#include <stdio.h>
#include "libavutil/log.h"
#include "libavformat/avio.h"
#include "libavformat/avformat.h"
//#define AacHeader
const char* fileName = "believe.flv";
#ifdef AacHeader
const char* outFileName = "outBelieve.aac";
#else
const char* outFileName = "outBelieveNoHeader.aac";
#endif
const int sampling_frequencies[] = {
96000, // 0x0
88200, // 0x1
64000, // 0x2
48000, // 0x3
44100, // 0x4
32000, // 0x5
24000, // 0x6
22050, // 0x7
16000, // 0x8
12000, // 0x9
11025, // 0xa
8000 // 0xb
// 0xc d e f是保留的
};
int adts_header(char * const p_adts_header, const int data_length,
const int profile, const int samplerate,
const int channels)
{
int sampling_frequency_index = 3; // 默认使用48000hz
int adtsLen = data_length + 7;
int frequencies_size = sizeof(sampling_frequencies) / sizeof(sampling_frequencies[0]);
int i = 0;
for(i = 0; i < frequencies_size; i++)
{
if(sampling_frequencies[i] == samplerate)
{
sampling_frequency_index = i;
break;
}
}
if(i >= frequencies_size)
{
printf("unsupport samplerate:%d\n", samplerate);
return -1;
}
p_adts_header[0] = 0xff; //syncword:0xfff 高8bits
p_adts_header[1] = 0xf0; //syncword:0xfff 低4bits
p_adts_header[1] |= (0 << 3); //MPEG Version:0 for MPEG-4,1 for MPEG-2 1bit
p_adts_header[1] |= (0 << 1); //Layer:0 2bits
p_adts_header[1] |= 1; //protection absent:1 1bit
p_adts_header[2] = (profile)<<6; //profile:profile 2bits
p_adts_header[2] |= (sampling_frequency_index & 0x0f)<<2; //sampling frequency index:sampling_frequency_index 4bits
p_adts_header[2] |= (0 << 1); //private bit:0 1bit
p_adts_header[2] |= (channels & 0x04)>>2; //channel configuration:channels 高1bit
p_adts_header[3] = (channels & 0x03)<<6; //channel configuration:channels 低2bits
p_adts_header[3] |= (0 << 5); //original:0 1bit
p_adts_header[3] |= (0 << 4); //home:0 1bit
p_adts_header[3] |= (0 << 3); //copyright id bit:0 1bit
p_adts_header[3] |= (0 << 2); //copyright id start:0 1bit
p_adts_header[3] |= ((adtsLen & 0x1800) >> 11); //frame length:value 高2bits
p_adts_header[4] = (uint8_t)((adtsLen & 0x7f8) >> 3); //frame length:value 中间8bits
p_adts_header[5] = (uint8_t)((adtsLen & 0x7) << 5); //frame length:value 低3bits
p_adts_header[5] |= 0x1f; //buffer fullness:0x7ff 高5bits
p_adts_header[6] = 0xfc; //11111100 //buffer fullness:0x7ff 低6bits
// number_of_raw_data_blocks_in_frame:
// 表示ADTS帧中有number_of_raw_data_blocks_in_frame + 1个AAC原始帧。
return 0;
}
int main()
{
printf("Hello World!\n");
// 1.打开文件
AVFormatContext *ctx = NULL;
int ret = avformat_open_input(&ctx, fileName, NULL, NULL);
if (ret < 0) {
char buf[1024] = {0};
av_strerror(ret, buf, sizeof (buf) - 1);
printf("avformat_open_input %s failed: %s\n", fileName, buf);
return -1;
}
// 2.获取码流信息
ret = avformat_find_stream_info(ctx, NULL);
if (ret < 0) {
char buf[1024] = {0};
av_strerror(ret, buf, sizeof (buf) - 1);
printf("avformat_find_stream_info %s failed: %s\n", fileName, buf);
return -1;
}
// 3.获取音频流
int audioIndex = av_find_best_stream(ctx, AVMEDIA_TYPE_AUDIO, -1, -1, NULL, 0);
if (audioIndex < 0) {
printf("av_find_best_stream failed: %s\n", av_get_media_type_string(AVMEDIA_TYPE_AUDIO));
return -1;
}
// 4.检查是否是aac
if (ctx->streams[audioIndex]->codecpar->codec_id != AV_CODEC_ID_AAC) {
printf("audio codec %d is not AAC.\n", ctx->streams[audioIndex]->codecpar->codec_id);
goto failed;
}
// 5.打开输出aac文件
FILE *fd = fopen(outFileName, "wb");
if (fd == NULL) {
printf("fopen open %s failed.\n", outFileName);
goto failed;
}
// 6.提取aac数据
AVPacket pkt;
av_init_packet(&pkt);
int len = 0;
while (av_read_frame(ctx, &pkt) >= 0) {
if (pkt.stream_index == audioIndex) {
#ifdef AacHeader // 写入aac头
char adts_header_buf[7] = {0};
adts_header(adts_header_buf, pkt.size,
ctx->streams[audioIndex]->codecpar->profile,
ctx->streams[audioIndex]->codecpar->sample_rate,
ctx->streams[audioIndex]->codecpar->channels);
fwrite(adts_header_buf, 1, 7, fd); // 写adts header , ts流不适用,ts流分离出来的packet带了adts header
#endif
len = fwrite( pkt.data, 1, pkt.size, fd); // 写adts data
if(len != pkt.size)
{
printf("warning, length of writed data isn't equal pkt.size(%d, %d)\n", len, pkt.size);
}
}
av_packet_unref(&pkt);
}
failed:
if (ctx) {
avformat_close_input(&ctx);
}
if (fd) {
fclose(fd);
}
return 0;
}
这个有个地方要注意,flv提取的aac流没有头,需要自己手动添加: