ffmpeg下讀取內存數據並解析

ffmpeg裏讀取文件是最基礎的操作，但是在很多行業裏面，讀取文件的操作實際作用的意義不大。還是讀取內存的操作作用大一些。其兩個之間主要的差距主要是在avformat_open_input的參書中的AVFormatContext->pb裏面只要這個pb用avio_alloc_context初始化過了，就可以從內存裏面的讀取了。但是因爲裏面的函數是回調函數，而且讀取的次數又很多，所以使用過程中還需要注意。

#include <stdio.h>
#include <iostream>

using namespace std;



extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"

};

typedef struct
{
	char *pbuff;
	int  ulSize;
	int  ulSizeOffset;
}stData;

int a =1;


class  AVParse
{
public:
	AVParse()
	{
		m_buff = (unsigned char *)malloc(50000);
		m_bufferSize = 50000;

		m_Data = (stData *)malloc(sizeof(stData));
		m_Data->pbuff = (char *)malloc(50000);
		m_Data->ulSize = 50000;
		m_Data->ulSizeOffset = 0;

		pavPacket = (AVPacket *)av_malloc(sizeof(AVPacket));

		videocount = 1;

		lVidepId = -1;
		lAudioId = -1;

		pOutputFile = NULL;
		bIsInit = false;
	}
	~AVParse()
	{
		if (NULL != m_buff)
		{
			free(m_buff);
			m_buff = NULL;
		}
		m_bufferSize = 0;
		if (NULL != m_Data->pbuff)
		{
			free(m_Data->pbuff);
			m_Data->pbuff = NULL;
		}
	}


	static int read_buffer(void *opaque, uint8_t *buf, int buf_size)
	{
		stData *pdata = (stData *)opaque;
		int cpysize = pdata->ulSizeOffset + buf_size < pdata->ulSize ? buf_size:(pdata->ulSize - pdata->ulSizeOffset);
		if (pdata->ulSizeOffset < pdata->ulSize)
		{
			memcpy(buf, pdata->pbuff + pdata->ulSizeOffset, cpysize);
			pdata->ulSizeOffset += cpysize;
			return cpysize;
		}
		else
		{
			return 0;
		}

	}

	static int wrete_buffer(void *opaque, uint8_t *buf, int buf_size)
	{
		return 0;
	}


	void InitOutputAudio()
	{
		avformat_alloc_output_context2(&m_pavformatOutput, NULL, "mp3", NULL);

	}

	void InitParse()
	{

		av_register_all();

		m_pavFormatContext = avformat_alloc_context();
		m_pavFormatContext->pb = avio_alloc_context(m_buff, m_bufferSize, 0, (void *)m_Data, read_buffer, NULL, NULL);

		int ulRet = avformat_open_input(&m_pavFormatContext , NULL ,NULL ,NULL);
		if(ulRet < 0)
		{
			cout << "avformat_open_input failed!!!" <<endl;
			//return ulRet;
		}
		//else
		//{
		//	return 0;
		//}

		for (int i =0 ;i< m_pavFormatContext->nb_streams; i++)
		{
			if (AVMEDIA_TYPE_VIDEO == m_pavFormatContext->streams[i]->codec->codec_type)
			{
				lVidepId = i;
				if (AV_CODEC_ID_H264 == m_pavFormatContext->streams[i]->codec->codec_id)
				{
					cout << "code id is AV_CODEC_ID_H264!!!"<< endl;
				}
			}
			if (AVMEDIA_TYPE_AUDIO == m_pavFormatContext->streams[i]->codec->codec_type)
			{
				lAudioId = i;
				if (AV_CODEC_ID_AAC == m_pavFormatContext->streams[i]->codec->codec_id)
				{
					cout << "code id is AV_CODEC_ID_AAC!!!" <<endl;
				}
			}

		}
		bIsInit = true;

	}
	void Muxing()
	{
		if (false ==bIsInit)
		{
			InitParse();
		}
		while(1)
		{
			if (av_read_frame(m_pavFormatContext, pavPacket) < 0)
			{
				break;
			}
			else
			{
				if (lVidepId == pavPacket->stream_index)
				{
					cout<< "Write " << videocount <<" Video Frame" << endl;
					FILE *pfile = fopen("F:\\test\\a.es", "ab+");
					fwrite(pavPacket->data,1, pavPacket->size, pfile);
					fclose(pfile);
					videocount ++;
				}
			}

		}

	}
	int InitOutputFile()
	{
		pOutputFile = fopen("F:\\test\\a.264","ab+");
	}

	AVFormatContext *m_pavformatOutput;	//輸出content
	AVFormatContext *m_pavFormatContext;  //輸入content
	unsigned char * m_buff;
	int   m_bufferSize;
	stData  *m_Data;
	int lVidepId;
	int lAudioId;
	FILE *pOutputFile;
	bool bIsInit;
	AVPacket *pavPacket;

	int  videocount;

};



int main(int argc, char* argv[])
{

	char szfilePath[100] = {"F:\\test\\ps.ps"};

	FILE *pFile = fopen(szfilePath, "rb+");

	AVParse *pavParse = new AVParse();

	while (1)
	{
		if (fread(pavParse->m_Data->pbuff, 1, pavParse->m_Data->ulSize, pFile) == pavParse->m_Data->ulSize)
		{
			pavParse->m_Data->ulSizeOffset = 0;
			pavParse->Muxing();
		}
		else
		{
			break;
		}

	}


	cout << "Parse File End!!!" << endl;
	system("pause");

	return 0;
}