商务网站建设策划书,域名到期查询,wordpress+微官网主题,替老外做网站前言 在ffmpeg命令行中#xff0c;ffmpeg -i test -pix_fmt rgb24 test.rgb#xff0c;会自动打开ff_vf_scale滤镜#xff0c;本章主要追踪这个流程。 通过gdb可以发现其基本调用栈如下#xff1a; 可以看到#xff0c;query_formats#xff08;#xff09;中创建的v…前言 在ffmpeg命令行中ffmpeg -i test -pix_fmt rgb24 test.rgb会自动打开ff_vf_scale滤镜本章主要追踪这个流程。 通过gdb可以发现其基本调用栈如下 可以看到query_formats中创建的vf_scale滤镜 这是ffmpeg滤镜框架中的操作当avfilter进行query format的时候如果发现前后两个filter的pixformat不一致的时候就会在中间插入一个vf_scale的滤镜。这就是标题的答案。 但是本章内容主要讨论ffmpeg工具里面是如何调用avfilter的也就是从哪里开始创建哪里开始销毁以及中间是如何传递信息的。特别是当命令行中没有vf_scale的操作时ffmpeg工具是否会打开filter? 为了分析上述问题我们先用一定使用到vf_scale的命令 ffmpeg -i test -pix_fmt rgb24 test.rgb先找到调用avfilter的两个函数 ret av_buffersrc_add_frame_flags(ifilter-filter, frame, buffersrc_flags); ret av_buffersink_get_frame_flags(filter, filtered_frame,AV_BUFFERSINK_FLAG_NO_REQUEST);ffmpeg.h中定义了有关filter的三个结构体 typedef struct InputFilter {AVFilterContext *filter;struct InputStream *ist;struct FilterGraph *graph;uint8_t *name;enum AVMediaType type; // AVMEDIA_TYPE_SUBTITLE for sub2videoAVFifoBuffer *frame_queue;// parameters configured for this inputint format;int width, height;AVRational sample_aspect_ratio;int sample_rate;int channels;uint64_t channel_layout;AVBufferRef *hw_frames_ctx;int32_t *displaymatrix;int eof; } InputFilter;typedef struct OutputFilter {AVFilterContext *filter;struct OutputStream *ost;struct FilterGraph *graph;uint8_t *name;/* temporary storage until stream maps are processed */AVFilterInOut *out_tmp;enum AVMediaType type;/* desired output stream properties */int width, height;AVRational frame_rate;int format;int sample_rate;uint64_t channel_layout;// those are only set if no format is specified and the encoder gives us multiple options// They point directly to the relevant lists of the encoder.const int *formats;const uint64_t *channel_layouts;const int *sample_rates; } OutputFilter;typedef struct FilterGraph {int index;const char *graph_desc;AVFilterGraph *graph;int reconfiguration;// true when the filtergraph contains only meta filters// that do not modify the frame dataint is_meta;InputFilter **inputs;int nb_inputs;OutputFilter **outputs;int nb_outputs; } FilterGraph;我们通过上述线索寻找buffersrc和buffersink是在哪里创建的。 首先看buffersink通过 decode_video(InputStream *ist, AVPacket *pkt, int *got_output, int64_t *duration_pts, int eof,int *decode_failed)decode(ist-dec_ctx, decoded_frame, got_output, pkt)send_frame_to_filters(ist, decoded_frame)ifilter_send_frame(ist-filters[i], decoded_frame, i ist-nb_filters - 1)configure_filtergraph(fg)//reinitav_buffersrc_add_frame_flags(ifilter-filter, frame, buffersrc_flags)通过上面结构可知其中的configure_filtergraph(fg)//reinit是关键在这里初始化整个avfilter。 在这里我们回顾一下avfilter的关键调用流程 char args[512];int ret 0;const AVFilter *buffersrc avfilter_get_by_name(buffer);const AVFilter *buffersink avfilter_get_by_name(buffersink);AVFilterInOut *outputs avfilter_inout_alloc();AVFilterInOut *inputs avfilter_inout_alloc();AVRational time_base fmt_ctx-streams[video_stream_index]-time_base;enum AVPixelFormat pix_fmts[] { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };filter_graph avfilter_graph_alloc();if (!outputs || !inputs || !filter_graph) {ret AVERROR(ENOMEM);goto end;}/* buffer video source: the decoded frames from the decoder will be inserted here. */snprintf(args, sizeof(args),video_size%dx%d:pix_fmt%d:time_base%d/%d:pixel_aspect%d/%d,dec_ctx-width, dec_ctx-height, dec_ctx-pix_fmt,time_base.num, time_base.den,dec_ctx-sample_aspect_ratio.num, dec_ctx-sample_aspect_ratio.den);ret avfilter_graph_create_filter(buffersrc_ctx, buffersrc, in,args, NULL, filter_graph);if (ret 0) {av_log(NULL, AV_LOG_ERROR, Cannot create buffer source\n);goto end;}/* buffer video sink: to terminate the filter chain. */ret avfilter_graph_create_filter(buffersink_ctx, buffersink, out,NULL, NULL, filter_graph);if (ret 0) {av_log(NULL, AV_LOG_ERROR, Cannot create buffer sink\n);goto end;}ret av_opt_set_int_list(buffersink_ctx, pix_fmts, pix_fmts,AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);if (ret 0) {av_log(NULL, AV_LOG_ERROR, Cannot set output pixel format\n);goto end;}outputs-name av_strdup(in);outputs-filter_ctx buffersrc_ctx;outputs-pad_idx 0;outputs-next NULL;/** The buffer sink input must be connected to the output pad of* the last filter described by filters_descr; since the last* filter output label is not specified, it is set to out by* default.*/inputs-name av_strdup(out);inputs-filter_ctx buffersink_ctx;inputs-pad_idx 0;inputs-next NULL;if ((ret avfilter_graph_parse_ptr(filter_graph, filters_descr,inputs, outputs, NULL)) 0)goto end;if ((ret avfilter_graph_config(filter_graph, NULL)) 0)goto end;...回到ifilter_send_frame()中来 static int ifilter_send_frame(InputFilter *ifilter, AVFrame *frame, int keep_reference) {FilterGraph *fg ifilter-graph;AVFrameSideData *sd;int need_reinit, ret;int buffersrc_flags AV_BUFFERSRC_FLAG_PUSH;if (keep_reference)buffersrc_flags | AV_BUFFERSRC_FLAG_KEEP_REF;/* determine if the parameters for this input changed *///如果输入和frame中的format不一致就会引起reinitneed_reinit ifilter-format ! frame-format;switch (ifilter-ist-st-codecpar-codec_type) {case AVMEDIA_TYPE_VIDEO:need_reinit | ifilter-width ! frame-width ||ifilter-height ! frame-height;break;}if (!ifilter-ist-reinit_filters fg-graph)need_reinit 0;if (!!ifilter-hw_frames_ctx ! !!frame-hw_frames_ctx ||(ifilter-hw_frames_ctx ifilter-hw_frames_ctx-data ! frame-hw_frames_ctx-data))need_reinit 1;if (sd av_frame_get_side_data(frame, AV_FRAME_DATA_DISPLAYMATRIX)) {if (!ifilter-displaymatrix || memcmp(sd-data, ifilter-displaymatrix, sizeof(int32_t) * 9))need_reinit 1;} else if (ifilter-displaymatrix)need_reinit 1;if (need_reinit) {//ifilter从这里获取到w,h,pix等信息ret ifilter_parameters_from_frame(ifilter, frame);if (ret 0)return ret;}/* (re)init the graph if possible, otherwise buffer the frame and return */if (need_reinit || !fg-graph) {ret configure_filtergraph(fg);if (ret 0) {av_log(NULL, AV_LOG_ERROR, Error reinitializing filters!\n);return ret;}}ret av_buffersrc_add_frame_flags(ifilter-filter, frame, buffersrc_flags);if (ret 0) {if (ret ! AVERROR_EOF)av_log(NULL, AV_LOG_ERROR, Error while filtering: %s\n, av_err2str(ret));return ret;}return 0; }继续回到onfigure_filtergraph(fg) 删除了与本题无关的代码 int configure_filtergraph(FilterGraph *fg) {AVFilterInOut *inputs, *outputs, *cur;//这里判断是否是simple因为我们的命令行中没有avfilter故此为trueint ret, i, simple filtergraph_is_simple(fg);//int filtergraph_is_simple(FilterGraph *fg)//{return !fg-graph_desc;}//这里其实就是NULLconst char *graph_desc simple ? fg-outputs[0]-ost-avfilter :fg-graph_desc;cleanup_filtergraph(fg);//创建图if (!(fg-graph avfilter_graph_alloc()))return AVERROR(ENOMEM);if (simple) {//获取到outputstreamOutputStream *ost fg-outputs[0]-ost;char args[512];const AVDictionaryEntry *e NULL;} else {fg-graph-nb_threads filter_complex_nbthreads;}//这里在我们这里可以跳过因为graph_desc为nullif ((ret avfilter_graph_parse2(fg-graph, graph_desc, inputs, outputs)) 0)goto fail;//这里是配置buffersrc的地方for (cur inputs, i 0; cur; cur cur-next, i){if ((ret configure_input_filter(fg, fg-inputs[i], cur)) 0) {avfilter_inout_free(inputs);avfilter_inout_free(outputs);goto fail;}}avfilter_inout_free(inputs);//这里是配置buffersink的地方for (cur outputs, i 0; cur; cur cur-next, i)configure_output_filter(fg, fg-outputs[i], cur);avfilter_inout_free(outputs);if (!auto_conversion_filters)avfilter_graph_set_auto_convert(fg-graph, AVFILTER_AUTO_CONVERT_NONE);//avfilter的标准调用if ((ret avfilter_graph_config(fg-graph, NULL)) 0)goto fail;fg-is_meta graph_is_meta(fg-graph);return 0; }接下来继续看如何配置input_filter的 static int configure_input_video_filter(FilterGraph *fg, InputFilter *ifilter,AVFilterInOut *in) {AVFilterContext *last_filter;//创建bufferconst AVFilter *buffer_filt avfilter_get_by_name(buffer);const AVPixFmtDescriptor *desc;InputStream *ist ifilter-ist;InputFile *f input_files[ist-file_index];AVRational tb ist-framerate.num ? av_inv_q(ist-framerate) :ist-st-time_base;AVRational fr ist-framerate;AVRational sar;AVBPrint args;char name[255];int ret, pad_idx 0;int64_t tsoffset 0;AVBufferSrcParameters *par av_buffersrc_parameters_alloc();if (!par)return AVERROR(ENOMEM);memset(par, 0, sizeof(*par));par-format AV_PIX_FMT_NONE;if (!fr.num)fr av_guess_frame_rate(input_files[ist-file_index]-ctx, ist-st, NULL);sar ifilter-sample_aspect_ratio;if(!sar.den)sar (AVRational){0,1};av_bprint_init(args, 0, AV_BPRINT_SIZE_AUTOMATIC);//这里是配置buffersrc的地方av_bprintf(args,video_size%dx%d:pix_fmt%d:time_base%d/%d:pixel_aspect%d/%d,ifilter-width, ifilter-height, ifilter-format,tb.num, tb.den, sar.num, sar.den);if (fr.num fr.den)av_bprintf(args, :frame_rate%d/%d, fr.num, fr.den);snprintf(name, sizeof(name), graph %d input from stream %d:%d, fg-index,ist-file_index, ist-st-index);//创建filterctxif ((ret avfilter_graph_create_filter(ifilter-filter, buffer_filt, name,args.str, NULL, fg-graph)) 0)goto fail;par-hw_frames_ctx ifilter-hw_frames_ctx;ret av_buffersrc_parameters_set(ifilter-filter, par);if (ret 0)goto fail;av_freep(par);last_filter ifilter-filter;desc av_pix_fmt_desc_get(ifilter-format);av_assert0(desc);snprintf(name, sizeof(name), trim_in_%d_%d,ist-file_index, ist-st-index);if (copy_ts) {tsoffset f-start_time AV_NOPTS_VALUE ? 0 : f-start_time;if (!start_at_zero f-ctx-start_time ! AV_NOPTS_VALUE)tsoffset f-ctx-start_time;}//插入trimret insert_trim(((f-start_time AV_NOPTS_VALUE) || !f-accurate_seek) ?AV_NOPTS_VALUE : tsoffset, f-recording_time,last_filter, pad_idx, name);if (ret 0)return ret;//链接if ((ret avfilter_link(last_filter, 0, in-filter_ctx, in-pad_idx)) 0)return ret;return 0; fail:av_freep(par);return ret; }下面是configure_output_filter static int configure_output_video_filter(FilterGraph *fg, OutputFilter *ofilter, AVFilterInOut *out) {OutputStream *ost ofilter-ost;OutputFile *of output_files[ost-file_index];AVFilterContext *last_filter out-filter_ctx;AVBPrint bprint;int pad_idx out-pad_idx;int ret;const char *pix_fmts;char name[255];snprintf(name, sizeof(name), out_%d_%d, ost-file_index, ost-index);//创建buffersinkret avfilter_graph_create_filter(ofilter-filter,avfilter_get_by_name(buffersink),name, NULL, NULL, fg-graph);if (ret 0)return ret;//这个scale完全就是尺寸的resizeif ((ofilter-width || ofilter-height) ofilter-ost-autoscale) {char args[255];AVFilterContext *filter;const AVDictionaryEntry *e NULL;//这里只有size的scale并没有颜色空间的转换snprintf(args, sizeof(args), %d:%d,ofilter-width, ofilter-height);while ((e av_dict_get(ost-sws_dict, , e,AV_DICT_IGNORE_SUFFIX))) {av_strlcatf(args, sizeof(args), :%s%s, e-key, e-value);}snprintf(name, sizeof(name), scaler_out_%d_%d,ost-file_index, ost-index);if ((ret avfilter_graph_create_filter(filter, avfilter_get_by_name(scale),name, args, NULL, fg-graph)) 0)return ret;if ((ret avfilter_link(last_filter, pad_idx, filter, 0)) 0)return ret;last_filter filter;pad_idx 0;}av_bprint_init(bprint, 0, AV_BPRINT_SIZE_UNLIMITED);//如果设置了输出的pix_fmt 那么就会在这里增加一个format的的avfilter//这个format其实什么也不做就是指定一个中间format用来在协商的时候//确定是否增加中间的csc swscaleif ((pix_fmts choose_pix_fmts(ofilter, bprint))) {AVFilterContext *filter;ret avfilter_graph_create_filter(filter,avfilter_get_by_name(format),format, pix_fmts, NULL, fg-graph);av_bprint_finalize(bprint, NULL);if (ret 0)return ret;if ((ret avfilter_link(last_filter, pad_idx, filter, 0)) 0)return ret;last_filter filter;pad_idx 0;}if (ost-frame_rate.num 0) {AVFilterContext *fps;char args[255];snprintf(args, sizeof(args), fps%d/%d, ost-frame_rate.num,ost-frame_rate.den);snprintf(name, sizeof(name), fps_out_%d_%d,ost-file_index, ost-index);ret avfilter_graph_create_filter(fps, avfilter_get_by_name(fps),name, args, NULL, fg-graph);if (ret 0)return ret;ret avfilter_link(last_filter, pad_idx, fps, 0);if (ret 0)return ret;last_filter fps;pad_idx 0;}snprintf(name, sizeof(name), trim_out_%d_%d,ost-file_index, ost-index);ret insert_trim(of-start_time, of-recording_time,last_filter, pad_idx, name);if (ret 0)return ret;if ((ret avfilter_link(last_filter, pad_idx, ofilter-filter, 0)) 0)return ret;return 0; }所以对于ffmpeg中的graph来说依次为 ff_vsrc_buffer-ff_vf_null-(scale resize)-ff_vf_format(命令行中由format的参数)-(fps )-(trim)-ff_buffersink。 中间括号内的是几个选择的avfilter。 协商format的时候最后会协商一个ff_vsrc_buffer的pix fomat. 最后用一个rawenc去将frame编码为pkt…