FFmpeg读取Mac摄像头的问题

在这篇文章中讲解了怎么使用FFmpeg读取摄像头，包括Windows,Linux和Mac。通过测试，发如今Mac 下avformat_open_input老是出错，提示Input/Output error。后来发现对于Mac下经过avfoudmation读取摄像头，须要提早设置framerate和video_size。正确的代码以下：ios

#include <iostream> extern "C" { #include "libavcodec/avcodec.h" #include "libavformat/avformat.h" #include <libavdevice/avdevice.h> } using namespace std; int main(int argc, const char *argv[]) { int ret = 0; int videoStreamIndex = -1; AVFormatContext *s = NULL; AVDictionary *options = NULL; AVCodecParameters *par = NULL; AVCodec *codec; AVCodecContext *cctx; av_register_all(); avdevice_register_all(); AVInputFormat *ifmt = av_find_input_format("avfoundation"); av_dict_set(&options, "framerate", "30", 0); av_dict_set(&options, "video_size", "1280x720", 0); ret = avformat_open_input(&s, "0", ifmt, &options); if (ret < 0) { cout << av_err2str(ret) << endl; goto error; } ret = avformat_find_stream_info(s, NULL); if (ret < 0) { cout << av_err2str(ret) << endl; goto error; } for (uint i = 0; i < s->nb_streams; i++) { if (s->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) { videoStreamIndex = i; break; } } if (-1 == videoStreamIndex) { cout << "can't find video stream" << endl; goto error; } par = s->streams[videoStreamIndex]->codecpar; codec = avcodec_find_decoder(par->codec_id); cctx = avcodec_alloc_context3(codec); avcodec_parameters_to_context(cctx, par); ret = avcodec_open2(cctx, codec, NULL); if (ret < 0) { cout << av_err2str(ret) << endl; goto error; } error: if (s) { avformat_free_context(s); } if (cctx) { avcodec_free_context(&cctx); } if (options) { av_dict_free(&options); } return ret; } 

avdevice_capabilities_create查询设备的能力参数。ide