEMENT(v4l2element),
+			"Failed to set value %d for control %d on device %s: %s",
+			value, attribute_num, v4l2element->device, sys_errlist[errno]);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+