Appsink is a sink plugin that supports many different methods for making the application get a handle on the GStreamer data in a pipeline. Unlike most GStreamer elements, Appsink provides external API functions. appsink can be used by linking to the gstappsink.h header file to access the methods or by using the appsink action signals and properties. The normal way of retrieving samples from appsink is by using the gst_app_sink_pull_sample() and gst_app_sink_pull_preroll() methods. These methods block until a sample becomes available in the sink or when the sink is shut down or reaches EOS. There are also timed variants of these methods, gst_app_sink_try_pull_sample() and gst_app_sink_try_pull_preroll(), which accept a timeout parameter to limit the amount of time to wait. Appsink will internally use a queue to collect buffers from the streaming thread. If the application is not pulling samples fast enough, this queue will consume a lot of memory over time. The "max-buffers" property can be used to limit the queue size. The "drop" property controls whether the streaming thread blocks or if older buffers are dropped when the maximum queue size is reached. Note that blocking the streaming thread can negatively affect real-time performance and should be avoided. If a blocking behaviour is not desirable, setting the "emit-signals" property to %TRUE will make appsink emit the "new-sample" and "new-preroll" signals when a sample can be pulled without blocking. The "caps" property on appsink can be used to control the formats that appsink can receive. This property can contain non-fixed caps, the format of the pulled samples can be obtained by getting the sample caps. If one of the pull-preroll or pull-sample methods return %NULL, the appsink is stopped or in the EOS state. You can check for the EOS state with the "eos" property or with the gst_app_sink_is_eos() method. The eos signal can also be used to be informed when the EOS state is reached to avoid polling. Get the last preroll sample in @appsink. This was the sample that caused the appsink to preroll in the PAUSED state. This sample can be pulled many times and remains available to the application even after EOS. This function is typically used when dealing with a pipeline in the PAUSED state. Calling this function after doing a seek will give the sample right after the seek position. Note that the preroll sample will also be returned as the first sample when calling gst_app_sink_pull_sample(). If an EOS event was received before any buffers, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. This function blocks until a preroll sample or EOS is received or the appsink element is set to the READY/NULL state. a #GstSample or NULL when the appsink is stopped or EOS. Call gst_sample_unref() after usage. a #GstAppSink This function blocks until a sample or EOS becomes available or the appsink element is set to the READY/NULL state. This function will only return samples when the appsink is in the PLAYING state. All rendered buffers will be put in a queue so that the application can pull samples at its own rate. Note that when the application does not pull samples fast enough, the queued buffers could consume a lot of memory, especially when dealing with raw video frames. If an EOS event was received before any buffers, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. a #GstSample or NULL when the appsink is stopped or EOS. Call gst_sample_unref() after usage. a #GstAppSink Get the last preroll sample in @appsink. This was the sample that caused the appsink to preroll in the PAUSED state. This sample can be pulled many times and remains available to the application even after EOS. This function is typically used when dealing with a pipeline in the PAUSED state. Calling this function after doing a seek will give the sample right after the seek position. Note that the preroll sample will also be returned as the first sample when calling gst_app_sink_pull_sample(). If an EOS event was received before any buffers or the timeout expires, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. This function blocks until a preroll sample or EOS is received, the appsink element is set to the READY/NULL state, or the timeout expires. a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. Call gst_sample_unref() after usage. a #GstAppSink the maximum amount of time to wait for the preroll sample This function blocks until a sample or EOS becomes available or the appsink element is set to the READY/NULL state or the timeout expires. This function will only return samples when the appsink is in the PLAYING state. All rendered buffers will be put in a queue so that the application can pull samples at its own rate. Note that when the application does not pull samples fast enough, the queued buffers could consume a lot of memory, especially when dealing with raw video frames. If an EOS event was received before any buffers or the timeout expires, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. Call gst_sample_unref() after usage. a #GstAppSink the maximum amount of time to wait for a sample Check if @appsink supports buffer lists. %TRUE if @appsink supports buffer lists. a #GstAppSink Get the configured caps on @appsink. the #GstCaps accepted by the sink. gst_caps_unref() after usage. a #GstAppSink Check if @appsink will drop old buffers when the maximum amount of queued buffers is reached. %TRUE if @appsink is dropping old buffers when the queue is filled. a #GstAppSink Check if appsink will emit the "new-preroll" and "new-sample" signals. %TRUE if @appsink is emiting the "new-preroll" and "new-sample" signals. a #GstAppSink Get the maximum amount of buffers that can be queued in @appsink. The maximum amount of buffers that can be queued. a #GstAppSink Check if @appsink will wait for all buffers to be consumed when an EOS is received. %TRUE if @appsink will wait for all buffers to be consumed when an EOS is received. a #GstAppSink Check if @appsink is EOS, which is when no more samples can be pulled because an EOS event was received. This function also returns %TRUE when the appsink is not in the PAUSED or PLAYING state. %TRUE if no more samples can be pulled and the appsink is EOS. a #GstAppSink Get the last preroll sample in @appsink. This was the sample that caused the appsink to preroll in the PAUSED state. This sample can be pulled many times and remains available to the application even after EOS. This function is typically used when dealing with a pipeline in the PAUSED state. Calling this function after doing a seek will give the sample right after the seek position. Note that the preroll sample will also be returned as the first sample when calling gst_app_sink_pull_sample(). If an EOS event was received before any buffers, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. This function blocks until a preroll sample or EOS is received or the appsink element is set to the READY/NULL state. a #GstSample or NULL when the appsink is stopped or EOS. Call gst_sample_unref() after usage. a #GstAppSink This function blocks until a sample or EOS becomes available or the appsink element is set to the READY/NULL state. This function will only return samples when the appsink is in the PLAYING state. All rendered buffers will be put in a queue so that the application can pull samples at its own rate. Note that when the application does not pull samples fast enough, the queued buffers could consume a lot of memory, especially when dealing with raw video frames. If an EOS event was received before any buffers, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. a #GstSample or NULL when the appsink is stopped or EOS. Call gst_sample_unref() after usage. a #GstAppSink Instruct @appsink to enable or disable buffer list support. For backwards-compatibility reasons applications need to opt in to indicate that they will be able to handle buffer lists. a #GstAppSink enable or disable buffer list support Set callbacks which will be executed for each new preroll, new sample and eos. This is an alternative to using the signals, it has lower overhead and is thus less expensive, but also less flexible. If callbacks are installed, no signals will be emitted for performance reasons. a #GstAppSink the callbacks a user_data argument for the callbacks a destroy notify function Set the capabilities on the appsink element. This function takes a copy of the caps structure. After calling this method, the sink will only accept caps that match @caps. If @caps is non-fixed, or incomplete, you must check the caps on the samples to get the actual used caps. a #GstAppSink caps to set Instruct @appsink to drop old buffers when the maximum amount of queued buffers is reached. a #GstAppSink the new state Make appsink emit the "new-preroll" and "new-sample" signals. This option is by default disabled because signal emission is expensive and unneeded when the application prefers to operate in pull mode. a #GstAppSink the new state Set the maximum amount of buffers that can be queued in @appsink. After this amount of buffers are queued in appsink, any more buffers will block upstream elements until a sample is pulled from @appsink. a #GstAppSink the maximum number of buffers to queue Instruct @appsink to wait for all buffers to be consumed when an EOS is received. a #GstAppSink the new state Get the last preroll sample in @appsink. This was the sample that caused the appsink to preroll in the PAUSED state. This sample can be pulled many times and remains available to the application even after EOS. This function is typically used when dealing with a pipeline in the PAUSED state. Calling this function after doing a seek will give the sample right after the seek position. Note that the preroll sample will also be returned as the first sample when calling gst_app_sink_pull_sample(). If an EOS event was received before any buffers or the timeout expires, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. This function blocks until a preroll sample or EOS is received, the appsink element is set to the READY/NULL state, or the timeout expires. a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. Call gst_sample_unref() after usage. a #GstAppSink the maximum amount of time to wait for the preroll sample This function blocks until a sample or EOS becomes available or the appsink element is set to the READY/NULL state or the timeout expires. This function will only return samples when the appsink is in the PLAYING state. All rendered buffers will be put in a queue so that the application can pull samples at its own rate. Note that when the application does not pull samples fast enough, the queued buffers could consume a lot of memory, especially when dealing with raw video frames. If an EOS event was received before any buffers or the timeout expires, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. Call gst_sample_unref() after usage. a #GstAppSink the maximum amount of time to wait for a sample Signal that the end-of-stream has been reached. This signal is emitted from the streaming thread. Signal that a new preroll sample is available. This signal is emitted from the streaming thread and only when the "emit-signals" property is %TRUE. The new preroll sample can be retrieved with the "pull-preroll" action signal or gst_app_sink_pull_preroll() either from this signal callback or from any other thread. Note that this signal is only emitted when the "emit-signals" property is set to %TRUE, which it is not by default for performance reasons. Signal that a new sample is available. This signal is emitted from the streaming thread and only when the "emit-signals" property is %TRUE. The new sample can be retrieved with the "pull-sample" action signal or gst_app_sink_pull_sample() either from this signal callback or from any other thread. Note that this signal is only emitted when the "emit-signals" property is set to %TRUE, which it is not by default for performance reasons. Get the last preroll sample in @appsink. This was the sample that caused the appsink to preroll in the PAUSED state. This sample can be pulled many times and remains available to the application even after EOS. This function is typically used when dealing with a pipeline in the PAUSED state. Calling this function after doing a seek will give the sample right after the seek position. Note that the preroll sample will also be returned as the first sample when calling gst_app_sink_pull_sample() or the "pull-sample" action signal. If an EOS event was received before any buffers, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. This function blocks until a preroll sample or EOS is received or the appsink element is set to the READY/NULL state. a #GstSample or NULL when the appsink is stopped or EOS. This function blocks until a sample or EOS becomes available or the appsink element is set to the READY/NULL state. This function will only return samples when the appsink is in the PLAYING state. All rendered samples will be put in a queue so that the application can pull samples at its own rate. Note that when the application does not pull samples fast enough, the queued samples could consume a lot of memory, especially when dealing with raw video frames. It's possible to control the behaviour of the queue with the "drop" and "max-buffers" properties. If an EOS event was received before any buffers, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. a #GstSample or NULL when the appsink is stopped or EOS. Get the last preroll sample in @appsink. This was the sample that caused the appsink to preroll in the PAUSED state. This sample can be pulled many times and remains available to the application even after EOS. This function is typically used when dealing with a pipeline in the PAUSED state. Calling this function after doing a seek will give the sample right after the seek position. Note that the preroll sample will also be returned as the first sample when calling gst_app_sink_pull_sample() or the "pull-sample" action signal. If an EOS event was received before any buffers or the timeout expires, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. This function blocks until a preroll sample or EOS is received, the appsink element is set to the READY/NULL state, or the timeout expires. a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. the maximum amount of time to wait for the preroll sample This function blocks until a sample or EOS becomes available or the appsink element is set to the READY/NULL state or the timeout expires. This function will only return samples when the appsink is in the PLAYING state. All rendered samples will be put in a queue so that the application can pull samples at its own rate. Note that when the application does not pull samples fast enough, the queued samples could consume a lot of memory, especially when dealing with raw video frames. It's possible to control the behaviour of the queue with the "drop" and "max-buffers" properties. If an EOS event was received before any buffers or the timeout expires, this function returns %NULL. Use gst_app_sink_is_eos () to check for the EOS condition. a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. the maximum amount of time to wait for a sample A set of callbacks that can be installed on the appsink with gst_app_sink_set_callbacks(). a #GstSample or NULL when the appsink is stopped or EOS. Call gst_sample_unref() after usage. a #GstAppSink a #GstSample or NULL when the appsink is stopped or EOS. Call gst_sample_unref() after usage. a #GstAppSink a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. Call gst_sample_unref() after usage. a #GstAppSink the maximum amount of time to wait for the preroll sample a #GstSample or NULL when the appsink is stopped or EOS or the timeout expires. Call gst_sample_unref() after usage. a #GstAppSink the maximum amount of time to wait for a sample The appsrc element can be used by applications to insert data into a GStreamer pipeline. Unlike most GStreamer elements, appsrc provides external API functions. appsrc can be used by linking with the libgstapp library to access the methods directly or by using the appsrc action signals. Before operating appsrc, the caps property must be set to fixed caps describing the format of the data that will be pushed with appsrc. An exception to this is when pushing buffers with unknown caps, in which case no caps should be set. This is typically true of file-like sources that push raw byte buffers. If you don't want to explicitly set the caps, you can use gst_app_src_push_sample. This method gets the caps associated with the sample and sets them on the appsrc replacing any previously set caps (if different from sample's caps). The main way of handing data to the appsrc element is by calling the gst_app_src_push_buffer() method or by emitting the push-buffer action signal. This will put the buffer onto a queue from which appsrc will read from in its streaming thread. It is important to note that data transport will not happen from the thread that performed the push-buffer call. The "max-bytes" property controls how much data can be queued in appsrc before appsrc considers the queue full. A filled internal queue will always signal the "enough-data" signal, which signals the application that it should stop pushing data into appsrc. The "block" property will cause appsrc to block the push-buffer method until free data becomes available again. When the internal queue is running out of data, the "need-data" signal is emitted, which signals the application that it should start pushing more data into appsrc. In addition to the "need-data" and "enough-data" signals, appsrc can emit the "seek-data" signal when the "stream-mode" property is set to "seekable" or "random-access". The signal argument will contain the new desired position in the stream expressed in the unit set with the "format" property. After receiving the seek-data signal, the application should push-buffers from the new position. These signals allow the application to operate the appsrc in two different ways: The push mode, in which the application repeatedly calls the push-buffer/push-sample method with a new buffer/sample. Optionally, the queue size in the appsrc can be controlled with the enough-data and need-data signals by respectively stopping/starting the push-buffer/push-sample calls. This is a typical mode of operation for the stream-type "stream" and "seekable". Use this mode when implementing various network protocols or hardware devices. The pull mode, in which the need-data signal triggers the next push-buffer call. This mode is typically used in the "random-access" stream-type. Use this mode for file access or other randomly accessable sources. In this mode, a buffer of exactly the amount of bytes given by the need-data signal should be pushed into appsrc. In all modes, the size property on appsrc should contain the total stream size in bytes. Setting this property is mandatory in the random-access mode. For the stream and seekable modes, setting this property is optional but recommended. When the application has finished pushing data into appsrc, it should call gst_app_src_end_of_stream() or emit the end-of-stream action signal. After this call, no more buffers can be pushed into appsrc until a flushing seek occurs or the state of the appsrc has gone through READY. Indicates to the appsrc element that the last buffer queued in the element is the last buffer of the stream. #GST_FLOW_OK when the EOS was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. a #GstAppSrc Adds a buffer to the queue of buffers that the appsrc element will push to its source pad. This function takes ownership of the buffer. When the block property is TRUE, this function can block until free space becomes available in the queue. #GST_FLOW_OK when the buffer was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. #GST_FLOW_EOS when EOS occured. a #GstAppSrc a #GstBuffer to push Extract a buffer from the provided sample and adds it to the queue of buffers that the appsrc element will push to its source pad. Any previous caps that were set on appsrc will be replaced by the caps associated with the sample if not equal. When the block property is TRUE, this function can block until free space becomes available in the queue. #GST_FLOW_OK when the buffer was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. #GST_FLOW_EOS when EOS occured. a #GstAppSrc a #GstSample from which buffer and caps may be extracted Indicates to the appsrc element that the last buffer queued in the element is the last buffer of the stream. #GST_FLOW_OK when the EOS was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. a #GstAppSrc Get the configured caps on @appsrc. the #GstCaps produced by the source. gst_caps_unref() after usage. a #GstAppSrc Get the number of currently queued bytes inside @appsrc. The number of currently queued bytes. a #GstAppSrc Get the duration of the stream in nanoseconds. A value of GST_CLOCK_TIME_NONE means that the duration is not known. the duration of the stream previously set with gst_app_src_set_duration(); a #GstAppSrc Check if appsrc will emit the "new-preroll" and "new-buffer" signals. %TRUE if @appsrc is emitting the "new-preroll" and "new-buffer" signals. a #GstAppSrc Retrieve the min and max latencies in @min and @max respectively. a #GstAppSrc the min latency the min latency Get the maximum amount of bytes that can be queued in @appsrc. The maximum amount of bytes that can be queued. a #GstAppSrc Get the size of the stream in bytes. A value of -1 means that the size is not known. the size of the stream previously set with gst_app_src_set_size(); a #GstAppSrc Get the stream type. Control the stream type of @appsrc with gst_app_src_set_stream_type(). the stream type. a #GstAppSrc Adds a buffer to the queue of buffers that the appsrc element will push to its source pad. This function takes ownership of the buffer. When the block property is TRUE, this function can block until free space becomes available in the queue. #GST_FLOW_OK when the buffer was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. #GST_FLOW_EOS when EOS occured. a #GstAppSrc a #GstBuffer to push Extract a buffer from the provided sample and adds it to the queue of buffers that the appsrc element will push to its source pad. Any previous caps that were set on appsrc will be replaced by the caps associated with the sample if not equal. When the block property is TRUE, this function can block until free space becomes available in the queue. #GST_FLOW_OK when the buffer was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. #GST_FLOW_EOS when EOS occured. a #GstAppSrc a #GstSample from which buffer and caps may be extracted Set callbacks which will be executed when data is needed, enough data has been collected or when a seek should be performed. This is an alternative to using the signals, it has lower overhead and is thus less expensive, but also less flexible. If callbacks are installed, no signals will be emitted for performance reasons. a #GstAppSrc the callbacks a user_data argument for the callbacks a destroy notify function Set the capabilities on the appsrc element. This function takes a copy of the caps structure. After calling this method, the source will only produce caps that match @caps. @caps must be fixed and the caps on the buffers must match the caps or left NULL. a #GstAppSrc caps to set Set the duration of the stream in nanoseconds. A value of GST_CLOCK_TIME_NONE means that the duration is not known. a #GstAppSrc the duration to set Make appsrc emit the "new-preroll" and "new-buffer" signals. This option is by default disabled because signal emission is expensive and unneeded when the application prefers to operate in pull mode. a #GstAppSrc the new state Configure the @min and @max latency in @src. If @min is set to -1, the default latency calculations for pseudo-live sources will be used. a #GstAppSrc the min latency the min latency Set the maximum amount of bytes that can be queued in @appsrc. After the maximum amount of bytes are queued, @appsrc will emit the "enough-data" signal. a #GstAppSrc the maximum number of bytes to queue Set the size of the stream in bytes. A value of -1 means that the size is not known. a #GstAppSrc the size to set Set the stream type on @appsrc. For seekable streams, the "seek" signal must be connected to. A stream_type stream a #GstAppSrc the new state Notify @appsrc that no more buffer are available. Signal that the source has enough data. It is recommended that the application stops calling push-buffer until the need-data signal is emitted again to avoid excessive buffer queueing. Signal that the source needs more data. In the callback or from another thread you should call push-buffer or end-of-stream. @length is just a hint and when it is set to -1, any number of bytes can be pushed into @appsrc. You can call push-buffer multiple times until the enough-data signal is fired. the amount of bytes needed. Adds a buffer to the queue of buffers that the appsrc element will push to its source pad. This function does not take ownership of the buffer so the buffer needs to be unreffed after calling this function. When the block property is TRUE, this function can block until free space becomes available in the queue. a buffer to push Extract a buffer from the provided sample and adds the extracted buffer to the queue of buffers that the appsrc element will push to its source pad. This function set the appsrc caps based on the caps in the sample and reset the caps if they change. Only the caps and the buffer of the provided sample are used and not for example the segment in the sample. This function does not take ownership of the sample so the sample needs to be unreffed after calling this function. When the block property is TRUE, this function can block until free space becomes available in the queue. a sample from which extract buffer to push Seek to the given offset. The next push-buffer should produce buffers from the new @offset. This callback is only called for seekable stream types. %TRUE if the seek succeeded. the offset to seek to A set of callbacks that can be installed on the appsrc with gst_app_src_set_callbacks(). #GST_FLOW_OK when the buffer was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. #GST_FLOW_EOS when EOS occured. a #GstAppSrc a #GstBuffer to push #GST_FLOW_OK when the EOS was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. a #GstAppSrc #GST_FLOW_OK when the buffer was successfuly queued. #GST_FLOW_FLUSHING when @appsrc is not PAUSED or PLAYING. #GST_FLOW_EOS when EOS occured. a #GstAppSrc a #GstSample from which buffer and caps may be extracted The stream type. No seeking is supported in the stream, such as a live stream. The stream is seekable but seeking might not be very fast, such as data from a webserver. The stream is seekable and seeking is fast, such as in a local file.