decode_video.cpp

#include <iostream>
#include <memory>

#include "ffmpegcpp.h"

class PGMFileSink : public ffmpegcpp::VideoFrameSink
{
public:

	PGMFileSink()
	{
	}

	void WriteFrame(AVFrame* frame, AVRational* timeBase) override
	{
		++frameNumber;
		printf("saving frame %3d\n", frameNumber);
		fflush(stdout);


		// write the first channel's color data to a PGM file.
		// This raw image file can be opened with most image editing programs.
		snprintf(fileNameBuffer, sizeof(fileNameBuffer), "pgm-%d.pgm", frameNumber);
		pgm_save(frame->data[0], frame->linesize[0],
			frame->width, frame->height, fileNameBuffer);
	}

	void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
		char *filename)
	{
		FILE *f;
		int i;

		f = fopen(filename, "w");
		fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
		for (i = 0; i < ysize; i++)
			fwrite(buf + i * wrap, 1, xsize, f);
		fclose(f);
	}

	void Close() override
	{
		// nothing to do here.
	}

	bool IsPrimed() const override
	{
		// Return whether we have all information we need to start writing out data.
		// Since we don't really need any data in this use case, we are always ready.
		// A container might only be primed once it received at least one frame from each source
		// it will be muxing together (see Muxer.cpp for how this would work then).
		return true;
	}

private:
	char fileNameBuffer[1024];
	int frameNumber = 0;

};

int main()
{
	// This example will decode a video stream from a container and output it as raw image data, one image per frame.
	try
	{
		// Load this container file so we can extract video from it.
		ffmpegcpp::Demuxer demuxer("samples/big_buck_bunny.mp4");

		// Create a file sink that will just output the raw frame data in one PGM file per frame.
		auto fileSink = std::make_unique<PGMFileSink>();

		// tie the file sink to the best video stream in the input container.
		demuxer.DecodeBestVideoStream(fileSink.get());

		// Prepare the output pipeline. This will push a small amount of frames to the file sink until it IsPrimed returns true.
		demuxer.PreparePipeline();

		// Push all the remaining frames through.
		while (!demuxer.IsDone())
		{
			demuxer.Step();
		}
	}
	catch (ffmpegcpp::FFmpegException e)
	{
		std::cerr << "Exception caught!" << '\n';
		std::cerr << e.what() << '\n';
		throw e;
	}

	std::cout << "Decoding complete!" << '\n';
	std::cout << "Press any key to continue..." << '\n';

	getchar();
}