// 解码分别写入对应文件
#include "myLog.h"
#include <iostream>extern "C"
{
#include <libavformat\avformat.h>
#include <libavutil\avutil.h>
#include <libavcodec\avcodec.h>
#include <libavutil\imgutils.h>
#include <libavutil\samplefmt.h>
}
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avcodec.lib")class Decoder
{
public:Decoder(std::string src_filename, std::string dst_audio_filename, std::string dst_video_filename);~Decoder();// 解封装int demuxer();// 解码int decodec();// 打印音视频播放格式void print_audio_play_str();
private:// 打开解码器int open_decodec();// 解码pktint decode_pkt(AVCodecContext* codec_ctx, AVPacket* pkt);// 输出视频帧int output_video_frame(AVFrame* frame);// 输出音频帧int output_audio_frame(AVFrame* frame);// 获取音频格式int get_format_from_sample_fmt(std::string& fmtStr, enum AVSampleFormat sample_fmt);
private:AVFormatContext* ifmt_ctx_;					// 格式上下文AVCodecContext*  video_decode_ctx_;			// 视频解码器上下文AVCodecContext*  audio_decode_ctx_;			// 音频解码器上下文int video_idx_;								// 视频索引						AVStream* video_stream_;					// 视频流int audio_idx_;								// 音频索引AVStream* audio_stream_;					// 音频流std::string src_filename_;					// 输入文件路径std::string dst_audio_filename_;			// 输出音频pcm文件路径std::string dst_video_filename_;			// 输出视频yuv路径							FILE* dst_video_fp_;FILE* dst_audio_fp_;AVFrame* frame_;uint8_t* video_dst_data_[4];				// 记录video一行数据int video_dst_buf_size_;					// 分配的真实buf大小 int linesize_[4];							// 每行数据大小（YUV RGB 第四个为保留字段）
};Decoder::Decoder(std::string src_filename, std::string dst_audio_filename, std::string dst_video_filename)
: ifmt_ctx_(nullptr)
, video_decode_ctx_(nullptr)
, audio_decode_ctx_(nullptr)
, video_stream_(nullptr)
, audio_stream_(nullptr)
, dst_video_fp_(nullptr)
, dst_audio_fp_(nullptr)
, frame_(nullptr)
, src_filename_(src_filename)
, dst_audio_filename_(dst_audio_filename)
, dst_video_filename_(dst_video_filename)
{for (int i = 0; i < 4; i++){video_dst_data_[i] = NULL;}
}Decoder::~Decoder()
{// 释放相关资源if (ifmt_ctx_){avformat_close_input(&ifmt_ctx_);}if (audio_decode_ctx_){avcodec_free_context(&audio_decode_ctx_);}if (video_decode_ctx_){avcodec_free_context(&video_decode_ctx_);}if (dst_audio_fp_){fclose(dst_audio_fp_);}	if (dst_video_fp_){fclose(dst_video_fp_);}if (frame_){av_frame_free(&frame_);}if (video_dst_data_){av_free(video_dst_data_[0]);	// 释放数据指针(其它三个指针无需释放) data[0]指向缓冲区开始位置，data[1] - data[3]也是指向data[0]的数据指针}
}int Decoder::demuxer()
{// 1. 打开文件int nRet = avformat_open_input(&ifmt_ctx_, src_filename_.c_str(), NULL, NULL);if (nRet < 0){LOG_WARNING("avformat_open_input error\n");return -1;}// 2. 查找流信息nRet = avformat_find_stream_info(ifmt_ctx_, NULL);if (nRet < 0){avformat_close_input(&ifmt_ctx_);LOG_WARNING("avformat_find_stream_info error\n");return -2;}// 3. 获取音视频流索引audio_idx_ = av_find_best_stream(ifmt_ctx_, AVMEDIA_TYPE_AUDIO, -1, -1, NULL, 0);video_idx_ = av_find_best_stream(ifmt_ctx_, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);return 0;
}int Decoder::open_decodec()
{// 打开音频解码器if (audio_idx_ >= 0){audio_stream_ = ifmt_ctx_->streams[audio_idx_];// 查找解码器AVCodec* audio_decodec = avcodec_find_decoder(audio_stream_->codecpar->codec_id);if (!audio_decodec){LOG_WARNING("avcodec_find_decoder error\n");return AVERROR(ENOMEM);}// 给解码上下文分配内存audio_decode_ctx_ = avcodec_alloc_context3(audio_decodec);if (!audio_decode_ctx_){LOG_WARNING("avcodec_alloc_context3 error\n");return AVERROR(ENOMEM);}// 拷贝解码参数到解码上下文int nRet = avcodec_parameters_to_context(audio_decode_ctx_, audio_stream_->codecpar);if (nRet < 0){LOG_WARNING("avcodec_parameters_to_context error\n");return -1;}// 打开解码器nRet = avcodec_open2(audio_decode_ctx_, audio_decodec, NULL);if (nRet < 0){LOG_WARNING("avcodec_open2 error\n");return -2;}dst_audio_fp_ = fopen(dst_audio_filename_.c_str(), "wb");if (!dst_audio_fp_){LOG_WARNING("fopen dst_audio_filename_ error\n");return -1;}}// 打开视频解码器if (video_idx_ >= 0){video_stream_ = ifmt_ctx_->streams[video_idx_];// 查找解码器AVCodec* video_decodec = avcodec_find_decoder(video_stream_->codecpar->codec_id);if (!video_decodec){LOG_WARNING("avcodec_find_decoder error\n");return AVERROR(ENOMEM);}// 给解码上下文分配内存video_decode_ctx_ = avcodec_alloc_context3(video_decodec);if (!video_decode_ctx_){LOG_WARNING("avcodec_alloc_context3 error\n");return AVERROR(ENOMEM);}// 拷贝解码参数到解码上下文int nRet = avcodec_parameters_to_context(video_decode_ctx_, video_stream_->codecpar);if (nRet < 0){LOG_WARNING("avcodec_parameters_to_context error\n");return -1;}// 打开解码器nRet = avcodec_open2(video_decode_ctx_,video_decodec, NULL);if (nRet < 0){LOG_WARNING("avcodec_open2 error\n");return -2;}video_dst_buf_size_ = av_image_alloc(video_dst_data_, linesize_,video_decode_ctx_->width, video_decode_ctx_->height, video_decode_ctx_->pix_fmt, 1);dst_video_fp_ = fopen(dst_video_filename_.c_str(), "wb");if (!dst_video_fp_){LOG_WARNING("fopen dst_video_filename_ error\n");return -1;}}
}int Decoder::decodec()
{// 打开解码器int nRet = open_decodec();if (nRet < 0){LOG_WARNING("open_decodec error\n");return -666;}AVPacket* pkt = av_packet_alloc();av_init_packet(pkt);pkt->data = NULL;pkt->size = 0;while (av_read_frame(ifmt_ctx_, pkt) >= 0){if (pkt->stream_index == audio_idx_)	// 音频包{nRet = decode_pkt(audio_decode_ctx_, pkt);}else if (pkt->stream_index == video_idx_) // 视频包{nRet = decode_pkt(video_decode_ctx_, pkt);}av_packet_unref(pkt);if (nRet < 0){break;}}// 冲刷解码器if (video_decode_ctx_){decode_pkt(video_decode_ctx_, NULL);}if (audio_decode_ctx_){decode_pkt(video_decode_ctx_, NULL);}return 0;
}int Decoder::decode_pkt(AVCodecContext* codec_ctx, AVPacket* pkt)
{int nRet = avcodec_send_packet(codec_ctx, pkt);if (nRet < 0){LOG_WARNING("avcodec_send_packet fflush codec\n");return -1;}// 一个包可能对应多个frameframe_ = av_frame_alloc();while (nRet >= 0){nRet = avcodec_receive_frame(codec_ctx, frame_);if (nRet < 0){if (nRet == AVERROR_EOF || nRet == AVERROR(EAGAIN))return 0;return nRet;}// 写数据if (codec_ctx->codec->type == AVMEDIA_TYPE_AUDIO){nRet = output_audio_frame(frame_);}else if (codec_ctx->codec->type == AVMEDIA_TYPE_VIDEO){nRet = output_video_frame(frame_);}av_frame_unref(frame_);if (nRet < 0)return nRet;}
}int Decoder::output_video_frame(AVFrame* frame)
{if (video_dst_buf_size_ < 0){LOG_WARNING("av_image_alloc error\n");return -2;}// 写入帧到文件if (frame->width != video_decode_ctx_->width ||frame->height != video_decode_ctx_->height ||frame->format != video_decode_ctx_->pix_fmt){LOG_WARNING("frame and video_decode_ctx_ error\n");return -3;}// 填充数据到 video_dst_dataav_image_copy(video_dst_data_, linesize_,(const uint8_t**)(frame->data), frame->linesize,video_decode_ctx_->pix_fmt, video_decode_ctx_->width, video_decode_ctx_->height);size_t write_video_size = fwrite(video_dst_data_[0], 1, video_dst_buf_size_, dst_video_fp_);fflush(dst_video_fp_);return 0;
}int Decoder::output_audio_frame(AVFrame* frame)
{// 计算一帧音频数据的bytessize_t a_sample_point_bytes = frame->nb_samples * av_get_bytes_per_sample((AVSampleFormat)frame->format);// 写入数据到文件fwrite(frame->extended_data[0], 1, a_sample_point_bytes, dst_audio_fp_);fflush(dst_audio_fp_);return 0;
}int Decoder::get_format_from_sample_fmt(std::string& fmtStr, enum AVSampleFormat sample_fmt)
{struct sample_fmt_entry {enum AVSampleFormat sample_fmt; std::string fmt_be;std::string fmt_le;} sample_fmt_entries[] = {{ AV_SAMPLE_FMT_U8, "u8", "u8" },{ AV_SAMPLE_FMT_S16, "s16be", "s16le" },{ AV_SAMPLE_FMT_S32, "s32be", "s32le" },{ AV_SAMPLE_FMT_FLT, "f32be", "f32le" },{ AV_SAMPLE_FMT_DBL, "f64be", "f64le" },};for (int i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {struct sample_fmt_entry *entry = &sample_fmt_entries[i];if (sample_fmt == entry->sample_fmt) {fmtStr = AV_NE(entry->fmt_be, entry->fmt_le);return 0;}}fprintf(stderr, "sample format %s is not supported as output format\n", av_get_sample_fmt_name(sample_fmt));return -1;
}void Decoder::print_audio_play_str()
{if (audio_stream_) {enum AVSampleFormat sfmt = audio_decode_ctx_->sample_fmt;int n_channels = audio_decode_ctx_->channels;std::string fmtStr;if (av_sample_fmt_is_planar(sfmt))	// 是planar格式{const char *packed = av_get_sample_fmt_name(sfmt);LOG_INFO("Warning: the sample format the decoder produced is planar ""(%s). This example will output the first channel only.\n",packed ? packed : "?");sfmt = av_get_packed_sample_fmt(sfmt);n_channels = 1;}int ret = -1;if ((ret = get_format_from_sample_fmt(fmtStr, sfmt)) < 0)return;LOG_INFO("Play the output audio file with the command:\n""ffplay -f %s -ac %d -ar %d %s\n",fmtStr.c_str(), n_channels, audio_decode_ctx_->sample_rate,dst_audio_filename_.c_str());LOG_INFO("play video yuv:\nffplay -video_size %dx%d -f rawvideo -pixel_format yuv420p %s",video_decode_ctx_->width, video_decode_ctx_->height, dst_video_filename_.c_str());}
}int main()
{std::string src_filename = "./MediaFile/HTA_13s.mp4";	// input_5sstd::string dst_audio_filename = "./MediaFile/HTA_13s_decodec_audio.pcm"; // HTA_13s_decodec_audiostd::string dst_video_filename = "./MediaFile/HTA_13s_decodec_video.yuv"; // HTA_13s_decodec_videoDecoder decoder(src_filename, dst_audio_filename, dst_video_filename);// 解复用int nRet = decoder.demuxer();if (nRet < 0){LOG_WARNING("main demuxer error\n");return -666;}// 解码写入到文件nRet = decoder.decodec();if (nRet < 0){LOG_WARNING("main decodec error\n");return -777;}LOG_INFO("decode finish, write file success\n");decoder.print_audio_play_str();getchar();return 0;
}

注意：使用av_image_alloc为一个char* data[4]的数组分配内存时，其内部只是为data[0]分配内存，其余的data[1] - data[3]指针指向data[0]的某个位置（根据像素格式的不同）