AVBuffer
struct AVBuffer {
uint8_t *data; /**< data described by this buffer */
int size; /**< size of data in bytes */
/**
* number of existing AVBufferRef instances referring to this buffer
*/
atomic_uint refcount;
/**
* a callback for freeing the data
*/
void (*free)(void *opaque, uint8_t *data);
/**
* an opaque pointer, to be used by the freeing callback
*/
void *opaque;
/**
* A combination of BUFFER_FLAG_*
*/
int flags;
};AVBufferRef
/**
* A reference to a data buffer.
*
* The size of this struct is not a part of the public ABI and it is not meant
* to be allocated directly.
*/
typedef struct AVBufferRef {
AVBuffer *buffer;
/**
* The data buffer. It is considered writable if and only if
* this is the only reference to the buffer, in which case
* av_buffer_is_writable() returns 1.
*/
uint8_t *data;
/**
* Size of data in bytes.
*/
int size;
} AVBufferRef;AVPacket
/**
* This structure stores compressed data. It is typically exported by demuxers
* and then passed as input to decoders, or received as output from encoders and
* then passed to muxers.
*
* For video, it should typically contain one compressed frame. For audio it may
* contain several compressed frames. Encoders are allowed to output empty
* packets, with no compressed data, containing only side data
* (e.g. to update some stream parameters at the end of encoding).
*
* AVPacket is one of the few structs in FFmpeg, whose size is a part of public
* ABI. Thus it may be allocated on stack and no new fields can be added to it
* without libavcodec and libavformat major bump.
*
* The semantics of data ownership depends on the buf field.
* If it is set, the packet data is dynamically allocated and is
* valid indefinitely until a call to av_packet_unref() reduces the
* reference count to 0.
*
* If the buf field is not set av_packet_ref() would make a copy instead
* of increasing the reference count.
*
* The side data is always allocated with av_malloc(), copied by
* av_packet_ref() and freed by av_packet_unref().
*
* @see av_packet_ref
* @see av_packet_unref
*/
typedef struct AVPacket {
/**
* A reference to the reference-counted buffer where the packet data is
* stored.
* May be NULL, then the packet data is not reference-counted.
*/
AVBufferRef *buf;
/**
* Presentation timestamp in AVStream->time_base units; the time at which
* the decompressed packet will be presented to the user.
* Can be AV_NOPTS_VALUE if it is not stored in the file.
* pts MUST be larger or equal to dts as presentation cannot happen before
* decompression, unless one wants to view hex dumps. Some formats misuse
* the terms dts and pts/cts to mean something different. Such timestamps
* must be converted to true pts/dts before they are stored in AVPacket.
*/
int64_t pts;
/**
* Decompression timestamp in AVStream->time_base units; the time at which
* the packet is decompressed.
* Can be AV_NOPTS_VALUE if it is not stored in the file.
*/
int64_t dts;
uint8_t *data;
int size;
int stream_index;
/**
* A combination of AV_PKT_FLAG values
*/
int flags;
/*
* Additional packet data that can be provided by the container.
* Packet can contain several types of side information.
*/
AVPacketSideData *side_data;
int side_data_elems;
/**
* Duration of this packet in AVStream->time_base units, 0 if unknown.
* Equals next_pts - this_pts in presentation order.
*/
int64_t duration;
int64_t pos; ///< byte position in stream, -1 if unknown
#if FF_API_CONVERGENCE_DURATION
/**
* @deprecated Same as the duration field, but as int64_t. This was required
* for Matroska subtitles, whose duration values could overflow when the
* duration field was still an int.
*/
attribute_deprecated
int64_t convergence_duration;
#endif
} AVPacket;调用函数：
AVPacket *av_packet_alloc()：分配一个AVPacket指针，AVBufferRef为空
av_packet_free(AVPacket *)：释放AVPacket指针空间
av_init_packet：只是初始化AVPacket
av_new_packet(AVPacket* ,int size)：创建一个AVPacket，并创建size大小的AVBufferRef，引用计数等于1
av_packet_ref(AVPacket *dst,AVPacket *src)：自己要创建AVPacket *dst，并引用计数+1
av_packet_unref：引用计数-1
av_packet_move_ref:转移引用计数
av_packet_clone:相当于av_packet_alloc和av_packet_ref AVPacket是新的，但内容是老的
AVPaket的使用要求：
