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;

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。