avformat_open_input打开不存在的rtsp阻塞

网上很多文章，说到avformat_open_input阻塞，就设置一下

av_dict_set(&avdic, "stimeout ", "300000", 0);

 

ffmpeg源码rtsp.c有这样一段定义

 

{ "timeout", "set maximum timeout (in seconds) to wait for incoming connections (-1 is infinite, imply flag listen)", OFFSET(initial_timeout), AV_OPT_TYPE_INT, {.i64 = -1}, INT_MIN, INT_MAX, DEC },

 

{ "stimeout", "set timeout (in microseconds) of socket TCP I/O operations", OFFSET(stimeout), AV_OPT_TYPE_INT, {.i64 = 0}, INT_MIN, INT_MAX, DEC },

 

按照正常的说法，应该没问题，但就是不行，设置了还是会一直阻塞。

不管那么多，下面是正解，需要设置一下回调函数。部分关键代码

 

// C++ Header

 

 

 

#ifdef __cplusplus

 

extern "C" {

 

#endif

 

 

 

#include <libavformat/avformat.h>

 

#include <libavfilter/avfiltergraph.h>

 

#include <libavfilter/buffersink.h>

 

#include <libavfilter/buffersrc.h>

 

#include <libavutil/opt.h>

 

#include <libavutil/time.h>

 

#ifdef __cplusplus

 

}

 

#endif

 

 

 

...

 

class CFfmpegCapture

 

{

 

private:

 

static int decode_interrupt_cb(void *ctx);

 

//

 

int64_t m_nStartOpenTS = 0;

 

}

 

//c++ body

 

int CFfmpegCapture::decode_interrupt_cb(void *ctx)

 

{

 

CFfmpegCapture *pThis = (CFfmpegCapture*)ctx;

 

//microseconds 微秒

 

int64_t nDurTime = av_gettime() - pThis->m_nStartOpenTS;

 

if (nDurTime > 3000000 && pThis->m_nStartOpenTS>0)

 

{

 

return 1;

 

}

 

return 0;

 

}

 

 

 

 

 

int CFfmpegCapture::StartCapture(const char *pUrl)

 

{

 

AVDictionary* avdic = NULL;

 

av_dict_set(&avdic, "rtsp_transport", "tcp", 0);

 

//set timeout (in microseconds) of socket TCP I/O operations

 

av_dict_set(&avdic, "stimeout ", "300000", 0);

 

//set maximum timeout (in seconds) to wait for incoming connections (-1 is infinite, imply flag listen)

 

//av_dict_set(&avdic, "timeout ", "2", 0);

 

 

 

m_pFmtCtx->interrupt_callback.callback = decode_interrupt_cb;

 

m_pFmtCtx->interrupt_callback.opaque = (void*)this;

 

m_nStartOpenTS = av_gettime();

 

 

 

int ret = -1;

 

ret = avformat_open_input(&m_pFmtCtx, pUrl, nullptr, &avdic);

 

if (ret != 0) {

 

return -1;

 

}

 

//成功open以后，置0

 

m_nStartOpenTS = 0;

 

}

回调函数返回1表示不在阻塞（ If the callback returns 1, the  blocking operation will be aborted.）

ffmpeg-》avio.h文件描述：

 

/**

 

* Callback for checking whether to abort blocking functions.

 

* AVERROR_EXIT is returned in this case by the interrupted

 

* function. During blocking operations, callback is called with

 

* opaque as parameter. If the callback returns 1, the

 

* blocking operation will be aborted.

 

*

 

* No members can be added to this struct without a major bump, if

 

* new elements have been added after this struct in AVFormatContext

 

* or AVIOContext.

 

*/

 

typedef struct AVIOInterruptCB {

 

int (*callback)(void*);

 

void *opaque;

 

} AVIOInterruptCB;

 

 

//其实ffmpeg从4.0开始不用stimeout,用的listen_timeout等待网络超时，不然会一直超时下去。

 

 

AVDictionary* options = nullptr;

 

//实时播放使用udp，减小带宽并防止断线

 

av_dict_set(&options, "rtsp_transport", "udp", 0);

 

//等待3秒超时

 

av_dict_set(&options, "listen_timeout", "3", 0);