vs2017+ffmpeg實現解碼及縮放
阿新 • • 發佈：2019-01-08
概述：
本文程式是對於雷神github上simplest_ffmpeg_decoder工程結合ffmpeg3的修改版
環境：win10 + vs2017 + ffmpeg（版本為3.4.2）
函式介紹：
//幾乎都是被第一個呼叫，初始化libavformat庫及註冊所有的複用器、解複用器以及協議，
//如果沒有呼叫這個函式，也可以使用下面的函式單獨選擇你想支援的格式
//av_register_input_format()
//av_register_input_format()
void av_register_all(void);
//初始化網路組元件，為後續提供網路相關支援，可選項，但是推薦呼叫
int avformat_network_init(void);
//分配一個AVFormatContext
AVFormatContext *avformat_alloc_context(void);
//開啟多媒體資料並獲取一些相關資訊
int avformat_open_input(AVFormatContext **ps, const char *url, AVInputFormat *fmt, AVDictionary **options);
//讀取一個packet資料並獲取一些資訊，avformat_open_input後再呼叫，獲取資訊更全
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options);
//分配一個AVCodecContext並填充個預設值
AVCodecContext *avcodec_alloc_context3(const AVCodec *codec);
//將AVCodecParameters中的碼流引數拷貝一份到AVCodecContext中
int avcodec_parameters_to_context(AVCodecContext *codec, const AVCodecParameters *par);
//使用給定的AVCodec初始化AVCodecContext
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options);
//分配一個AVFrame並初始化位預設數值，用來存放AVPacket解碼出來的原始資料，
//必須使用av_frame_free（）釋放
AVFrame *av_frame_alloc(void);
//讀取碼流中的一幀資料，
int av_read_frame(AVFormatContext *s, AVPacket *pkt);
//釋放packet空間
void av_packet_unref(AVPacket *pkt);
//傳送編碼資料包
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt);
//接收解碼後的資料
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);
//分配一個SwsContext結構體用來做縮放
struct SwsContext *sws_getContext(int srcW, int srcH, enum AVPixelFormat srcFormat, int dstW, int dstH, enum AVPixelFormat dstFormat, int flags, SwsFilter *srcFilter, SwsFilter *dstFilter, const double *param);
//縮放
int sws_scale(struct SwsContext *c, const uint8_t *const srcSlice[], const int srcStride[], int srcSliceY, int srcSliceH, uint8_t *const dst[], const int dstStride[]);
程式例項：
/* ffmpeg_decoder_v2.cpp: 定義控制檯應用程式的入口點。
實現功能：解碼mkv檔案（640x272） --- > yuv檔案() ---> 縮放到1080p ---> 儲存成檔案 out.yuv
主要函式：
av_register_all()
avformat_alloc_context()
avformat_open_input()
avcodec_alloc_context3()
avcodec_open2()
av_read_frame()
avcodec_send_packet()
avcodec_receive_frame()
sws_scale()
*/
#include "stdafx.h"
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};
//連結庫
#pragma comment(lib , "avformat.lib")
#pragma comment(lib , "avcodec.lib")
#pragma comment(lib , "avdevice.lib")
#pragma comment(lib , "avfilter.lib")
#pragma comment(lib , "avutil.lib")
#pragma comment(lib , "postproc.lib")
#pragma comment(lib , "swresample.lib")
#pragma comment(lib , "swscale.lib")
#define dst_w 1920
#define dst_h 1080
int main(int argc, char* argv[])
{
AVFormatContext *pFormatCtx = NULL;
int videoindex = -1;
AVCodecContext *pCodecCtx = NULL;
AVCodec *pCodec = NULL;
AVFrame *pFrame = NULL, *pFrameYUV = NULL;
uint8_t *out_buffer = NULL;
AVPacket *packet = NULL;
struct SwsContext *img_convert_ctx;
int y_size = 0;
int ret = -1;
char filepath[] = "Titanic.mkv";
FILE *fp_yuv = fopen("output.yuv", "wb+");
//avcodec_register_all();//複用器等並沒有使用到，不需要初始化，直接呼叫av_register_all就行
av_register_all();
//avformat_network_init();
if (!(pFormatCtx = avformat_alloc_context()))
{
printf("avformat_alloc_context error!!,ret=%d\n", AVERROR(ENOMEM));
return -1;
}
if (avformat_open_input(&pFormatCtx, filepath, NULL, NULL) != 0) {
printf("Couldn't open input stream.\n");
return -1;
}
if (avformat_find_stream_info(pFormatCtx, NULL)<0) {
printf("Couldn't find stream information.\n");
return -1;
}
/*
//another way to get the stream id
for (i = 0; i < pFormatCtx->nb_streams; i++) {
if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
videoindex = i;
break;
}
}
*/
/* select the video stream */
ret = av_find_best_stream(pFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &pCodec, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
return ret;
}
videoindex = ret; //video stream id
pCodec = avcodec_find_decoder(pFormatCtx->streams[videoindex]->codecpar->codec_id);
if (pCodec == NULL) {
printf("Codec not found.\n");
return -1;
}
pCodecCtx = avcodec_alloc_context3(pCodec);
if (pCodecCtx == NULL)
{
printf("Could not allocate AVCodecContext\n");
return -1;
}
if ((ret = avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[videoindex]->codecpar)) < 0)
{
printf("Failed to copy codec parameters to decoder context\n");
return ret;
}
if (avcodec_open2(pCodecCtx, pCodec, NULL)<0) {
printf("Could not open codec.\n");
return -1;
}
printf("www=%d,hhh=%d\n", pCodecCtx->width, pCodecCtx->height);
pFrame = av_frame_alloc(); //the data after decoder
pFrameYUV = av_frame_alloc(); //the data after scale
out_buffer = (uint8_t *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, dst_w, dst_h, 1));
av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, out_buffer, AV_PIX_FMT_YUV420P, dst_w, dst_h, 1);
packet = (AVPacket *)av_malloc(sizeof(AVPacket));
if (!packet) {
fprintf(stderr, "Can not alloc packet\n");
return -1;
}
av_dump_format(pFormatCtx, 0, filepath, 0);
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
dst_w, dst_h, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
while (av_read_frame(pFormatCtx, packet) >= 0) {
if (packet->stream_index == videoindex) {
ret = avcodec_send_packet(pCodecCtx, packet);
if (ret != 0)
{
printf("send pkt error.\n");
return ret;
}
if (avcodec_receive_frame(pCodecCtx, pFrame) == 0) {
sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
pFrameYUV->data, pFrameYUV->linesize);
//y_size = pCodecCtx->width*pCodecCtx->height;
y_size = dst_w * dst_h;
fwrite(pFrameYUV->data[0], 1, y_size, fp_yuv); //Y
fwrite(pFrameYUV->data[1], 1, y_size / 4, fp_yuv); //U
fwrite(pFrameYUV->data[2], 1, y_size / 4, fp_yuv); //V
printf("Succeed to decode 1 frame!\n");
}
}
av_packet_unref(packet);
}
//flush decoder
//FIX: Flush Frames remained in Codec
while (1) {
ret = avcodec_send_packet(pCodecCtx, NULL);
if (ret != 0)
{
printf("send pkt error.\n");
break;
}
if (avcodec_receive_frame(pCodecCtx, pFrame) != 0)
{
break;
}
sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
pFrameYUV->data, pFrameYUV->linesize);
//int y_size = pCodecCtx->width*pCodecCtx->height;
fwrite(pFrameYUV->data[0], 1, y_size, fp_yuv); //Y
fwrite(pFrameYUV->data[1], 1, y_size / 4, fp_yuv); //U
fwrite(pFrameYUV->data[2], 1, y_size / 4, fp_yuv); //V
printf("Flush Decoder: Succeed to decode 1 frame!\n");
}
sws_freeContext(img_convert_ctx);
fclose(fp_yuv);
av_frame_free(&pFrameYUV);
av_frame_free(&pFrame);
avcodec_free_context(&pCodecCtx);
avformat_close_input(&pFormatCtx);
return 0;
}