linux环境C语言实现：h264与pcm封装成mp4视频格式

前言

H.264是压缩过的数据，PCM是原始数据，MP4是一种视频封装格式。实际H.264与PCM不能直接合成MP4格式，因为音频格式不对。这里需要中间对音频做一次压缩处理。基本流程为：将PCM音频数据压缩成AAC格式音频数据，再将AAC与H.264合成MP4视频格式。

（一）PCM压缩为AAC格式

直接上代码，接口函数的实现如下：

#include <stdio.h>
#include "faac.h"
#include "pcm2acc.h" 

int Hst_PCM_To_AAC(PCM_TO_MP4_PARA_S stPara)
{
	// 定义别名
	typedef unsigned char   BYTE;
	unsigned long	nSampleRate = 8000;
	unsigned int	nChannels = 1;
	unsigned int	nPCMBitSize = 16;
	unsigned long	nInputSamples = 0;
	unsigned long	nMaxOutputBytes = 0;
	faacEncHandle	hEncoder = {0};
 
	//nSampleRate = stPara.u64SampleRate;
	//nChannels   = stPara.u32Channels;
	//nPCMBitSize = stPara.u32PCMBitSize;


	FILE* fpIn = fopen(stPara.arrs8PCMFilename, "rb");
	FILE* fpOut = fopen(stPara.arrs8AACFilename, "wb");
	//FILE* fpIn = fopen("./ExportChannel0Audio.cpm", "rb");
	//FILE* fpOut = fopen("./test.aac", "wb");
 
	if(fpIn==NULL || fpOut==NULL)
	{
		printf("File Open error \n");
		return -1;
	}
 
	// 打开faac编码器引擎
	hEncoder = faacEncOpen(nSampleRate, nChannels, &nInputSamples, &nMaxOutputBytes);
	if(hEncoder == NULL)
	{
		printf("open faac encoder error !\n");
		return -1;
	}
 
	// 分配内存信息
	int		nPCMBufferSize = nInputSamples*nPCMBitSize/8;
	BYTE*	pbPCMBuffer = new BYTE[nPCMBufferSize];
	BYTE*	pbAACBuffer = new BYTE[nMaxOutputBytes];
 
	// 获取当前编码器信息
	faacEncConfigurationPtr pConfiguration = {0};
	pConfiguration = faacEncGetCurrentConfiguration(hEncoder);
 
	// 设置编码配置信息
	/*
		PCM Sample Input Format
		0	FAAC_INPUT_NULL			invalid, signifies a misconfigured config
		1	FAAC_INPUT_16BIT		native endian 16bit
		2	FAAC_INPUT_24BIT		native endian 24bit in 24 bits		(not implemented)
		3	FAAC_INPUT_32BIT		native endian 24bit in 32 bits		(DEFAULT)
		4	FAAC_INPUT_FLOAT		32bit floating point
    */
	pConfiguration->inputFormat = FAAC_INPUT_16BIT;
 
	// 0 = Raw; 1 = ADTS
	pConfiguration->outputFormat = 1;
 
	// AAC object types 
	//#define MAIN 1
	//#define LOW  2
	//#define SSR  3
	//#define LTP  4
	pConfiguration->aacObjectType = LOW;
	pConfiguration->allowMidside = 0;
	pConfiguration->useLfe = 0;
	pConfiguration->bitRate = 48000;
	pConfiguration->bandWidth = 32000;
 
	// 其他的参数不知道怎么配置，毕竟对音频不熟
	// 不过当前的设置可以实现转换，不过声音好像有一丢丢怪异
	// 这一块的配置信息很重要，错了会导致转码失败，然后你以为代码其他地方错了
 
	// 重置编码器的配置信息
	faacEncSetConfiguration(hEncoder, pConfiguration);
 
	size_t nRet = 0;
 
	printf("start data convert : \n");
	int i = 0;
	while( (nRet = fread(pbPCMBuffer, 1, nPCMBufferSize, fpIn)) > 0)
	{
		printf("\b\b\b\b\b\b\b\b%-8d", ++i);
		nInputSamples = nRet / (nPCMBitSize/8);
 
		// 编码
		nRet = faacEncEncode(hEncoder, (int*) pbPCMBuffer, nInputSamples, pbAACBuffer, nMaxOutputBytes);
 
		// 写入转码后的数据
		fwrite(pbAACBuffer, 1, nRet, fpOut);
	}
 
	// 扫尾工作
	faacEncClose(hEncoder);
	fclose(fpOut);
	fclose(fpIn);
 
	delete[] pbAACBuffer;
	delete[] pbPCMBuffer;
	
	return 0;
}


int main(void)
{
	PCM_TO_MP4_PARA_S l_stPara;
	
	Hst_PCM_To_AAC(l_stPara);
}

整个工程如下：

.
├── faac-1.29.9.2_ARM.tar.gz
├── faaccfg.h
├── faac.h
├── lib
│   ├── libfaac.a
│   ├── libfaac.la
│   ├── libfaac.so
│   ├── libfaac.so.0
│   └── libwisdom_aac.so
├── pcm2acc.cpp
├── pcm2acc.h
└── test.c

注意：我这些库是使用了海思的交叉编译，并不能直接在PC机上运行。如果需要在PC机上运行，需要自己重新编译库文件，这里只提供一种方法。完整工程下载路径：PCM音频转AAC格式

（二）H264与PCM合成MP4

这套代码是在网上下载的，初步使用并没发现其他的什么异常。他原来是用来做AVI转MP4和MP4转AVI的，中间的音频转换他们没有提供，于是我在这基础上做了一些修改，直接将h264与AAC合成MP4格式。主要代码如下：

int H264AacToMp4(H264_AAC_PARA stPara,char* mp4FilePath)
{
	int VIDEO_BUF_LEN = 327680;
	int AUDIO_BUF_LEN = 100000;
	CAviFmtInterface aviFormatInsatance;
	CMp4FmtInterface mp4FormatInsatance;
	int framew = stPara.u32VideoFrameW;
	int frameh = stPara.u32VideoFrameH;
	long framerate = stPara.u32VideoFrameRate;

	char * vidbuf = (char*)malloc(VIDEO_BUF_LEN);
    char * audbuf = (char*)malloc(AUDIO_BUF_LEN);
	if(vidbuf==NULL || audbuf==NULL)
	{
		return -1;
	}

	mp4FormatInsatance.OpenFile(mp4FilePath,OPEN_MODEL_W);
	mp4FormatInsatance.SetMp4Param((u_int16_t)framew,(u_int16_t)frameh,framerate);

	FILE *in_aac = NULL;
	FILE *in_h264 = NULL;

	in_aac = fopen(stPara.arrs8AACFileName,"rb");
	if(in_aac == NULL)
	{
		printf("Can't open the aac file\n");
		return -1;
	}
	
	in_h264 = fopen(stPara.arrs8H264FileName,"rb") ;
	if(in_h264== NULL)
	{
		printf("Can't open the h264 file\n");
		return -1;
	}

	//音频
	fseek(in_aac,0,SEEK_END);
	file_aac_length = ftell(in_aac);
	fseek(in_aac,0,SEEK_SET);
	if(file_aac_length == 0)
	{
		return -1;
	}

	//音频
	AACBUFFER aacbuffer;
	init_aac_buf(&aacbuffer);
	fread(aacbuffer.buf,1,AACBUFSIZE,in_aac);
	ADTS_HEADER adts_header;


	int idx = 0;
	int idxAudio = 0;

	while (1)//read and write avi per fream
	{
		init_adts_header(&adts_header);

		long readLen = 0;
		readLen = aviFormatInsatance.GetAnnexbNALU(in_h264, vidbuf);
		if(readLen<=0)
		{
			break;
		};
		
		if(!mp4FormatInsatance.WriteVideoFrameData((unsigned char*)vidbuf,readLen))
		{
			printf("Write video frame data fail. The frame index is:%05d.\n",idx);
		}
		idx++;	
	}
	
	idx = 0;
	while(1)
	{
		if(read_aac_frame(&aacbuffer,&adts_header))
		{
			if(!mp4FormatInsatance.WriteAudioFrameData((const unsigned char*)(adts_header.aac_frame_start-7),adts_header.aac_frame_length+7))//此接口需要的数据信息，需要包含7个字节的头信息
			{
				printf("error!\n");
				break;
			}
			idx++;
		}
		else
		{
			printf("Reach to the end of aac file!\n");
			break;
		}
	}

	mp4FormatInsatance.Close(); 
	
	if(NULL!=in_h264)
	{
		fclose(in_h264);
		in_h264 = NULL;
	}

	if(NULL!=in_aac)
	{
		fclose(in_aac);
		in_h264 = NULL;
	}

	free(vidbuf);
	free(audbuf);
	return 0;
}

代码结构如下：

.
├── avilib
├── AviToMp4.h
├── include
├── libwisdom_hi3520_avi2mp4.so
├── Makefile
├── mediaconvert
├── mp4file
├── mp4lib
├── Mp4ToAvi.h
├── obj
├── test.cpp
└── type.h

​在 liwen01 公众号中回复 音视频 获取工程代码，本章代码工程名为：MP4格式合成.zip

​