本文介绍了一个基于FFmpeg的简单AVDevice示例，该示例能够进行屏幕录制及声音采集，视频采用mpeg4编码，音频采用aac编码，并最终生成mp4文件。通过使用fifo缓冲区来协调视频和音频数据的同步。
原文地址：https://blog.youkuaiyun.com/dancing_night/article/details/46698853
1、概述
最简单的基于FFmpeg的AVDevice例子（屏幕录制+声音采集），视频采用mpeg4编码，音频采用aac编码，并生成mp4文件，其中fifo是此程序的关键，此程序只是一个demo很多优化都没做，仅供参考。
2、代码
- <pre name="code" class="cpp">/**
- *最简单的基于FFmpeg的AVDevice例子（屏幕录制+声音采集），视频采用mpeg4编码，音频采用aac编码，并生成mp4文件
- *缪国凯 MK
- *821486004@qq.com
- */
- #include "stdafx.h"
- #ifdef __cplusplus
- extern "C"
- {
- #endif
- #include "libavcodec/avcodec.h"
- #include "libavformat/avformat.h"
- #include "libswscale/swscale.h"
- #include "libavdevice/avdevice.h"
- #include "libavutil/audio_fifo.h"
- #pragma comment(lib, "avcodec.lib")
- #pragma comment(lib, "avformat.lib")
- #pragma comment(lib, "avutil.lib")
- #pragma comment(lib, "avdevice.lib")
- #pragma comment(lib, "avfilter.lib")
- //#pragma comment(lib, "avfilter.lib")
- //#pragma comment(lib, "postproc.lib")
- //#pragma comment(lib, "swresample.lib")
- #pragma comment(lib, "swscale.lib")
- #ifdef __cplusplus
- };
- #endif
- AVFormatContext *pFormatCtx_Video = NULL, *pFormatCtx_Audio = NULL, *pFormatCtx_Out = NULL;
- AVCodecContext *pCodecCtx_Video;
- AVCodec *pCodec_Video;
- AVFifoBuffer *fifo_video = NULL;
- AVAudioFifo *fifo_audio = NULL;
- int VideoIndex, AudioIndex;
- CRITICAL_SECTION AudioSection, VideoSection;
- SwsContext *img_convert_ctx;
- int frame_size = 0;
- uint8_t *picture_buf = NULL, *frame_buf = NULL;
- bool bCap = true;
- DWORD WINAPI ScreenCapThreadProc( LPVOID lpParam );
- DWORD WINAPI AudioCapThreadProc( LPVOID lpParam );
- int OpenVideoCapture()
- {
- AVInputFormat *ifmt=av_find_input_format("gdigrab");
- //这里可以加参数打开，例如可以指定采集帧率
- AVDictionary *options = NULL;
- av_dict_set(&options, "framerate", "15", NULL);
- //av_dict_set(&options,"offset_x","20",0);
- //The distance from the top edge of the screen or desktop
- //av_dict_set(&options,"offset_y","40",0);
- //Video frame size. The default is to capture the full screen
- //av_dict_set(&options,"video_size","320x240",0);
- if(avformat_open_input(&pFormatCtx_Video, "desktop", ifmt, &options)!=0)
- {
- printf("Couldn't open input stream.（无法打开视频输入流）\n");
- return -1;
- }
- if(avformat_find_stream_info(pFormatCtx_Video,NULL)<0)
- {
- printf("Couldn't find stream information.（无法获取视频流信息）\n");
- return -1;
- }
- if (pFormatCtx_Video->streams[0]->codec->codec_type != AVMEDIA_TYPE_VIDEO)
- {
- printf("Couldn't find video stream information.（无法获取视频流信息）\n");
- return -1;
- }
- pCodecCtx_Video = pFormatCtx_Video->streams[0]->codec;
- pCodec_Video = avcodec_find_decoder(pCodecCtx_Video->codec_id);
- if(pCodec_Video == NULL)
- {
- printf("Codec not found.（没有找到解码器）\n");
- return -1;
- }
- if(avcodec_open2(pCodecCtx_Video, pCodec_Video, NULL) < 0)
- {
- printf("Could not open codec.（无法打开解码器）\n");
- return -1;
- }
- img_convert_ctx = sws_getContext(pCodecCtx_Video->width, pCodecCtx_Video->height, pCodecCtx_Video->pix_fmt,
- pCodecCtx_Video->width, pCodecCtx_Video->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
- frame_size = avpicture_get_size(pCodecCtx_Video->pix_fmt, pCodecCtx_Video->width, pCodecCtx_Video->height);
- //申请30帧缓存
- fifo_video = av_fifo_alloc(30 * avpicture_get_size(AV_PIX_FMT_YUV420P, pCodecCtx_Video->width, pCodecCtx_Video->height));
- return 0;
- }
- static char *dup_wchar_to_utf8(wchar_t *w)
- {
- char *s = NULL;
- int l = WideCharToMultiByte(CP_UTF8, 0, w, -1, 0, 0, 0, 0);
- s = (char *) av_malloc(l);
- if (s)
- WideCharToMultiByte(CP_UTF8, 0, w, -1, s, l, 0, 0);
- return s;
- }
- int OpenAudioCapture()
- {
- //查找输入方式
- AVInputFormat *pAudioInputFmt = av_find_input_format("dshow");
- //以Direct Show的方式打开设备，并将 输入方式 关联到格式上下文
- char * psDevName = dup_wchar_to_utf8(L"audio=麦克风 (Realtek High Definition Au");
- if (avformat_open_input(&pFormatCtx_Audio, psDevName, pAudioInputFmt,NULL) < 0)
- {
- printf("Couldn't open input stream.（无法打开音频输入流）\n");
- return -1;
- }
- if(avformat_find_stream_info(pFormatCtx_Audio,NULL)<0)
- return -1;
- if(pFormatCtx_Audio->streams[0]->codec->codec_type != AVMEDIA_TYPE_AUDIO)
- {
- printf("Couldn't find video stream information.（无法获取音频流信息）\n");
- return -1;
- }
- AVCodec *tmpCodec = avcodec_find_decoder(pFormatCtx_Audio->streams[0]->codec->codec_id);
- if(0 > avcodec_open2(pFormatCtx_Audio->streams[0]->codec, tmpCodec, NULL))
- {
- printf("can not find or open audio decoder!\n");
- }
- return 0;
- }
- int OpenOutPut()
- {
- AVStream *pVideoStream = NULL, *pAudioStream = NULL;
- const char *outFileName = "test.mp4";
- avformat_alloc_output_context2(&pFormatCtx_Out, NULL, NULL, outFileName);
- if (pFormatCtx_Video->streams[0]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
- {
- AVCodecContext *videoCodecCtx;
- VideoIndex = 0;
- pVideoStream = avformat_new_stream(pFormatCtx_Out, NULL);
- if (!pVideoStream)
- {
- printf("can not new stream for output!\n");
- return -1;
- }
- //set codec context param
- pVideoStream->codec->codec = avcodec_find_encoder(AV_CODEC_ID_MPEG4);
- pVideoStream->codec->height = pFormatCtx_Video->streams[0]->codec->height;
- pVideoStream->codec->width = pFormatCtx_Video->streams[0]->codec->width;
- pVideoStream->codec->time_base = pFormatCtx_Video->streams[0]->codec->time_base;
- pVideoStream->codec->sample_aspect_ratio = pFormatCtx_Video->streams[0]->codec->sample_aspect_ratio;
- // take first format from list of supported formats
- pVideoStream->codec->pix_fmt = pFormatCtx_Out->streams[VideoIndex]->codec->codec->pix_fmts[0];
- //open encoder
- if (!pVideoStream->codec->codec)
- {
- printf("can not find the encoder!\n");
- return -1;
- }
- if (pFormatCtx_Out->oformat->flags & AVFMT_GLOBALHEADER)
- pVideoStream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
- if ((avcodec_open2(pVideoStream->codec, pVideoStream->codec->codec, NULL)) < 0)
- {
- printf("can not open the encoder\n");
- return -1;
- }
- }
- if(pFormatCtx_Audio->streams[0]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
- {
- AVCodecContext *pOutputCodecCtx;
- AudioIndex = 1;
- pAudioStream = avformat_new_stream(pFormatCtx_Out, NULL);
- pAudioStream->codec->codec = avcodec_find_encoder(pFormatCtx_Out->oformat->audio_codec);
- pOutputCodecCtx = pAudioStream->codec;
- pOutputCodecCtx->sample_rate = pFormatCtx_Audio->streams[0]->codec->sample_rate;
- pOutputCodecCtx->channel_layout = pFormatCtx_Out->streams[0]->codec->channel_layout;
- pOutputCodecCtx->channels = av_get_channel_layout_nb_channels(pAudioStream->codec->channel_layout);
- if(pOutputCodecCtx->channel_layout == 0)
- {
- pOutputCodecCtx->channel_layout = AV_CH_LAYOUT_STEREO;
- pOutputCodecCtx->channels = av_get_channel_layout_nb_channels(pOutputCodecCtx->channel_layout);
- }
- pOutputCodecCtx->sample_fmt = pAudioStream->codec->codec->sample_fmts[0];
- AVRational time_base={1, pAudioStream->codec->sample_rate};
- pAudioStream->time_base = time_base;
- //audioCodecCtx->time_base = time_base;
- pOutputCodecCtx->codec_tag = 0;
- if (pFormatCtx_Out->oformat->flags & AVFMT_GLOBALHEADER)
- pOutputCodecCtx->flags |= CODEC_FLAG_GLOBAL_HEADER;
- if (avcodec_open2(pOutputCodecCtx, pOutputCodecCtx->codec, 0) < 0)
- {
- //编码器打开失败，退出程序
- return -1;
- }
- }
- if (!(pFormatCtx_Out->oformat->flags & AVFMT_NOFILE))
- {
- if(avio_open(&pFormatCtx_Out->pb, outFileName, AVIO_FLAG_WRITE) < 0)
- {
- printf("can not open output file handle!\n");
- return -1;
- }
- }
- if(avformat_write_header(pFormatCtx_Out, NULL) < 0)
- {
- printf("can not write the header of the output file!\n");
- return -1;
- }
- return 0;
- }
- int _tmain(int argc, _TCHAR* argv[])
- {
- av_register_all();
- avdevice_register_all();
- if (OpenVideoCapture() < 0)
- {
- return -1;
- }
- if (OpenAudioCapture() < 0)
- {
- return -1;
- }
- if (OpenOutPut() < 0)
- {
- return -1;
- }
- InitializeCriticalSection(&VideoSection);
- InitializeCriticalSection(&AudioSection);
- AVFrame *picture = av_frame_alloc();
- int size = avpicture_get_size(pFormatCtx_Out->streams[VideoIndex]->codec->pix_fmt,
- pFormatCtx_Out->streams[VideoIndex]->codec->width, pFormatCtx_Out->streams[VideoIndex]->codec->height);
- picture_buf = new uint8_t[size];
- avpicture_fill((AVPicture *)picture, picture_buf,
- pFormatCtx_Out->streams[VideoIndex]->codec->pix_fmt,
- pFormatCtx_Out->streams[VideoIndex]->codec->width,
- pFormatCtx_Out->streams[VideoIndex]->codec->height);
- //star cap screen thread
- CreateThread( NULL, 0, ScreenCapThreadProc, 0, 0, NULL);
- //star cap audio thread
- CreateThread( NULL, 0, AudioCapThreadProc, 0, 0, NULL);
- int64_t cur_pts_v=0,cur_pts_a=0;
- int VideoFrameIndex = 0, AudioFrameIndex = 0;
- while(1)
- {
- if (_kbhit() != 0 && bCap)
- {
- bCap = false;
- Sleep(2000);//简单的用sleep等待采集线程关闭
- }
- if (fifo_audio && fifo_video)
- {
- int sizeAudio = av_audio_fifo_size(fifo_audio);
- int sizeVideo = av_fifo_size(fifo_video);
- //缓存数据写完就结束循环
- if (av_audio_fifo_size(fifo_audio) <= pFormatCtx_Out->streams[AudioIndex]->codec->frame_size &&
- av_fifo_size(fifo_video) <= frame_size && !bCap)
- {
- break;
- }
- }
- if(av_compare_ts(cur_pts_v, pFormatCtx_Out->streams[VideoIndex]->time_base,
- cur_pts_a,pFormatCtx_Out->streams[AudioIndex]->time_base) <= 0)
- {
- //read data from fifo
- if (av_fifo_size(fifo_video) < frame_size && !bCap)
- {
- cur_pts_v = 0x7fffffffffffffff;
- }
- if(av_fifo_size(fifo_video) >= size)
- {
- EnterCriticalSection(&VideoSection);
- av_fifo_generic_read(fifo_video, picture_buf, size, NULL);
- LeaveCriticalSection(&VideoSection);
- avpicture_fill((AVPicture *)picture, picture_buf,
- pFormatCtx_Out->streams[VideoIndex]->codec->pix_fmt,
- pFormatCtx_Out->streams[VideoIndex]->codec->width,
- pFormatCtx_Out->streams[VideoIndex]->codec->height);
- //pts = n * (（1 / timbase）/ fps);
- picture->pts = VideoFrameIndex * ((pFormatCtx_Video->streams[0]->time_base.den / pFormatCtx_Video->streams[0]->time_base.num) / 15);
- int got_picture = 0;
- AVPacket pkt;
- av_init_packet(&pkt);
- pkt.data = NULL;
- pkt.size = 0;
- int ret = avcodec_encode_video2(pFormatCtx_Out->streams[VideoIndex]->codec, &pkt, picture, &got_picture);
- if(ret < 0)
- {
- //编码错误,不理会此帧
- continue;
- }
- if (got_picture==1)
- {
- pkt.stream_index = VideoIndex;
- pkt.pts = av_rescale_q_rnd(pkt.pts, pFormatCtx_Video->streams[0]->time_base,
- pFormatCtx_Out->streams[VideoIndex]->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
- pkt.dts = av_rescale_q_rnd(pkt.dts, pFormatCtx_Video->streams[0]->time_base,
- pFormatCtx_Out->streams[VideoIndex]->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
- pkt.duration = ((pFormatCtx_Out->streams[0]->time_base.den / pFormatCtx_Out->streams[0]->time_base.num) / 15);
- cur_pts_v = pkt.pts;
- ret = av_interleaved_write_frame(pFormatCtx_Out, &pkt);
- //delete[] pkt.data;
- av_free_packet(&pkt);
- }
- VideoFrameIndex++;
- }
- }
- else
- {
- if (NULL == fifo_audio)
- {
- continue;//还未初始化fifo
- }
- if (av_audio_fifo_size(fifo_audio) < pFormatCtx_Out->streams[AudioIndex]->codec->frame_size && !bCap)
- {
- cur_pts_a = 0x7fffffffffffffff;
- }
- if(av_audio_fifo_size(fifo_audio) >=
- (pFormatCtx_Out->streams[AudioIndex]->codec->frame_size > 0 ? pFormatCtx_Out->streams[AudioIndex]->codec->frame_size : 1024))
- {
- AVFrame *frame;
- frame = av_frame_alloc();
- frame->nb_samples = pFormatCtx_Out->streams[AudioIndex]->codec->frame_size>0 ? pFormatCtx_Out->streams[AudioIndex]->codec->frame_size: 1024;
- frame->channel_layout = pFormatCtx_Out->streams[AudioIndex]->codec->channel_layout;
- frame->format = pFormatCtx_Out->streams[AudioIndex]->codec->sample_fmt;
- frame->sample_rate = pFormatCtx_Out->streams[AudioIndex]->codec->sample_rate;
- av_frame_get_buffer(frame, 0);
- EnterCriticalSection(&AudioSection);
- av_audio_fifo_read(fifo_audio, (void **)frame->data,
- (pFormatCtx_Out->streams[AudioIndex]->codec->frame_size > 0 ? pFormatCtx_Out->streams[AudioIndex]->codec->frame_size : 1024));
- LeaveCriticalSection(&AudioSection);
- if (pFormatCtx_Out->streams[0]->codec->sample_fmt != pFormatCtx_Audio->streams[AudioIndex]->codec->sample_fmt
- || pFormatCtx_Out->streams[0]->codec->channels != pFormatCtx_Audio->streams[AudioIndex]->codec->channels
- || pFormatCtx_Out->streams[0]->codec->sample_rate != pFormatCtx_Audio->streams[AudioIndex]->codec->sample_rate)
- {
- //如果输入和输出的音频格式不一样 需要重采样，这里是一样的就没做
- }
- AVPacket pkt_out;
- av_init_packet(&pkt_out);
- int got_picture = -1;
- pkt_out.data = NULL;
- pkt_out.size = 0;
- frame->pts = AudioFrameIndex * pFormatCtx_Out->streams[AudioIndex]->codec->frame_size;
- if (avcodec_encode_audio2(pFormatCtx_Out->streams[AudioIndex]->codec, &pkt_out, frame, &got_picture) < 0)
- {
- printf("can not decoder a frame");
- }
- av_frame_free(&frame);
- if (got_picture)
- {
- pkt_out.stream_index = AudioIndex;
- pkt_out.pts = AudioFrameIndex * pFormatCtx_Out->streams[AudioIndex]->codec->frame_size;
- pkt_out.dts = AudioFrameIndex * pFormatCtx_Out->streams[AudioIndex]->codec->frame_size;
- pkt_out.duration = pFormatCtx_Out->streams[AudioIndex]->codec->frame_size;
- cur_pts_a = pkt_out.pts;
- int ret = av_interleaved_write_frame(pFormatCtx_Out, &pkt_out);
- av_free_packet(&pkt_out);
- }
- AudioFrameIndex++;
- }
- }
- }
- delete[] picture_buf;
- av_fifo_free(fifo_video);
- av_audio_fifo_free(fifo_audio);
- av_write_trailer(pFormatCtx_Out);
- avio_close(pFormatCtx_Out->pb);
- avformat_free_context(pFormatCtx_Out);
- if (pFormatCtx_Video != NULL)
- {
- avformat_close_input(&pFormatCtx_Video);
- pFormatCtx_Video = NULL;
- }
- if (pFormatCtx_Audio != NULL)
- {
- avformat_close_input(&pFormatCtx_Audio);
- pFormatCtx_Audio = NULL;
- }
- return 0;
- }
- DWORD WINAPI ScreenCapThreadProc( LPVOID lpParam )
- {
- AVPacket packet;/* = (AVPacket *)av_malloc(sizeof(AVPacket))*/;
- int got_picture;
- AVFrame *pFrame;
- pFrame=avcodec_alloc_frame();
- AVFrame *picture = avcodec_alloc_frame();
- int size = avpicture_get_size(pFormatCtx_Out->streams[VideoIndex]->codec->pix_fmt,
- pFormatCtx_Out->streams[VideoIndex]->codec->width, pFormatCtx_Out->streams[VideoIndex]->codec->height);
- //picture_buf = new uint8_t[size];
- avpicture_fill((AVPicture *)picture, picture_buf,
- pFormatCtx_Out->streams[VideoIndex]->codec->pix_fmt,
- pFormatCtx_Out->streams[VideoIndex]->codec->width,
- pFormatCtx_Out->streams[VideoIndex]->codec->height);
- FILE *p = NULL;
- p = fopen("proc_test.yuv", "wb+");
- av_init_packet(&packet);
- int height = pFormatCtx_Out->streams[VideoIndex]->codec->height;
- int width = pFormatCtx_Out->streams[VideoIndex]->codec->width;
- int y_size=height*width;
- while(bCap)
- {
- packet.data = NULL;
- packet.size = 0;
- if (av_read_frame(pFormatCtx_Video, &packet) < 0)
- {
- continue;
- }
- if(packet.stream_index == 0)
- {
- if (avcodec_decode_video2(pCodecCtx_Video, pFrame, &got_picture, &packet) < 0)
- {
- printf("Decode Error.（解码错误）\n");
- continue;
- }
- if (got_picture)
- {
- sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0,
- pFormatCtx_Out->streams[VideoIndex]->codec->height, picture->data, picture->linesize);
- if (av_fifo_space(fifo_video) >= size)
- {
- EnterCriticalSection(&VideoSection);
- av_fifo_generic_write(fifo_video, picture->data[0], y_size, NULL);
- av_fifo_generic_write(fifo_video, picture->data[1], y_size/4, NULL);
- av_fifo_generic_write(fifo_video, picture->data[2], y_size/4, NULL);
- LeaveCriticalSection(&VideoSection);
- }
- }
- }
- av_free_packet(&packet);
- //Sleep(50);
- }
- av_frame_free(&pFrame);
- av_frame_free(&picture);
- //delete[] picture_buf;
- return 0;
- }
- DWORD WINAPI AudioCapThreadProc( LPVOID lpParam )
- {
- AVPacket pkt;
- AVFrame *frame;
- frame = av_frame_alloc();
- int gotframe;
- while(bCap)
- {
- pkt.data = NULL;
- pkt.size = 0;
- if(av_read_frame(pFormatCtx_Audio,&pkt) < 0)
- {
- continue;
- }
- if (avcodec_decode_audio4(pFormatCtx_Audio->streams[0]->codec, frame, &gotframe, &pkt) < 0)
- {
- av_frame_free(&frame);
- printf("can not decoder a frame");
- break;
- }
- av_free_packet(&pkt);
- if (!gotframe)
- {
- continue;//没有获取到数据，继续下一次
- }
- if (NULL == fifo_audio)
- {
- fifo_audio = av_audio_fifo_alloc(pFormatCtx_Audio->streams[0]->codec->sample_fmt,
- pFormatCtx_Audio->streams[0]->codec->channels, 30 * frame->nb_samples);
- }
- int buf_space = av_audio_fifo_space(fifo_audio);
- if (av_audio_fifo_space(fifo_audio) >= frame->nb_samples)
- {
- EnterCriticalSection(&AudioSection);
- av_audio_fifo_write(fifo_audio, (void **)frame->data, frame->nb_samples);
- LeaveCriticalSection(&AudioSection);
- }
- }
- av_frame_free(&frame);
- return 0;
- }
注：上面的代码已经过修改，请重新下载工程(或者用代码覆盖以前的版本)。//8-25-15
3、工程地址
http://download.youkuaiyun.com/detail/dancing_night/9044441
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