Figuring out a race condition - c++

Question

I am building a screen recorder, I am using ffmpeg to make the video out from frames I get from Google Chrome. I get green screen in the output video. I think there is a race condition in the threads since I am not allowed to use main thread to do the processing. here how the code look like
This function works each time I get a new frame, I suspect the functions avpicture_fill & vpx_codec_get_cx_data are being rewritten before write_ivf_frame_header & WriteFile are done.
I am thinking of creating a queue where this function push the object pp::VideoFrame then another thread with mutex will dequeue and do the processing below.
What is the best solution for this problem? and what is the optimal way of debugging it
void EncoderInstance::OnGetFrame(int32_t result, pp::VideoFrame frame) {
if (result != PP_OK)
return;
const uint8_t* data = static_cast<const uint8_t*>(frame.GetDataBuffer());
pp::Size size;
frame.GetSize(&size);
uint32_t buffersize = frame.GetDataBufferSize();
if (is_recording_) {
vpx_codec_iter_t iter = NULL;
const vpx_codec_cx_pkt_t *pkt;
// copy the pixels into our "raw input" container.
int bytes_filled = avpicture_fill(&pic_raw, data, AV_PIX_FMT_YUV420P, out_width, out_height);
if(!bytes_filled) {
Logger::Log("Cannot fill the raw input buffer");
return;
}
if(vpx_codec_encode(&codec, &raw, frame_cnt, 1, flags, VPX_DL_REALTIME))
die_codec(&codec, "Failed to encode frame");
while( (pkt = vpx_codec_get_cx_data(&codec, &iter)) ) {
switch(pkt->kind) {
case VPX_CODEC_CX_FRAME_PKT:
glb_app_thread.message_loop().PostWork(callback_factory_.NewCallback(&EncoderInstance::write_ivf_frame_header, pkt));
glb_app_thread.message_loop().PostWork(callback_factory_.NewCallback(&EncoderInstance::WriteFile, pkt));
break;
default:break;
}
}
frame_cnt++;
}
video_track_.RecycleFrame(frame);
if (need_config_) {
ConfigureTrack();
need_config_ = false;
} else {
video_track_.GetFrame(
callback_factory_.NewCallbackWithOutput(
&EncoderInstance::OnGetFrame));
}
}