Documentation/Maemo 5 Developer Guide/Using Multimedia Components/Camera API Usage - Revision history

imported_>amigadave: use


2010-08-17T09:49:46Z
use <code>

				
				
				
				
				
				← Older revision
				Revision as of 09:49, 17 August 2010
				
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Data exchanged between the device file and user-level application has a standardized format for each device class. This allows the application to be instantly compatible with every video capture device that has a driver for Linux. Data exchanged between the device file and user-level application has a standardized format for each device class. This allows the application to be instantly compatible with every video capture device that has a driver for Linux.



The built-in cameras present in Maemo devices are compatible with [http://linux.bytesex.org/v4l2/ Video-4-Linux version 2 API]. In principle, any application compatible with this API is easily portable to the maemo platform. The built-in cameras present in Maemo devices are compatible with [http://linux.bytesex.org/v4l2/ Video-4-Linux version 2 API]. In principle, any application compatible with this API is easily portable to the Maemo platform.



Since the Maemo platform delegates all multimedia handling to the GStreamer framework, applications that need access to the built-in camera should employ GStreamer for this, instead of directly accessing Video4Linux devices, via the <code>v4l2src</code> GStreamer module. Since the Maemo platform delegates all multimedia handling to the GStreamer framework, applications that need access to the built-in camera should employ GStreamer for this, instead of directly accessing Video4Linux devices, via the <code>v4l2src</code> GStreamer module.
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One important note about the camera in the maemo device: only one application can use it at any given time. So, while using the camera in an application, other tasks that could possibly make use of it (e.g. a video call) will be blocked. One important note about the camera in the maemo device: only one application can use it at any given time. So, while using the camera in an application, other tasks that could possibly make use of it (e.g. a video call) will be blocked.



To ease developing an application that does video recording and still image capture, a high level gstreamer element has been developed. CameraBin follows the idea behind other high level elements like playbin2. One can add capture support to an application without the need to deal with the lowlevel media-processing graph. To ease developing an application that does video recording and still image capture, a high level gstreamer element has been developed. CameraBin follows the idea behind other high level elements like <code>playbin2</code>. One can add capture support to an application without the need to deal with the lowlevel media-processing graph.



To demonstrate how the camera manipulation is performed, a low-level example application is provided and discussed. To demonstrate how the camera manipulation is performed, a low-level example application is provided and discussed.




==Camera Manipulation in C Language == ==Camera Manipulation in C Language ==



imported_>amigadave: wikify slightly, use  and 

2010-07-23T12:48:33Z
wikify slightly, use <source> and <code>
Show changes


imported_>amigadave: categorise
2010-02-12T12:55:34Z
categorise

				
				
				
				
				
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				Revision as of 12:55, 12 February 2010
				
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  	<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>   	<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>
  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>

[[Category:Development]]
[[Category:Documentation]]
[[Category:Fremantle]]



imported_>tapio: /* Camera Manipulation in C Language */
2010-02-11T15:41:03Z
Camera Manipulation in C Language

				
				
				
				
				
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				Revision as of 15:41, 11 February 2010
				
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This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation). This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).



In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>
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Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other. Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.



This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>   <tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>
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  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>



The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):
  <tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>
  <span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>   <span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>
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  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>



The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>



imported_>tapio: /* Camera Manipulation in C Language */
2010-02-11T15:39:11Z
Camera Manipulation in C Language

				
				
				
				
				
				← Older revision
				Revision as of 15:39, 11 February 2010
				
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Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other. Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.



This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>   <tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>
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  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>



The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):
  <tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>
  <span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>   <span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>



imported_>tapio: /* Camera Manipulation in C Language */
2010-02-11T15:37:50Z
Camera Manipulation in C Language

				
				
				
				
				
				← Older revision
				Revision as of 15:37, 11 February 2010
				
Line 27:
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This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation). This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).



In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]): In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>



imported_>dneary at 17:46, 29 December 2009
2009-12-29T17:46:44Z


				
				
				
				
				
				← Older revision
				Revision as of 17:46, 29 December 2009
				
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This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation). This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).



In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows: example_camera.c In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>
Line 45:
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Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other. Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.



This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps: example_camera.c This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>   <tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>
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  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>



The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()''<nowiki>: </nowiki>example_camera.c The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):
  
  <tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>
  <span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>   <span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>
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  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>



The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists: example_camera.c The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):



  <tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>
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  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>



For the sake of completeness, it follows the JPEG encoding function. It is worthwhile to mention that the buffer that came from GStreamer is a simple linear framebuffer: example_camera.c For the sake of completeness, it follows the JPEG encoding function. It is worthwhile to mention that the buffer that came from GStreamer is a simple linear framebuffer ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):
  
  <tt><span>''<span><font color="#9A1900">/* Creates a jpeg file from the buffer's raw image data */</font></span>''</span>   <tt><span>''<span><font color="#9A1900">/* Creates a jpeg file from the buffer's raw image data */</font></span>''</span>
  <span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">create_jpeg</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#009900">unsigned</font></span> <span><font color="#009900">char</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>data<span><font color="#990000">)</font></span>   <span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">create_jpeg</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#009900">unsigned</font></span> <span><font color="#009900">char</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>data<span><font color="#990000">)</font></span>



imported_>bijjal at 15:06, 13 July 2009
2009-07-13T15:06:14Z


				
				
				
				
				
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				Revision as of 15:06, 13 July 2009
				
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  	<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>   	<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>
  <span><font color="#FF0000">}</font></span></tt>   <span><font color="#FF0000">}</font></span></tt>

[[Category:Maemo training material]] 



imported_>danielwilms: 1 revision
2009-07-13T11:45:15Z
1 revision

				
				← Older revision
				Revision as of 11:45, 13 July 2009
				
(No difference)



imported_>wikiadmin: moved Maemo 5 Developer Guide/Using Multimedia Components/Camera API Usage to Documentation/Maemo 5 Developer Guide/Using Multimedia Components/Camera API Usage
2009-07-13T11:40:09Z
moved Maemo 5 Developer Guide/Using Multimedia Components/Camera API Usage to Documentation/Maemo 5 Developer Guide/Using Multimedia Components/Camera API Usage
Show changes

← Older revision		Revision as of 09:49, 17 August 2010
Line 12:		Line 12:
	Data exchanged between the device file and user-level application has a standardized format for each device class. This allows the application to be instantly compatible with every video capture device that has a driver for Linux.		Data exchanged between the device file and user-level application has a standardized format for each device class. This allows the application to be instantly compatible with every video capture device that has a driver for Linux.

	The built-in cameras present in Maemo devices are compatible with [http://linux.bytesex.org/v4l2/ Video-4-Linux version 2 API]. In principle, any application compatible with this API is easily portable to the ~~maemo~~ platform.		The built-in cameras present in Maemo devices are compatible with [http://linux.bytesex.org/v4l2/ Video-4-Linux version 2 API]. In principle, any application compatible with this API is easily portable to the Maemo platform.

	Since the Maemo platform delegates all multimedia handling to the GStreamer framework, applications that need access to the built-in camera should employ GStreamer for this, instead of directly accessing Video4Linux devices, via the <code>v4l2src</code> GStreamer module.		Since the Maemo platform delegates all multimedia handling to the GStreamer framework, applications that need access to the built-in camera should employ GStreamer for this, instead of directly accessing Video4Linux devices, via the <code>v4l2src</code> GStreamer module.
Line 20:		Line 20:
	One important note about the camera in the maemo device: only one application can use it at any given time. So, while using the camera in an application, other tasks that could possibly make use of it (e.g. a video call) will be blocked.		One important note about the camera in the maemo device: only one application can use it at any given time. So, while using the camera in an application, other tasks that could possibly make use of it (e.g. a video call) will be blocked.

	To ease developing an application that does video recording and still image capture, a high level gstreamer element has been developed. CameraBin follows the idea behind other high level elements like playbin2. One can add capture support to an application without the need to deal with the lowlevel media-processing graph.		To ease developing an application that does video recording and still image capture, a high level gstreamer element has been developed. CameraBin follows the idea behind other high level elements like <code>playbin2</code>. One can add capture support to an application without the need to deal with the lowlevel media-processing graph.

	To demonstrate how the camera manipulation is performed, a low-level example application is provided and discussed.		To demonstrate how the camera manipulation is performed, a low-level example application is provided and discussed.


	==Camera Manipulation in C Language ==		==Camera Manipulation in C Language ==

← Older revision		Revision as of 12:55, 12 February 2010
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	<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>		<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

			[[Category:Development]]
			[[Category:Documentation]]
			[[Category:Fremantle]]

← Older revision		Revision as of 15:41, 11 February 2010
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	This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).		This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).

	In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0~~/maemo-examples~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>
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	Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.		Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.

	This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0~~/maemo-examples~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>		<tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>
Line 142:		Line 142:
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0~~/maemo-examples~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):
	<tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>
	<span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>		<span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>
Line 178:		Line 178:
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists ([https://~~garage~~.maemo.org/svn/maemoexamples/~~trunk~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>

← Older revision		Revision as of 15:39, 11 February 2010
Line 45:		Line 45:
	Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.		Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.

	This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://~~garage~~.maemo.org/svn/maemoexamples/~~trunk~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>		<tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>
Line 142:		Line 142:
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://~~garage~~.maemo.org/svn/maemoexamples/~~trunk~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):
	<tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>
	<span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>		<span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>

← Older revision		Revision as of 15:37, 11 February 2010
Line 27:		Line 27:
	This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).		This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).

	In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://~~garage~~.maemo.org/svn/maemoexamples/~~trunk~~/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):		In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://vcs.maemo.org/svn/maemoexamples/tags/maemo_5.0/maemo-examples/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>

← Older revision		Revision as of 17:46, 29 December 2009
Line 27:		Line 27:
	This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).		This C application allows to use the maemo device as a "mirror" (i.e. showing the camera input in the screen), as well as allows to take pictures to be saved as JPEG files (which illustrates the video frame buffer manipulation).

	In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows: example_camera.c		In this example, the function initialize_pipeline() is most interesting, since it is responsible for creating the GStreamer pipeline, sourcing data from Video4Linux and sinking it to a ''xvimagesink'' (which is an optimized X framebuffer). The pipeline scheme is as follows ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* Initialize the the Gstreamer pipeline. Below is a diagram</font></span>''</span>
Line 45:		Line 45:
	Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.		Because there are two sinks, the queues are important, since they guarantee that each pipeline segment operates on its own thread downstream the queue. This ensures that the different sinks can synchronize without waiting for each other.

	This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps: example_camera.c		This sample application is not different from other GStreamer applications, be it Linux-generic or maemo-specific apps ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>		<tt><span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">initialize_pipeline</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#008080">AppData</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>appdata<span><font color="#990000">,</font></span>
Line 142:		Line 142:
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()''~~<nowiki>~~: </~~nowiki>~~example_camera.c		The following function is called back when the user has pressed the "Take photo" button, and the image sink has data. It will forward the image buffer to ''create_jpeg()'' ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* This callback will be registered to the image sink</font></span>''</span>
	<span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>		<span>''<span><font color="#9A1900"> * after user requests a photo */</font></span>''</span>
Line 179:		Line 178:
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists: example_camera.c		The ''xvimagesink'' GStreamer module will normally create a new window just for itself. Since the video is supposed to be shown inside the main application window, the X-Window window ID needs to be passed to the module, as soon as the ID exists ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* Callback to be called when the screen-widget is exposed */</font></span>''</span>
Line 192:		Line 191:
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	For the sake of completeness, it follows the JPEG encoding function. It is worthwhile to mention that the buffer that came from GStreamer is a simple linear framebuffer: example_camera.c		For the sake of completeness, it follows the JPEG encoding function. It is worthwhile to mention that the buffer that came from GStreamer is a simple linear framebuffer ([https://garage.maemo.org/svn/maemoexamples/trunk/maemo-examples/example_camera.c see example_camera.c in maemo-examples]):

	<tt><span>''<span><font color="#9A1900">/* Creates a jpeg file from the buffer's raw image data */</font></span>''</span>		<tt><span>''<span><font color="#9A1900">/* Creates a jpeg file from the buffer's raw image data */</font></span>''</span>
	<span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">create_jpeg</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#009900">unsigned</font></span> <span><font color="#009900">char</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>data<span><font color="#990000">)</font></span>		<span>'''<span><font color="#0000FF">static</font></span>'''</span> <span><font color="#008080">gboolean</font></span> <span>'''<span><font color="#000000">create_jpeg</font></span>'''</span><span><font color="#990000">(</font></span><span><font color="#009900">unsigned</font></span> <span><font color="#009900">char</font></span> <span><font color="#990000"><nowiki>*</nowiki></font></span>data<span><font color="#990000">)</font></span>

← Older revision		Revision as of 15:06, 13 July 2009
Line 250:		Line 250:
	<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>		<span>'''<span><font color="#0000FF">return</font></span>'''</span> TRUE<span><font color="#990000"><nowiki>;</nowiki></font></span>
	<span><font color="#FF0000">}</font></span></tt>		<span><font color="#FF0000">}</font></span></tt>

	~~[[Category:Maemo training material]]~~

← Older revision	Revision as of 11:45, 13 July 2009
(No difference)