#include <iostream>
#include <string>
extern "C" {
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
}
int main(int argc, char *argv[]) {
av_register_all();
std::string inputFile;
std::string outputFile;
std::cout << "Enter the name of the MP4 file: ";
std::cin >> inputFile;
std::cout << "Enter the name of the output 3GP file: ";
std::cin >> outputFile;
AVFormatContext *inputFormatContext = avformat_alloc_context();
if (avformat_open_input(&inputFormatContext, inputFile.c_str(), nullptr, nullptr) != 0) {
std::cerr << "Could not open input file" << std::endl;
return 1;
}
if (avformat_find_stream_info(inputFormatContext, nullptr) < 0) {
std::cerr << "Could not find stream information" << std::endl;
return 1;
}
AVFormatContext *outputFormatContext = avformat_alloc_context();
AVOutputFormat *outputFormat = av_guess_format("3gp", nullptr, nullptr);
outputFormatContext->oformat = outputFormat;
if (!(outputFormat->flags & AVFMT_NOFILE)) {
if (avio_open(&outputFormatContext->pb, outputFile.c_str(), AVIO_FLAG_WRITE) < 0) {
std::cerr << "Could not open output file" << std::endl;
return 1;
}
}
for (unsigned int i = 0; i < inputFormatContext->nb_streams; i++) {
AVStream *inStream = inputFormatContext->streams[i];
AVStream *outStream = avformat_new_stream(outputFormatContext, inStream->codec->codec);
if (!outStream) {
std::cerr << "Failed allocating output stream" << std::endl;
return 1;
}
if (avcodec_copy_context(outStream->codec, inStream->codec) != 0) {
std::cerr << "Failed to copy codec context" << std::endl;
return 1;
}
outStream->codec->codec_tag = 0;
if (outputFormatContext->oformat->flags & AVFMT_GLOBALHEADER)
outStream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
}
av_dump_format(outputFormatContext, 0, outputFile.c_str(), 1);
if (avformat_write_header(outputFormatContext, nullptr) < 0) {
std::cerr << "Error while writing header to output file" << std::endl;
return 1;
}
AVPacket packet;
while (av_read_frame(inputFormatContext, &packet) >= 0) {
AVStream *inStream = inputFormatContext->streams[packet.stream_index];
AVStream *outStream = outputFormatContext->streams[packet.stream_index];
packet.pts = av_rescale_q_rnd(packet.pts, inStream->time_base, outStream->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
packet.dts = av_rescale_q_rnd(packet.dts, inStream->time_base, outStream->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
packet.duration = av_rescale_q(packet.duration, inStream->time_base, outStream->time_base);
packet.pos = -1;
if (av_interleaved_write_frame(outputFormatContext, &packet) < 0) {
std::cerr << "Error while writing video frame" << std::endl;
return 1;
}
av_packet_unref(&packet);
}
if (av_write_trailer(outputFormatContext) < 0) {
std::cerr << "Error while writing trailer to output file" << std::endl;
return 1;
}
avformat_close_input(&inputFormatContext);
if (!(outputFormat->flags & AVFMT_NOFILE))
avio_closep(&outputFormatContext->pb);
avformat_free_context(inputFormatContext);
avformat_free_context(outputFormatContext);
return 0;
}
Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!
OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.
#include <iostream>
#include <string>
using namespace std;
int main()
{
string name;
cout << "Enter name:";
getline (cin, name);
cout << "Hello " << name;
return 0;
}
C++ is a widely used middle-level programming language.
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
//code
}
else {
//code
}
You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.
Switch is an alternative to If-Else-If ladder.
switch(conditional-expression){
case value1:
// code
break; // optional
case value2:
// code
break; // optional
......
default:
code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while (condition) {
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (condition);
Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.
return_type function_name(parameters);
function_name (parameters)
return_type function_name(parameters) {
// code
}