CODEWITHSUNDEEP
c++ffmpeglibav
zhang
zhang

Reputation: 11

Why is get_frame_defaults in libavutil an internal function?

See the following code from https://ffmpeg.org/doxygen/trunk/frame_8c_source.html#l00622:

static void get_frame_defaults(AVFrame *frame)
 {
     memset(frame, 0, sizeof(*frame));
  
     frame->pts                   =
     frame->pkt_dts               = AV_NOPTS_VALUE;
     frame->best_effort_timestamp = AV_NOPTS_VALUE;
     frame->duration            = 0;
 #if FF_API_PKT_DURATION
 FF_DISABLE_DEPRECATION_WARNINGS
     frame->pkt_duration        = 0;
 FF_ENABLE_DEPRECATION_WARNINGS
 #endif
 #if FF_API_FRAME_PKT
 FF_DISABLE_DEPRECATION_WARNINGS
     frame->pkt_pos             = -1;
     frame->pkt_size            = -1;
 FF_ENABLE_DEPRECATION_WARNINGS
 #endif
     frame->time_base           = (AVRational){ 0, 1 };
     frame->sample_aspect_ratio = (AVRational){ 0, 1 };
     frame->format              = -1; /* unknown */
     frame->extended_data       = frame->data;
     frame->color_primaries     = AVCOL_PRI_UNSPECIFIED;
     frame->color_trc           = AVCOL_TRC_UNSPECIFIED;
     frame->colorspace          = AVCOL_SPC_UNSPECIFIED;
     frame->color_range         = AVCOL_RANGE_UNSPECIFIED;
     frame->chroma_location     = AVCHROMA_LOC_UNSPECIFIED;
     frame->flags               = 0;
 }

You can see the get_frame_defaults function is marked as static, so not callable from other files. The only way to initialize AVFrame is via av_frame_alloc (plus av_frame_unref and av_frame_move_ref which operated on already initialized AVFrame), which allocates AVFrame in heap.

So there are no native method to initialize non-dynamically-allocated AVFrame object.

By comparison, libavcodec has a similar function av_init_packet which is public, and can be called for AVPacket object created elsewhere (e.g. on stack).

Upvotes: 0

Views: 49

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