libav c++ raw h264 TCP Stream to opencv Mat - c++

Question

I writting a software for my classes that receive a h264 stream from a drone and i need to convert the video stream to opencv Mat.
I have no trouble to receive the frame and if i save it to a .264 file i can read the output with VLC.
The drone is sending IDR-Frame and P-Frame , since i don't need to see the video stream juste some frame of it, i was thinking of only using the IDR-Frame to get the image but i have trouble to understand how to use libavcodec from FFMPEG, how can i create a AVFrame from my IDR-Frame and how to convert it to cv::Mat after.
i have try the following code, i have store the full frame in .raw file and i try to decode them , but i get read error when i try to parse the packet to a frame, i don't thing a initialize the buffer of ARPacket the right way :
AVFormatContext* fc = 0;
int vi = -1; // vi veut dire video index
inline cv::Mat avframe_to_mat(const AVFrame* avframe)
{
AVFrame dst;
cv::Mat m;
memset(&dst, 0, sizeof(dst));
int w = avframe->width, h = avframe->height;
m = cv::Mat(h, w, CV_8UC3);
dst.data[0] = (uint8_t*)m.data;
avpicture_fill((AVPicture*)&dst, dst.data[0], AV_PIX_FMT_BGR24, w, h);
struct SwsContext *convert_ctx = NULL;
enum AVPixelFormat src_pixfmt = AV_PIX_FMT_BGR24;
enum AVPixelFormat dst_pixfmt = AV_PIX_FMT_BGR24;
convert_ctx = sws_getContext(w, h, src_pixfmt, w, h, dst_pixfmt, SWS_FAST_BILINEAR, NULL, NULL, NULL);
sws_scale(convert_ctx, avframe->data, avframe->linesize, 0, h, dst.data, dst.linesize);
sws_freeContext(convert_ctx);
return m;
}
inline bool init_stream(unsigned char* data, int len)
{
const char* file = "test.avi";
const AVCodecID codec_id = AV_CODEC_ID_H264;
AVCodec* codec = avcodec_find_encoder(codec_id);
// Crée le container pour le stream
fc = avformat_alloc_context();
/*
AVOutputFormat *of = av_guess_format(0, file, 0);
fc = avformat_alloc_context();
fc->oformat = of;
strcpy(fc->filename, file);
*/
int br = 1000000;
int w = 640;
int h = 360;
int fps = 24;
// ajoute un stream video
AVStream* pst = avformat_new_stream(fc, codec); // Pourquoi je passe pas le codec ici ?
vi = pst->index;
codec_context = avcodec_alloc_context3(codec);
codec_context->bit_rate = br;
codec_context->width = w;
codec_context->height = h;
codec_context->time_base = {1,fps};
codec_context->gop_size = 10; // Emit one intra frame every ten frames
codec_context->max_b_frames = 1;
codec_context->pix_fmt = AV_PIX_FMT_YUV420P;
// Vu quon n'est en h264
av_opt_set(codec_context->priv_data, "preset", "slow", 0);
// Ouvre notre codec
if(avcodec_open2(codec_context, codec,nullptr) < 0)
{
cerr << "Impossible d'ouvrir le codec" << endl;
return false;
}
if (!(fc->oformat->flags & AVFMT_NOFILE))
avio_open(&fc->pb, fc->filename,0);
// avformat_write_header(fc,nullptr);
return true;
}
inline void append_stream(uint8_t* data, int len)
{
if( 0 > vi)
{
cerr << "video index is less than 0" << endl;
return;
}
AVStream* pst = fc->streams[vi];
AVPacket pkt;
// Init un nouveau packet
av_init_packet(&pkt);
pkt.flags |= AV_PKT_FLAG_KEY;
pkt.data = data;
pkt.stream_index = pst->index;
pkt.size = len;
pkt.dts = AV_NOPTS_VALUE;
pkt.pts = AV_NOPTS_VALUE;
// ERROR accessing location
av_interleaved_write_frame(fc, &pkt);
}
inline void execute_staging_test(const fs::path& folder, int nbr_trame)
{
fs::path file_name = folder / "stream.bin";
if(!fs::exists(file_name))
{
cerr << "The file " << file_name.string() << " does not exists" << endl;
return;
}
avcodec_register_all();
av_log_set_level(AV_LOG_DEBUG);
int length = 0;
char* buffer;
for(int i = 0; i < nbr_trame;i++)
{
fs::path file = std::to_string(i) + ".raw";
file = folder / file;
cout << "Got frame on " << file.string() << endl;
ifstream ifs(file, ofstream::binary);
// Get la longeur du fichier pour savoir le buffer a prendre
ifs.seekg(0, ios::end);
length = ifs.tellg();
ifs.seekg(0, ios::beg);
if (length == 0) {
std::cerr << "No data in file " << file << std::endl;
return;
}
buffer = new char[length];
std::cout << "File " << file << " length is " << length << std::endl;
ifs.read(buffer, length);
cv::VideoWriter vw;
int codec = cv::VideoWriter::fourcc('X', '2', '6', '4');
if(!fc)
{
if(!init_stream((unsigned char*)buffer, length))
{
return;
}
}
if(fc)
{
append_stream((unsigned char*)buffer, length);
}
}
}
Thanks you very mutch if you can help me , i'm a novice in c++ and i have never deal with video stream. If you want to see the full code its host on github repo to this project