用C编写的ffmpeg程序，无法在macOS Catalina 10.15.7中打开我的相机

Question

#include <stdio.h>
#include <stdlib.h>
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libavdevice/avdevice.h"

AVFormatContext* openCamera(void) {
    avdevice_register_all();
    AVFormatContext *ctx = avformat_alloc_context();
    AVInputFormat *ifmt = av_find_input_format("avfoundation");
    if (ifmt != NULL) {
        AVDictionary *opts = NULL;
        av_dict_set(&opts, "video_size", "1280x720", 0);
        av_dict_set(&opts, "framerate", "30", 0);
        av_dict_set(&opts, "pixel_format", "uyvy422", 0);
        
        int ret = avformat_open_input(&ctx, "0", ifmt, &opts);
        if (ret != 0) {
            printf("no");
            avformat_free_context(ctx);
            return NULL;
        }
    }
    return ctx;
}

int main(int argc, const char *argv[]) {
    openCamera();
}

我的代码在 Xcode 上运行。添加 plist 文件后，正在运行的程序相机打开大约半秒，然后关闭。和控制台输出

2022-02-22 00:39:19.372178+0800 ffmpeg-tool[5977:195724] [plugin] AddInstanceForFactory: No factory registered for id <CFUUID 0x10640cf60> F8BB1C28-BAE8-11D6-9C31-00039315CD46
2022-02-22 00:39:19.434783+0800 ffmpeg-tool[5977:195724]  HALC_ShellDriverPlugIn::Open: Can't get a pointer to the Open routine
2022-02-22 00:39:19.435262+0800 ffmpeg-tool[5977:195724]  HALC_ShellDriverPlugIn::Open: Can't get a pointer to the Open routine
2022-02-22 00:39:19.501780+0800 ffmpeg-tool[5977:195724] [plugin] AddInstanceForFactory: No factory registered for id <CFUUID 0x10640f860> 30010C1C-93BF-11D8-8B5B-000A95AF9C6A
2022-02-22 00:39:19.605797+0800 ffmpeg-tool[5977:195724] Metal API Validation Enabled
2022-02-22 00:39:21.701071+0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:917:CMIODeviceStopStream the System is exiting
2022-02-22 00:39:21.701268+0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:1332:CMIOStreamCopyBufferQueue the System is exiting
2022-02-22 00:39:21.701538+0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:333:CMIOObjectGetPropertyData the System is exiting
2022-02-22 00:39:21.701767+0800 ffmpeg-tool[5977:195724] [] CMIO_DALA_System.cpp:264:GetPropertyData error 1970171760 (unop) getting property selector (inot) scope (glob) element 0
2022-02-22 00:39:21.702472+0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:333:CMIOObjectGetPropertyData the System is exiting
2022-02-22 00:39:21.702662+0800 ffmpeg-tool[5977:195724] [] CMIO_DALA_System.cpp:264:GetPropertyData error 1970171760 (unop) getting property selector (inot) scope (glob) element 0
Program ended with exit code: 0

如何解决这个问题？

Answer 1

从您发布的代码来看，它所做的只是打开相机，然后返回到主程序，程序完成后它将退出并关闭连接。如果您想保持连接打开并从相机读取数据，您可能需要开始循环读取数据包。