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POGStreamer caps filtering issue when converting from command line to C code
 

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  1. POGStreamer caps filtering issue when converting from command line to C code
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    <p>I am having issues converting my working GStreamer pipeline from a command line version to C code. From the command line the following command will successfully play my headerless mu-law audio file:</p> <pre><code>gst-launch filesrc location=test.ulaw ! audio/x-mulaw, rate=8000, channels=1 ! mulawdec ! audioconvert ! audioresample ! autoaudiosink </code></pre> <p>However, my issues are arising when trying to add in the "audio/x-mulaw, rate=8000, channels=1" bit into my C program. The program started off playing wav files (using wavparse in place of mulawdec) so that I know my base C code works, and it must just be that I am misinterpreting how the caps bit needs to be added in to make it work with mu-law files. </p> <p>I am creating the caps, then using the gst_element_link_filtered to use this:</p> <pre><code>GstCaps *gstMuLawCaps = gst_caps_from_string("audio/x-mulaw, rate=8000, channels=1"); gst_element_link_filtered(gstFileSource, gstMuLawDecoder, gstMuLawCaps); </code></pre> <p>But this is not working, and running the program produces the following output:</p> <pre><code>&gt;gst-mulaw.exe test.ulaw Playing. Error: Internal data flow error. Playback Finished. </code></pre> <p>I would be grateful if anyone is able to help shed some light on what I am doing wrong. The full code is given below:</p> <pre><code>#include &lt;gst/gst.h&gt; #include &lt;glib.h&gt; static gboolean bus_call (GstBus *bus, GstMessage *msg, gpointer data) { GMainLoop *loop = (GMainLoop *) data; switch (GST_MESSAGE_TYPE (msg)) { case GST_MESSAGE_EOS: g_print ("End of stream\n"); g_main_loop_quit (loop); break; case GST_MESSAGE_ERROR: { gchar *debug; GError *error; gst_message_parse_error (msg, &amp;error, &amp;debug); g_free (debug); g_printerr ("Error: %s\n", error-&gt;message); g_error_free (error); g_main_loop_quit (loop); break; } default: break; } return TRUE; } static void on_pad_added (GstElement *gstSourceElement, GstPad *gstSourcePad, gpointer data) { g_print("Linking dynamic pad.\n"); GstPad *gstSinkPad; GstElement *gstSinkElement = (GstElement *) data; gstSinkPad = gst_element_get_static_pad (gstSinkElement, "sink"); gst_pad_link (gstSourcePad, gstSinkPad); gst_object_unref (gstSinkPad); } int main (int argc, char *argv[]) { GMainLoop *loop; GstElement *gstPipeline, *gstFileSource, *gstMuLawDecoder, *gstAudioConvert, *gstAudioResample, *gstAudioSink; GstBus *bus; // GStreamer initialisation. gst_init (&amp;argc, &amp;argv); loop = g_main_loop_new (NULL, FALSE); // Check input arguments. if (argc != 2) { g_printerr ("Usage: %s &lt;mu-law File&gt;\n", argv[0]); return -1; } // Create the GStreamer elements. gstPipeline = gst_pipeline_new ("player"); gstFileSource = gst_element_factory_make ("filesrc", "filesource"); gstMuLawDecoder = gst_element_factory_make ("mulawdec", "mulawdecoder"); gstAudioConvert = gst_element_factory_make ("audioconvert", "audioconverter"); gstAudioResample = gst_element_factory_make ("audioresample", "audioresampler"); gstAudioSink = gst_element_factory_make ("autoaudiosink", "audiosink"); if (!gstPipeline || !gstFileSource || !gstMuLawDecoder || !gstAudioConvert || !gstAudioResample || !gstAudioSink) { g_printerr ("An element could not be created. Exiting.\n"); return -1; } // Linke the filesrc object to that passed on the command line. g_object_set (G_OBJECT (gstFileSource), "location", argv[1], NULL); // Setup the GStreamer bus. bus = gst_pipeline_get_bus (GST_PIPELINE (gstPipeline)); gst_bus_add_watch (bus, bus_call, loop); gst_object_unref (bus); // Add the objects to the pipeline. gst_bin_add_many (GST_BIN (gstPipeline), gstFileSource, gstMuLawDecoder, gstAudioConvert, gstAudioResample, gstAudioSink, NULL); // Link the elements together. GstCaps *gstMuLawCaps = gst_caps_from_string("audio/x-mulaw, rate=8000, channels=1"); gst_element_link_filtered(gstFileSource, gstMuLawDecoder, gstMuLawCaps); gst_caps_unref(gstMuLawCaps); gst_element_link_many (gstAudioConvert, gstAudioResample, gstAudioSink, NULL); g_signal_connect (gstMuLawDecoder, "pad-added", G_CALLBACK (on_pad_added), gstAudioConvert); // Set the pipeline to state playing, and run the main loop. g_print ("Playing.\n"); gst_element_set_state (gstPipeline, GST_STATE_PLAYING); g_main_loop_run (loop); // Finished playback, cleanup. g_print ("Playback Finished.\n"); gst_element_set_state (gstPipeline, GST_STATE_NULL); gst_object_unref (GST_OBJECT (gstPipeline)); return 0; } </code></pre> <p>Thanks.</p>
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