ffmpeg basic data structures and objects: AVPacket, AVPicture, AVFrame

1. AVPacket

[cpp] view plain copy  

1. /** 
2.  * AVPacket as the input of the decoder or the output of the encoder. 
3.  * When used as input to the decoder, it is generated by the demuxer and then passed to the decoder 
4.  * When used as the output of the encoder, it is generated by the encoder and then passed to the muxer 
5.  * In the video, AVPacket can only contain content no larger than 1 frame, and 1 frame of the video may be included in multiple AVPackets, AVPacket < AVFrame 
6.  *  
7.  * 
8.  * AVPacket is one of the few public ABIs in ffmpeg, it can only be allocated on the stack by libavcodec and libformat 
9.  * 
10.  * The side data is always allocated with av_malloc() and is freed in 
11.  * av_free_packet (). 
12.  */  
13. typedef struct AVPacket {  
14. /** 
15.      * The memory space of packet comes from a place called "reference count buffer", which points to a reference count buffer 
16.      */  
17.     AVBufferRef *buf;  
18. /** 
19.      * Display timestamp units are AVStream->time_base units 
20.      */  
21.     int64_t pts;  
22. /** 
23.      * Decompression timestamp, at which point the packet needs to be decoded 
24.      */  
25.     int64_t dts;  
26.     uint8_t *data;  
27. int   size;  
28. int   stream_index;  
29. /** 
30.      * A combination of AV_PKT_FLAG values 
31.      */  
32. int   flags;  
33. /** 
34.      * Store additional package information 
35.      */  
36. struct {  
37.         uint8_t *data;  
38. int      size;  
39. enum AVPacketSideDataType type;  
40.     } *side_data;  
41. int side_data_elems;  
42. /** 
43.      * The time length of this packet in AVStream->time_base units, setting 0 means unknown. 
44.      * duration = next_pts - this_pts i. 
45.      */  
46. int   duration;  
47.     int64_t pos;                             ///< byte offset in data stream, -1 if unknown  
48.     int64_t convergence_duration;  
49. } AVPacket;  

二、AVPicture

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1. typedef struct AVPicture {  
2.     uint8_t *data[AV_NUM_DATA_POINTERS];    ///< pointers to the image data planes  
3. int linesize[AV_NUM_DATA_POINTERS];     ///< number of bytes per line  
4. }  

3. AVFrame

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1. /** 
2.  * AVFrame represents a decoded data frame 
3.  * 
4.  * AVFrame is created by using av_frame_alloc(). This function just creates the AVFrame structure itself, in the structure 
5.  * The buffer pointers to other memory blocks defined in must be allocated by other methods 
6.  * Use av_frame_free() to free AVFrame. 
7.  * 
8.  */  
9. typedef struct AVFrame {  
10. #define AV_NUM_DATA_POINTERS 8  
11. /** 
12.      * pointer to the picture/channel planes. 
13.      */  
14.     uint8_t * data [AV_NUM_DATA_POINTERS];  
15. /** 
16.      * For video, size in bytes of each picture line. 
17.      * For audio, size in bytes of each plane. 
18.      */  
19. int linesize[AV_NUM_DATA_POINTERS];  
20. /** 
21.      * pointers to the data planes/channels. 
22.      */  
23.     uint8_t **extended_data;  
24. /** 
25.      * width and height of the video frame 
26.      */  
27. int width, height;  
28. /** 
29.      * number of audio samples (per channel) described by this frame 
30.      */  
31. int nb_samples;  
32. /** 
33.      * format of the frame, -1 if unknown or unset 
34.      */  
35. int format;  
36. /** 
37.      * 1 -> keyframe, 0-> not 
38.      */  
39. int key_frame;  
40. /** 
41.      * Picture type of the frame. 
42.      */  
43. enum AVPictureType pict_type;  
44. /** 
45.      * Sample aspect ratio for the video frame, 0/1 if unknown/unspecified. 
46.      */  
47.     AVRational sample_aspect_ratio;  
48. /** 
49.      * Presentation timestamp in time_base units (time when frame should be shown to user). 
50.      */  
51.     int64_t pts;  
52. /** 
53.      * PTS copied from the AVPacket that was decoded to produce this frame. 
54.      */  
55.     int64_t pkt_pts;  
56. /** 
57.      * DTS copied from the AVPacket that triggered returning this frame. (if frame threading isnt used) 
58.      * This is also the Presentation time of this AVFrame calculated from 
59.      * only AVPacket.dts values without pts values. 
60.      */  
61.     int64_t pkt_dts;  
62. /** 
63.      * picture number in bitstream order 
64.      */  
65. int coded_picture_number;  
66. /** 
67.      * picture number in display order 
68.      */  
69. int display_picture_number;  
70. /** 
71.      * quality (between 1 (good) and FF_LAMBDA_MAX (bad)) 
72.      */  
73. int quality;  
74. /** 
75.      * for some private data of the user 
76.      */  
77. void *opaque;  
78. /** 
79.      * error 
80.      */  
81.     uint64_t error [AV_NUM_DATA_POINTERS];  
82. /** 
83.      * When decoding, this signals how much the picture must be delayed. 
84.      * extra_delay = repeat_pict / (2*fps) 
85.      */  
86. int repeat_pict;  
87. /** 
88.      * The content of the picture is interlaced. 
89.      */  
90. int interlaced_frame;  
91. /** 
92.      * If the content is interlaced, is top field displayed first. 
93.      */  
94. int top_field_first;  
95. /** 
96.      * Tell user application that palette has changed from previous frame. 
97.      */  
98. int palette_has_changed;  
99. /** 
100.      * Sample rate of the audio data. 
101.      */  
102. int sample_rate;  
103. /** 
104.      * Channel layout of the audio data. 
105.      */  
106.     uint64_t channel_layout;  
107. /** 
108.      * Point to the data buffer in the AVBuffer to be used by this frame. 
109.      * 
110.      * Generally, each image bit plane (data[0], data[1] data[2]) has only one buffer pointing to AVBuffer, so for video this array 
111.      * always contains all the references. For planar audio with more than 
112.      * AV_NUM_DATA_POINTERS channels, there may be more buffers than can fit in 
113.      * this array. Then the extra AVBufferRef pointers are stored in the 
114.      * extended_buf array. 
115.      */  
116.     AVBufferRef * buf [AV_NUM_DATA_POINTERS];  
117. /** 
118.      * For planar audio which requires more than AV_NUM_DATA_POINTERS 
119.      * AVBufferRef pointers, this array will hold all the references which 
120.      * cannot fit into AVFrame.buf. 
121.      */  
122.     AVBufferRef **extended_buf;  
123. /** 
124.      * Number of elements in extended_buf. 
125.      */  
126. int        nb_extended_buf;  
127.     AVFrameSideData **side_data;  
128. int            nb_side_data;  
129. /** 
130.  * May be due to decoding errors, the data frame Frame will become an invalid frame, the following structure is used when the data frame is invalid 
131.  */  
132. #define AV_FRAME_FLAG_CORRUPT       (1 << 0)  
133. /** 
134.      * Frame flags, a combination of AV_FRAME_FLAG_* 
135.      */  
136. int flags;  
137.     int64_t best_effort_timestamp;  
138.     int64_t point_pos;  
139.     int64_t pkt_duration;  
140.     AVDictionary *metadata;  
141. int decode_error_flags;  
142. #define FF_DECODE_ERROR_INVALID_BITSTREAM   1  
143. #define FF_DECODE_ERROR_MISSING_REFERENCE   2  
144. int channels;  
145. int pkt_size;  
146. enum AVColorSpace colorspace;  
147. enum AVColorRange color_range;  
148. /** 
149.      * Not to be accessed directly from outside libavutil 
150.      */  
151.     AVBufferRef *qp_table_buf;  
152. } AVFrame;  

from：http://blog.csdn.net/chance_yin/article/details/16817957