Loop streaming .ogg audio - OpenAL - c++

Question

I have problem looping a streamed ogg vorbis file.
This is the code :
fslStream_OGG::fslStream_OGG()
{
className = "fslSound";
iMemSize = 0;
iLength = 0;
bSourceRelative = false;
bIsLooping = false;
bForceStop = false;
bActive = false;
source = buffer = 0;
current_gain = 1.0f;
outer_gain = 0;
snd_info.uiChannels = snd_info.uiFrequency = snd_info.uiSampling = 0;
}
fslStream_OGG::~fslStream_OGG()
{
if (bStreamCreated)
{
alSourceStop(source);
Empty();
alDeleteSources(1,&source);
alDeleteBuffers(2,buffers);
ov_clear(&oggStream);
}
}
bool fslStream_OGG::Update()
{
ALenum state;
alGetSourcei(source,AL_SOURCE_STATE,&state);
if (state == AL_PAUSED || !bActive) return false;
int processed;
alGetSourcei(source,AL_BUFFERS_PROCESSED,&processed);
while (processed--)
{
ALuint bufferI;
alSourceUnqueueBuffers(source,1,&bufferI);
Stream(bufferI);
if (bActive) alSourceQueueBuffers(source,1,&bufferI);
}
if (state == AL_STOPPED || !bActive)
{
bActive = false;
StreamSetPos(0.0f);
if (bForceStop) return false;
if (bIsLooping)
{
alSourceStop(source); // <- *** note these ***
Empty(); // <- *** 2 lines of code ***
StreamPlay();
alSourcePlay(source);
}
else
{
return true;
}
}
return false;
}
void fslStream_OGG::StreamPlay()
{
if (!bActive)
{
bActive = true;
bForceStop = false;
Stream(buffers[0]);
Stream(buffers[1]);
alSourceQueueBuffers(source,2,buffers);
}
}
bool fslStream_OGG::Open(const char* strFile)
{
bStreamCreated = false;
vorbis_info* vorbisInfo;
oggFile = fopen(strFile,"rb");
if (!oggFile) return false;
if (ov_open_callbacks(oggFile,&oggStream,NULL,0,OV_CALLBACKS_DEFAULT) != 0)
{
fclose(oggFile);
return false;
}
vorbisInfo = ov_info(&oggStream,-1);
if (vorbisInfo->channels == 1)
format = AL_FORMAT_MONO16;
else format = AL_FORMAT_STEREO16;
alGenBuffers(2,buffers);
alGenSources(1,&source);
iLength = (long)(ov_time_total(&oggStream,-1) * 1000.0);
snd_info.uiChannels = (format == AL_FORMAT_MONO8 || format == AL_FORMAT_MONO16)? 1:2;
snd_info.uiSampling = (format == AL_FORMAT_MONO8 || format == AL_FORMAT_STEREO8)? 8:16;
snd_info.uiFrequency = vorbisInfo->rate;
bStreamCreated = true;
bIsStream = true;
return true;
}
void fslStream_OGG::Stream(ALuint bufferI)
{
int size = 0;
int section;
int result;
bActive = true;
while (size < OGG_STREAM_BUFFER_SIZE)
{
result = ov_read(&oggStream,data + size,OGG_STREAM_BUFFER_SIZE - size,0,2,1,&section);
if (result > 0)
{
size += result;
}
else
{
if (result < 0) return; else break;
}
}
if (size == 0) { bActive = false; return; }
alBufferData(bufferI,format,data,size,snd_info.uiFrequency);
}
void fslStream_OGG::Empty()
{
int queued;
alGetSourcei(source,AL_BUFFERS_QUEUED,&queued);
while (queued--)
{
ALuint bufferI;
alSourceUnqueueBuffers(source,1,&bufferI);
}
}
void fslStream_OGG::StreamSetPos(float p)
{
ov_time_seek(&oggStream,p);
}
float fslStream_OGG::StreamGetPos()
{
return (float)ov_time_tell(&oggStream);
}
Note the 2 lines of code I have marked with ***.
In all cases, the file starts playing fine and rewinds when it ends. However :
Without those 2 lines of code, when repeated the file sounds "corrupted". If let to repeat again, it sounds even more "corrupted". I believe this is because OpenAl and the Vorbis decoder get "unsynchronized" writing/reading the buffer when the stream is repeated.
If I add those 2 lines of code, the file repeats without sounding corrupted. However, the file isn't repeated seamlessly; it rewinds a few centiseconds before it ends. I suspect this is because the buffers are not played to the end before rewinding to start.
I would be obliged if anyone could lend a helping hand.
Many thanks in advance,
Bill

Answer 1

It seems that I have fixed the problem (I won't be sure without extensive testing).
I have fixed the Update method as follows :
bool fslStream_OGG::Update()
{
ALenum state;
alGetSourcei(source,AL_SOURCE_STATE,&state);
//if (state == AL_PAUSED || !bActive) return false; // <- WRONG
if (state == AL_PAUSED) return false;
int processed;
alGetSourcei(source,AL_BUFFERS_PROCESSED,&processed);
while (processed--)
{
ALuint bufferI;
alSourceUnqueueBuffers(source,1,&bufferI);
Stream(bufferI);
if (bActive) alSourceQueueBuffers(source,1,&bufferI);
}
//if (state == AL_STOPPED || !bActive) /// <- WRONG
if (state == AL_STOPPED)
{
bActive = false;
StreamSetPos(0.0f);
if (bForceStop) return false;
if (bIsLooping)
{
//alSourceStop(source); // <- I have added these
//Empty(); // <- 2 lines of code
StreamPlay();
alSourcePlay(source);
}
else
{
return true;
}
}
return false;
}
Those 2 lines of code seem not to be necessary now. Will have to test it with different OSes, hardware etc...