ffmpeg C代码实现 YUV数据编码
流程
下面附一张使用FFmpeg编码视频的流程图。使用该流程，不仅可以编码H.264的视频，而且可以编码MPEG4/MPEG2/VP8等等各种FFmpeg支持的视频。图中蓝色背景的函数是实际输出数据的函数。浅绿色的函数是视频编码的函数。
简单介绍一下流程中各个函数的意义：
av_register_all()：注册FFmpeg所有编解码器。
avformat_alloc_output_context2()：初始化输出码流的AVFormatContext。
avio_open()：打开输出文件。
av_new_stream()：创建输出码流的AVStream。
avcodec_find_encoder()：查找编码器。
avcodec_open2()：打开编码器。
avformat_write_header()：写文件头（对于某些没有文件头的封装格式，不需要此函数。比如说MPEG2TS）。
avcodec_encode_video2()：编码一帧视频。即将AVFrame（存储YUV像素数据）编码为AVPacket（存储H.264等格式的码流数据）。
av_write_frame()：将编码后的视频码流写入文件。
flush_encoder()：输入的像素数据读取完成后调用此函数。用于输出编码器中剩余的AVPacket。
av_write_trailer()：写文件尾（对于某些没有文件头的封装格式，不需要此函数。比如说MPEG2TS）。
#代码
#include <stdlib.h>
#include <stdio.h>
#include "libavformat/avformat.h"
#include "libavcodec/avcodec.h"
#include "libavutil/log.h"
AVFormatContext* inputContext;
AVFormatContext* outputContext;
AVCodecContext* decodeContext;
AVCodecContext* encodeContext;
AVStream* stream;
void init(){
avcodec_register_all();
}
int open_output_context(char* filename){
outputContext = avformat_alloc_context();
int ret = avformat_alloc_output_context2(&outputContext,NULL,NULL,filename);
if(ret < 0){
av_log(NULL,AV_LOG_ERROR,"create outputContext failed \n");
return -1;
}else{
av_log(NULL,AV_LOG_INFO,"create outputContext success \n");
}
ret = avio_open(&outputContext->pb,filename,AVIO_FLAG_READ_WRITE);
if(ret < 0){
av_log(NULL,AV_LOG_ERROR,"open file failed \n");
return -1;
}else{
av_log(NULL,AV_LOG_INFO,"open file success \n");
}
stream = avformat_new_stream(outputContext,NULL);
av_dump_format(outputContext,0,filename,1);
return ret;
}
void close(){
if(decodeContext){
avcodec_close(decodeContext);
}
if(inputContext){
avformat_close_input(&inputContext);
}
if(outputContext){
for(int i = 0 ; i < outputContext->nb_streams; i++){
AVCodecContext* codecContext = outputContext->streams[i]->codec;
avcodec_close(codecContext);
}
avformat_close_input(&outputContext);
}
}
int init_encode(int width ,int height,AVStream* video_stream){
encodeContext = video_stream->codec;
encodeContext->codec_id = outputContext->oformat->video_codec;
encodeContext->codec_type = AVMEDIA_TYPE_VIDEO;
encodeContext->pix_fmt = AV_PIX_FMT_YUV420P;
encodeContext->width = width;
encodeContext->height = height;
encodeContext->bit_rate = 400000;
encodeContext->gop_size=250;
encodeContext->time_base.num = 1;
encodeContext->time_base.den = 25;
encodeContext->qmin = 10;
encodeContext->qmax = 51;
//Optional Param
encodeContext->max_b_frames=3;
AVCodec* pCodec = avcodec_find_encoder(encodeContext->codec_id);
return avcodec_open2(encodeContext,pCodec,NULL);
}
static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt)
{
int ret;
/* send the frame to the encoder */
if (frame)
printf("Send frame %3"PRId64"\n", frame->pts);
ret = avcodec_send_frame(enc_ctx, frame);
if (ret < 0) {
fprintf(stderr, "Error sending a frame for encoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_packet(enc_ctx, pkt);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during encoding\n");
exit(1);
}
printf("Write packet %3"PRId64" (size=%5d)\n", pkt->pts, pkt->size);
av_write_frame(outputContext,pkt);
av_packet_unref(pkt);
}
}
int main(){
init();
char* inputFile = "jichi.yuv";
char* outputFile = "jichitext2.h264";
FILE* in_file = fopen(inputFile,"rb");
int in_width = 540;
int in_height = 960;
if(in_file){
av_log(NULL,AV_LOG_INFO,"open file success \n");
}else{
av_log(NULL,AV_LOG_ERROR,"can't open file! \n");
goto _END;
}
int ret = open_output_context(outputFile);
if(ret >= 0){
av_log(NULL,AV_LOG_INFO,"open_output_context success \n");
}else{
av_log(NULL,AV_LOG_ERROR,"open_output_context failed! \n");
goto _END;
}
if (stream==NULL){
av_log(NULL,AV_LOG_ERROR,"avformat_new_stream failed \n");
return -1;
}else{
av_log(NULL,AV_LOG_INFO,"avformat_new_stream success \n");
}
stream->time_base.num = 1;
stream->time_base.den =25;
ret = init_encode(in_width,in_height,stream);
if(ret < 0){
av_log(NULL,AV_LOG_ERROR,"init_encoder failed \n");
goto _END;
}else{
av_log(NULL,AV_LOG_INFO,"init encoder success \n");
}
ret = avcodec_parameters_from_context(stream->codecpar, encodeContext);
if(ret < 0){
printf("avcodec_parameters_from_context failed \n");
}else{
printf("avcodec_parameters_from_context success \n");
}
AVPacket packet;
AVFrame* picture = av_frame_alloc();
int size = avpicture_get_size(encodeContext->pix_fmt, encodeContext->width, encodeContext->height);
int8_t* picture_buf = (uint8_t *)av_malloc(size);
avpicture_fill((AVPicture *)picture, picture_buf, encodeContext->pix_fmt, encodeContext->width, encodeContext->height);
picture->width=encodeContext->width;
picture->height=encodeContext->height;
picture->format=encodeContext->pix_fmt;
int y_size = encodeContext->width*encodeContext->height;
av_new_packet(&packet,size);
int i = 0;
int got_picture;
AVDictionary* option = NULL;
ret = avformat_write_header(outputContext,&option);
if(ret < 0){
printf("avformat_write_header failed \n");
}else{
printf("avformat_write_header success \n");
}
int framecnt=0;
while(1){
if (fread(picture_buf, 1, y_size*3/2, in_file) <= 0){
printf("Failed to read raw data! \n");
break;
}else if(feof(in_file)){
printf("Failed to read raw data! \n");
break;
}
picture->data[0] = picture_buf; //亮度Y
picture->data[1] = picture_buf+y_size; //U
picture->data[2] = picture_buf+y_size*5/4; //V
//AVFrame PTS
picture->pts=i*(stream->time_base.den)/((stream->time_base.num)*25);
encode(encodeContext,picture,&packet);
i++;
}
av_write_trailer(outputContext);
printf("编码完成\n");
AVCodec* encoder = avcodec_find_encoder(outputContext->oformat->video_codec);
if(!encoder){
av_log(NULL,AV_LOG_ERROR,"can't find endcoder \n");
}else{
av_log(NULL,AV_LOG_INFO," find endcoder \n");
av_log(NULL,AV_LOG_ERROR,"encoder name = %s \n",encoder->name);
}
av_free(picture_buf);
_END:
av_frame_unref(picture);
if(in_file){
fclose(in_file);
}
close();
return 0;
}
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