Decoding loop logic from matroska (mkv, webm) to audio (C++ via libvorbis) - c++

Question

(I'm not fluent in english i'll try to do my best)
I try to code (C++) a simple mkv player. I'm very new in this subject, so I discover all I need little by little. For the beginning, I use VP8 codec for video and Vorbis for audio.
The video side seem ok for now, but I'm in trouble with audio.
I can't figure out the loop logic to decode the audio frames I get from mkvparser with the libvorbis.
I looked up to this sample and this brief explanation but can't manage to make it work in my case. And I didn't find other simple examples.
Here is a chunk of my code:
const mkvparser::Block* const pBlock = m_pMkvContext->pBlockEntry->GetBlock();
const mkvparser::Track* const pTrack = m_pMkvContext->pTracks->GetTrackByNumber( (unsigned long)pBlock->GetTrackNumber() );
if ( pTrack != NULL )
{
const long long trackType = pTrack->GetType();
const int frameCount = pBlock->GetFrameCount();
if ( frameCount > 0 )
{
const mkvparser::Block::Frame& oFrame = pBlock->GetFrame( 0 );
unsigned char* pData = (unsigned char*)malloc( (size_t)oFrame.len );
oFrame.Read( &m_pMkvContext->oReader, pData );
if ( trackType == mkvparser::Track::kVideo )
{
// i'm ok here
}
else if ( trackType == mkvparser::Track::kAudio )
{
// what to do here with my audio frame data ?
}
free( pData );
}
}
And maybe the way I get frames is good for video and not for audio...
Do you guys know some good resources to share about it? Or some advices?
Thanks for help !
[EDIT] : I forgot to add one of my try:
bool MoviePlayer::DecodeAudioData( unsigned char* pData, uint32 iSize )
{
int ret;
char* pBuffer = NULL;
pBuffer = ogg_sync_buffer( &m_pOVContext->oOggSyncState, iSize );
memcpy( pBuffer, pData, iSize );
ogg_sync_wrote( &m_pOVContext->oOggSyncState, iSize );
ret = ogg_sync_pageout( &m_pOVContext->oOggSyncState, &m_pOVContext->oOggPage );
ret = ogg_stream_init( &m_pOVContext->oOggStreamState, ogg_page_serialno(&m_pOVContext->oOggPage) );
ret = ogg_stream_pagein( &m_pOVContext->oOggStreamState, &m_pOVContext->oOggPage );
int iPacketsCount = ogg_page_packets( &m_pOVContext->oOggPage );
for ( int i = 0; i < iPacketsCount; ++i )
{
ret = ogg_stream_packetout(&m_pOVContext->oOggStreamState, &m_pOVContext->oOggPacket);
// do something with the packet...
}
return true;
}
It crashes at ogg_sync_pageout, as my ogg_page was not correctly initialized.
But, not coming from a proper .ogg file as in the examples i found, i don't know how to correctly initialize the vorbis structures.

Answer 1

https://matroska.org/technical/specs/codecid/index.html
in A_VORBIS section
The private data contains the first three Vorbis packet in order....
and the codec private is here
https://matroska.org/technical/specs/index.html
"CodecPrivate 3 [63][A2]"