examples: Improve documentation in V3C examples

examples/v3c/v3c_util.cc

@@ -250,6 +250,10 @@ void parse_v3c_header(v3c_unit_header &hdr, char* buf, uint64_t ptr)
 uint64_t get_size(std::string filename)
 {
     std::ifstream infile(filename, std::ios_base::binary);
+    if (!infile.is_open()) {
+        std::cout << "File not found" << std::endl;
+        return 0;
+    }
 
     //get length of file
     infile.seekg(0, infile.end);
@@ -263,6 +267,11 @@ char* get_cmem(std::string filename)
 {
     std::ifstream infile(filename, std::ios_base::binary);
 
+    if (!infile.is_open()) {
+        std::cout << "File not found" << std::endl;
+        return 0;
+    }
+
     //get length of file
     infile.seekg(0, infile.end);
     size_t length = infile.tellg();

examples/v3c_receiver.cc

@@ -6,7 +6,7 @@
 #include <fstream>
 #include <chrono>
 
-/* This example demonstrates receiving V3C Sample Stream via uvgRTP. It can be used to send V-PCC encoded files, but with
+/* This example demonstrates receiving a V3C Sample Stream via uvgRTP. It can be used to send V-PCC encoded files, but with
  * minor modifications (addition of V3C_CAD and V3C_PVD streams) it can be used also for MIV encoded files. See the comments
  * in v3c_sender for more comprehensive documentation on V3C RTP streaming.
  

examples/v3c_sender.cc

@@ -10,49 +10,54 @@
 
 constexpr char REMOTE_ADDRESS[] = "127.0.0.1";
 
-// Path to the V3C file that you want to send
-std::string PATH = "";
+// Path to the V-PCC file that you want to send
+std::string PATH = "longdress.vpcc";
 void sender_func(uvgrtp::media_stream* stream, const char* cbuf, const std::vector<v3c_unit_info> &units, rtp_flags_t flags, int fmt);
 
 std::atomic<uint64_t> bytes_sent;
 int main(void)
 {
-    /* This example demonstrates sending a file that is in the V3C sample stream format via uvgRTP. It can be used to send V-PCC
-     * encoded files, but with minor modifications (addition of V3C_CAD and V3C_PVD streams) it can be used also for MIV
+    /* This example demonstrates transmitting a file that is in the V3C sample stream format via uvgRTP. It can be used to transmit
+     * V-PCC encoded files, but with minor modifications (addition of V3C_CAD and V3C_PVD streams) it can also be used for MIV
      * encoded files.
      * 
-     * The V3C Sample Stream contains a V3C Sample Stream
-     * header byte and multiple V3C Units with their sizes specified before each unit. A V3C Unit then contains a V3C header
-     * and Atlas or Video NAL units, depending on the V3C unit type. Video data can be either AVC, HEVC or VVC encoded. This
-     * example uses HEVC encoding. Using AVC or VVC requires you to set the media streams payload format accordingly.
+     * The V3C sample stream contains a V3C sample stream header byte and multiple V3C Units with their sizes specified before
+     * each unit. A V3C Unit then contains a V3C header and Atlas or Video NAL units, depending on the V3C unit type. Video
+     * data can be either AVC, HEVC or VVC encoded. By default this example uses HEVC encoding. Using AVC or VVC only requires
+     * you to set the media streams payload format accordingly.
      * 
-     * The process of sending and receiving a V3C Sample Stream file via uvgRTP contains the following steps:
+     * The process of sending and receiving a V3C sample stream via uvgRTP contains the following steps:
      * Parse file and extract locations and sizes of NAL units -> Send NAL units in separate uvgRTP media streams
      * -> Receive NAL units -> Reconstruct V3C Sample Stream
      * 
      * In this example there are in total 5 media streams, one for each component:
-     * 1. Parameter set stream (NOTE: Parameter set should be carried via a signaling protocol such as SDP. It is only
-     *    transmitted using RTP for the simplicity of this demonstration.)
+     * 1. Parameter set stream (NOTE: Parameter set should be carried via a signaling protocol such as SDP at the start of the
+          stream. In this demonstration, it is only transmitted using an RTP stream for simplicity.)
      * 2. Atlas stream
      * 3. Occupancy Video stream
      * 4. Geometry Video stream
      * 5. Attribute Video Stream
      * 
      * There is also the possibility to have two more streams: Packed Video and Common Atlas Data. These are not included in
-     * this example as our test files (V-PCC) don't have them. If you need these (MIV), it should be quite easy to implement them
+     * this example as V-PCC files don't have them. If you need these (MIV), it is easy to add them
      *
      A few notes for users:
-     - This example expects there to be no packet loss. If some NAL units are lost in transmission,
-       the reconstruction will not work.
-     - Please also read the documentation on v3c_receiver.cc before testing this example. 
-     - Use RTP_NO_H26X_SCL when sending video frames, as there is no start codes in the video sub-streams
+     - This demonstration expects there to be no packet loss. If some NAL units are lost in transmission,
+       issues may occur in the reconstruction
+     - Please also read the documentation on v3c_receiver.cc before testing this example.
+     - The information in V3C unit headers is also supposed to be transmitted once at the start of the stream via SDP. For
+       simplicity, in this example they are just deduced at the receiver.
+     - Remember to use RTP_NO_H26X_SCL flag when sending video frames, as there is no start codes in the video sub-streams
      - v3c_sender and v3c_receiver programs use common functions defined in v3c_util. */
 
     bytes_sent = 0;
     v3c_file_map mmap;
 
     /* Read the file and its size */
     uint64_t len = get_size(PATH);
+    if (len == 0) {
+        return EXIT_FAILURE;
+    }
     char* cbuf = get_cmem(PATH);
     std::cout << "Parsing V3C file, size " << len << std::endl;