食品企业网站建设,网页制作协议,网站建设课程ppt,兰州网页制作公司网站在有一些嵌入式平台中#xff0c;H264数据流一般来自芯片内部的硬编码器#xff0c; AAC音频数据则是通过采集PCM进行软编码#xff0c;但是如何对它实时进行封装多媒体文件 #xff0c;参考ffmpeg example#xff0c;花了一些时间终于实现了该功能。
流程图如下#xf…在有一些嵌入式平台中H264数据流一般来自芯片内部的硬编码器 AAC音频数据则是通过采集PCM进行软编码但是如何对它实时进行封装多媒体文件 参考ffmpeg example花了一些时间终于实现了该功能。
流程图如下 本文只展示DEMO
一.视频输入流 创建 //内存数据回调部分
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
{char * input_filename (char *)opaque;static FILE *fl NULL;if(fl NULL){fl fopen(input_filename,r);}static unsigned long long read_len0;static unsigned long long fps_count0;int len0;int i 0;if(!feof(fl))len fread(buf,1,buf_size,fl);else return AVERROR_EOF;read_len len;printf(%s len:%d read_len:%d\n,__FUNCTION__, len ,read_len);for(i0;i4091;i){if(buf[i0] 0 buf[i1] 0 buf[i2] 0 buf[i3] 1){// int data buf[i4] 31;printf(0 0 0 1 %x %d\n,buf[i4],fps_count);fps_count;}}return len;
}static AVFormatContext * getInputVideoCtx(const char *fileName) {uint8_t *avio_ctx_buffer NULL;AVIOContext *avio_ctx NULL;//缓存buffersizesize_t buffer_size, avio_ctx_buffer_size 4096;AVFormatContext * video_fmt_ctx NULL;int ret 0;if (!(video_fmt_ctx avformat_alloc_context())) {ret AVERROR(ENOMEM);return NULL;}//创建数据缓存Bufferavio_ctx_buffer av_malloc(avio_ctx_buffer_size);if (!avio_ctx_buffer) {ret AVERROR(ENOMEM);return NULL;}avio_ctx avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size,0, fileName, read_packet, NULL, NULL);if (!avio_ctx) {ret AVERROR(ENOMEM);return NULL;}video_fmt_ctx-pb avio_ctx;//打开数据ret avformat_open_input(video_fmt_ctx, NULL, NULL, NULL);if (ret 0) {fprintf(stderr, Could not open input\n);return NULL;}//获取数据格式ret avformat_find_stream_info(video_fmt_ctx, NULL);if (ret 0) {fprintf(stderr, Could not find stream information\n);return NULL;}//打印数据参数av_dump_format(video_fmt_ctx, 0, fileName, 0);return video_fmt_ctx;
}
1.注册内存回调read_packetavformat_find_stream_info会从回调里读取大概2S的h264视频数据并解析。首先会读取SPS PPS然后是帧数据读取2S的数据结束如果给的数据不对解析不正常会一直读所以要确保刚开始给的数据是否正常。av_dump_format打印出数据格式
执行如下 二.创建多媒体输出添加视频输出流音频输出流 avformat_alloc_output_context2(oc, NULL, NULL, filename);...//fmt oc-oformat;if (fmt-video_codec ! AV_CODEC_ID_NONE) {add_video_stream(video_st, oc, video_fmt_ctx, fmt-video_codec);...}/* Add the audio and video streams using the default format codecs* and initialize the codecs. */if (fmt-audio_codec ! AV_CODEC_ID_NONE) {add_audio_stream(audio_st, oc, audio_codec, fmt-audio_codec);...}1.添加视频流和初始化 /* media file output */
static void add_video_stream(OutputStream *ost, AVFormatContext *oc,const AVFormatContext *video_fmt_ctx,enum AVCodecID codec_id)
{...//创建一个输出流ost-st avformat_new_stream(oc, NULL);...ost-st-id oc-nb_streams-1;c avcodec_alloc_context3(NULL);...//流的time_base初始化for (i 0; i video_fmt_ctx-nb_streams; i) {if(video_fmt_ctx-streams[i]-codecpar-codec_type AVMEDIA_TYPE_VIDEO){avcodec_parameters_to_context(c, video_fmt_ctx-streams[i]-codecpar);video_fmt_ctx-streams[i]-time_base.den video_fmt_ctx-streams[i]-avg_frame_rate.num;}}//初始化av_packetost-tmp_pkt av_packet_alloc();...ost-enc c;
}
2.添加音频流 初始化编解码器
/* Add an output stream. */
static void add_audio_stream(OutputStream *ost, AVFormatContext *oc,const AVCodec **codec,enum AVCodecID codec_id)
{*codec avcodec_find_encoder(codec_id);...//初始化有音频packetost-tmp_pkt av_packet_alloc();...//初始化流ost-st avformat_new_stream(oc, NULL);...switch ((*codec)-type) {case AVMEDIA_TYPE_AUDIO:c-sample_fmt (*codec)-sample_fmts ?(*codec)-sample_fmts[0] : AV_SAMPLE_FMT_FLTP;c-bit_rate 64000;c-sample_rate 44100;//采样率if ((*codec)-supported_samplerates) {c-sample_rate (*codec)-supported_samplerates[0];for (i 0; (*codec)-supported_samplerates[i]; i) {if ((*codec)-supported_samplerates[i] 44100)c-sample_rate 44100;}}av_channel_layout_copy(c-ch_layout, (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO);//输出audio流的time_base初始化ost-st-time_base (AVRational){ 1, c-sample_rate };break;default:break;}}
3.初始化输出流音频和视频codecpar
static int open_video(AVFormatContext *oc, const AVCodec *codec,AVFormatContext *vedio_fmt_ctx,OutputStream *ost)
{...ret avcodec_parameters_copy(ost-st-codecpar, vedio_fmt_ctx-streams[index]-codecpar);...
}
static void open_audio(AVFormatContext *oc, const AVCodec *codec,OutputStream *ost, AVDictionary *opt_arg)
{.../* copy the stream parameters to the muxer */ret avcodec_parameters_from_context(ost-st-codecpar, c);if (ret 0) {fprintf(stderr, Could not copy the stream parameters\n);exit(1);}...
}
三.开始写入多媒体文件
1.比较写入音视频的时间戳判断下一次要写入音频还是视频
while (encode_video) {/* select the stream to encode */if (encode_video ( !encode_audio || av_compare_ts(video_st.next_pts, video_fmt_ctx-streams[v_ctx_index]-time_base,audio_st.next_pts, audio_st.enc-time_base) 0)) {encode_video !write_video_frame(oc, video_fmt_ctx, video_st, video_st.tmp_pkt);} else {encode_audio !write_audio_frame(oc, audio_st);}}
av_compare_ts 通过对比当前Audio Video帧的写入量判断当前要写入Audio 还是Video
例如 Video 写入10帧* 1/25 Audio 写入 10240*1/44100 则写入audio
2.写入一帧Video
static int write_video_frame(AVFormatContext *oc,AVFormatContext *vic, OutputStream *ost, AVPacket *pkt)
{int ret,i; static int frame_index 0;AVStream *in_stream, *out_stream;int stream_index;stream_index av_find_best_stream(vic, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);//读一帧H264ret av_read_frame(vic, pkt);if(ret AVERROR_EOF)return ret AVERROR_EOF ? 1 : 0;av_packet_rescale_ts(pkt, ost-enc-time_base, ost-st-time_base);if(pkt-ptsAV_NOPTS_VALUE){in_stream vic-streams[stream_index];out_stream ost-st;//Write PTSAVRational time_base1in_stream-time_base;int64_t calc_duration(double)AV_TIME_BASE/av_q2d(in_stream-avg_frame_rate);//计算出包的解码时间pkt-pts(double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE);pkt-dtspkt-pts;pkt-duration(double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE);//帧的计数累加frame_index;//pkt的pts dts是输入流的时间戳 要转换成 输出流的时间戳av_packet_rescale_ts(pkt, in_stream-time_base, out_stream-time_base);pkt-pos -1;pkt-stream_indexost-st-index;}//写入到多媒体文件ret av_interleaved_write_frame(oc, pkt);if (ret 0) {fprintf(stderr, Error while writing output packet: %s\n, av_err2str(ret));exit(1);}return ret AVERROR_EOF ? 1 : 0;
}
av_read_frame会回调read_packet 获取一帧H264数据再通过计算时间戳 pts dts 再转换对应的输出流时间戳才能写入多媒体文件
3.写入一帧Audio
//获取一帧原始的Audio PCM 数据
/* Prepare a 16 bit dummy audio frame of frame_size samples and* nb_channels channels. */
static AVFrame *get_audio_frame(OutputStream *ost)
{...c ost-enc;for (j 0; j frame-nb_samples; j) {v (int)(sin(ost-t) * 10000);for (i 0; i ost-enc-ch_layout.nb_channels; i)*q v;ost-t ost-tincr;ost-tincr ost-tincr2;}...frame-pts ost-next_pts;ost-next_pts frame-nb_samples;count;return frame;
}
static int write_audio_frame(AVFormatContext *oc, OutputStream *ost)
{....//获取一帧原始的Audio PCM 数据 frame get_audio_frame(ost);if (frame) {dst_nb_samples av_rescale_rnd(swr_get_delay(ost-swr_ctx, c-sample_rate) frame-nb_samples,c-sample_rate, c-sample_rate, AV_ROUND_UP);ret av_frame_make_writable(ost-frame);/* convert to destination format */ret swr_convert(ost-swr_ctx,ost-frame-data, dst_nb_samples,(const uint8_t **)frame-data, frame-nb_samples);frame ost-frame;frame-pts av_rescale_q(ost-samples_count, (AVRational){1, c-sample_rate}, c-time_base);ost-samples_count dst_nb_samples;}//先送去编码再写入多媒体文件return write_frame(oc, c, ost, frame, ost-tmp_pkt);
}static int write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c,OutputStream *ost, AVFrame *frame, AVPacket *pkt)
{...ret avcodec_send_frame(c, frame);...while (ret 0) {ret avcodec_receive_packet(c, pkt);.../* rescale output packet timestamp values from codec to stream timebase */av_packet_rescale_ts(pkt, c-time_base, st-time_base);printf(%d %d\n, c-time_base.den, st-time_base.den);pkt-stream_index st-index;ret av_interleaved_write_frame(fmt_ctx, pkt);...count;}return ret AVERROR_EOF ? 1 : 0;
}
四.写入多媒体尾部结束
av_write_trailer(oc);
一些BUG
控制写入时间可以在写入循环里添加break。写入数据过长会出现音视频不同步的情况建议写入时间不超过30分钟
DEMO
有需要源码可以后台私信我
