Qt+ffmpeg实现视频流播放

1.版本

Qt版本：5.11 64位

ffmpeg版本：>3.0 64位

2.实现思路

ffmpeg拉流、解码，因为Qt不支持显示yuv数据，需要ffmpeg转换为rgb数据，再用QImage显示，这种方式性能会不好，暂时先实现这种简单的。一般情况下会用opengl渲染。

3.示例

拉流cctv1：http://ivi.bupt.edu.cn/hls/cctv1hd.m3u8，此例子只解码视频数据，不处理音频。

代码：解码线程

#pragma once

#include 
#include 

extern "C"
{
#include "libavformat/avformat.h"
#include "libavutil/dict.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"  
};

class DecodeThread : public QThread
{
	Q_OBJECT

public:
	DecodeThread(QObject *parent);
	~DecodeThread();

Q_SIGNALS:
	void sigData(uint8_t* rgbBuffer);

public:
	void setUrl(QString url);

	void setStoped(bool stop);

protected:
	void run();

protected:
	double r2d(AVRational r);
	void decodeStream();

private:
	QString m_url;

	bool m_isStop = false;

private:
	AVFormatContext* m_pFormatCtx = NULL;
	AVCodecContext* m_pCodecCtx = NULL;
	AVPacket* m_avpacket = NULL;
	AVFrame *m_frame = NULL;
	//视频index
	int m_videoIndex = -1;
	//视频总时间,单位ms
	int64_t m_totalTime = 0;
	//视频宽度;
	int m_width = 0;
	//视频高度;
	int m_height = 0;
	//视频帧率;
	int m_fps = 0;
};

#include "DecodeThread.h"


DecodeThread::DecodeThread(QObject *parent)
	: QThread(parent)
{
}

DecodeThread::~DecodeThread()
{
	if (m_pFormatCtx != NULL)
	{
		avformat_close_input(&m_pFormatCtx);
		avformat_free_context(m_pFormatCtx);
		m_pFormatCtx = NULL;
	}
	if (m_pCodecCtx != NULL)
	{
		avcodec_close(m_pCodecCtx);
		avcodec_free_context(&m_pCodecCtx);
		m_pCodecCtx = NULL;
	}
	if (m_avpacket != NULL)
	{
		av_packet_unref(m_avpacket);
		delete m_avpacket;
		m_avpacket = NULL;
	}
	if (m_frame != NULL)
	{
		av_frame_free(&m_frame);
		m_frame = NULL;
	}
}

void DecodeThread::setUrl(QString url)
{
	m_url = url;

}

void DecodeThread::setStoped(bool stop)
{
	m_isStop = stop;
}

void DecodeThread::run()
{
	//注册所有组件 新版本已弃用
	av_register_all();

	//打开输入视频文件
	if (avformat_open_input(&m_pFormatCtx, m_url.toStdString().c_str(), NULL, NULL) != 0)
	{
		printf("Couldn't open input stream.\n");
	}

	if (avformat_find_stream_info(m_pFormatCtx, NULL) < 0)
	{
		printf("Couldn't find stream information.\n");
	}

	for (int i = 0; i < m_pFormatCtx->nb_streams/*视音频流的个数*/; i++)
	{
		//查找视频
		if (m_pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
		{
			m_videoIndex = i;
			break;
		}
	}
	if (m_videoIndex == -1)
	{
		printf("Couldn't find a video stream.\n");
	}

	/**
	*  不赞成这样使用
	*  pCodecCtx = pFormatCtx->streams[videoIndex]->codec;	//指向AVCodecContext的指针
	*/

	m_pCodecCtx = avcodec_alloc_context3(NULL);
	if (m_pCodecCtx == NULL)
	{
		printf("Could not allocate AVCodecContext\n");
	}
	avcodec_parameters_to_context(m_pCodecCtx, m_pFormatCtx->streams[m_videoIndex]->codecpar);

	//指向AVCodec的指针.查找解码器
	AVCodec *pCodec = avcodec_find_decoder(m_pCodecCtx->codec_id);
	if (pCodec == NULL)
	{
		printf("Codec not found pCodec\n");
	}
	//打开解码器
	if (avcodec_open2(m_pCodecCtx, pCodec, NULL) < 0)
	{
		printf("Could not open codec.\n");
	}

	//视频宽
	m_width = m_pFormatCtx->streams[m_videoIndex]->codecpar->width;

	//视频高
	m_height = m_pFormatCtx->streams[m_videoIndex]->codecpar->height;

	//获取帧率;
	m_fps = r2d(m_pFormatCtx->streams[m_videoIndex]->avg_frame_rate);
	if (m_fps == 0)
	{
		m_fps = 25;
	}

	//初始化AVPacket
	m_avpacket = new AVPacket;
	av_init_packet(m_avpacket);
	m_avpacket->data = NULL;

	//初始化frame,
	m_frame = av_frame_alloc();
	if (!m_frame)
	{
		printf("av_frame_alloc fail\n");
	}

	//开始解码
	decodeStream();
}

double DecodeThread::r2d(AVRational r)
{
	return r.den == 0 ? 0 : (double)r.num / (double)r.den;
}

void DecodeThread::decodeStream()
{
	while (av_read_frame(m_pFormatCtx, m_avpacket) >= 0)
	{
		if (m_avpacket->stream_index == m_videoIndex)
		{
			int ret = avcodec_send_packet(m_pCodecCtx, m_avpacket);
			if (ret >= 0)
			{
				ret = avcodec_receive_frame(m_pCodecCtx, m_frame);
				if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
				{
					return;
				}
				else if (ret < 0)
				{
					return;
				}

				switch (m_pCodecCtx->pix_fmt)
				{
				case AV_PIX_FMT_YUV420P:
				{
					int width = m_frame->width;
					int height = m_frame->height;

					AVFrame *pFrameRGB = av_frame_alloc();
					int numBytes = avpicture_get_size(AV_PIX_FMT_RGB32, width, height);

					int nBGRFrameSize = av_image_get_buffer_size(AV_PIX_FMT_RGB32, width, height, 1);
					uint8_t* rgbBuffer = (uint8_t*)av_malloc(nBGRFrameSize);
					av_image_fill_arrays(pFrameRGB->data, pFrameRGB->linesize, rgbBuffer, AV_PIX_FMT_RGB32, width, height, 1);

					//改变像素格式
					SwsContext *img_convert_ctx = sws_getContext(width, height, AV_PIX_FMT_YUV420P, width, height, AV_PIX_FMT_RGB32, SWS_BICUBIC, NULL, NULL, NULL);
					
					//颜色空间转换 yuv420p --> rgb32
					sws_scale(img_convert_ctx,
						(uint8_t const *const *)m_frame->data,
						m_frame->linesize, 0, height, pFrameRGB->data,
						pFrameRGB->linesize);

					//发送信号，转换后的rgb buffer
					emit sigData(rgbBuffer);

					//释放内存
					av_frame_free(&pFrameRGB);
				}break;
				default:
				{
					printf("default format:%d\n", m_pCodecCtx->pix_fmt);
					return;
				}
				}
			}
		}
	}
}

代码：ui界面

#pragma once

#include 
#include "ui_QtGuiApplication1.h"
#include "DecodeThread.h"


class QtGuiApplication1 : public QWidget
{
	Q_OBJECT

public:
	QtGuiApplication1(QWidget *parent = Q_NULLPTR);
	~QtGuiApplication1();

private:
	Ui::QtGuiApplication1Class ui;

private Q_SLOTS:
	void slotBtnClicked();
	void slotData(uint8_t* data);

private:
	DecodeThread *m_thead = nullptr;
};

#include "QtGuiApplication1.h"

QtGuiApplication1::QtGuiApplication1(QWidget *parent)
	: QWidget(parent)
{
	ui.setupUi(this);

	m_thead = new DecodeThread(this);
	connect(ui.pushButton, &QPushButton::clicked, this, &QtGuiApplication1::slotBtnClicked);
	connect(m_thead, &DecodeThread::sigData, this, &QtGuiApplication1::slotData);
}

QtGuiApplication1::~QtGuiApplication1()
{

}

void QtGuiApplication1::slotBtnClicked()
{
	QString url = ui.lineEdit->text();
	m_thead->setUrl(url);
	m_thead->start();
}

void QtGuiApplication1::slotData(uint8_t* data)
{
	QImage image(data, 1920, 1080, QImage::Format_ARGB32);
	ui.lbImage->setPixmap(QPixmap::fromImage(image));
	av_free(data);
}