A reference to the reference-counted buffer where the packet data is stored. May be NULL, then the packet data is not reference-counted.
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.
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.
Duration of this packet in AVStream->time_base units, 0 if unknown. Equals next_pts - this_pts in presentation order.
A combination of AV_PKT_FLAG values
< byte position in stream, -1 if unknown
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.
Additional packet data that can be provided by the container. Packet can contain several types of side information.
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.
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 or destruct (deprecated) fields. If either is set, the packet data is dynamically allocated and is valid indefinitely until av_free_packet() is called (which in turn calls av_buffer_unref()/the destruct callback to free the data). If neither is set, the packet data is typically backed by some static buffer somewhere and is only valid for a limited time (e.g. until the next read call when demuxing).
The side data is always allocated with av_malloc() and is freed in av_free_packet().