Decoding with OGG/Vorbis gives no sound

Question

I'd like to play an Ogg/Vorbis audio/video file, but right now I can't get to read audio from a file.

My algorithm to read audio is:

• Initialize required structures:

vorbis_info info;
vorbis_comment comment;
vorbis_dsp_state dsp;
vorbis_block block;

vorbis_info_init(&info);
vorbis_comment_init(&comment);

• Read headers:
  • Call vorbis_synthesis_headerin(&info, &comment, packet); until it returns OV_ENOTVORBIS
  • vorbis_synthesis_init(&dsp, &info);
  • vorbis_block_init(&dsp, &block);
  • Pass the first non-header packet to function below
• Parse packets, do it until audioReady == READY

putPacket(ogg_packet *packet) {
    int ret;
    ret = vorbis_synthesis(&block, packet);
    if( ret == 0 ) {
        ret = vorbis_synthesis_blockin(&dsp, &block);
        audioReady = (ret == 0) ? READY : NOT_READY;
    } else {
        audioReady = NOT_READY;
    }
}

• Read audio data:

float** rawData = nullptr;
readSamples = vorbis_synthesis_pcmout(&dsp, &rawData);
if( readSamples == 0 ) {
    audioReady = NOT_READY;
    return;
}

int16_t* newData = new int16_t[readSamples * getChannels()];
int16_t* dst = newData;
for(unsigned int i=0; i<readSamples; ++i) {
    for(unsigned char ch=0; ch<getChannels(); ++ch) {
        *(dst++) = math::clamp<int16_t>(rawData[ch][i]*32767 + 0.5f, -32767, 32767);
    }
}
audioData.push_back({readSamples * getChannels() , newData});
vorbis_synthesis_read(&dsp, static_cast<int>(readSamples));

audioReady = NOT_READY;

This is where it gets wrong: after examining the newData contents it is revealed that it contains a very silent sound. I doubt if it is the right data which means somewhere along my algorithm I did something wrong.

I tried to find some examples of similar programs, but all I got are sources with very spaghetti-like code, which seems to do the same algorithm like mine, yet they do their job. (There is one off such library: https://github.com/icculus/theoraplay )

Is there any reason why I'm getting (almost) silence in my application?

PS: If you are wondering if I might getting OGG packets wrong, then I assure you this part of my code is working right, as I'm also reading video data from the same file, using the same code and it shows the video right.

Answer 1

I've found it: during reading packets I assumed that one Ogg Page = one Ogg packet. I's wrong: for audio one page can contain many packets. To read it properly one has to make a code like:

do{
   putPacket(&packet);
}while( ogg_stream_packetout(&state, &packet) == 1 );

I did this mistake because for video packets (which I did first) a page contains only one packet.