这篇和ffmpeg进行截图类似，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，直接进行写文件即可，本文以写MP4文件为例进行讲解。
1.创建线程执行开启录像
代码语言：txt复制 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
代码语言：txt复制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 filen");
return NULL;
}
int nRet = avformat_find_stream_info(i_fmt_ctx, NULL);
if (nRet<0)
{
///fprintf(stderr, "could not find stream infon");
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);
}
//创建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;
//视频频格式过滤（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;
//录像时间，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 ;
//关闭已经完成切片的文件
CloseMediaFile(o_fmt_ctx);
memset(sSliceupName, 0x00, MAX_PATH_LENGTH);
sprintf(sSliceupName, "%s_%d.mp4", csFileName, play->record_piece_id);
//创建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;
//录像时间，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 ;
//关闭已经完成切片的文件
CloseMediaFile(o_fmt_ctx);
memset(sSliceupName, 0x00, 512);
sprintf(sSliceupName, "%s_%d.mp4", csFileName, play->record_piece_id);
//创建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)//不支持的视频 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 )//不支持的音频 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，通过另外开辟线程进行录像，线程执行过程分为以下几个部分：
1.拉流读取流数据模块
关于这块不做过多赘述，大家有兴趣可以参考系列文章的前几篇文章；
2.录像切片
由于mp4文件过长可能导致播放不了的问题，所以我们支持对录制mp4文件进行切片录像，录像参考时间戳默认以视频为准，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：
代码语言：txt复制if (play->record_duration > 0 && fRecTime > play->record_duration)当达到可以切片的条件时，创建文件进行切片，也就是关掉上一次的录像，重新开启下一个录像，创建和关闭录像如下:
代码语言：txt复制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;
//视频频格式过滤（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结构，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 contextn");
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);
}需要注意的是，编译ffmpeg的时候需要将写文件相关的模块编译进去，否则avformat_alloc_output_context2就会调用出错，还需要注意的就是写MP4支持的格式有限，上文代码中限定只支持aac和MP3格式，为了格式统一，这里应该将其他不支持的格式均转成aac或者MP3这种MP4录制、所支持的格式，大家可以参考上文截图的做法进行重编码
