Question

I am trying to make an app that plays audio stream using ffmpeg, libmms.
I can open mms server, get stream, and decode audio frame to raw frame using suitable codec.
However I don’t know how to do next.
I think I must use AudioToolbox/AudioToolbox.h and make audioqueue.
but however when I give audioqueuebuffer decode buffer’s memory and play, Only plays the white noise.
Here is my code.

What am i missing?
Any comment and hint is very appreciated.
Thanks very much.

while(av_read_frame(pFormatCtx, &pkt)>=0)
{
    int pkt_decoded_len = 0;
    int frame_decoded_len;
    int decode_buff_remain=AVCODEC_MAX_AUDIO_FRAME_SIZE * 5;
    if(pkt.stream_index==audiostream)
    {
        frame_decoded_len=decode_buff_remain;
        int16_t *decode_buff_ptr = decode_buffer;
        int decoded_tot_len=0;
        pkt_decoded_len = avcodec_decode_audio2(pCodecCtx, decode_buff_ptr, &frame_decoded_len,
                                                pkt.data, pkt.size);
        if (pkt_decoded_len <0) break;
        AudioQueueAllocateBuffer(audioQueue, kBufferSize, &buffers[i]);
        AQOutputCallback(self, audioQueue, buffers[i], pkt_decoded_len);

        if(i == 1){
            AudioQueueSetParameter(audioQueue, kAudioQueueParam_Volume, 1.0);
            AudioQueueStart(audioQueue, NULL);
        }
        i++;
    }
}


void AQOutputCallback(void *inData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer, int copySize)
{
    mmsDemoViewController *staticApp = (mmsDemoViewController *)inData;
    [staticApp handleBufferCompleteForQueue:inAQ buffer:inBuffer size:copySize];
}

- (void)handleBufferCompleteForQueue:(AudioQueueRef)inAQ
                          buffer:(AudioQueueBufferRef)inBuffer
                            size:(int)copySize
{
    inBuffer->mAudioDataByteSize = inBuffer->mAudioDataBytesCapacity;
    memcpy((char*)inBuffer->mAudioData, (const char*)decode_buffer, copySize);

    AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL);
}

Answer 1

You called AQOutputCallback wrongly. You don’t have to necessarilly call that method.
That method will be called automatically when audio buffers used by audio queue.
And the prototype of AQOutputCallback was wrong.
According to your code That method will not be called automatically I think.
You can Override

typedef void (*AudioQueueOutputCallback) (
   void                 *inUserData,
   AudioQueueRef        inAQ,
   AudioQueueBufferRef  inBuffer
);

like this

void AudioQueueCallback(void* inUserData, AudioQueueRef inAQ, AudioQueueBufferRef 
                       inBuffer);

And you should set the Audio Session When your app starts.
The important references are here.

However, What is the extension of Audio you are willing to decode?
AudioStreamPacketDescription is important if the Audio is Variable Frame per packet.
Otherwise, if One Frame per One Packet, AudioStreamPacketDescription is not significant.

What you do next is
To Set the audio session, To Get raw audio frame using decoder, To Put the frame into the Audio Buffer.
Instead of you, Make the system to fill the empty buffer.