SDL2 + ffmpeg2 intermittent clicks instead of audio - c++

Question

Using c++, SDL2, SDL2_mix, ffmpeg2.
Inited SDL2_mix with callback
Mix_HookMusic(MusicPlayer, &g_audioPos);
Decoded audio from ogg to AVFrame* by this code:
while(av_read_frame(m_formatContext, &m_packet) >= 0)
{
if(m_packet.stream_index == m_audioStream)
{
int audio_frame_finished;
avcodec_decode_audio4(m_audioCodecContext, m_audioFrame, &audio_frame_finished, &m_packet);
if(!audio_frame_finished)
{
continue;
}
}
}
After this code i have frame with some m_audioFrame->data[0] and m_audioFrame->linesize[0] == 4096
Once in a while my callback being called:
void MusicPlayer(void *_udata, Uint8 *_stream, int _len)
{
if(!g_audioData)
{
return;
}
AudioData* audio = reinterpret_cast<AudioData*>(g_audioData);
if(!audio || audio->Frame->linesize[0] == 0)
{
return;
}
SDL_memcpy((Uint8*)audio->Data + audio->Pos, (Uint8*)audio->Frame->data[0], audio->Frame->linesize[0]);
audio->Pos+= audio->Frame->linesize[0];
int rest = g_chunkSize - audio->Pos;//frame->linesize[0];
if(rest <= 0)
{
SDL_memcpy(_stream, audio->Data, _len);
audio->Pos = 0;
*(int*)_udata += _len;
}
}
_len == 8192, so i must push 2 frames to fill stream, but all i get - clicks in my speaker. What am i doing wrong?
PS: Tried to reopen MIX with Mix_OpenAudio(m_audioCodecContext->sample_rate, AUDIO_S16SYS, m_audioCodecContext->channels, 4096);. Interesting thing is m_audioCodecContext->channels == 2 and when my callback being called _len = 16384. Have no idea what to do. Please help!!!

Answer 1

You did not show how you perform the ffmpeg initialization; I'd speculate you forgot to specify the requested sample format:
aCodecCtx->request_sample_fmt = AV_SAMPLE_FMT_S16;
Take a look at the source code of my Karaoke lyrics editor which uses the SDL/ffmpeg audio player based on the latest ffmpeg (and hence decode_audio4): https://sourceforge.net/p/karlyriceditor/code/HEAD/tree/src/audioplayerprivate.cpp