[SDL] problems with repetitive playback

[Daniel Grace]

I have made a test programs that is supposed to play a sound five
times each time with the sound getting closer to the listener.  What
happens is that the sound is played once at full volume and then it is
played 5 times each time getting closer.  Below is the playback code,
note MixPlaySnd and PlayingChannel is written below.  What is very
confusing is if I use PlayingSnd instead to check for playback
finishing, then I get the sound playing 10 times, getting louder each
time.  Something seems to be interferring with the continuity of the
program.  Where do these extra playbacks come from ?


	for (i = 5; i >= 0; i--)
	{
		// Play sound A (at position i*40, i*40)
		CalcAngleDistance(0, 0, i*40, i*40, angle, dist);
		if ((!MixPlaySnd(testsndA, MIX_MAX_VOLUME, angle, dist, 0,
		free_channel, channelA)) && (free_channel))
			exit(1);
		// wait for sound to finish
		while (PlayingChannelSnd(channelA)) {};
		//while (PlayingSnd()) {};
	}


int MixPlaySnd(int const &snd_index, int const &volume, int const &angle,
	int const &distance, int const &loop, bool &free_channel,
	int &channel)
// This looks for a free channel and if found plays the specified sound on
// that channel.  distance is in 0-255 range, and angle is in degrees,
// 0-360 range.  A loop value of 0 indicates no looping
// free channel returns true if a free channel was found, and
// channel the number of the channel assigned.
{
	channel = 0;
	while((Mix_Playing(channel) != 0) && (channel < n_channels))
		channel++;

	if (channel < n_channels)	
	{
		// set the channel volume and the position
		Mix_Volume(channel, volume);
		Mix_SetPosition(channel, angle, distance);
		channel = Mix_PlayChannel(channel, sound[snd_index], loop);
		free_channel = true;
		if (channel == -1)
			OutputSndError("Unable to play WAV file: %s\n");
		return (channel != -1);
	}
	else
	{
		free_channel = false;
		return (false);
	}
}

int PlayingChannelSnd(int const &channel)
// returns true if specified channel is playing a sound
{
	return (Mix_Playing(channel) != 0);
}

int PlayingSnd()
// returns true if any channel is playing a sound (excluding music)
{
	int channel = 0;
	while((channel < n_channels) && (Mix_Playing(channel) == 0))
		channel++;
	if (channel < n_channels)	
	{
		return (true);
	}
	else return (false);
}