pcm data encoding into aac format file (can be played in Kugou)
For the aac adts format, please refer to: AAC ADTS format analysis
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 body
adts_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_NAME
char* codec_name = "aac";
#else
char* codec_name = "";
#endif
char* 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->linesize
ret = av_samples_fill_arrays(frame->data, frame->linesize,
pcm_buf, frame->channels,
frame->nb_samples, frame->format, 0);
//设置每帧的pts
pts += 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;
}