使用AAC裸流解析器将aac裸流文件解析为pcm数据，然后写入文件
#include "myLog.h"
#include <iostream>extern "C"
{
#include <libavcodec\avcodec.h>
}#define AUDIO_INBUF_SIZE 20480 // 读取 20KB数据
#define AUDIO_REFILL_THRESH 4096/*从src复制size字符到dst(dstBuff 与 srcBuff内存块可重叠)memmove(dst, src, size);
*/static char* av_get_err(int errnum)
{char err_buf[128] = { 0 };av_strerror(errnum, err_buf, 128);return err_buf;
}static void print_sample_format(const AVFrame *frame)
{printf("ar_samplerate: %uHz\n", frame->sample_rate);printf("ac_channel: %u\n", frame->channels);printf("f_format: %u\n", frame->format); // 格式需要注意，实际存储到本地文件时已经改成交错模式 FLT
}static void decode(AVCodecContext* dec_ctx, AVPacket* pkt, AVFrame* frame, FILE* out_fp)
{int nRet = avcodec_send_packet(dec_ctx, pkt);if (nRet == AVERROR(EAGAIN)) // 需要更多pkt{LOG_WARNING("need more pkt\n");return;}else if (nRet < 0){// 当为mp3文件时,因为前面的一部分字节解码器解不出来, 直接退出程序的话,会导致mp3文件解析失败,应该函数返回解析下一帧LOG_WARNING("Error submitting the packet to the decoder, err:%s, pkt_size:%d\n",av_get_err(nRet), pkt->size);return;}// 一个pkt可能对应多个framewhile (nRet >= 0){nRet = avcodec_receive_frame(dec_ctx, frame);if (nRet == AVERROR(EAGAIN) || nRet == AVERROR_EOF){return;}else if (nRet < 0){LOG_WARNING("Error during decoding\n");return;}// 一个采样点字节数int data_size = av_get_bytes_per_sample(dec_ctx->sample_fmt);if (data_size < 0){LOG_WARNING("av_get_bytes_per_sample error\n");return;}// 打印一次信息static bool is_print = 0;if (!is_print){is_print = !is_print;print_sample_format(frame);}// planar to packedfor (int i = 0; i < frame->nb_samples; i++){for (int ch = 0; ch < frame->channels; ch++){fwrite(frame->data[ch] + i * data_size, 1, data_size, out_fp);}}}
}int main_audio_decodec()
{// ffplay -ar 44100 -ac 2 -f f32le -i out_put_48000_2_f32le.pcmconst char* in_file_name = "./out_put.aac";const char* out_file_name = "./out_put_48000_2_f32le.pcm";enum AVCodecID audio_codec_id = AV_CODEC_ID_AAC; // 指定aac// 1. 查找解码器AVCodec* audio_decoder = avcodec_find_decoder(audio_codec_id);if (nullptr == audio_decoder){LOG_WARNING("avcodec_find_decoder error\n");return -1;}// 2. 获取(aac)裸流解析器AVCodecParserContext* parser = av_parser_init(audio_decoder->id);if (nullptr == parser){LOG_WARNING("av_parser_init error\n");return -2;}// 3. 根据解码器创建解码上下文auto audio_decoder_ctx = avcodec_alloc_context3(audio_decoder);if (audio_decoder_ctx == nullptr){LOG_WARNING("avcodec_alloc_context3 error\n");return -3;}// 4. 打开解码器int nRet = avcodec_open2(audio_decoder_ctx, audio_decoder, NULL);if (nRet < 0){LOG_WARNING("avcodec_open2 error\n");return -4;}// 5. 打开输入输出文件FILE* in_fp = fopen(in_file_name, "rb");if (NULL == in_fp){LOG_WARNING("fopen in_file_name error\n");return -5;}FILE* out_fp = fopen(out_file_name, "wb");if (NULL == out_fp){LOG_WARNING("out_fp out_file_name error\n");return -5;}// 6.从输入文件中读取数据// AV_INPUT_BUFFER_PADDING_SIZE 在用于解码的输入比特流末尾所需的额外分配的字节数uint8_t inbuf[AUDIO_INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];uint8_t *data = NULL;size_t data_size = 0;data = inbuf;data_size = fread(inbuf, 1, AUDIO_INBUF_SIZE, in_fp);AVPacket* pkt = av_packet_alloc();AVFrame* decoded_frame = av_frame_alloc();while (data_size > 0){if (decoded_frame == nullptr){LOG_WARNING("av_frame_alloc error\n");return -6;}// pkt->data 不会分配内存而是直接指向data的内存// av_read_frame()：获取媒体的一帧压缩编码数据。其中调用了av_parser_parse2()// 返回值为 该函数返回读取的bytesnRet = av_parser_parse2(parser, audio_decoder_ctx,&pkt->data, &pkt->size, // 输出 pktdata, data_size, // 输入 buff裸流数据(h264, aac等)AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);if (nRet < 0){LOG_WARNING("av_parser_parse2 error\n");return -7;}data += nRet; // 将指针挪动到未解析的buff位置data_size -= nRet;if (pkt->size >= 0){// 解码decode(audio_decoder_ctx, pkt, decoded_frame, out_fp);}// 数据不够了继续读取if (data_size < AUDIO_REFILL_THRESH){memmove(inbuf, data, data_size); // 将未读取完的拷贝到inbuf开始位置data = inbuf;int len = fread(data + data_size, 1, AUDIO_INBUF_SIZE - data_size, in_fp);if (len > 0){data_size += len;}}}// 空包冲刷解码器pkt->data = NULL;pkt->size = 0;decode(audio_decoder_ctx, pkt, decoded_frame, out_fp);// 释放相关资源fclose(in_fp);fclose(out_fp);av_frame_free(&decoded_frame);av_packet_free(&pkt);avcodec_free_context(&audio_decoder_ctx);av_parser_close(parser);getchar();return 0;
}
