手撕FLV协议
实现效果
纯代码实现分离FLV音视频流，并组装成AAC和H264文件，最后能正常播放。注：本文只对有AAC和H264格式音视频流组成的flv进行分离。
FLV协议
注：脚本部分本文未使用，可前往这查看。
实现代码
代码注释已经很详细了，其实就是对照协议表进行数据解析，其中：
- (1) H264协议请看直播推流全过程：视频编码之H.264（3）;
- (2) AAC协议请看直播推流全过程：音频编码之AAC（4）;
#include <cstdlib>
/**
* @author 秦城季
* @email xhunmon@126.com
* @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;
}
使用ffplay查看输出文件
h264文件播放：
ffplay xxx.h264
aac文件播放：
ffplay xxx.aac
测试文件下载地址
参考
- https://www.cnblogs.com/chyingp/p/flv-getting-started.html
- ISO/IEC_14496-3