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FFmpeg【SDK02】关于AVIO的一些使用

news 来源：原创 2024/5/9 4:04:41

读取本地文件（网络流）信息

#include <iostream>
#include <stdio.h>extern "C"
{
#include <libavformat\avformat.h>
#include <libavutil\avutil.h>
#include <libavutil\log.h>
#include <libavformat\avio.h>
#include <libavutil\file.h>
#include <libavcodec\avcodec.h>
#include <libavutil\error.h>
}#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avutil.lib")// 1. 读取本地文件 和 网络流（rtsp）
void readLoadHostFile()
{// av_register_all();		// ffmpeg4.0 版本后被抛弃avformat_network_init();	// 使用网络流时需要添加AVFormatContext* pAVFmtCtx = NULL;AVInputFormat*   pAVInputFmt = NULL;pAVFmtCtx = avformat_alloc_context();		// 申请AVFormatContext内存// 打开文件流或网络流// No1. 本地文件流		input_5s.mp4// No2. VLC推rtsp流		rtsp://:8554/rtsp1	rtsp://localhost:8554/rtsp1if (avformat_open_input(&pAVFmtCtx, "input_5s.mp4", pAVInputFmt, NULL)){av_log(pAVFmtCtx, AV_LOG_WARNING, "open file/networkStream faild!\n");avformat_free_context(pAVFmtCtx);		// 释放AVFormatContext内存avformat_network_deinit();return;}av_log(pAVFmtCtx, AV_LOG_INFO, "open file/networkStream success!\n");// 查找流信息if (avformat_find_stream_info(pAVFmtCtx, NULL) < 0){av_log(pAVFmtCtx, AV_LOG_WARNING, "find stream info faild!\n");	avformat_close_input(&pAVFmtCtx); avformat_free_context(pAVFmtCtx);		avformat_network_deinit();return;}av_log(pAVFmtCtx, AV_LOG_INFO, "find stream info success!\n");// 打印流的个数av_log(pAVFmtCtx, AV_LOG_INFO, "nbstream: %d\n", pAVFmtCtx->nb_streams);avformat_close_input(&pAVFmtCtx);			// 先关闭再释放avformat_free_context(pAVFmtCtx);		avformat_network_deinit();
}

使AVIO获取视频文件信息

// 2. 自定义AVIO
// 读回调（返回读取的字节数）
int read_callback(void *opaque, uint8_t *buf, int buf_size)
{FILE* fp = (FILE*)opaque;size_t size = fread(buf, sizeof(uint8_t), buf_size, fp);printf("Read Bytes: %d\n", size);return (int)size;
}// 返回seek到的位置
int64_t seek_callback(void *opaque, int64_t offset, int whence)
{FILE *fp = (FILE*)opaque;if (whence == AVSEEK_SIZE) {return -1;}fseek(fp, offset, whence);return ftell(fp);
}void selfDefAVIO()
{AVFormatContext* pAVFmtCtx = NULL;AVInputFormat*   pAVInputFmt = NULL;pAVFmtCtx = avformat_alloc_context();FILE* fp = fopen("input_5s.mp4", "rb");int nBuffSize = 1024;// unsigned char* buffer = (unsigned char*)malloc(nBuffSize);	// 此处使用malloc会中断uint8_t* buffer = (uint8_t*)av_malloc(nBuffSize);AVIOContext* pAVIOCtx = avio_alloc_context(buffer, nBuffSize, 0,fp,				// 文件指针read_callback,	// 读回调0,				// 写回调seek_callback);	// 定位回调if (NULL == pAVIOCtx){av_log(NULL, AV_LOG_WARNING, "AVIOContext alloc faild!\n");av_free(pAVIOCtx);return;}pAVFmtCtx->pb = pAVIOCtx;					// 将AVIOContext绑定到AVFormatContextpAVFmtCtx->flags = AVFMT_FLAG_CUSTOM_IO;	// 告诉ffmpeg自己创建AVIOContext（不需要它再创建）// 打开流if (avformat_open_input(&pAVFmtCtx, "", pAVInputFmt, NULL) < 0){av_log(pAVFmtCtx, AV_LOG_WARNING, "open file stream faild!\n");av_free(pAVIOCtx);avformat_free_context(pAVFmtCtx);		// 释放AVFormatContext内存return;}av_log(pAVFmtCtx, AV_LOG_INFO, "open file stream success!\n");// 进一步读取流信息（为 pFormatCtx->streams 填充上正确的信息）if (avformat_find_stream_info(pAVFmtCtx, NULL) < 0){av_log(pAVFmtCtx, AV_LOG_WARNING, "find stream info faild!\n");avformat_close_input(&pAVFmtCtx);av_free(pAVIOCtx);avformat_free_context(pAVFmtCtx);	return;}av_log(pAVFmtCtx, AV_LOG_INFO, "find stream info success!\n");// 打印流的个数av_log(pAVFmtCtx, AV_LOG_INFO, " nbstream: %d\n", pAVFmtCtx->nb_streams);avformat_close_input(&pAVFmtCtx);av_free(pAVIOCtx);avformat_free_context(pAVFmtCtx);
}

使用AVIO和自定义数据类型获取视频文件信息

// 3. 自定义数据来源(可以是文件，内存，网络流)
struct buffer_data	// 自定义缓冲区
{uint8_t *ptr;size_t size;	// size left in the buffer
};//读取数据（回调函数）
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
{struct buffer_data *bd = (struct buffer_data*)opaque;buf_size = FFMIN(buf_size, bd->size);if (!buf_size)			// 0return AVERROR_EOF;printf("ptr:%p size:%d\n", bd->ptr, bd->size);/// 灵活应用[内存buf]：读取的是内存，例如：加密播放器,这里解密memcpy(buf, bd->ptr, buf_size);bd->ptr += buf_size;bd->size -= buf_size;return buf_size;
}void selfDefDataSrc()
{struct buffer_data bd = { 0 };// 1. 将文件映射到内存上int nRet = av_file_map("input_5s.mp4", &bd.ptr, &bd.size, 0, NULL);if (nRet < 0){av_log(NULL, AV_LOG_ERROR, "map file to memory faild!\n");return;}av_log(NULL, AV_LOG_INFO, "map file to memory success!\n");// 2. 创建AVFormatContext对象AVFormatContext* pAVFmtCtx = NULL;pAVFmtCtx = avformat_alloc_context();if (NULL == pAVFmtCtx){av_log(NULL, AV_LOG_ERROR, "create AVFormatContext faild!\n");av_file_unmap(bd.ptr, bd.size);	// 内存映射文件：解绑定return;}av_log(NULL, AV_LOG_INFO, "create AVFormatContext success!\n");// 3. 为avio buffer分配内存uint8_t* avio_ctx_buffer = NULL;size_t avio_ctx_buffer_size = 4096;				// 回调每次读取 4096 bytesavio_ctx_buffer = (uint8_t*)av_malloc(avio_ctx_buffer_size);if (!avio_ctx_buffer) {av_log(NULL, AV_LOG_ERROR, "av_malloc avio_ctx_buffer faild!\n");avformat_free_context(pAVFmtCtx);av_file_unmap(bd.ptr, bd.size);return;}av_log(NULL, AV_LOG_INFO, "av_malloc avio_ctx_buffer success!\n");AVIOContext* avio_ctx = avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size,0,&bd,					// 从bd里面读数据&read_packet,			NULL,NULL);if (!avio_ctx) {av_log(NULL, AV_LOG_ERROR, "avio_alloc_context AVIOContext faild!\n");av_freep(avio_ctx_buffer);avformat_free_context(pAVFmtCtx);av_file_unmap(bd.ptr, bd.size);return;}pAVFmtCtx->pb = avio_ctx;av_log(NULL, AV_LOG_INFO, "avio_alloc_context AVIOContext success!\n");nRet = avformat_open_input(&pAVFmtCtx, NULL, NULL, NULL);if (nRet){av_log(NULL, AV_LOG_ERROR, "avformat_open_input faild!\n");avio_context_free(&avio_ctx);av_freep(avio_ctx_buffer);avformat_free_context(pAVFmtCtx);av_file_unmap(bd.ptr, bd.size);return;}av_log(NULL, AV_LOG_INFO, "avformat_open_input success!\n");// 查找流信息nRet = avformat_find_stream_info(pAVFmtCtx, NULL);if (nRet < 0) {av_log(NULL, AV_LOG_ERROR, "avformat_find_stream_info faild!\n");avformat_close_input(&pAVFmtCtx);avio_context_free(&avio_ctx);av_freep(avio_ctx_buffer);avformat_free_context(pAVFmtCtx);av_file_unmap(bd.ptr, bd.size);return;}av_log(NULL, AV_LOG_INFO, "avformat_find_stream_info success!\n");printf(" 》》》nb_streams=%d\n", pAVFmtCtx->nb_streams);av_dump_format(pAVFmtCtx, 0, "input_5s.mp4", 0);// 关闭释放资源avformat_close_input(&pAVFmtCtx);if (avio_ctx)av_freep(&avio_ctx->buffer);avio_context_free(&avio_ctx);av_file_unmap(bd.ptr, bd.size);
}