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Diffstat (limited to 'sdk-playback-tutorial-short-cutting-the-pipeline.md')
| -rw-r--r-- | sdk-playback-tutorial-short-cutting-the-pipeline.md | 104 |
1 files changed, 41 insertions, 63 deletions
diff --git a/sdk-playback-tutorial-short-cutting-the-pipeline.md b/sdk-playback-tutorial-short-cutting-the-pipeline.md index bf913f5..ffc5d38 100644 --- a/sdk-playback-tutorial-short-cutting-the-pipeline.md +++ b/sdk-playback-tutorial-short-cutting-the-pipeline.md @@ -1,42 +1,30 @@ # Playback tutorial 3: Short-cutting the pipeline -# Goal +## Goal -[Basic tutorial 8: Short-cutting the -pipeline](Basic%2Btutorial%2B8%253A%2BShort-cutting%2Bthe%2Bpipeline.html) showed +[](sdk-basic-tutorial-short-cutting-the-pipeline.md) showed how an application can manually extract or inject data into a pipeline -by using two special elements called `appsrc` and `appsink`. -`playbin` allows using these elements too, but the method to connect -them is different. To connect an `appsink` to `playbin` see [Playback -tutorial 7: Custom playbin -sinks](Playback%2Btutorial%2B7%253A%2BCustom%2Bplaybin%2Bsinks.html). +by using two special elements called `appsrc` and `appsink`. +`playbin` allows using these elements too, but the method to connect +them is different. To connect an `appsink` to `playbin` see [](sdk-playback-tutorial-custom-playbin-sinks.md). This tutorial shows: - - How to connect `appsrc` with `playbin` - - How to configure the `appsrc` + - How to connect `appsrc` with `playbin` + - How to configure the `appsrc` -# A playbin waveform generator +## A playbin waveform generator -Copy this code into a text file named `playback-tutorial-3.c`. - -<table> -<tbody> -<tr class="odd"> -<td><img src="images/icons/emoticons/information.png" width="16" height="16" /></td> -<td><p>This tutorial is included in the SDK since release 2012.7. If you cannot find it in the downloaded code, please install the latest release of the GStreamer SDK.</p></td> -</tr> -</tbody> -</table> +Copy this code into a text file named `playback-tutorial-3.c`. **playback-tutorial-3.c** ``` c #include <gst/gst.h> +#include <gst/audio/audio.h> #include <string.h> #define CHUNK_SIZE 1024 /* Amount of bytes we are sending in each buffer */ #define SAMPLE_RATE 44100 /* Samples per second we are sending */ -#define AUDIO_CAPS "audio/x-raw-int,channels=1,rate=%d,signed=(boolean)true,width=16,depth=16,endianness=BYTE_ORDER" /* Structure to contain all our information, so we can pass it to callbacks */ typedef struct _CustomData { @@ -59,6 +47,7 @@ static gboolean push_data (CustomData *data) { GstBuffer *buffer; GstFlowReturn ret; int i; + GstMapInfo map; gint16 *raw; gint num_samples = CHUNK_SIZE / 2; /* Because each sample is 16 bits */ gfloat freq; @@ -71,7 +60,8 @@ static gboolean push_data (CustomData *data) { GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale (CHUNK_SIZE, GST_SECOND, SAMPLE_RATE); /* Generate some psychodelic waveforms */ - raw = (gint16 *)GST_BUFFER_DATA (buffer); + gst_buffer_map (buffer, &map, GST_MAP_WRITE); + raw = (gint16 *)map.data; data->c += data->d; data->d -= data->c / 1000; freq = 1100 + 1000 * data->d; @@ -80,6 +70,7 @@ static gboolean push_data (CustomData *data) { data->b -= data->a / freq; raw[i] = (gint16)(500 * data->a); } + gst_buffer_unmap (buffer, &map); data->num_samples += num_samples; /* Push the buffer into the appsrc */ @@ -133,16 +124,16 @@ static void error_cb (GstBus *bus, GstMessage *msg, CustomData *data) { /* This function is called when playbin has created the appsrc element, so we have * a chance to configure it. */ static void source_setup (GstElement *pipeline, GstElement *source, CustomData *data) { - gchar *audio_caps_text; + GstAudioInfo info; GstCaps *audio_caps; g_print ("Source has been created. Configuring.\n"); data->app_source = source; /* Configure appsrc */ - audio_caps_text = g_strdup_printf (AUDIO_CAPS, SAMPLE_RATE); - audio_caps = gst_caps_from_string (audio_caps_text); - g_object_set (source, "caps", audio_caps, NULL); + gst_audio_info_set_format (&info, GST_AUDIO_FORMAT_S16, SAMPLE_RATE, 1, NULL); + audio_caps = gst_audio_info_to_caps (&info); + g_object_set (source, "caps", audio_caps, "format", GST_FORMAT_TIME, NULL); g_signal_connect (source, "need-data", G_CALLBACK (start_feed), data); g_signal_connect (source, "enough-data", G_CALLBACK (stop_feed), data); gst_caps_unref (audio_caps); @@ -185,16 +176,16 @@ int main(int argc, char *argv[]) { } ``` -To use an `appsrc` as the source for the pipeline, simply instantiate a -`playbin` and set its URI to `appsrc://` +To use an `appsrc` as the source for the pipeline, simply instantiate a +`playbin` and set its URI to `appsrc://` ``` c /* Create the playbin element */ data.pipeline = gst_parse_launch ("playbin uri=appsrc://", NULL); ``` -`playbin` will create an internal `appsrc` element and fire the -`source-setup` signal to allow the application to configure +`playbin` will create an internal `appsrc` element and fire the +`source-setup` signal to allow the application to configure it: ``` c @@ -202,7 +193,7 @@ g_signal_connect (data.pipeline, "source-setup", G_CALLBACK (source_setup), &dat ``` In particular, it is important to set the caps property of `appsrc`, -since, once the signal handler returns, `playbin` will instantiate the +since, once the signal handler returns, `playbin` will instantiate the next element in the pipeline according to these caps: @@ -210,16 +201,16 @@ caps: /* This function is called when playbin has created the appsrc element, so we have * a chance to configure it. */ static void source_setup (GstElement *pipeline, GstElement *source, CustomData *data) { - gchar *audio_caps_text; + GstAudioInfo info; GstCaps *audio_caps; g_print ("Source has been created. Configuring.\n"); data->app_source = source; /* Configure appsrc */ - audio_caps_text = g_strdup_printf (AUDIO_CAPS, SAMPLE_RATE); - audio_caps = gst_caps_from_string (audio_caps_text); - g_object_set (source, "caps", audio_caps, NULL); + gst_audio_info_set_format (&info, GST_AUDIO_FORMAT_S16, SAMPLE_RATE, 1, NULL); + audio_caps = gst_audio_info_to_caps (&info); + g_object_set (source, "caps", audio_caps, "format", GST_FORMAT_TIME, NULL); g_signal_connect (source, "need-data", G_CALLBACK (start_feed), data); g_signal_connect (source, "enough-data", G_CALLBACK (stop_feed), data); gst_caps_unref (audio_caps); @@ -227,41 +218,28 @@ static void source_setup (GstElement *pipeline, GstElement *source, CustomData * } ``` -The configuration of the `appsrc` is exactly the same as in [Basic -tutorial 8: Short-cutting the -pipeline](Basic%2Btutorial%2B8%253A%2BShort-cutting%2Bthe%2Bpipeline.html): -the caps are set to `audio/x-raw-int`, and two callbacks are registered, +The configuration of the `appsrc` is exactly the same as in +[](sdk-basic-tutorial-short-cutting-the-pipeline.md): +the caps are set to `audio/x-raw`, and two callbacks are registered, so the element can tell the application when it needs to start and stop -pushing data. See [Basic tutorial 8: Short-cutting the -pipeline](Basic%2Btutorial%2B8%253A%2BShort-cutting%2Bthe%2Bpipeline.html) +pushing data. See [](sdk-basic-tutorial-short-cutting-the-pipeline.md) for more details. -From this point onwards, `playbin` takes care of the rest of the +From this point onwards, `playbin` takes care of the rest of the pipeline, and the application only needs to worry about generating more data when told so. -To learn how data can be extracted from `playbin` using the -`appsink` element, see [Playback tutorial 7: Custom playbin -sinks](Playback%2Btutorial%2B7%253A%2BCustom%2Bplaybin%2Bsinks.html). +To learn how data can be extracted from `playbin` using the +`appsink` element, see [](sdk-playback-tutorial-custom-playbin-sinks.md). -# Conclusion +## Conclusion -This tutorial applies the concepts shown in [Basic tutorial 8: -Short-cutting the -pipeline](Basic%2Btutorial%2B8%253A%2BShort-cutting%2Bthe%2Bpipeline.html) to +This tutorial applies the concepts shown in +[](sdk-basic-tutorial-short-cutting-the-pipeline.md) to `playbin`. In particular, it has shown: - - How to connect `appsrc` with `playbin` using the special - URI `appsrc://` - - How to configure the `appsrc` using the `source-setup` signal - -It has been a pleasure having you here, and see you soon\! - -## Attachments: + - How to connect `appsrc` with `playbin` using the special + URI `appsrc://` + - How to configure the `appsrc` using the `source-setup` signal - -[playback-tutorial-3.c](attachments/1442200/2424850.c) (text/plain) - -[vs2010.zip](attachments/1442200/2424849.zip) (application/zip) - -[playback-tutorial-3.c](attachments/1442200/2424848.c) (text/plain) +It has been a pleasure having you here, and see you soon!
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