The starting address will be even more wrong
achieve effect
Pure code realizes the separation of FLV audio and video streams, and assembles them into AAC and H264 files, and finally can play normally. Note: This article only separates the flv composed of AAC and H264 format audio and video streams.
FLV protocol
[External link picture transfer failed, the source site may have an anti-leeching mechanism, it is recommended to save the picture and upload it directly (img-oyU21eaj-1610869332555)(07_flv/flv-pr.jpg)]
Note: The script part is not used in this article, you can go here to view it .
implement the code
The code comments are already very detailed. In fact, it is to analyze the data against the protocol table, among which:
- (1) For the H264 protocol, please refer to the whole process of live streaming: H.264 of video encoding (3) ;
- (2) For the AAC protocol, please refer to the whole process of live streaming: AAC of audio coding (4) ;
#include <cstdlib>
/**
* @author 秦城季
* @email [email protected]
* @Blog https://qincji.gitee.io
* @date 2021/01/01
* description: <br>
*/
#include <cstdio>
#include <iostream>
using namespace std;
typedef struct Tag {
int TagType;
unsigned DataSize;
unsigned Timestamp;
unsigned TimestampExtended;
int StreamID;
unsigned char *Data;
} Tag;
//从flv中第一帧获取的数据
typedef struct FLV_AAC_HEAD {
unsigned char audioObjectType: 5;
unsigned char samplingFrequencyIndex: 4;
unsigned char channelConfiguration: 4;
unsigned char other: 3;//占位；这个值不需要的 000
} FLV_AAC_HEAD;
//aac封装 每个帧头结构设定恒为7Byte
typedef struct AAC_ADST_HEAD {
//1. adts_fixed_header
unsigned short syncword: 12; /* 恒为 1111 1111 1111*/
unsigned char ID: 1; /* 0：MPEG-4，1：MPEG-2*/
unsigned char layer: 2; /* 00*/
unsigned char protection_absent: 1; /* 是否使用error_check()。0：使用，1：不使用。*/
unsigned char profile: 2; /* AAC类型*/
unsigned char sampling_frequency_index: 4;/* 采样率的数组下标，即：sampling frequeny[sampling_frequency_index] */
unsigned char private_bit: 1; /* 0*/
unsigned char channel_configuration: 3; /* 声道数*/
unsigned char original_copy: 1; /* 0*/
unsigned char home: 1; /* 0*/
//2. adts_variable_header
unsigned char copyright_identification_bit: 1; /* 0*/
unsigned char copyright_identification_start: 1; /* 0*/
unsigned short frame_length: 13; /* 帧的长度，包括head*/
unsigned short adts_buffer_fullness: 11; /* 固定0x7FF*/
unsigned char number_of_raw_data_blocks_in_frame: 2; /*在ADTS帧中有number_of_raw_data_blocks_in_frame + 1个AAC原始数据块。number_of_raw_data_blocks_in_frame == 0 表示说ADTS帧中有一个AAC原始数据块。*/
} AAC_ADST_HEAD;
int checkFLV(FILE *fp_in) {
int ret = 1;
char *head = (char *) malloc(9);
fread(head, 1, 9, fp_in);
//Signature(FLV)
if (head[0] != 'F' || head[1] != 'L' || head[2] != 'V') {
printf("Not FLV File !\n");
ret = 0;
}
//第5个字节为Flags(流信息)，视频标志位：.... ...1；音频标志位：.... .1..
int vFlags = head[4] & 0x01;
int aFlags = (head[4] & 0x04) >> 1;
if (!vFlags) {
printf("Not Video Data !\n");
ret = 0;
}
if (!aFlags) {
printf("Not Audio Data !\n");
ret = 0;
}
free(head);
return ret;
}
int getTagAndTagSize(FILE *fp_in, Tag *tag) {
int length = -1;
//Tag表中除了Data之外，其他所有的字节
unsigned char *buf = (unsigned char *) malloc(11);
//读取Tag前面11个字节
fread(buf, 1, 11, fp_in);
tag->TagType = buf[0];
tag->DataSize = (buf[1] << 16) + (buf[2] << 8) + buf[3];
tag->Timestamp = (buf[4] << 16) + (buf[5] << 8) + buf[6];
tag->TimestampExtended = buf[7];
tag->StreamID = (buf[8] << 16) + (buf[9] << 8) + buf[10];
tag->Data = (unsigned char *) calloc(tag->DataSize, sizeof(char));
//读取Data
fread(tag->Data, 1, tag->DataSize, fp_in);
//读取PreviousTagSize的4个字节
fread(buf, 1, 4, fp_in);
//这个长度就是 Tag(n)+PreviousTagSize(n)的长度
length = 11 + tag->DataSize + 4;
unsigned PreviousTagSize = (buf[0] << 24) + (buf[1] << 16) + (buf[2] << 8) + buf[3];
free(buf);
fprintf(stdout, "%9d| %9d| %10d| %18d| %9d| %16d|\n", tag->TagType, tag->DataSize, tag->Timestamp,
tag->TimestampExtended,
tag->StreamID, PreviousTagSize);
return length;
}
unsigned char *sps_nalu = NULL;
unsigned char *pps_nalu = NULL;
char *buf_start = NULL;
unsigned sps_nalu_size = 0;
unsigned pps_nalu_size = 0;
int videoToH264(FILE *fp_video, Tag *tag) {
int ret = 1;
//tag->Data = FrameType + CodecID + VideoData ;
//VideoData = AVCPacketType + CompositionTime + 【Data（注：视频数据）】
unsigned FrameType = (tag->Data[0] & 0xF0) >> 4;//Data表(视频)：高4bit
unsigned CodecID = tag->Data[0] & 0x0F; //Data表(视频)：低4bit
unsigned AVCPacketType = tag->Data[1]; //VideoData表( AVCVIDEOPACKE)
unsigned CompositionTime = (tag->Data[2] << 16) + (tag->Data[3] << 8) + tag->Data[4];//VideoData表( AVCVIDEOPACKE)
if (CodecID != 7) {
//7: AVC(高级视频编码)
ret = 0;
printf("Not AVC Error\n");
goto end;
}
printf("FrameType=%d\t|CodecID=%d\t|AVCPacketType=%d\t|CompositionTime=%d\t\n", FrameType, CodecID, AVCPacketType,
CompositionTime);
//从tag->Data[5]开始至结束为【Data（注：视频数据）】
//一般FLV第一个视频Tag为sps和pps数据，需要根据AVCDecoderConfigurationRecord进行解析，单独抽出来封装成NALU数据
if (AVCPacketType == 0) {
//0: AVC sequence header
printf("0: AVC sequence header\n");
if (sps_nalu) {
free(sps_nalu);
}
if (pps_nalu) {
free(pps_nalu);
}
unsigned Version = tag->Data[5];//sps：版本
unsigned AVCProfileIndication = tag->Data[6];//sps：编码规格
unsigned profile_compatibility = tag->Data[7];//sps：编码规格
unsigned AVCLevelIndication = tag->Data[8];//sps：编码规格
unsigned reserved_And_lengthSizeMinusOne = tag->Data[9];//sps：应恒为0xFF
unsigned numOfSequenceParameterSets = tag->Data[10] & 0x1F;//sps：sps个数，取低5位；tag->Data[10]一般为0xE1
unsigned sps_len = (tag->Data[11] << 8) + tag->Data[12];//sps：sps长度
sps_nalu_size = sps_len + 4;
sps_nalu = (unsigned char *) malloc(sps_nalu_size);//加4个为起始位
memcpy(sps_nalu, buf_start, 4);
memcpy(sps_nalu + 4, tag->Data + 13, sps_len);
printf("sps_len=%d\nsps_data=", sps_len);
for (int i = 4; i < sps_nalu_size; ++i) {
printf("%.2x", sps_nalu[i]);
}
printf("\n");
fwrite(sps_nalu, 1, sps_nalu_size, fp_video);
unsigned ppsIndex = 13 + sps_len;
unsigned numOfPictureParameterSets = tag->Data[ppsIndex];//pps：pps个数，1个字节；
unsigned pps_len = (tag->Data[ppsIndex + 1] << 8) + tag->Data[ppsIndex + 2];//pps：pps长度
pps_nalu_size = pps_len + 4;
pps_nalu = (unsigned char *) malloc(pps_nalu_size);//加4个为起始位
memcpy(pps_nalu, buf_start, 4);
memcpy(pps_nalu + 4, tag->Data + ppsIndex + 3, pps_len);
printf("pps_len=%d\npps_data=", pps_len);
for (int i = 4; i < pps_nalu_size; ++i) {
printf("%.2x", pps_nalu[i]);
}
printf("\n");
fwrite(pps_nalu, 1, pps_nalu_size, fp_video);
} else if (AVCPacketType == 1) {
//1: AVC NALU：可能包括多个NALU，需要重新封装
printf("1: AVC NALU\n");
//【Data（注：视频数据）】= [size1+pic1]+...+[sizen+picn] 转成 [起始码+pic1]+...+[起始码+picn]
unsigned int pic_start = 5;
unsigned int pic_size = 0;
unsigned int pic_next_index = 0;
while (1) {
if (pic_start + 4 >= tag->DataSize) {
printf("----break-----, pic_start + 4 >= tag->DataSize\n");
break;
}
printf("pic_size=0x%.2x%.2x%.2x%.2x\n", tag->Data[pic_start], tag->Data[pic_start + 1],
tag->Data[pic_start + 2],
tag->Data[pic_start + 3]);
pic_size =
(tag->Data[pic_start] << 24) + (tag->Data[pic_start + 1] << 16) + (tag->Data[pic_start + 2] << 8) +
tag->Data[pic_start + 3];
pic_next_index = pic_start + 4 + pic_size;
if (pic_size <= 0 || tag->DataSize < pic_next_index) {
printf("----break-----, Data Error ! pic_start=%d\tpic_size=%d\tpic_next_index=%d\tDataSize=%d \n",
pic_start, pic_size, pic_next_index,
tag->DataSize);
break;
}
printf("write pic data,pic_start=%d\tpic_size=%d\tpic_next_index=%d\tDataSize=%d \n", pic_start, pic_size,
pic_next_index,
tag->DataSize);
//当前帧数据范围 pic_start + 4 ~ pic_next_index
fwrite(buf_start, 1, 4, fp_video);
fwrite(tag->Data + pic_start + 4, 1, pic_size, fp_video);
pic_start = pic_next_index;
}
} else if (AVCPacketType == 2) {
//2: AVC end of sequence
printf("2: AVC end of sequence\n");
}
end:
free(tag->Data);
return ret;
}
AAC_ADST_HEAD *aacAdstHead = NULL;
int getAACHeadBuf(unsigned char *buf, AAC_ADST_HEAD *aacAdstHead, const unsigned int frame_size) {
int ret = 0;
aacAdstHead->frame_length = frame_size;
//取syncword高位1Byte
buf[0] = aacAdstHead->syncword >> 4;
//syncword(低4位)+ID(1)+layer(2)+protection_absent(1)
buf[1] = ((aacAdstHead->syncword & 0x00F) << 4) + (aacAdstHead->ID >> 3) + (aacAdstHead->layer >> 1) +
aacAdstHead->protection_absent;
//profile(2)+sampling_frequency_index(4)+private_bit(1)+channel_configuration(3bit取最高1bit)
buf[2] = (aacAdstHead->profile << 6) + (aacAdstHead->sampling_frequency_index << 2) + (aacAdstHead->private_bit
<< 1) + (aacAdstHead->channel_configuration
>> 2);
// ...00000 00000000
//channel_configuration(3bit取低2bit)+original_copy(1)+home(1)+copyright_identification_bit(1)+copyright_identification_start(1)+frame_length(13bit取最高2bit)
buf[3] = (aacAdstHead->channel_configuration << 6) + (aacAdstHead->original_copy << 5) + (aacAdstHead->home << 4)
+ (aacAdstHead->copyright_identification_bit << 3) + (aacAdstHead->copyright_identification_start << 2)
+ (aacAdstHead->frame_length >> 11);
//frame_length(13bit取：去掉最高2bit开始8位)
buf[4] = (aacAdstHead->frame_length >> 3) & 0x0FF;
//frame_length(13bit取最低3bit)+adts_buffer_fullness(11bit取高5bit)
buf[5] = (aacAdstHead->frame_length << 5) + (aacAdstHead->adts_buffer_fullness >> 6);
//adts_buffer_fullness(11bit取低6bit) + number_of_raw_data_blocks_in_frame(2)
buf[6] = (aacAdstHead->adts_buffer_fullness << 2) + aacAdstHead->number_of_raw_data_blocks_in_frame;
return ret;
}
int audioToAac(FILE *fp_audio, Tag *tag) {
int ret = 1;
unsigned SoundFormat = tag->Data[0] >> 4;
unsigned SoundRate = (tag->Data[0] & 0x0F) >> 2;
unsigned SoundSize = (tag->Data[0] & 0x02) >> 1;
unsigned SoundType = tag->Data[0] & 0x01;
//SoundData = AACPacketType + Data
unsigned AACPacketType = tag->Data[1];
if (SoundFormat != 10) {
//10 = AAC
printf("Not AAC Error\n");
ret = 0;
goto end;
}
if (AACPacketType == 0) {
//0: AAC sequence header(参考14496-3 AudioSpecificConfig https://wiki.multimedia.cx/index.php/MPEG-4_Audio#Audio_Specific_Config)
printf("0: AAC sequence header\n");
//读取flv文件中的头信息
FLV_AAC_HEAD *flvAacHead = (FLV_AAC_HEAD *) malloc(sizeof(FLV_AAC_HEAD));
//只要前面两个字节就行，如0x1390=00010011 10010000
flvAacHead->audioObjectType = tag->Data[2] >> 3;//UB[5]=00010... ........
flvAacHead->samplingFrequencyIndex =
((tag->Data[2] & 0x07) << 1) + (tag->Data[3] >> 7);//UB[4]=.....011 1.......
flvAacHead->channelConfiguration = (tag->Data[3] & 0x7F) >> 3;//UB[4]=........ .0010...
flvAacHead->other = tag->Data[3] & 0x07;//两个字节剩余的bit，为0也行。
//构造AAC_ADST_HEAD
if (aacAdstHead) {
free(aacAdstHead);
}
aacAdstHead = (AAC_ADST_HEAD *) malloc(sizeof(AAC_ADST_HEAD));
aacAdstHead->syncword = 0xFFF;
aacAdstHead->ID = 1;
aacAdstHead->layer = 0;
aacAdstHead->protection_absent = 1;
aacAdstHead->profile = flvAacHead->audioObjectType;
// aacAdstHead->profile = 1;
aacAdstHead->sampling_frequency_index = flvAacHead->samplingFrequencyIndex;
aacAdstHead->private_bit = 0;
aacAdstHead->channel_configuration = flvAacHead->channelConfiguration;
aacAdstHead->original_copy = 0;
aacAdstHead->home = 0;
aacAdstHead->copyright_identification_bit = 0;
aacAdstHead->copyright_identification_start = 0;
// aacAdstHead->frame_length = xx; //帧的长度动态计算的
aacAdstHead->adts_buffer_fullness = 0x7FF;
aacAdstHead->number_of_raw_data_blocks_in_frame = 0;
printf("audioObjectType=%d\tsamplingFrequencyIndex=%d\t channelConfiguration=%d\n ",
flvAacHead->audioObjectType, flvAacHead->samplingFrequencyIndex, flvAacHead->channelConfiguration);
free(flvAacHead);
} else if (AACPacketType == 1) {
//1: AAC raw
printf("1: AAC raw\n");
unsigned char *buf = (unsigned char *) malloc(7);;
if (getAACHeadBuf(buf, aacAdstHead, tag->DataSize - 2 + 7) == -1) {
printf("get AAC Head Buf Error\n");
ret = 0;
goto end;
}
fwrite(buf, 1, 7, fp_audio);
fwrite(tag->Data + 2, 1, tag->DataSize - 2, fp_audio);
free(buf);
}
end:
free(tag->Data);
return ret;
}
int test() {
return 0;
}
int main() {
if (test()) {
//非0位true
exit(1);
}
printf("delete cache video file ? %d\n", remove("output/Kobe.h264"));
printf("delete cache audio file ? %d\n", remove("output/Kobe.aac"));
FILE *fp_in = fopen("assets/Kobe.flv", "rb+");
FILE *fp_video = fopen("output/Kobe.h264", "wb+");
FILE *fp_audio = fopen("output/Kobe.aac", "wb+");
Tag *tag;
if (!fp_in) {
cout << "源文件不存在！" << endl;
exit(1);
}
if (!fp_video) {
cout << "输出文件不存在！" << endl;
exit(1);
}
if (!checkFLV(fp_in)) {
exit(1);
}
//跳过PreviousTagSize(0) 4byte
fseek(fp_in, 4, SEEK_CUR);
tag = (Tag *) calloc(1, sizeof(Tag));
//初始化h264中NALU的起始码（0x00 00 00 01或者0x00 00 01）
buf_start = (char *) malloc(4);
buf_start[0] = 0x00;
buf_start[1] = 0x00;
buf_start[2] = 0x00;
buf_start[3] = 0x01;
if (!tag) {
printf("Alloc Tag Error\n");
return 0;
}
printf("---------+----------+----------Tag------------------+----------+-----------------+\n");
printf(" TagType | DataSize | Timestamp | TimestampExtended | StreamID | PreviousTagSize |\n");
printf("---------+----------+-----------+-------------------+----------+-----------------+\n");
while (!feof(fp_in)) {
//查找一组：Tag + PreviousTagSize
int data_lenth;
int ret;
data_lenth = getTagAndTagSize(fp_in, tag);
if (tag->TagType == 0x12) {
//脚本数据
}
if (tag->TagType == 0x08) {
//音频数据
ret = audioToAac(fp_audio, tag);
}
if (tag->TagType == 0x09) {
//视频数据
ret = videoToH264(fp_video, tag);
}
}
if (sps_nalu) {
free(sps_nalu);
}
if (pps_nalu) {
free(pps_nalu);
}
if (buf_start) {
free(buf_start);
}
fclose(fp_video);
return 0;
}
Use ffplay to view the output file
h264 file playback:
ffplay xxx.h264
aac file playback:
ffplay xxx.aac
Test file download address
reference
- https://www.cnblogs.com/chyingp/p/flv-getting-started.html
- ISO/IEC_14496-3