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// Authors
// Copyright (C) 2014 Stephan Sundermann <stephansundermann@gmail.com>
using System;
using Gst;
using System.Runtime.InteropServices;
namespace GstreamerSharp
{
class Playback
{
const int ChunkSize = 1024;
const int SampleRate = 44100;
static Gst.App.AppSrc AppSource;
static Element Pipeline;
static long NumSamples; // Number of samples generated so far (for timestamp generation)
static float a, b, c, d; // For waveform generation
static uint Sourceid; // To control the GSource
static GLib.MainLoop MainLoop; // GLib's Main Loop
// This method is called by the idle GSource in the mainloop, to feed CHUNK_SIZE bytes into appsrc.
// The idle handler is added to the mainloop when appsrc requests us to start sending data (need-data signal)
// and is removed when appsrc has enough data (enough-data signal).
static bool PushData () {
var numSamples = ChunkSize / 2; // Because each sample is 16 bits
MapInfo map;
// Create a new empty buffer
var buffer = new Gst.Buffer (null, ChunkSize, AllocationParams.Zero);
// Set its timestamp and duration
buffer.Pts = Util.Uint64Scale ((ulong)NumSamples, (ulong)Constants.SECOND, (ulong)SampleRate);
buffer.Dts = Util.Uint64Scale ((ulong)NumSamples, (ulong)Constants.SECOND, (ulong)SampleRate);
buffer.Duration = Util.Uint64Scale ((ulong)NumSamples, (ulong)Constants.SECOND, (ulong)SampleRate);
// Generate some psychodelic waveforms
buffer.Map (out map, MapFlags.Write);
c += d;
d -= c / 1000f;
var freq = 1100f + 1000f * d;
short[] data = new short[numSamples];
for (int i = 0; i < numSamples; i++) {
a += b;
b -= a / freq;
data[i] = (short)(500f * a);
}
// convert the short[] to a byte[] by marshalling
var native = Marshal.AllocHGlobal (data.Length * sizeof(short));
Marshal.Copy (data, 0, native, data.Length);
byte[] bytedata = new byte[2 * data.Length];
Marshal.Copy (native, bytedata, 0, data.Length * sizeof(short));
map.Data = bytedata;
buffer.Unmap (map);
NumSamples += numSamples;
// Push the buffer into the appsrc
var ret = AppSource.PushBuffer (buffer);
// Free the buffer now that we are done with it
buffer.Dispose ();
if (ret != FlowReturn.Ok) {
// We got some error, stop sending data
return false;
}
return true;
}
// This signal callback triggers when appsrc needs Here, we add an idle handler
// to the mainloop to start pushing data into the appsrc
static void StartFeed (object sender, Gst.App.NeedDataArgs args) {
if (Sourceid == 0) {
Console.WriteLine ("Start feeding");
Sourceid = GLib.Idle.Add (PushData);
}
}
// This callback triggers when appsrc has enough data and we can stop sending.
// We remove the idle handler from the mainloop
static void StopFeed (object sender, EventArgs args) {
if (Sourceid != 0) {
Console.WriteLine ("Stop feeding");
GLib.Source.Remove (Sourceid);
Sourceid = 0;
}
}
// This function is called when playbin has created the appsrc element, so we have a chance to configure it.
static void SourceSetup (object sender, GLib.SignalArgs args) {
var info = new Gst.Audio.AudioInfo();
var source = new Gst.App.AppSrc(((Element)args.Args [0]).Handle);
Console.WriteLine ("Source has been created. Configuring.");
AppSource = source;
// Configure appsrc
info.SetFormat (Gst.Audio.AudioFormat.S16, SampleRate, 1, (Gst.Audio.AudioChannelPosition)0);
var audioCaps = info.ToCaps ();
source ["caps"] = audioCaps;
source ["format"] = Format.Time;
source.NeedData += StartFeed;
source.EnoughData += StopFeed;
}
// This function is called when an error message is posted on the bus
static void HandleError (object sender, GLib.SignalArgs args) {
GLib.GException err;
string debug;
var msg = (Message) args.Args[0];
// Print error details on the screen
msg.ParseError (out err, out debug);
Console.WriteLine ("Error received from element {0}: {1}", msg.Src.Name, err.Message);
Console.WriteLine ("Debugging information: {0}", debug != null ? debug : "none");
MainLoop.Quit ();
}
public static void Main (string[] args)
{
b = 1;
d = 1;
// Initialize Gstreamer
Gst.Application.Init(ref args);
// Create the playbin element
Pipeline = Parse.Launch ("playbin uri=appsrc://");
Pipeline.Connect ("source-setup", SourceSetup);
// Instruct the bus to emit signals for each received message, and connect to the interesting signals
var bus = Pipeline.Bus;
bus.AddSignalWatch ();
bus.Connect ("message::error", HandleError);
// Start playing the pipeline
Pipeline.SetState (State.Playing);
// Create a GLib Main Loop and set it to run
MainLoop = new GLib.MainLoop ();
MainLoop.Run ();
// Free resources
Pipeline.SetState (State.Null);
}
}
}
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