pcm数据编码成为aac格式文件(可以在酷狗播放)
关于其中的aac adts格式可以参考:AAC ADTS格式分析
main.c
#include <stdio.h>
#include <stdlib.h>
#include <stdlib.h>#include <libavcodec/avcodec.h>
#include <libavutil/channel_layout.h>
#include <libavutil/common.h>
#include <libavutil/frame.h>
#include <libavutil/samplefmt.h>
#include <libavutil/opt.h>//生成adts头部信息
static void make_adts_header(AVCodecContext* ctx, uint8_t* adts_header, int aac_length)
{//采样率索引uint8_t freq_idx = 0;switch (ctx->sample_rate) {case 96000:freq_idx = 0;break;case 88200:freq_idx = 1;break;case 64000:freq_idx = 2;break;case 48000:freq_idx = 3;break;case 44100:freq_idx = 4;break;case 32000:freq_idx = 5;break;case 24000:freq_idx = 6;break;case 22050:freq_idx = 7;break;case 16000:freq_idx = 8;break;case 12000:freq_idx = 9;break;case 11025:freq_idx = 10;break;case 8000:freq_idx = 11;break;case 7350:freq_idx = 12;break;default:freq_idx = 4;break;}uint8_t chanCfg = ctx->channels;//通道数uint32_t frame_length = aac_length + 7;//整个adts帧长度,包括header 和 bodyadts_header[0] = 0xFF;adts_header[1] = 0xF1;adts_header[2] = ((ctx->profile) << 6) + (freq_idx << 2) + (chanCfg >> 2);adts_header[3] = (((chanCfg & 3) << 6) + (frame_length >> 11));adts_header[4] = ((frame_length & 0x7FF) >> 3);adts_header[5] = (((frame_length & 7) << 5) + 0x1F);adts_header[6] = 0xFC;
}static int encode(AVCodecContext* ctx, AVFrame* frame, AVPacket* pkt, FILE* outFile)
{int ret;//发送一帧进行编码ret = avcodec_send_frame(ctx, frame);if(ret < 0){fprintf(stderr, "avcodec_send_frame failed! errorcode : %d\n", ret);char buf[128] = {0};av_strerror(ret, buf, 128);printf("---------%s\n", buf);return -1;}while (ret >= 0){//获取编码后数据包ret = avcodec_receive_packet(ctx, pkt);if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF){return 0;}else if(ret < 0){fprintf(stderr, "avcodec_receive_packet failed! errorcode : %d\n", ret);return -1;}//aac adts 头部信息uint8_t aac_header[7];make_adts_header(ctx, aac_header, pkt->size);size_t len = 0;//写出头部信息len = fwrite(aac_header, 1, 7, outFile);if(len != 7){fprintf(stderr, "fwrite aac_header failed!\n");return -1;}//写出aac数据len = fwrite(pkt->data, 1, pkt->size, outFile);if(len != pkt->size){fprintf(stderr, "fwrite aac data failed!\n");return -1;}}return -1;
}#define USE_CODEC_NAME 1
int main()
{printf("Hello Audio Encodeer!\n");FILE* infile = NULL;FILE* outfile = NULL;const AVCodec* codec = NULL;AVCodecContext* codec_ctx = NULL;AVFrame* frame = NULL;AVPacket* pkt = NULL;int ret = 0;//注意:// 输入的pcm文件的采样点格式必须要与相应编码器支持的格式匹配才可以的,// 否则在avcodec_send_frame时就有可能出错。// aac这个编码器就是要求格式:float, planar
#if USE_CODEC_NAMEchar* codec_name = "aac";
#elsechar* codec_name = "";
#endifchar* in_pcm_file = "test.pcm";char* out_aac_file = "out_test.aac";enum AVCodecID code_id = AV_CODEC_ID_AAC;//如果有指定的编码器就根据名字查找if(codec_name && strlen(codec_name)){codec = avcodec_find_encoder_by_name(codec_name);}else{//否则根据ID查找是在编码器链表中找的第一个匹配code_id的编码器codec = avcodec_find_encoder(code_id);}//如果没有找到编码器就是没有安装这个编码器if(!codec){fprintf(stderr, "avcodec_find_encoder failed!\n");return 0;}//分配编码器上下文codec_ctx = avcodec_alloc_context3(codec);if(!codec_ctx){fprintf(stderr, "avcodec_alloc_context3 failed!\n");return 0;}codec_ctx->codec_id = code_id;codec_ctx->codec_type = AVMEDIA_TYPE_AUDIO;codec_ctx->bit_rate = 128 * 1024;//比特率codec_ctx->channel_layout = AV_CH_LAYOUT_STEREO;//立体声codec_ctx->sample_rate = 48000;//采样率codec_ctx->channels = av_get_channel_layout_nb_channels(codec_ctx->channel_layout);//通道数codec_ctx->profile = FF_PROFILE_AAC_LOW;//质量//因为不同编码器支持不同的采样格式,可以在源码中查看得到,做个判断if(strcmp(codec->name, "aac") == 0){//aac 编码器 : 只支持AV_SAMPLE_FMT_FLTP这一种格式codec_ctx->sample_fmt = AV_SAMPLE_FMT_FLTP;//float, planar}else{sprintf(stderr, "codec->name failed!\n");return 0;}printf("use codec name :%s\n", codec_name);printf("bit rate : %ldkbps\n", codec_ctx->bit_rate / 1024);printf("sample_rate : %d\n", codec_ctx->sample_rate);printf("sample_fmt : %s\n", av_get_sample_fmt_name(codec_ctx->sample_fmt));printf("channels : %d\n", codec_ctx->channels);if(avcodec_open2(codec_ctx, codec, NULL) < 0){fprintf(stderr, "avcodec_open2 failed!\n");return 0;}//每个音频帧在单个通道下的采样数,只有音频这个参数才有效(在调用avcodec_open2()后就有效了)printf("frame_size : %d\n", codec_ctx->frame_size);//打开输入输出文件infile = fopen(in_pcm_file, "rb");if(!infile){fprintf(stderr, "fopen(in_pcm_file) failed!\n");return 0;}outfile = fopen(out_aac_file, "wb");if(!outfile){fprintf(stderr, "fopen(out_aac_file) failed!\n");return 0;}//分配AVPacket 本身结构的内存pkt = av_packet_alloc();if(!pkt){fprintf(stderr, "av_packet_alloc() failed!\n");return 0;}//分配AVFrame本身结构的内存frame = av_frame_alloc();if(!frame){fprintf(stderr, "av_frame_alloc() failed!\n");return 0;}frame->nb_samples = codec_ctx->frame_size;//每帧单个通道的采样数frame->format = codec_ctx->sample_fmt;//采样格式frame->channel_layout = codec_ctx->channel_layout;//通道布局frame->channels = av_get_channel_layout_nb_channels(frame->channel_layout);//通道数printf("frame nb_samples : %d\n", frame->nb_samples);printf("frame format : %d \n", frame->format);printf("frame channel_layout : %d\n", frame->channel_layout);//计算一帧的数据长度(字节数量)// av_get_bytes_per_sample(frame->format) : 一个采样点占用的字节数// 比如:AV_SAMPLE_FMT_S16 = 两个字节// AV_SAMPLE_FMT_FLTP = 四个字节// frame->channels : 有几个通道// frame->nb_samples : 单个通道的一帧的采样数int frame_bytes = av_get_bytes_per_sample(frame->format) * frame->channels * frame->nb_samples;printf("frame_bytes : %d\n", frame_bytes);uint8_t* pcm_buf = (uint8_t*)malloc(frame_bytes);if(!pcm_buf){printf("pcm_buf malloc failed!\n");return 0;}uint8_t* pcm_temp_buf = (uint8_t*)malloc(frame_bytes);if(!pcm_temp_buf){printf("pcm_temp_buf malloc failed!\n");return 0;}int64_t pts = 0;while (1){memset(pcm_buf, 0, frame_bytes);size_t read_byte = fread(pcm_buf, 1, frame_bytes, infile);if(read_byte <= 0){sprintf(stderr, "read infile end!\n");break;}//将读取到的数据填充到frame,会根据不同输的不同参数填充到frame->data,frame->linesizeret = av_samples_fill_arrays(frame->data, frame->linesize,pcm_buf, frame->channels,frame->nb_samples, frame->format, 0);//设置每帧的ptspts += frame->nb_samples;frame->pts = pts;//使用采样率作为pts的单位,换算成实际时间(秒)pts * 1 / 采样率ret = encode(codec_ctx, frame, pkt, outfile);if(ret < 0){sprintf(stderr, "encode failed!\n");break;}}//冲刷编码器encode(codec_ctx, NULL, pkt, outfile);fclose(infile);fclose(outfile);if(pcm_buf)free(pcm_buf);if(pcm_temp_buf)free(pcm_temp_buf);av_frame_free(&frame);av_packet_free(&pkt);avcodec_free_context(&codec_ctx);printf("aac encoder end!\n");return 0;}