AVFrame * frame = (AVFrame *)args;

This line of code declares a pointer variable named "frame" that points to an AVFrame structure. The value assigned to the pointer is the memory address stored in the variable "args", which is assumed to be a pointer to an AVFrame structure.

This code is typically used in a multi-threaded environment where the AVFrame structure needs to be passed as an argument to a function or method executed in a separate thread. By passing a pointer to the AVFrame structure, the function or method can access and modify the structure's data without needing to make a copy of it.

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AVFrame * frame = (AVFrame *)args;SS_Vdec_BufInfo *stVdecBuf = (SS_Vdec_BufInfo *)frame->opaque;

This code is casting a void pointer called "args" to an AVFrame pointer called "frame". It then casts the "opaque" field of the AVFrame to an SS_Vdec_BufInfo pointer called "stVdecBuf". The "opaque" field is a generic pointer that can be used to store custom data for the AVFrame. In this case, it is being used to store a structure of type SS_Vdec_BufInfo.

给AVFrame图像帧加上时间显示

要给AVFrame图像帧加上时间显示，可以使用FFmpeg中提供的AVFilter来实现。具体步骤如下：

1. 创建AVFilterGraph对象和AVFilterContext对象。

AVFilterGraph *filter_graph = avfilter_graph_alloc();
AVFilterContext *buffer_filter_ctx = NULL;
AVFilterContext *timeoverlay_filter_ctx = NULL;

2. 创建buffer和timeoverlay AVFilter对象，并初始化其参数。

AVFilter *buffer_filter = avfilter_get_by_name("buffer");
AVFilter *timeoverlay_filter = avfilter_get_by_name("timeoverlay");

char args[512];
snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
    frame->width, frame->height, frame->format,
    time_base.num, time_base.den,
    frame->sample_aspect_ratio.num, frame->sample_aspect_ratio.den);

avfilter_graph_create_filter(&buffer_filter_ctx, buffer_filter, "in", args, NULL, filter_graph);

avfilter_graph_create_filter(&timeoverlay_filter_ctx, timeoverlay_filter, "overlay", NULL, NULL, filter_graph);
av_opt_set_int(timeoverlay_filter_ctx, "fontsize", 20, AV_OPT_SEARCH_CHILDREN);
av_opt_set("timeformat", "%Y-%m-%d %H:%M:%S", 0, timeoverlay_filter_ctx);

其中，args参数表示输入视频帧的属性，timeformat参数表示时间格式，这里使用“年-月-日 时:分:秒”。

3. 将AVFilter对象连接起来。

avfilter_link(buffer_filter_ctx, 0, timeoverlay_filter_ctx, 0);
avfilter_link(timeoverlay_filter_ctx, 0, sink_filter_ctx, 0);

avfilter_graph_config(filter_graph, NULL);

4. 将AVFrame送入filter_graph进行处理。

av_buffersrc_add_frame_flags(buffer_filter_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF);

AVFrame *filtered_frame = av_frame_alloc();
int ret = av_buffersink_get_frame(sink_filter_ctx, filtered_frame);

5. 释放资源。

avfilter_graph_free(&filter_graph);
av_frame_free(&filtered_frame);

通过以上步骤，可以将AVFrame图像帧加上时间显示，生成一个新的AVFrame图像帧。