ffmpeg系列：使用ffmpeg转换为RGB数据并缩放视频

main.cpp文件代码如下：

#include "myplayer.h"
#include <QtWidgets/QApplication>
#pragma comment(lib,"avformat.lib")
#pragma comment(lib,"avutil.lib")
#pragma comment(lib,"avcodec.lib")
#pragma comment(lib,"swscale.lib")
extern "C"{
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
}
static double r2d(AVRational r){
return r.num == 0 || r.den == 0 ? 0. : (double)r.num / (double)r.den;
}
int main(int argc, char *argv[])
{
av_register_all();
char *path = "test.mp4";
AVFormatContext *ac = NULL;
int re = avformat_open_input(&ac, path, 0, 0);

if (re != 0){//打开文件失败
char buf[1024] = { 0 };
av_strerror(re, buf, sizeof(buf));
printf("file %s open failed because of : %s", path, buf);
getchar();
return -1;
}

int totalSec = ac->duration / AV_TIME_BASE;
printf("指定的视频文件有 %d分%d秒\n", totalSec / 60, totalSec % 60);

int videoStream = 0;
AVCodecContext *videoCtx = NULL;
SwsContext *cCtx = NULL;
int outWidth = 640;
int outHeight = 480;
char *rgb = new char[outWidth * outHeight * 4];

for (int i = 0; i < ac->nb_streams; i++)
{
AVCodecContext *enc = ac->streams[i]->codec;

if (enc->codec_type == AVMEDIA_TYPE_VIDEO){
videoStream = i;
videoCtx = enc;
AVCodec *codec = avcodec_find_decoder(enc->codec_id);
if (!codec){
printf("无法解码此视频文件\n");
return -1;
}
int err = avcodec_open2(enc, codec, NULL);
if (err != 0){
char buf[1024] = { 0 };
av_strerror(err, buf, sizeof(buf));
printf(buf);
return -2;
}
printf("\n");
printf("成功打开视频编码流\n");
}
}
AVFrame *yuv = av_frame_alloc();
for (;;){
AVPacket pkt;
re = av_read_frame(ac, &pkt);
if (re != 0){
break;
}
if (pkt.stream_index != videoStream)
{
av_packet_unref(&pkt);
continue;
}
int pts = pkt.pts * r2d(ac->streams[pkt.stream_index]->time_base) * 1000;//得到帧的毫秒值

int re = avcodec_send_packet(videoCtx,&pkt);
if (re != 0){
av_packet_unref(&pkt);
continue;
}
re = avcodec_receive_frame(videoCtx,yuv);
if (re != 0){
av_packet_unref(&pkt);
continue;
}
printf("[D]___");

//打开ffmpeg格式转换和缩放器
cCtx = sws_getCachedContext(cCtx, videoCtx->width, videoCtx->height, videoCtx->pix_fmt,
outWidth, outHeight, AV_PIX_FMT_BGRA, SWS_BICUBIC,
NULL, NULL, NULL);
if (!cCtx){
printf("sws_getCachedContext failed!\n");
break;
}
uint8_t *data[AV_NUM_DATA_POINTERS] = {0};
data[0] = (uint8_t *)rgb;
int linesize[AV_NUM_DATA_POINTERS] = { 0 };
linesize[0] = outWidth * 4;
int h = sws_scale(cCtx, yuv->data, yuv->linesize, 0, videoCtx->height, data, linesize);
if (h > 0){
printf("(%d)", h);
}
printf("pts = %d 毫秒\n", pts);
av_packet_unref(&pkt);
}

if (cCtx){
sws_freeContext(cCtx);
cCtx = NULL;
}

avformat_close_input(&ac);
ac = NULL;

QApplication a(argc, argv);
MyPlayer w;
w.show();
return a.exec();
}


运行结果如图：