FFMPEG（YUV編碼爲H.264）
下面附一張使用FFmpeg編碼視頻的流程圖。使用該流程，不僅可以編碼H.264的視頻，而且可以編碼MPEG4/MPEG2/VP8等等各種FFmpeg支持的視頻。圖中藍色背景的函數是實際輸出數據的函數。淺綠色的函數是視頻編碼的函數。
簡單介紹一下流程中各個函數的意義：
av_register_all()：註冊FFmpeg所有編解碼器。
avformat_alloc_output_context2()：初始化輸出碼流的AVFormatContext。
avio_open()：打開輸出文件。
av_new_stream()：創建輸出碼流的AVStream。
avcodec_find_encoder()：查找編碼器。
avcodec_open2()：打開編碼器。
avformat_write_header()：寫文件頭（對於某些沒有文件頭的封裝格式，不需要此函數。比如說MPEG2TS）。
avcodec_encode_video2()：編碼一幀視頻。即將AVFrame（存儲YUV像素數據）編碼爲AVPacket（存儲H.264等格式的碼流數據）。
av_write_frame()：將編碼後的視頻碼流寫入文件。
flush_encoder()：輸入的像素數據讀取完成後調用此函數。用於輸出編碼器中剩餘的AVPacket。
av_write_trailer()：寫文件尾（對於某些沒有文件頭的封裝格式，不需要此函數。比如說MPEG2TS）
#include <stdio.h>
#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
//Windows
extern "C"
{
#include "libavutil/opt.h"
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavutil/opt.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#ifdef __cplusplus
};
#endif
#endif
int flush_encoder(AVFormatContext *fmt_ctx,unsigned int stream_index){
int ret;
int got_frame;
AVPacket enc_pkt;
if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &
CODEC_CAP_DELAY))
return 0;
while (1) {
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
ret = avcodec_encode_video2 (fmt_ctx->streams[stream_index]->codec, &enc_pkt,
NULL, &got_frame);
av_frame_free(NULL);
if (ret < 0)
break;
if (!got_frame){
ret=0;
break;
}
printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n",enc_pkt.size);
/* mux encoded frame */
ret = av_write_frame(fmt_ctx, &enc_pkt);
if (ret < 0)
break;
}
return ret;
}
int main(int argc, char* argv[])
{
AVFormatContext* pFormatCtx;
AVOutputFormat* fmt;
AVStream* video_st;
AVCodecContext* pCodecCtx;
AVCodec* pCodec;
AVPacket pkt;
uint8_t* picture_buf;
AVFrame* pFrame;
int picture_size;
int y_size;
int framecnt=0;
//FILE *in_file = fopen("src01_480x272.yuv", "rb"); //Input raw YUV data
FILE *in_file = fopen("output.yuv", "rb"); //Input raw YUV data
int in_w=480,in_h=272; //Input data's width and height
int framenum=100; //Frames to encode
//const char* out_file = "src01.h264"; //Output Filepath
//const char* out_file = "src01.ts";
//const char* out_file = "src01.hevc";
const char* out_file = "ds.h264";
av_register_all();
//Method1.
pFormatCtx = avformat_alloc_context();
//Guess Format
fmt = av_guess_format(NULL, out_file, NULL);
pFormatCtx->oformat = fmt;
//Method 2.
//avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);
//fmt = pFormatCtx->oformat;
//Open output URL
if (avio_open(&pFormatCtx->pb,out_file, AVIO_FLAG_READ_WRITE) < 0){
printf("Failed to open output file! \n");
return -1;
}
video_st = avformat_new_stream(pFormatCtx, 0);
//video_st->time_base.num = 1;
//video_st->time_base.den = 25;
if (video_st==NULL){
return -1;
}
//Param that must set
pCodecCtx = video_st->codec;
//pCodecCtx->codec_id =AV_CODEC_ID_HEVC;
pCodecCtx->codec_id = fmt->video_codec;
pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
pCodecCtx->width = in_w;
pCodecCtx->height = in_h;
pCodecCtx->bit_rate = 400000;
pCodecCtx->gop_size=250;
pCodecCtx->time_base.num = 1;
pCodecCtx->time_base.den = 25;
//H264
//pCodecCtx->me_range = 16;
//pCodecCtx->max_qdiff = 4;
//pCodecCtx->qcompress = 0.6;
pCodecCtx->qmin = 10;
pCodecCtx->qmax = 51;
//Optional Param
pCodecCtx->max_b_frames=3;
// Set Option
AVDictionary *param = 0;
//H.264
if(pCodecCtx->codec_id == AV_CODEC_ID_H264) {
av_dict_set(¶m, "preset", "slow", 0);
av_dict_set(¶m, "tune", "zerolatency", 0);
//av_dict_set(¶m, "profile", "main", 0);
}
//H.265
if(pCodecCtx->codec_id == AV_CODEC_ID_H265){
av_dict_set(¶m, "preset", "ultrafast", 0);
av_dict_set(¶m, "tune", "zero-latency", 0);
}
//Show some Information
av_dump_format(pFormatCtx, 0, out_file, 1);
pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
if (!pCodec){
printf("Can not find encoder! \n");
return -1;
}
if (avcodec_open2(pCodecCtx, pCodec,¶m) < 0){
printf("Failed to open encoder! \n");
return -1;
}
pFrame = av_frame_alloc();
picture_size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
picture_buf = (uint8_t *)av_malloc(picture_size);
avpicture_fill((AVPicture *)pFrame, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
//Write File Header
avformat_write_header(pFormatCtx,NULL);
av_new_packet(&pkt,picture_size);
y_size = pCodecCtx->width * pCodecCtx->height;
for (int i=0; i<framenum; i++){
//Read raw YUV data
if (fread(picture_buf, 1, y_size*3/2, in_file) <= 0){
printf("Failed to read raw data! \n");
return -1;
}else if(feof(in_file)){
break;
}
pFrame->data[0] = picture_buf; // Y
pFrame->data[1] = picture_buf+ y_size; // U
pFrame->data[2] = picture_buf+ y_size*5/4; // V
//PTS
//pFrame->pts=i;
pFrame->pts=i*(video_st->time_base.den)/((video_st->time_base.num)*25);
int got_picture=0;
//Encode
int ret = avcodec_encode_video2(pCodecCtx, &pkt,pFrame, &got_picture);
if(ret < 0){
printf("Failed to encode! \n");
return -1;
}
if (got_picture==1){
printf("Succeed to encode frame: %5d\tsize:%5d\n",framecnt,pkt.size);
framecnt++;
pkt.stream_index = video_st->index;
ret = av_write_frame(pFormatCtx, &pkt);
av_free_packet(&pkt);
}
}
//Flush Encoder
int ret = flush_encoder(pFormatCtx,0);
if (ret < 0) {
printf("Flushing encoder failed\n");
return -1;
}
//Write file trailer
av_write_trailer(pFormatCtx);
//Clean
if (video_st){
avcodec_close(video_st->codec);
av_free(pFrame);
av_free(picture_buf);
}
avio_close(pFormatCtx->pb);
avformat_free_context(pFormatCtx);
fclose(in_file);
return 0;
}