函数 av_packet_alloc 

pub unsafe extern "C" fn av_packet_alloc() -> *mut AVPacket

Allocate an AVPacket and set its fields to default values. The resulting struct must be freed using av_packet_free().

@return An AVPacket filled with default values or NULL on failure.

@note this only allocates the AVPacket itself, not the data buffers. Those must be allocated through other means such as av_new_packet.

@see av_new_packet