FFmpeg-- c++实现：pcm和yuv编码

pcm和yuv编码为aac和h264，封装为c++的AudioEncoder类和VideoEncoder类

流程

音频

• 初始化音频参数
  int InitAAC(int channels, int sample_rate, int bit_rate);

• 音频编码，pts需要转化为编码时的pts, 发送帧frame, 获取 packet
  AVPacket *Encode(AVFrame *farme, int stream_index, int64_t pts, int64_t time_base);

• 获取一帧数据通道号的采样点
  int GetFrameSize()

• 获取编码器需要的采样格式
  int GetSampleFormat()

• 释放资源
  void DeInit();

视频

• 初始化视频参数
  int InitH264(int width, int height, int fps, int bit_rate);

• 视频编码，pts需要转化为编码时的pts, 需要初始化AVFrame结构体，发送帧frame, 获取 packet
  AVPacket *Encode(AVFrame *farme, int stream_index, int64_t pts, int64_t time_base);

• 释放资源
  void DeInit();

api

• 用于初始化一个AVFrame结构体，包括设置AVFrame中的各项参数，不需要重新分配buffer，需要传入一个指向AVFrame结构体的指针

int av_image_fill_arrays(uint8_t *dst_data[4], int dst_linesize[4],const uint8_t *src,enum AVPixelFormat pix_fmt, int width, int height, int align);

核心代码

audioencoder.h

#ifndef AUDIOENCODER_H
#define AUDIOENCODER_Hextern "C"
{
#include "libavformat/avformat.h"
#include "libavcodec/avcodec.h"
}
class AudioEncoder
{
public:AudioEncoder();~AudioEncoder();int InitAAC(int channels, int sample_rate, int bit_rate);
//    int InitMP3(/*int channels, int sample_rate, int bit_rate*/);void DeInit();  // 释放资源AVPacket *Encode(AVFrame *farme, int stream_index, int64_t pts, int64_t time_base);int GetFrameSize(); // 获取一帧数据 每个通道需要多少个采样点int GetSampleFormat();  // 编码器需要的采样格式
private:int channels_ = 2;int sample_rate_ = 44100;int bit_rate_ = 128*1024;int64_t pts_ = 0;AVCodecContext * codec_ctx_ = NULL;
};#endif // AUDIOENCODER_H

audioencoder.cpp

#include "audioencoder.h"AudioEncoder::AudioEncoder()
{}AudioEncoder::~AudioEncoder()
{if(codec_ctx_) {DeInit();}
}int AudioEncoder::InitAAC(int channels, int sample_rate, int bit_rate)
{channels_ = channels;sample_rate_ = sample_rate;bit_rate_ = bit_rate;AVCodec *codec = avcodec_find_encoder(AV_CODEC_ID_AAC);if(!codec) {printf("avcodec_find_encoder AV_CODEC_ID_AAC failed\n");return -1;}codec_ctx_ = avcodec_alloc_context3(codec);if(!codec_ctx_) {printf("avcodec_alloc_context3 AV_CODEC_ID_AAC failed\n");return -1;}codec_ctx_->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;codec_ctx_->bit_rate = bit_rate_;codec_ctx_->sample_rate = sample_rate_;codec_ctx_->sample_fmt = AV_SAMPLE_FMT_FLTP;codec_ctx_->channels = channels_;codec_ctx_->channel_layout = av_get_default_channel_layout(codec_ctx_->channels);int ret = avcodec_open2(codec_ctx_, NULL, NULL);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avcodec_open2 failed:%s\n", errbuf);return -1;}printf("InitAAC success\n");return 0;
}void AudioEncoder::DeInit()
{if(codec_ctx_) {avcodec_free_context(&codec_ctx_);  // codec_ctx_被设置为NULL
//        codec_ctx_ = NULL;  // 不需要再写}
}AVPacket *AudioEncoder::Encode(AVFrame *frame, int stream_index, int64_t pts, int64_t time_base)
{if(!codec_ctx_) {printf("codec_ctx_ null\n");return NULL;}pts = av_rescale_q(pts, AVRational{1, (int)time_base}, codec_ctx_->time_base);if(frame) {frame->pts = pts;}int ret = avcodec_send_frame(codec_ctx_, frame);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avcodec_send_frame failed:%s\n", errbuf);return NULL;}AVPacket *packet = av_packet_alloc();ret = avcodec_receive_packet(codec_ctx_, packet);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avcodec_receive_packet failed:%s\n", errbuf);av_packet_free(&packet);return NULL;}packet->stream_index = stream_index;return packet;
}int AudioEncoder::GetFrameSize()
{if(codec_ctx_)return codec_ctx_->frame_size;return 0;
}int AudioEncoder::GetSampleFormat()
{if(codec_ctx_)return codec_ctx_->sample_fmt;return -1;  // AV_SAMPLE_FMT_NONE
}

videoencoder.h

#ifndef VIDEOENCODER_H
#define VIDEOENCODER_H
extern "C"
{
#include "libavformat/avformat.h"
#include "libavcodec/avcodec.h"
}class VideoEncoder
{
public:VideoEncoder();~VideoEncoder();int InitH264(int width, int height, int fps, int bit_rate);void DeInit();AVPacket *Encode(uint8_t *yuv_data, int yuv_size,int stream_index, int64_t pts, int64_t time_base);private:int width_ = 0;int height_ = 0;int fps_ = 25;int bit_rate_ = 500*1024;int64_t pts_ = 0;AVCodecContext * codec_ctx_ = NULL;AVFrame *frame_ = NULL;
};#endif // VIDEOENCODER_H

videoencoder.cpp

#include "videoencoder.h"
extern "C"
{
#include "libavutil/imgutils.h"
}
VideoEncoder::VideoEncoder()
{}VideoEncoder::~VideoEncoder()
{if(codec_ctx_) {DeInit();}
}int VideoEncoder::InitH264(int width, int height, int fps, int bit_rate)
{width_ = width;height_ = height;fps_ = fps;bit_rate_ = bit_rate;AVCodec *codec = avcodec_find_encoder(AV_CODEC_ID_H264);if(!codec) {printf("avcodec_find_encoder AV_CODEC_ID_H264 failed\n");return -1;}codec_ctx_ = avcodec_alloc_context3(codec);if(!codec_ctx_) {printf("avcodec_alloc_context3 AV_CODEC_ID_H264 failed\n");return -1;}codec_ctx_->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;codec_ctx_->bit_rate = bit_rate_;codec_ctx_->width = width_;codec_ctx_->height = height_;codec_ctx_->framerate = {fps_, 1};codec_ctx_->time_base = {1, 1000000};   // 单位为微妙codec_ctx_->gop_size = fps_;codec_ctx_->max_b_frames = 0;codec_ctx_->pix_fmt = AV_PIX_FMT_YUV420P;int ret = avcodec_open2(codec_ctx_, NULL, NULL);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avcodec_open2 failed:%s\n", errbuf);return -1;}frame_ = av_frame_alloc();if(!frame_) {printf("av_frame_alloc failed\n");return -1;}frame_->width = width_;frame_->height = height_;frame_->format = codec_ctx_->pix_fmt;printf("Inith264 success\n");return 0;
}void VideoEncoder::DeInit()
{if(codec_ctx_) {avcodec_free_context(&codec_ctx_);}if(frame_) {av_frame_free(&frame_);}
}AVPacket *VideoEncoder::Encode(uint8_t *yuv_data, int yuv_size, int stream_index, int64_t pts, int64_t time_base)
{if(!codec_ctx_) {printf("codec_ctx_ null\n");return NULL;}int ret = 0;pts = av_rescale_q(pts, AVRational{1, (int)time_base}, codec_ctx_->time_base);frame_->pts = pts;if(yuv_data) {//该函数用于初始化一个AVFrame结构体，包括设置AVFrame中的各项参数，不需要重新分配buffer//使用该函数需要传入一个指向AVFrame结构体的指针int ret_size = av_image_fill_arrays(frame_->data, frame_->linesize,yuv_data, (AVPixelFormat)frame_->format,frame_->width, frame_->height, 1);if(ret_size != yuv_size) {printf("ret_size:%d != yuv_size:%d -> failed\n", ret_size, yuv_size);return NULL;}ret = avcodec_send_frame(codec_ctx_, frame_);} else {ret = avcodec_send_frame(codec_ctx_, NULL);}if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avcodec_send_frame failed:%s\n", errbuf);return NULL;}AVPacket *packet = av_packet_alloc();ret = avcodec_receive_packet(codec_ctx_, packet);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avcodec_receive_packet failed:%s\n", errbuf);av_packet_free(&packet);return NULL;}packet->stream_index = stream_index;return packet;
}