位于libavutil下frame.h文件中
- 这个结构体用来描述解码出音视频数据。
- AVFrame必须使用av_frame_alloc分配()。
- AVFrame必须与av_frame_free释放()。
- AVFrame通常分配一次,然后重复使用多次，不同的数据（如一个AVFrame持有来自解码器的frames。)在再次使用时,av_frame_unref()将自由持有的任何之前的帧引用并重置它变成初始态。
- 一个AVFrame所描述的数据通常是通过参考AVBuffer API计算。内部的buffer引用存储在AVFrame.buf /AVFrame.extended_buf。
- AVFrame将用于引用计数,当至少一个引用被set时,如果AVFrame.buf[0] != NULL, 每个单个数据至少包含一个AVFrame.buf /AVFrame.extended_buf.可能会有一个缓冲的数据,或一个单独的缓冲对每个plane, 或介于两者之间的任何东西。
- sizeof(AVFrame)不是一个public的API,因此新的成员将被添加到末尾。同样字段标记为只访问av_opt_ptr()可以重新排序
typedef struct AVFrame {
#define AV_NUM_DATA_POINTERS 8 /**
* pointer to the picture/channel planes.
* This might be different from the first allocated byte
*
* Some decoders access areas outside 0,0 - width,height, please
* see avcodec_align_dimensions2(). Some filters and swscale can read
* up to 16 bytes beyond the planes, if these filters are to be used,
* then 16 extra bytes must be allocated.
*
* NOTE: Except for hwaccel formats, pointers not needed by the format
* MUST be set to NULL.
*/ uint8_t *data[AV_NUM_DATA_POINTERS]; /**
* For video, size in bytes of each picture line.
* For audio, size in bytes of each plane.
*
* For audio, only linesize[0] may be set. For planar audio, each channel
* plane must be the same size.
*
* For video the linesizes should be multiples of the CPUs alignment
* preference, this is 16 or 32 for modern desktop CPUs.
* Some code requires such alignment other code can be slower without
* correct alignment, for yet other it makes no difference.
*
* @note The linesize may be larger than the size of usable data -- there
* may be extra padding present for performance reasons.
*/ int linesize[AV_NUM_DATA_POINTERS]; /**
* pointers to the data planes/channels.
*
* For video, this should simply point to data[].
*
* For planar audio, each channel has a separate data pointer, and
* linesize[0] contains the size of each channel buffer.
* For packed audio, there is just one data pointer, and linesize[0]
* contains the total size of the buffer for all channels.
*
* Note: Both data and extended_data should always be set in a valid frame,
* but for planar audio with more channels that can fit in data,
* extended_data must be used in order to access all channels.
*/ uint8_t **extended_data; /**
* width and height of the video frame
*/ int width, height; /**
* number of audio samples (per channel) described by this frame
*/ int nb_samples; /**
* format of the frame, -1 if unknown or unset
* Values correspond to enum AVPixelFormat for video frames,
* enum AVSampleFormat for audio)
*/ int format; /**
* 1 -> keyframe, 0-> not
*/ int key_frame; /**
* Picture type of the frame.
*/ enum AVPictureType pict_type; /**
* Sample aspect ratio for the video frame, 0/1 if unknown/unspecified.
*/ AVRational sample_aspect_ratio; /**
* Presentation timestamp in time_base units (time when frame should be shown to user).
*/ int64_t pts; /**
* PTS copied from the AVPacket that was decoded to produce this frame.
*/ int64_t pkt_pts; /**
* DTS copied from the AVPacket that triggered returning this frame. (if frame threading isn't used)
* This is also the Presentation time of this AVFrame calculated from
* only AVPacket.dts values without pts values.
*/ int64_t pkt_dts; /**
* picture number in bitstream order
*/ int coded_picture_number; /**
* picture number in display order
*/ int display_picture_number; /**
* quality (between 1 (good) and FF_LAMBDA_MAX (bad))
*/ int quality; /**
* for some private data of the user
*/ void *opaque;
#if FF_API_ERROR_FRAME /**
* @deprecated unused
*/ attribute_deprecated
uint64_t error[AV_NUM_DATA_POINTERS];
#endif /**
* When decoding, this signals how much the picture must be delayed.
* extra_delay = repeat_pict / (2*fps)
*/ int repeat_pict; /**
* The content of the picture is interlaced.
*/ int interlaced_frame; /**
* If the content is interlaced, is top field displayed first.
*/ int top_field_first; /**
* Tell user application that palette has changed from previous frame.
*/ int palette_has_changed; /**
* reordered opaque 64 bits (generally an integer or a double precision float
* PTS but can be anything).
* The user sets AVCodecContext.reordered_opaque to represent the input at
* that time,
* the decoder reorders values as needed and sets AVFrame.reordered_opaque
* to exactly one of the values provided by the user through AVCodecContext.reordered_opaque
* @deprecated in favor of pkt_pts
*/ int64_t reordered_opaque; /**
* Sample rate of the audio data.
*/ int sample_rate; /**
* Channel layout of the audio data.
*/ uint64_t channel_layout; /**
* AVBuffer references backing the data for this frame. If all elements of
* this array are NULL, then this frame is not reference counted. This array
* must be filled contiguously -- if buf[i] is non-NULL then buf[j] must
* also be non-NULL for all j < i.
*
* There may be at most one AVBuffer per data plane, so for video this array
* always contains all the references. For planar audio with more than
* AV_NUM_DATA_POINTERS channels, there may be more buffers than can fit in
* this array. Then the extra AVBufferRef pointers are stored in the
* extended_buf array.
*/ AVBufferRef *buf[AV_NUM_DATA_POINTERS]; /**
* For planar audio which requires more than AV_NUM_DATA_POINTERS
* AVBufferRef pointers, this array will hold all the references which
* cannot fit into AVFrame.buf.
*
* Note that this is different from AVFrame.extended_data, which always
* contains all the pointers. This array only contains the extra pointers,
* which cannot fit into AVFrame.buf.
*
* This array is always allocated using av_malloc() by whoever constructs
* the frame. It is freed in av_frame_unref().
*/ AVBufferRef **extended_buf; /**
* Number of elements in extended_buf.
*/ int nb_extended_buf;
AVFrameSideData **side_data; int nb_side_data; /**
* @defgroup lavu_frame_flags AV_FRAME_FLAGS
* Flags describing additional frame properties.
*
* @{
*/ /**
* The frame data may be corrupted, e.g. due to decoding errors.
*/ #define AV_FRAME_FLAG_CORRUPT (1 << 0) /**
* @}
*/ /**
* Frame flags, a combination of @ref lavu_frame_flags
*/ int flags; /**
* MPEG vs JPEG YUV range.
* It must be accessed using av_frame_get_color_range() and
* av_frame_set_color_range().
* - encoding: Set by user
* - decoding: Set by libavcodec
*/ enum AVColorRange color_range; enum AVColorPrimaries color_primaries; enum AVColorTransferCharacteristic color_trc; /**
* YUV colorspace type.
* It must be accessed using av_frame_get_colorspace() and
* av_frame_set_colorspace().
* - encoding: Set by user
* - decoding: Set by libavcodec
*/ enum AVColorSpace colorspace; enum AVChromaLocation chroma_location; /**
* frame timestamp estimated using various heuristics, in stream time base
* Code outside libavutil should access this field using:
* av_frame_get_best_effort_timestamp(frame)
* - encoding: unused
* - decoding: set by libavcodec, read by user.
*/ int64_t best_effort_timestamp; /**
* reordered pos from the last AVPacket that has been input into the decoder
* Code outside libavutil should access this field using:
* av_frame_get_pkt_pos(frame)
* - encoding: unused
* - decoding: Read by user.
*/ int64_t pkt_pos; /**
* duration of the corresponding packet, expressed in
* AVStream->time_base units, 0 if unknown.
* Code outside libavutil should access this field using:
* av_frame_get_pkt_duration(frame)
* - encoding: unused
* - decoding: Read by user.
*/ int64_t pkt_duration; /**
* metadata.
* Code outside libavutil should access this field using:
* av_frame_get_metadata(frame)
* - encoding: Set by user.
* - decoding: Set by libavcodec.
*/ AVDictionary *metadata; /**
* decode error flags of the frame, set to a combination of
* FF_DECODE_ERROR_xxx flags if the decoder produced a frame, but there
* were errors during the decoding.
* Code outside libavutil should access this field using:
* av_frame_get_decode_error_flags(frame)
* - encoding: unused
* - decoding: set by libavcodec, read by user.
*/ int decode_error_flags;
#define FF_DECODE_ERROR_INVALID_BITSTREAM 1 #define FF_DECODE_ERROR_MISSING_REFERENCE 2 /**
* number of audio channels, only used for audio.
* Code outside libavutil should access this field using:
* av_frame_get_channels(frame)
* - encoding: unused
* - decoding: Read by user.
*/ int channels; /**
* size of the corresponding packet containing the compressed
* frame. It must be accessed using av_frame_get_pkt_size() and
* av_frame_set_pkt_size().
* It is set to a negative value if unknown.
* - encoding: unused
* - decoding: set by libavcodec, read by user.
*/ int pkt_size;
#if FF_API_FRAME_QP /**
* QP table
* Not to be accessed directly from outside libavutil
*/ attribute_deprecated
int8_t *qscale_table; /**
* QP store stride
* Not to be accessed directly from outside libavutil
*/ attribute_deprecated int qstride;
attribute_deprecated int qscale_type; /**
* Not to be accessed directly from outside libavutil
*/ AVBufferRef *qp_table_buf;
#endif /**
* For hwaccel-format frames, this should be a reference to the
* AVHWFramesContext describing the frame.
*/ AVBufferRef *hw_frames_ctx;
} AVFrame;
-
uint8_t *data[AV_NUM_DATA_POINTERS]：指针数组，存放YUV数据的地方。如图所示，一般占用前3个指针，分别指向Y，U，V数据。
- 对于packed格式的数据（例如RGB24），会存到data[0]里面。 对于planar格式的数据（例如YUV420P），则会分开成data[0]，data[1]，data[2]…（YUV420P中data[0]存Y，data[1]存U，data[2]存V）
- int linesize[AV_NUM_DATA_POINTERS]：图像各个分量数据在此结构体中的的宽度。注意这并不是图像的宽度。在此例子中图像的尺寸为672X272，而亮度分量的宽度为704，应该是图像宽度经过64对齐后的结果。
- uint8_t **extended_data：指向了图像数据。
- int width, height：图像的宽高。
- int nb_samples：此帧音频的点数。
- int format：像素类型（视频），样点类型（音频）
- int key_frame：是否关键帧，此例中为视频的第一帧，当然是关键帧了。
- enum AVPictureType pict_type：图像类型，I，P，B等，同样，第一帧是I帧。
- AVRational sample_aspect_ratio：像素的宽高比，注意不是图像的。
- int64_t pts，pkt_pts，pkt_dts：和时间戳有关的变量，以后会详细介绍。
- int coded_picture_number：编码顺序的图像num。
- int display_picture_number：播放顺序的图像num。
- int interlaced_frame：图像是否是隔行的。
- int top_field_first：图像的top field first变量。
- int64_t pkt_duration：对应packet的显示时长。
- int pkt_size：对应packet的尺寸。
- int8_t *qscale_table：据推测是存放qp（量化参数）的数组
- AVBufferRef *qp_table_buf：成员data指向qscale_table。
