BASS.NET API for the Un4seen BASS Audio Library


BASS.NET API for the Un4seen BASS Audio Library
User defined synchronizer callback function (see BASS_ChannelSetSync(Int32, BASSSync, Int64, SYNCPROC, IntPtr) for details).

Namespace:  Un4seen.Bass
Assembly:  Bass.Net (in Bass.Net.dll) Version:

public delegate void SYNCPROC(
	int handle,
	int channel,
	int data,
	IntPtr user


Type: SystemInt32
The sync handle that has occured (as returned by BASS_ChannelSetSync(Int32, BASSSync, Int64, SYNCPROC, IntPtr)).
Type: SystemInt32
The channel that the sync occured on.
Type: SystemInt32
Additional data associated with the sync's occurance.
Type: SystemIntPtr
The user instance data given when BASS_ChannelSetSync(Int32, BASSSync, Int64, SYNCPROC, IntPtr) was called.

BASS creates a single thread dedicated to executing sync callback functions, so a callback function should be quick as other syncs cannot be processed until it has finished. Attribute slides (BASS_ChannelSlideAttribute(Int32, BASSAttribute, Single, Int32)) are also performed by the sync thread, so are also affected if a sync callback takes a long time.

"Mixtime" syncs (BASS_SYNC_MIXTIME) are not executed in the sync thread, but immediately in whichever thread triggers them. In most cases that will be an update thread, and so the same restrictions that apply to stream callbacks (STREAMPROC) also apply here.

BASS_ChannelSetPosition(Int32, Int64, BASSMode) can be used in a mixtime sync to implement custom looping, eg. set a BASS_SYNC_POS sync at the loop end position and seek to the loop start position in the callback.

NOTE: When you pass an instance of a callback delegate to one of the BASS functions, this delegate object will not be reference counted. This means .NET would not know, that it might still being used by BASS. The Garbage Collector might (re)move the delegate instance, if the variable holding the delegate is not declared as global. So make sure to always keep your delegate instance in a variable which lives as long as BASS needs it, e.g. use a global variable or member.


Do some processing until a MOD music reaches the 10th order
private volatile bool _order10 = false; // the order 10 flag
private SYNCPROC _mySyncProc;
// set the one-time order 10 sync
_mySyncProc = new SYNCPROC(MySync);
     Utils.MakeLong64(10,0), _mySyncProc, IntPtr.Zero);
while (!_order10) 
  // order 10 has not arrived, so do some processing
// order 10 has arrived!
// the sync callback
private void MySync(int syncHandle, int channel, int data, IntPtr user) 
    _order10 = true; // set the order 10 flag
Process metadata received from an internet stream:
private SYNCPROC _mySync;
int stream = Bass.BASS_StreamCreateURL(url, 0, BASSFlag.BASS_DEFAULT, null, 0);
// set a sync to get notified on stream title updates
_mySync = new SYNCPROC(MetaSync);
Bass.BASS_ChannelSetSync(stream, BASSSync.BASS_SYNC_META, 0, _mySync, IntPtr.Zero);
Bass.BASS_ChannelPlay(stream, false);
private void MetaSync(int handle, int channel, int data, IntPtr user)
  // BASS_SYNC_META is triggered
  string[] tags = Bass.BASS_ChannelGetTagsMETA(channel);
  foreach (string tag in tags)
Perform a loop between a start and end position:
private int _loopSync = 0;
private SYNCPROC _loopSyncCallback;
long loopStartPos = 1024;  // set to whatever you need
long loopEndPos   = 20480; // set to whatever you need
_loopSyncCallback = new SYNCPROC(LoopSync);
_loopSync = Bass.BASS_ChannelSetSync(stream, BASSSync.BASS_SYNC_POS | BASSSync.BASS_SYNC_MIXTIME, 
                                     loopEndPos, _loopSyncCallback, new IntPtr(loopStartPos));
// to remove the loop call this
Bass.Bass.BASS_ChannelRemoveSync(stream, _loopSync);
// the sync callback
private void LoopSync(int syncHandle, int channel, int data, IntPtr user) 
    // move the position to the start (which is given in the user data)
    Bass.BASS_ChannelSetPosition(channel, user.ToInt64());
See Also