使用FFMPEG库将YUV编码为H264

准备

ffmpeg 4.4

p准备一段yuv420p的格式的视频原始数据

这里我们使用命令直接提取

ffmpeg -i .\beautlWorld.mp4 -pixel_format yuv420p -s 1280x720 yuv420p_1280x720.yuv

编码流程

大致可以分为以下几步：

1.初始化编码器并设置参数

2.初始化AVPacket和AVFrame,设置参数

3.读取视频文件，进行编码

4.释放内存，结束

编码

以下是完整代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavutil/time.h>
#include <libavutil/opt.h>
#include <libavutil/imgutils.h>
}using namespace std;const char* inFileName = "D:/测试工程/sound/yuv420p_1280x720.yuv";
const char* outFileName = "D:/测试工程/sound/3333encode_yuv420p_1280x720.h264";int encode(AVCodecContext* codecContent, AVPacket * packet, AVFrame* frame, FILE* outFile)
{//解码int ret = avcodec_send_frame(codecContent, frame);if (ret < 0){fprintf(stderr, "Error sending a frame for encoding\n");return -1;}while (ret == 0){ret = avcodec_receive_packet(codecContent, packet);if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {return 0;}else if (ret < 0) {fprintf(stderr, "Error encoding video frame\n");return -1;}if (ret == 0){fwrite(packet->data, 1, packet->size, outFile);}}
}int main(int argc, char* argv[])
{int ret = 0;AVCodec* codec = nullptr;AVCodecContext* codecContent = nullptr;AVPacket* packet = nullptr;AVFrame* frame = nullptr;FILE* inFile = nullptr;FILE* outFile = nullptr;//编码器初始化codec = avcodec_find_encoder(AV_CODEC_ID_H264);if (codec == nullptr){printf("could not find h264 encoder!");return -1;}codecContent = avcodec_alloc_context3(codec);if (codecContent == nullptr){printf("could not alloc h264 content!");return -1;}//必设参数codecContent->width = 1280;codecContent->height = 720;codecContent->time_base = AVRational{ 1, 25 };codecContent->pix_fmt = AV_PIX_FMT_YUV420P;codecContent->gop_size = 25; //关键帧间隔，默认250codecContent->framerate = AVRational{ 25, 1 };ret = avcodec_open2(codecContent, codec, NULL);if (ret < 0) {fprintf(stderr, "Could not open codec: %d\n", ret);exit(1);}packet = av_packet_alloc();if (packet == nullptr){printf("alloc packet error");return -1;}frame = av_frame_alloc();if (packet == nullptr){printf("alloc frame error");return -1;}frame->width = codecContent->width;frame->height = codecContent->height;frame->format = codecContent->pix_fmt;ret =  av_frame_get_buffer(frame, 0);if (ret){printf("alloc frame buffer error!");return -1;}inFile = fopen(inFileName, "rb");if (inFile == nullptr){printf("error to open file: %s\n", inFileName);return -1;}outFile = fopen(outFileName, "wb");if (inFile == nullptr){printf("error to open file: %s\n", outFileName);return -1;}int framecount = 0;frame->pts = 0;while (!feof(inFile)){ret = av_frame_is_writable(frame);if (ret < 0) {ret = av_frame_make_writable(frame);}fread(frame->data[0], 1, frame->width * frame->height, inFile); //yfread(frame->data[1], 1, frame->width * frame->height / 4, inFile); //ufread(frame->data[2], 1, frame->width * frame->height / 4, inFile);  //vprintf("encode frame num: %d\n", ++framecount);frame->pts += 1000 / (codecContent->time_base.den / codecContent->time_base.num);encode(codecContent, packet, frame, outFile);}encode(codecContent, packet, nullptr, outFile);av_packet_free(&packet);av_frame_free(&frame);avcodec_free_context(&codecContent);fclose(inFile);fclose(outFile);return 0;
}

小结

AVCodecContext

对于视频编码器而言必须设置以下参数：

AVRational time_base;

int width, height;

以下由用户设置，可选

gop_size: 默认250，也就是每250帧一个关键帧，可选设置

max_b_frames：默认3， b帧最大连续个数

bit_rate：平均比特率

avcodec_alloc_context3

AVCodecContext *avcodec_alloc_context3(const AVCodec *codec);

为AVCodecContext结构申请空间，并使用默认值初始化！最后使用avcodec_free_context进行释放。

avcodec_open2

int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options);

调用该函数前：time_base(也就是每帧显示的时间)，width(帧宽), height(帧高)

av_frame_get_buffer

int av_frame_get_buffer(AVFrame *frame, int align);

为音视频分配数据存储空间。调用该函数前需要设置AVFRAME几个初始值。

音频：1.sample format 2.nb_samples 3.channel_layout

视频：1.pixel format 2.width 3.height

align:直接对其，默认给0，根据当前CPU自行设置