# FFmpeg 结构体学习(三)： AVPacket 分析

AVPacket是存储压缩编码数据相关信息的结构体。下面我们来分析一下该结构体里重要变量的含义和作用。

# 一、源码整理

typedef struct AVPacket {
/**
* 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.
*/
struct {
uint8_t *data;
int      size;
enum AVPacketSideDataType type;
} *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.
*/
int   duration;
void  (*destruct)(struct AVPacket *);
void  *priv;
int64_t pos;                            ///< byte position in stream, -1 if unknown

/**
* Time difference in AVStream->time_base units from the pts of this
* packet to the point at which the output from the decoder has converged
* independent from the availability of previous frames. That is, the
* frames are virtually identical no matter if decoding started from
* the very first frame or from this keyframe.
* Is AV_NOPTS_VALUE if unknown.
* This field is not the display duration of the current packet.
* This field has no meaning if the packet does not have AV_PKT_FLAG_KEY
* set.
*
* The purpose of this field is to allow seeking in streams that have no
* keyframes in the conventional sense. It corresponds to the
* recovery point SEI in H.264 and match_time_delta in NUT. It is also
* essential for some types of subtitle streams to ensure that all
* subtitles are correctly displayed after seeking.
*/
int64_t convergence_duration;
} AVPacket;

# 二、AVPacket 重点字段

uint8_t *data：压缩编码的数据。

int   size：data的大小

int64_t pts：显示时间戳

int64_t dts：解码时间戳

int   stream_index：标识该AVPacket所属的视频/音频流。

posted @ 2018-08-16 17:43  灰色飘零  阅读(...)  评论(...编辑  收藏