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Android 音视频入门05 FLV封装格式解析

bigegpt 2024-08-07 17:50 4 浏览

本文记录了FLV封装格式解析，封装格式数据在视频播放器中的位置如下所示


原理

FLV封装格式是由一个FLV Header文件头和一个一个的Tag组成。Tag中包含了音频数据以及视频数据。其结构如下图所示。

有关FLV的格式本文的说明见雷神《视音频编解码学习工程：FLV封装格式分析器》。本程序对FLV中的FLV Header和Tag的解析，并可以分离出其中的音视频流。


代码

#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <math.h>

#ifdef ANDROID
#include <jni.h>
#include <android/log.h>
#define LOGE(format, ...)  __android_log_print(ANDROID_LOG_ERROR, "xohnffmpeg", format, ##__VA_ARGS__)
#define LOGI(format, ...)  __android_log_print(ANDROID_LOG_INFO,  "xohnffmpeg", format, ##__VA_ARGS__)
#else
#define LOGE(format, ...)  printf("xohnffmpeg" format "\n", ##__VA_ARGS__)
#define LOGI(format, ...)  printf("xohnffmpeg " format "\n", ##__VA_ARGS__)
#endif


//Important!
#pragma pack(1)


#define TAG_TYPE_SCRIPT 18
#define TAG_TYPE_AUDIO  8
#define TAG_TYPE_VIDEO  9

typedef unsigned char byte;
typedef unsigned int uint;

typedef struct {
    byte Signature[3];
    byte Version;
    byte Flags;
    uint DataOffset;
} FLV_HEADER;

typedef struct {
    byte TagType;
    byte DataSize[3];
    byte Timestamp[3];
    uint Reserved;
} TAG_HEADER;


//reverse_bytes - turn a BigEndian byte array into a LittleEndian integer
uint reverse_bytes(byte *p, char c) {
    int r = 0;
    int i;
    for (i=0; i<c; i++)
        r |= ( *(p+i) << (((c-1)*8)-8*i));
    return r;
}

unsigned int getw(FILE *fp){
    char *s;
    unsigned int i;
    s = (char*)&i;
    s[0] = getc(fp);
    s[1] = getc(fp);
    s[2] = getc(fp);
    s[3] = getc(fp);
    return(i);
}

/**
 * Analysis FLV file
 * @param jstr_url    Location of input FLV file.
 */
extern "C" JNIEXPORT jint JNICALL
Java_com_xohn_ffmpeg_AVUtils_flvParser(
        JNIEnv *env,jobject /* this */,
        jstring jstr_url) {
    //whether output audio/video stream
    int output_a = 1;
    int output_v = 1;
    //-------------
    FILE *ifh = NULL,*vfh = NULL, *afh = NULL;

    //FILE *myout = fopen("output_log.txt","wb+");
    //FILE *myout = stdout;

    FLV_HEADER flv;
    TAG_HEADER tagheader;
    uint previoustagsize, previoustagsize_z=0;
    uint ts = 0, ts_new = 0;

    char input_url[100] = {0};
    const char *str = env->GetStringUTFChars(jstr_url, NULL);
    sprintf(input_url,"%s",str);
    env->ReleaseStringUTFChars(jstr_url,str);

    ifh = fopen(input_url, "rb+");
    if (ifh == NULL) {
        LOGE("Failed to open files!");
        return -1;
    }

    //FLV file header
    fread((char *)&flv,1,sizeof(FLV_HEADER),ifh);

    LOGI("============== FLV Header ==============\n");
    LOGI("Signature:  %c %c %c\n",flv.Signature[0],flv.Signature[1],flv.Signature[2]);
    LOGI("Version:    0x%02X\n",flv.Version);
    LOGI("Flags  :    0x%02X\n",flv.Flags);
    LOGI("HeaderSize: 0x%02X\n",reverse_bytes((byte *)&flv.DataOffset, sizeof(flv.DataOffset)));
    LOGI("========================================\n");

    //move the file pointer to the end of the header
    fseek(ifh, reverse_bytes((byte *)&flv.DataOffset, sizeof(flv.DataOffset)), SEEK_SET);

    //process each tag
    do {
        char print_str[150] = {0};
        //previoustagsize = _getw(ifh);
        previoustagsize = getw(ifh);

        fread((void *)&tagheader,sizeof(TAG_HEADER),1,ifh);

        //int temp_datasize1=reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize));
        int tagheader_datasize = tagheader.DataSize[0]*65536+tagheader.DataSize[1]*256+tagheader.DataSize[2];
        int tagheader_timestamp = tagheader.Timestamp[0]*65536+tagheader.Timestamp[1]*256+tagheader.Timestamp[2];

        char tagtype_str[10];
        switch(tagheader.TagType){
            case TAG_TYPE_AUDIO:sprintf(tagtype_str,"AUDIO");break;
            case TAG_TYPE_VIDEO:sprintf(tagtype_str,"VIDEO");break;
            case TAG_TYPE_SCRIPT:sprintf(tagtype_str,"SCRIPT");break;
            default:sprintf(tagtype_str,"UNKNOWN");break;
        }
        //LOGI("[%6s] %6d %6d |",tagtype_str,tagheader_datasize,tagheader_timestamp);
        sprintf(print_str,"[%6s] %6d %6d |",tagtype_str,tagheader_datasize,tagheader_timestamp);

        //if we are not past the end of file, process the tag
        if (feof(ifh)) {
            break;
        }

        //process tag by type
        switch (tagheader.TagType) {
            case TAG_TYPE_AUDIO:{
                char audiotag_str[100] = {0};
                strcat(audiotag_str,"| ");
                char tagdata_first_byte;
                tagdata_first_byte = fgetc(ifh);
                int x = tagdata_first_byte&0xF0;
                x = x>>4;
                switch (x){
                    case 0:strcat(audiotag_str,"Linear PCM, platform endian");break;
                    case 1:strcat(audiotag_str,"ADPCM");break;
                    case 2:strcat(audiotag_str,"MP3");break;
                    case 3:strcat(audiotag_str,"Linear PCM, little endian");break;
                    case 4:strcat(audiotag_str,"Nellymoser 16-kHz mono");break;
                    case 5:strcat(audiotag_str,"Nellymoser 8-kHz mono");break;
                    case 6:strcat(audiotag_str,"Nellymoser");break;
                    case 7:strcat(audiotag_str,"G.711 A-law logarithmic PCM");break;
                    case 8:strcat(audiotag_str,"G.711 mu-law logarithmic PCM");break;
                    case 9:strcat(audiotag_str,"reserved");break;
                    case 10:strcat(audiotag_str,"AAC");break;
                    case 11:strcat(audiotag_str,"Speex");break;
                    case 14:strcat(audiotag_str,"MP3 8-Khz");break;
                    case 15:strcat(audiotag_str,"Device-specific sound");break;
                    default:strcat(audiotag_str,"UNKNOWN");break;
                }
                strcat(audiotag_str,"| ");
                x = tagdata_first_byte&0x0C;
                x = x>>2;
                switch (x){
                    case 0:strcat(audiotag_str,"5.5-kHz");break;
                    case 1:strcat(audiotag_str,"1-kHz");break;
                    case 2:strcat(audiotag_str,"22-kHz");break;
                    case 3:strcat(audiotag_str,"44-kHz");break;
                    default:strcat(audiotag_str,"UNKNOWN");break;
                }
                strcat(audiotag_str,"| ");
                x = tagdata_first_byte&0x02;
                x = x>>1;
                switch (x){
                    case 0:strcat(audiotag_str,"8Bit");break;
                    case 1:strcat(audiotag_str,"16Bit");break;
                    default:strcat(audiotag_str,"UNKNOWN");break;
                }
                strcat(audiotag_str,"| ");
                x = tagdata_first_byte&0x01;
                switch (x){
                    case 0:strcat(audiotag_str,"Mono");break;
                    case 1:strcat(audiotag_str,"Stereo");break;
                    default:strcat(audiotag_str,"UNKNOWN");break;
                }
                //LOGI("%s",audiotag_str);
                strcat(print_str,audiotag_str);

                //if the output file hasn't been opened, open it.
                if(output_a!=0 && afh == NULL){
                    strcpy(input_url+strlen(input_url)-4,".mp3");
                    afh = fopen(input_url, "wb");
                }

                //TagData - First Byte Data
                int data_size = reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize))-1;
                if(output_a != 0){
                    //TagData+1
                    for (int i=0; i<data_size; i++)
                        fputc(fgetc(ifh),afh);
                }else{
                    for (int i=0; i<data_size; i++)
                        fgetc(ifh);
                }
                break;
            }
            case TAG_TYPE_VIDEO:{
                char videotag_str[100] = {0};
                strcat(videotag_str,"| ");
                char tagdata_first_byte;
                tagdata_first_byte = fgetc(ifh);
                int x = tagdata_first_byte&0xF0;
                x = x>>4;
                switch (x){
                    case 1:strcat(videotag_str,"key frame  ");break;
                    case 2:strcat(videotag_str,"inter frame");break;
                    case 3:strcat(videotag_str,"disposable inter frame");break;
                    case 4:strcat(videotag_str,"generated keyframe");break;
                    case 5:strcat(videotag_str,"video info/command frame");break;
                    default:strcat(videotag_str,"UNKNOWN");break;
                }
                strcat(videotag_str,"| ");
                x = tagdata_first_byte&0x0F;
                switch (x){
                    case 1:strcat(videotag_str,"JPEG (currently unused)");break;
                    case 2:strcat(videotag_str,"Sorenson H.263");break;
                    case 3:strcat(videotag_str,"Screen video");break;
                    case 4:strcat(videotag_str,"On2 VP6");break;
                    case 5:strcat(videotag_str,"On2 VP6 with alpha channel");break;
                    case 6:strcat(videotag_str,"Screen video version 2");break;
                    case 7:strcat(videotag_str,"AVC");break;
                    default:strcat(videotag_str,"UNKNOWN");break;
                }
                //LOGI("%s",videotag_str);
                strcat(print_str,videotag_str);

                fseek(ifh, -1, SEEK_CUR);
                //if the output file hasn't been opened, open it.
                if (output_v!=0 && vfh == NULL) {
                    //write the flv header (reuse the original file's hdr) and first previoustagsize
                    strcpy(input_url+strlen(input_url)-4,"_extract.flv");
                    vfh = fopen(input_url, "wb");
                    fwrite((char *)&flv,1, sizeof(flv),vfh);
                    fwrite((char *)&previoustagsize_z,1,sizeof(previoustagsize_z),vfh);
                }

                #if 0
                //Change Timestamp
                //Get Timestamp
                ts = reverse_bytes((byte *)&tagheader.Timestamp, sizeof(tagheader.Timestamp));
                ts = ts*2;
                //Writeback Timestamp
                ts_new = reverse_bytes((byte *)&ts, sizeof(ts));
                memcpy(&tagheader.Timestamp, ((char *)&ts_new) + 1, sizeof(tagheader.Timestamp));
                #endif


                //TagData + Previous Tag Size
                int data_size = reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize))+4;
                if(output_v != 0){
                    //TagHeader
                    fwrite((char *)&tagheader,1, sizeof(tagheader),vfh);
                    //TagData
                    for (int i=0; i<data_size; i++)
                        fputc(fgetc(ifh),vfh);
                }else{
                    for (int i=0; i<data_size; i++)
                        fgetc(ifh);
                }
                //rewind 4 bytes, because we need to read the previoustagsize again for the loop's sake
                fseek(ifh, -4, SEEK_CUR);

                break;
            }
            default:
                //skip the data of this tag
                fseek(ifh, reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize)), SEEK_CUR);
        }

        //LOGI("\n");
        strcat(print_str,"\n");
        LOGI("%s",print_str);

    } while (!feof(ifh));


    //_fcloseall();
    fclose(ifh);
    if(output_a!=0 && afh != NULL){
        fclose(afh);
    }
    if (output_v!=0 && vfh != NULL) {
        fclose(vfh);
    }

    return 0;
}

函数调用

AVUtils.getInstance().flvParser(ROOT+"cuc_ieschool.flv");

输出为FLV的统计数据，如下图

并且会在同目录下提取出 cuc_ieschool_extract.mp3 & cuc_ieschool_extract.flv，单纯的音视频文件



参考文章：

雷神文章 https://blog.csdn.net/leixiaohua1020/article/details/50535082

FLV封装格式分析器 https://blog.csdn.net/leixiaohua1020/article/details/17934487


项目git地址：

https://gitee.com/xohn/FFmpeg.git 中的FFMpeg1 - xohn_avutils_flv.cpp

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