如何从 AAC-ADTS header 构造编解码器特定数据 (CSD)？

Question

如何从ADTS构造CSD数据header？我可以为 CSD 数据创建 ADTS header，但如何反向操作？

/* function to construct ADTS header from CSD
 * header_info - contains CSD
 * frameLength - total frame size */    
void addHeaderADTS(uint8_t header_info[], uint32_t frameLength) {

int profile = (csd_data[0] >> 3) & 0x1F;
int frequency_idx = ((csd_data[0] & 0x7) << 1) | ((csd_data[1] >> 7) & 0x1);
int channels = (csd_data[1] >> 3) & 0xF;

header_info[0] = 0xFF;
header_info[1] = 0xF1;
header_info[2] = (((profile - 1) << 6) + (frequency_idx << 2) + (channels >> 2));
header_info[3] = (((channels & 3) << 6) + (frameLength >> 11));
header_info[4] = ((frameLength & 0x7FF) >> 3);
header_info[5] = (((frameLength & 7) << 5) + 0x1F);
header_info[6] = 0xFC;
return;

}

Answer 1

找到。使用 MakeAACCodecSpecificData 函数构造的 CSD 数据 avc_utils.cpp

如何从 AAC-ADTS header 构造编解码器特定数据 (CSD)？

How to construct Codec Specific Data (CSD) from AAC-ADTS header?

android

header

codec

aac

adts