[C++知识库]ffmpeg mp4转gif

gif，即动态图，只带视频，不带声音，主要原因是声音太敏感，自动播放不得了。
pix_fmt是rgb的，不会是yuv，主要是计算机在显示图像时，是按着rgb的方式进行显示；所以gif的pix_fmt是rgb，就减少了一次yuv到rgb的转换，使得播放效果流畅。

本文读取一个mp4里面的内容，读出来是yuv420p格式，然后转成AV_PIX_FMT_BGR8，进行编码，产生最终的gif文件。

其中转换器构建的代码如下：

m_pImgConvertCtx = sws_getContext(m_pReadCodecCtx_VideoA->width, m_pReadCodecCtx_VideoA->height, (AVPixelFormat)m_pFormatCtx_FileA->streams[0]->codecpar->format,
			m_iVideoWidth, m_iVideoHeight, m_pCodecEncodeCtx_Video->pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);

转换过程代码如下：

int iScale = sws_scale(m_pImgConvertCtx, (const uint8_t* const*)pFrameVideoA->data, pFrameVideoA->linesize, 0, iOutVideoHeight, pFrameGif->data, pFrameGif->linesize);

代码工程结构如下：

其中FfmpegGifTest.cpp的代码如下：

#include <iostream>
#include <vector>

#include "ConvertToGif.h"

#ifdef	__cplusplus
extern "C"
{
#endif

#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avutil.lib")
#pragma comment(lib, "avdevice.lib")
#pragma comment(lib, "avfilter.lib")
#pragma comment(lib, "postproc.lib")
#pragma comment(lib, "swresample.lib")
#pragma comment(lib, "swscale.lib")


#ifdef __cplusplus
};
#endif



int main()
{
	CConvertToGif cConvertToGif;
	const char *pFileA = "E:\\learn\\ffmpeg\\FfmpegGifTest\\x64\\Release\\huoluan3.mp4";

	const char *pFileOut = "E:\\learn\\ffmpeg\\FfmpegGifTest\\x64\\Release\\huoluan3.gif";


	cConvertToGif.StartConvert(pFileA, pFileOut);
	cConvertToGif.WaitFinish();
	return 0;
}

ConvertToGif.h的代码如下：

#pragma once

#include <Windows.h>

#ifdef	__cplusplus
extern "C"
{
#endif
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libswresample/swresample.h"
#include "libavdevice/avdevice.h"
#include "libavutil/audio_fifo.h"
#include "libavutil/avutil.h"
#include "libavutil/fifo.h"
#include "libavutil/frame.h"
#include "libavutil/imgutils.h"

#include "libavfilter/avfilter.h"
#include "libavfilter/buffersink.h"
#include "libavfilter/buffersrc.h"


#ifdef __cplusplus
};
#endif

class CConvertToGif
{
public:
	CConvertToGif();
	~CConvertToGif();
public:
	int StartConvert(const char *pFileA, const char *pFileOut);
	int WaitFinish();
private:
	int OpenFileA(const char *pFileA);
	int OpenOutPut(const char *pFileOut);
private:
	static DWORD WINAPI VideoAReadProc(LPVOID lpParam);
	void VideoARead();


	static DWORD WINAPI VideoConvertProc(LPVOID lpParam);
	void VideoConvert();
private:
	AVFormatContext *m_pFormatCtx_FileA = NULL;

	AVCodecContext *m_pReadCodecCtx_VideoA = NULL;
	AVCodec *m_pReadCodec_VideoA = NULL;


	AVCodecContext	*m_pCodecEncodeCtx_Video = NULL;
	AVFormatContext *m_pFormatCtx_Out = NULL;

	AVFifoBuffer *m_pVideoAFifo = NULL;


	int m_iVideoWidth = 1920;
	int m_iVideoHeight = 1080;
	int m_iYuv420FrameSize = 0;
private:
	CRITICAL_SECTION m_csVideoASection;
	HANDLE m_hVideoAReadThread = NULL;
	HANDLE m_hVideoConvertThread = NULL;
	AVRational m_streamTimeBase;
	SwsContext *m_pImgConvertCtx = NULL;
};

ConvertToGif.cpp的代码如下：

#include "ConvertToGif.h"





CConvertToGif::CConvertToGif()
{
	InitializeCriticalSection(&m_csVideoASection);
}

CConvertToGif::~CConvertToGif()
{
	DeleteCriticalSection(&m_csVideoASection);
}

int CConvertToGif::StartConvert(const char *pFileA, const char *pFileOut)
{
	int ret = -1;
	do
	{
		ret = OpenFileA(pFileA);
		if (ret != 0)
		{
			break;
		}

		ret = OpenOutPut(pFileOut);
		if (ret != 0)
		{
			break;
		}

		m_pImgConvertCtx = sws_getContext(m_pReadCodecCtx_VideoA->width, m_pReadCodecCtx_VideoA->height, (AVPixelFormat)m_pFormatCtx_FileA->streams[0]->codecpar->format,
			m_iVideoWidth, m_iVideoHeight, m_pCodecEncodeCtx_Video->pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);


		m_iYuv420FrameSize = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, m_pReadCodecCtx_VideoA->width, m_pReadCodecCtx_VideoA->height, 1);
		//申请30帧缓存
		m_pVideoAFifo = av_fifo_alloc(30 * m_iYuv420FrameSize);

		m_hVideoAReadThread = CreateThread(NULL, 0, VideoAReadProc, this, 0, NULL);

		m_hVideoConvertThread = CreateThread(NULL, 0, VideoConvertProc, this, 0, NULL);

	} while (0);

	return ret;
}

int CConvertToGif::WaitFinish()
{
	int ret = 0;
	do
	{
		if (NULL == m_hVideoAReadThread)
		{
			break;
		}
		WaitForSingleObject(m_hVideoAReadThread, INFINITE);

		CloseHandle(m_hVideoAReadThread);
		m_hVideoAReadThread = NULL;

		WaitForSingleObject(m_hVideoConvertThread, INFINITE);
		CloseHandle(m_hVideoConvertThread);
		m_hVideoConvertThread = NULL;
	} while (0);

	return ret;
}

int CConvertToGif::OpenFileA(const char *pFileA)
{
	int ret = -1;

	do
	{
		if ((ret = avformat_open_input(&m_pFormatCtx_FileA, pFileA, 0, 0)) < 0) {
			printf("Could not open input file.");
			break;
		}
		if ((ret = avformat_find_stream_info(m_pFormatCtx_FileA, 0)) < 0) {
			printf("Failed to retrieve input stream information");
			break;
		}

		if (m_pFormatCtx_FileA->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)
		{
			break;
		}

		m_streamTimeBase = m_pFormatCtx_FileA->streams[0]->time_base;

		m_pReadCodec_VideoA = (AVCodec *)avcodec_find_decoder(m_pFormatCtx_FileA->streams[0]->codecpar->codec_id);

		m_pReadCodecCtx_VideoA = avcodec_alloc_context3(m_pReadCodec_VideoA);

		if (m_pReadCodecCtx_VideoA == NULL)
		{
			break;
		}
		avcodec_parameters_to_context(m_pReadCodecCtx_VideoA, m_pFormatCtx_FileA->streams[0]->codecpar);

		m_iVideoWidth = m_pReadCodecCtx_VideoA->width;
		m_iVideoHeight = m_pReadCodecCtx_VideoA->height;

		m_pReadCodecCtx_VideoA->framerate = m_pFormatCtx_FileA->streams[0]->r_frame_rate;

		if (avcodec_open2(m_pReadCodecCtx_VideoA, m_pReadCodec_VideoA, NULL) < 0)
		{
			break;
		}

		ret = 0;
	} while (0);


	return ret;
}


int CConvertToGif::OpenOutPut(const char *pFileOut)
{
	int iRet = -1;

	AVStream *pAudioStream = NULL;
	AVStream *pVideoStream = NULL;

	do
	{
		avformat_alloc_output_context2(&m_pFormatCtx_Out, NULL, NULL, pFileOut);

		{
			AVCodec* pCodecEncode_Video = (AVCodec *)avcodec_find_encoder(m_pFormatCtx_Out->oformat->video_codec);

			m_pCodecEncodeCtx_Video = avcodec_alloc_context3(pCodecEncode_Video);
			if (!m_pCodecEncodeCtx_Video)
			{
				break;
			}

			pVideoStream = avformat_new_stream(m_pFormatCtx_Out, pCodecEncode_Video);
			if (!pVideoStream)
			{
				break;
			}

			int frameRate = m_pFormatCtx_FileA->streams[0]->r_frame_rate.num / m_pFormatCtx_FileA->streams[0]->r_frame_rate.den;
			m_pCodecEncodeCtx_Video->flags |= AV_CODEC_FLAG_QSCALE;
			m_pCodecEncodeCtx_Video->bit_rate = 4000000;
			m_pCodecEncodeCtx_Video->rc_min_rate = 4000000;
			m_pCodecEncodeCtx_Video->rc_max_rate = 4000000;
			m_pCodecEncodeCtx_Video->bit_rate_tolerance = 4000000;
			m_pCodecEncodeCtx_Video->time_base.den = frameRate;
			m_pCodecEncodeCtx_Video->time_base.num = 1;

			m_pCodecEncodeCtx_Video->width = m_iVideoWidth;
			m_pCodecEncodeCtx_Video->height = m_iVideoHeight;
			//pH264Encoder->pCodecCtx->frame_number = 1;
			m_pCodecEncodeCtx_Video->gop_size = 12;
			m_pCodecEncodeCtx_Video->max_b_frames = 0;
			m_pCodecEncodeCtx_Video->thread_count = 4;
			m_pCodecEncodeCtx_Video->pix_fmt = AV_PIX_FMT_BGR8;
			m_pCodecEncodeCtx_Video->codec_type = AVMEDIA_TYPE_VIDEO;

			av_opt_set(m_pCodecEncodeCtx_Video->priv_data, "b-pyramid", "none", 0);
			av_opt_set(m_pCodecEncodeCtx_Video->priv_data, "preset", "superfast", 0);
			av_opt_set(m_pCodecEncodeCtx_Video->priv_data, "tune", "zerolatency", 0);

			if (m_pFormatCtx_Out->oformat->flags & AVFMT_GLOBALHEADER)
				m_pCodecEncodeCtx_Video->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

			if (avcodec_open2(m_pCodecEncodeCtx_Video, pCodecEncode_Video, 0) < 0)
			{
				//编码器打开失败，退出程序
				break;
			}
		}

		if (!(m_pFormatCtx_Out->oformat->flags & AVFMT_NOFILE))
		{
			if (avio_open(&m_pFormatCtx_Out->pb, pFileOut, AVIO_FLAG_WRITE) < 0)
			{
				break;
			}
		}

		avcodec_parameters_from_context(pVideoStream->codecpar, m_pCodecEncodeCtx_Video);

		if (avformat_write_header(m_pFormatCtx_Out, NULL) < 0)
		{
			break;
		}

		iRet = 0;
	} while (0);


	if (iRet != 0)
	{
		if (m_pCodecEncodeCtx_Video != NULL)
		{
			avcodec_free_context(&m_pCodecEncodeCtx_Video);
			m_pCodecEncodeCtx_Video = NULL;
		}

		if (m_pFormatCtx_Out != NULL)
		{
			avformat_free_context(m_pFormatCtx_Out);
			m_pFormatCtx_Out = NULL;
		}
	}

	return iRet;
}


DWORD WINAPI CConvertToGif::VideoAReadProc(LPVOID lpParam)
{
	CConvertToGif *pConvertToGif = (CConvertToGif *)lpParam;
	if (pConvertToGif != NULL)
	{
		pConvertToGif->VideoARead();
	}
	return 0;
}

void CConvertToGif::VideoARead()
{
	AVFrame *pFrame;
	pFrame = av_frame_alloc();

	int y_size = m_pReadCodecCtx_VideoA->width * m_pReadCodecCtx_VideoA->height;

	char *pY = new char[y_size];
	char *pU = new char[y_size / 4];
	char *pV = new char[y_size / 4];

	AVPacket packet = { 0 };
	int ret = 0;
	while (1)
	{
		av_packet_unref(&packet);

		ret = av_read_frame(m_pFormatCtx_FileA, &packet);
		if (ret == AVERROR(EAGAIN))
		{
			continue;
		}
		else if (ret == AVERROR_EOF)
		{
			break;
		}
		else if (ret < 0)
		{
			break;
		}

		if (packet.stream_index != 0)
		{
			continue;
		}

		ret = avcodec_send_packet(m_pReadCodecCtx_VideoA, &packet);

		if (ret >= 0)
		{
			ret = avcodec_receive_frame(m_pReadCodecCtx_VideoA, pFrame);
			if (ret == AVERROR(EAGAIN))
			{
				continue;
			}
			else if (ret == AVERROR_EOF)
			{
				break;
			}
			else if (ret < 0) {
				break;
			}


			while (1)
			{
				if (av_fifo_space(m_pVideoAFifo) >= m_iYuv420FrameSize)
				{
					///Y
					int contY = 0;
					for (int i = 0; i < pFrame->height; i++)
					{
						memcpy(pY + contY, pFrame->data[0] + i * pFrame->linesize[0], pFrame->width);
						contY += pFrame->width;
					}


					///U
					int contU = 0;
					for (int i = 0; i < pFrame->height / 2; i++)
					{
						memcpy(pU + contU, pFrame->data[1] + i * pFrame->linesize[1], pFrame->width / 2);
						contU += pFrame->width / 2;
					}


					///V
					int contV = 0;
					for (int i = 0; i < pFrame->height / 2; i++)
					{
						memcpy(pV + contV, pFrame->data[2] + i * pFrame->linesize[2], pFrame->width / 2);
						contV += pFrame->width / 2;
					}


					EnterCriticalSection(&m_csVideoASection);
					av_fifo_generic_write(m_pVideoAFifo, pY, y_size, NULL);
					av_fifo_generic_write(m_pVideoAFifo, pU, y_size / 4, NULL);
					av_fifo_generic_write(m_pVideoAFifo, pV, y_size / 4, NULL);
					LeaveCriticalSection(&m_csVideoASection);

					break;
				}
				else
				{
					Sleep(100);
				}
			}

		}


		if (ret == AVERROR(EAGAIN))
		{
			continue;
		}
	}

	av_frame_free(&pFrame);
	delete[] pY;
	delete[] pU;
	delete[] pV;
}

DWORD WINAPI CConvertToGif::VideoConvertProc(LPVOID lpParam)
{
	CConvertToGif *pVideoConvert = (CConvertToGif *)lpParam;
	if (pVideoConvert != NULL)
	{
		pVideoConvert->VideoConvert();
	}
	return 0;
}


void CConvertToGif::VideoConvert()
{
	int ret = 0;

	int iYuv420PadFrameSize = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, m_iVideoWidth, m_iVideoHeight, 1);
	int y_size = m_iVideoWidth * m_iVideoHeight;


	DWORD dwBeginTime = ::GetTickCount();


	AVFrame *pFrameVideoA = av_frame_alloc();
	uint8_t *videoA_buffer_yuv420 = (uint8_t *)av_malloc(m_iYuv420FrameSize);
	av_image_fill_arrays(pFrameVideoA->data, pFrameVideoA->linesize, videoA_buffer_yuv420, AV_PIX_FMT_YUV420P, m_pReadCodecCtx_VideoA->width, m_pReadCodecCtx_VideoA->height, 1);

	pFrameVideoA->width = m_iVideoWidth;
	pFrameVideoA->height = m_iVideoHeight;
	pFrameVideoA->format = AV_PIX_FMT_YUV420P;

	int iOutVideoWidth = m_pReadCodecCtx_VideoA->width;
	int iOutVideoHeight = m_pReadCodecCtx_VideoA->height;




	AVFrame *pFrameGif = av_frame_alloc();
	int frame_size = av_image_get_buffer_size(m_pCodecEncodeCtx_Video->pix_fmt, m_iVideoWidth, m_iVideoHeight, 1);

	uint8_t *out_buffer_bgr8 = (uint8_t *)av_malloc(frame_size);

	av_image_fill_arrays(pFrameGif->data, pFrameGif->linesize, out_buffer_bgr8, m_pCodecEncodeCtx_Video->pix_fmt, iOutVideoWidth, iOutVideoHeight, 1);
	pFrameGif->width = m_iVideoWidth;
	pFrameGif->height = m_iVideoHeight;
	pFrameGif->format = m_pCodecEncodeCtx_Video->pix_fmt;


	AVPacket packet = { 0 };
	int iPicCount = 0;

	while (1)
	{
		if (NULL == m_pVideoAFifo)
		{
			break;
		}

		int iVideoASize = av_fifo_size(m_pVideoAFifo);

		if (iVideoASize >= m_iYuv420FrameSize)
		{
			EnterCriticalSection(&m_csVideoASection);
			av_fifo_generic_read(m_pVideoAFifo, videoA_buffer_yuv420, m_iYuv420FrameSize, NULL);
			LeaveCriticalSection(&m_csVideoASection);


			int iScale = sws_scale(m_pImgConvertCtx, (const uint8_t* const*)pFrameVideoA->data, pFrameVideoA->linesize, 0, iOutVideoHeight, pFrameGif->data, pFrameGif->linesize);

			pFrameGif->pkt_dts = pFrameGif->pts = av_rescale_q_rnd(iPicCount, m_pCodecEncodeCtx_Video->time_base, m_pFormatCtx_Out->streams[0]->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
			pFrameGif->pkt_duration = 0;
			pFrameGif->pkt_pos = -1;

			ret = avcodec_send_frame(m_pCodecEncodeCtx_Video, pFrameGif);

			ret = avcodec_receive_packet(m_pCodecEncodeCtx_Video, &packet);

			av_write_frame(m_pFormatCtx_Out, &packet);

			iPicCount++;
		}
		else
		{
			if (m_hVideoAReadThread == NULL)
			{
				break;
			}
			Sleep(1);
		}
	}

	av_write_trailer(m_pFormatCtx_Out);
	avio_close(m_pFormatCtx_Out->pb);

	av_frame_free(&pFrameVideoA);
}