ffmpeg hangs in avcodec_encode_video2 - c++

Question

I encode the video stream using ffmeg. Shell QT Creator. OC Windows 7. The compiler MinGW. H264 codec.
There is a function, which I give to the input frame, and I must return an encoded byte array. Within this function it hangs when calling avcodec_encode_video2, but not on the first call, and at random.
That is, an arbitrary coding frame hangs (100 to 10000).
QByteArray VideoEncoder::createFrameVideoFromImage(QImage picture)
{
AVFrame* frame_source = av_frame_alloc();
avpicture_fill((AVPicture*)frame_source, picture.bits(), AV_PIX_FMT_RGB24, this->width_frame, this->height_frame);
AVFrame* frame_dst = av_frame_alloc();
avpicture_fill((AVPicture*)frame_dst, (uint8_t*)this->inbuffer, AV_PIX_FMT_YUV420P, this->width_frame, this->height_frame);
sws_scale(this->convert_rgb_yuv, frame_source->data, frame_source->linesize,
0, this->ctx_codec_in->height, frame_dst->data, frame_dst->linesize);
AVPacket packet;
av_init_packet(&packet);
packet.data = NULL;
packet.size = 0;
packet.pts = packet.dts = AV_NOPTS_VALUE;
int nOutputSize = 0;
if (avcodec_encode_video2(this->ctx_codec_in, &packet, frame_dst, &nOutputSize) < 0)
{
qDebug() << "VideoEncoder error";
}
this->traffic += packet.size;
QByteArray data_frame = QByteArray((char*)packet.data, packet.size);
av_frame_free(&frame_source);
av_frame_free(&frame_dst);
av_free_packet(&packet);
return data_frame;
}
Thank you in advance!