这篇和ffmpeg进行截图相似，不过省略掉编码的过程，从网络上或者文件读取的数据为编码后的数据，间接进行写文件即可，本文以写MP4文件为例进行解说。
1.创立线程执行开启录像
player->record_duration = duration*60; player->record_piece_id = 0; player->record_time = 0.0f; memset(player->record_path, 0, sizeof(MAX_PATH_LENGTH)); strcpy(player->record_path, file); player->bRecording = true; //开启录像线程 player->record_thread = CreateThread(NULL, 0, av_record_thread_proc, player, 0, NULL);2.初始化拉去流进行录像
void* av_record_thread_proc(void *thread_param){ PLAYER* play = (PLAYER*)thread_param; if (!play) { return NULL; } AVFormatContext *i_fmt_ctx = NULL; AVStream *i_video_stream = NULL; AVFormatContext *o_fmt_ctx = NULL; AVStream *o_video_stream = NULL; av_register_all(); avcodec_register_all(); avformat_network_init(); /* should set to NULL so that avformat_open_input() allocate a new one */ i_fmt_ctx = NULL; if (avformat_open_input(&i_fmt_ctx, play->file_url, NULL, NULL) != 0) { //fprintf(stderr, "could not open input file\n"); return NULL; } int nRet = avformat_find_stream_info(i_fmt_ctx, NULL); if (nRet<0) { ///fprintf(stderr, "could not find stream info\n"); return NULL; } //bool bSupportVideo = true; //bool bSupportAudio = true; int nVideoIndex = -1; int nAudioIndex = -1; int nPathLen = strlen(play->record_path); char *csFileName = new char[nPathLen]; memset(csFileName, 0, nPathLen); strncpy(csFileName, play->record_path, nPathLen-4); char sSliceupName[MAX_PATH_LENGTH] = {0,}; if (play->record_duration > 0) { sprintf(sSliceupName, "%s_%d.mp4", csFileName, play->record_piece_id); } else { sprintf(sSliceupName, "%s.mp4", csFileName); } //创立MP4文件 if (CreateMediaFile(&o_fmt_ctx, i_fmt_ctx, sSliceupName) == 0) { return 0; } /* * since all input files are supposed to be identical (framerate, dimension, color format, ...) * we can safely set output codec values from first input file */ int nOutStreamId = 0; for (int i = 0; i < i_fmt_ctx->nb_streams; i++) { AVStream *in_stream = i_fmt_ctx->streams[i]; if (in_stream->codec->codec_type == AVMEDIA_TYPE_AUDIO) { AVCodecID codecId = in_stream->codec->codec_id; //音频格式过滤（just support aac,mp3） if ((codecId != AV_CODEC_ID_MP3 && codecId != AV_CODEC_ID_AAC )/*|| in_stream->codec->extradata_size==0*/) ///< preferred ID for decoding MPEG audio layer 1, 2 or 3 { //bSupportAudio = false; continue; } nAudioIndex = nOutStreamId; } if (i_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) { AVCodecID codecId = in_stream->codec->codec_id; //视频频格局过滤（just support h264,265） if ((codecId != AV_CODEC_ID_H264 && codecId != AV_CODEC_ID_H265) /*|| in_stream->codec->extradata_size == 0*/) ///< preferred ID for decoding MPEG audio layer 1, 2 or 3 { //bSupportVideo = false; continue; } nVideoIndex = nOutStreamId; } nOutStreamId++; } int start_pts = -1; int start_dts = -1; int64_t audio_start_pts = -1; int64_t audio_start_dts = -1; int64_t video_start_pts = -1; int64_t video_start_dts = -1; bool audio_re_record = false; bool video_re_record = false; int64_t pts, dts; //int total_frame = 3000;//写3000帧文件 //while (total_frame--) while (play->bRecording) { AVPacket i_pkt; av_init_packet(&i_pkt); i_pkt.size = 0; i_pkt.data = NULL; if (av_read_frame(i_fmt_ctx, &i_pkt) <0) break; //ret = av_interleaved_write_frame(pOFormat, tmppkt); AVStream *in_stream = i_fmt_ctx->streams[i_pkt.stream_index]; AVStream *out_stream = NULL; if (in_stream->codec->codec_type == AVMEDIA_TYPE_VIDEO && nVideoIndex > -1 ) { int nTimeBase = in_stream->time_base.den; if (nTimeBase>0) play->record_time = (float)(i_pkt.dts - start_dts) / nTimeBase; //TRACE("Video Timestamp: %f time_base = %d %lld %lld duration = %d \n", m_fRecordTime, in_stream->time_base.den, i_pkt.pts, i_pkt.dts, i_pkt.duration); if (start_pts < 0) start_pts = i_pkt.pts; if (start_dts < 0) start_dts = i_pkt.dts; //录像工夫，单位: S float fRecTime = 0.0f; if (nTimeBase>0) fRecTime = (float)(i_pkt.dts - start_dts) / nTimeBase; //判断是否达到切片的要求 if (play->record_duration > 0 && fRecTime > play->record_duration && i_pkt.flags == AV_PKT_FLAG_KEY) { play->record_piece_id++; //敞开曾经实现切片的文件 CloseMediaFile(o_fmt_ctx); memset(sSliceupName, 0x00, MAX_PATH_LENGTH); sprintf(sSliceupName, "%s_%d.mp4", csFileName, play->record_piece_id); //创立MP4文件 if (CreateMediaFile(&o_fmt_ctx, i_fmt_ctx, sSliceupName) == 0) { return 0; } start_pts = i_pkt.pts; start_dts = i_pkt.dts; audio_re_record = true; video_re_record = true; } } else if (in_stream->codec->codec_type == AVMEDIA_TYPE_AUDIO && nAudioIndex > -1 && nVideoIndex == -1) { int nTimeBase = in_stream->time_base.den; if (nTimeBase>0) play->record_time = (float)(i_pkt.dts) / nTimeBase; //TRACE("Audio Timestamp: %f time_base = %d %lld %lld duration = %d \n", play->record_time, in_stream->time_base.den, i_pkt.pts, i_pkt.dts, i_pkt.duration); if (start_pts < 0) start_pts = i_pkt.pts; if (start_dts < 0) start_dts = i_pkt.dts; //录像工夫，单位: S float fRecTime = 0.0f; if (nTimeBase>0) fRecTime = (float)(i_pkt.dts - start_dts) / nTimeBase; //判断是否达到切片的要求 if (play->record_duration > 0 && fRecTime > play->record_duration) { play->record_piece_id++; //敞开曾经实现切片的文件 CloseMediaFile(o_fmt_ctx); memset(sSliceupName, 0x00, 512); sprintf(sSliceupName, "%s_%d.mp4", csFileName, play->record_piece_id); //创立MP4文件 if (CreateMediaFile(&o_fmt_ctx, i_fmt_ctx, sSliceupName) == 0) { return 0; } start_pts = i_pkt.pts; start_dts = i_pkt.dts; audio_re_record = true; video_re_record = true; } } if (in_stream->codec->codec_type == AVMEDIA_TYPE_VIDEO)//不反对的视频 过滤 { if( nVideoIndex == -1) continue; out_stream = o_fmt_ctx->streams[nVideoIndex]; if (video_start_pts < 0) video_start_pts = i_pkt.pts; if (video_start_dts < 0) video_start_dts = i_pkt.dts; if (video_re_record) { video_start_pts = i_pkt.pts; video_start_dts = i_pkt.dts; video_re_record = false; } i_pkt.pts = i_pkt.pts - video_start_pts; i_pkt.dts = i_pkt.dts - video_start_dts; } if (in_stream->codec->codec_type == AVMEDIA_TYPE_AUDIO )//不反对的音频 过滤 { if (nAudioIndex == -1) continue; out_stream = o_fmt_ctx->streams[nAudioIndex]; if (audio_start_pts < 0) audio_start_pts = i_pkt.pts; if (audio_start_dts < 0) audio_start_dts = i_pkt.dts; if (audio_re_record) { audio_start_pts = i_pkt.pts; audio_start_dts = i_pkt.dts; audio_re_record = false; } i_pkt.pts = i_pkt.pts - audio_start_pts; i_pkt.dts = i_pkt.dts - audio_start_dts; } if (!out_stream) continue; i_pkt.pts = (i_pkt.pts > 0) ? i_pkt.pts : 0; i_pkt.dts = (i_pkt.dts > 0) ? i_pkt.dts : 0; i_pkt.duration = (i_pkt.duration > 0) ? i_pkt.duration : 0; i_pkt.pts = av_rescale_q_rnd(i_pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF); i_pkt.dts = av_rescale_q_rnd(i_pkt.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF); i_pkt.duration = av_rescale_q(i_pkt.duration, in_stream->time_base, out_stream->time_base); i_pkt.pos = -1; int ret = av_interleaved_write_frame(o_fmt_ctx, &i_pkt); if (ret < 0) continue; //break; } avformat_close_input(&i_fmt_ctx); av_write_trailer(o_fmt_ctx); avcodec_close(o_fmt_ctx->streams[0]->codec); av_freep(&o_fmt_ctx->streams[0]->codec); av_freep(&o_fmt_ctx->streams[0]); avio_close(o_fmt_ctx->pb); av_free(o_fmt_ctx); av_bitstream_filter_close(aacBsf); if (csFileName) delete[] csFileName; return NULL;}纵观以上录像代码，通过另外开拓线程进行录像，线程执行过程分为以下几个局部：
1.拉流读取流数据模块
对于这块不做过多赘述，大家有趣味能够参考系列文章的前几篇文章；
2.录像切片
因为mp4文件过长可能导致播放不了的问题，所以咱们反对对录制mp4文件进行切片录像，录像参考工夫戳默认以视频为准，如果没有视频则以音频为准，判断条件以设置的一段MP4长度为准：
if (play->record_duration > 0 && fRecTime > play->record_duration)当达到能够切片的条件时，创立文件进行切片，也就是关掉上一次的录像，从新开启下一个录像，创立和敞开录像如下:
int CreateMediaFile(AVFormatContext ** o_fmt_ctx, AVFormatContext *i_fmt_ctx, char *csFileName){ int RET = avformat_alloc_output_context2(o_fmt_ctx, NULL, NULL, csFileName); /* * since all input files are supposed to be identical (framerate, dimension, color format, ...) * we can safely set output codec values from first input file */ for (int i = 0; i < i_fmt_ctx->nb_streams; i++) { AVStream *in_stream = i_fmt_ctx->streams[i]; if (in_stream->codec->codec_type == AVMEDIA_TYPE_AUDIO) { AVCodecID codecId = in_stream->codec->codec_id; //音频格式过滤（just support aac,mp3） if ((codecId != AV_CODEC_ID_MP3 && codecId != AV_CODEC_ID_AAC) /*|| in_stream->codec->extradata_size == 0*/) ///< preferred ID for decoding MPEG audio layer 1, 2 or 3 { //bSupportAudio = false; continue; } } if (i_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) { AVCodecID codecId = in_stream->codec->codec_id; //视频频格局过滤（just support h264,265） if ((codecId != AV_CODEC_ID_H264 && codecId != AV_CODEC_ID_H265) /*|| in_stream->codec->extradata_size == 0*/) ///< preferred ID for decoding MPEG audio layer 1, 2 or 3 { //bSupportVideo = false; continue; } } //// 获取AVC构造，包涵SPS和PPS [Dingshuai 2017/07/12] //for (int j = 0;j<i_fmt_ctx->streams[i]->codec->extradata_size;j++) //{ // TRACE("%x ", i_fmt_ctx->streams[i]->codec->extradata[j]); //} AVStream *out_stream = avformat_new_stream(*o_fmt_ctx, in_stream->codec->codec); if (!out_stream) { continue; //return 0; } int ret = 0; ret = avcodec_copy_context(out_stream->codec, in_stream->codec); if (ret < 0) { fprintf(stderr, "Failed to copy context from input to output stream codec context\n"); return 0; } out_stream->codec->codec_tag = 0; if ((*o_fmt_ctx)->oformat->flags & AVFMT_GLOBALHEADER) out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER; } avio_open(&((*o_fmt_ctx)->pb), csFileName, AVIO_FLAG_WRITE); av_dump_format((*o_fmt_ctx), 0, csFileName, 1); if (avformat_write_header((*o_fmt_ctx), NULL) < 0) { return 0; } return 1;}void CloseMediaFile(AVFormatContext* o_fmt_ctx){ av_write_trailer(o_fmt_ctx); avcodec_close(o_fmt_ctx->streams[0]->codec); av_freep(&o_fmt_ctx->streams[0]->codec); av_freep(&o_fmt_ctx->streams[0]); avio_close(o_fmt_ctx->pb); av_free(o_fmt_ctx);}须要留神的是，编译ffmpeg的时候须要将写文件相干的模块编译进去，否则avformat_alloc_output_context2就会调用出错，还须要留神的就是写MP4反对的格局无限，上文代码中限定只反对aac和MP3格局，为了格局对立，这里应该将其余不反对的格局均转成aac或者MP3这种MP4录制、所反对的格局，大家能够参考上文截图的做法进行重编码