FFmpeg key structural bodies

FFMPEG Key Structures:
Reprint http://blog.csdn.net/leixiaohua1020/article/details/14214577
2016.2.26

Avframe (located in the AVCODEC.H) structure is typically used to store raw data.
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Here are a few of the main variables (consider the case of decoding here):
uint8_t *data[av_num_data_pointers]: Decoded raw data (Yuv,rgb for video, PCM for audio)
The size of the "row" of data in int linesize[av_num_data_pointers]:data. Note: Not necessarily equal to the width of the image, generally greater than the width of the image.
int width, Height: Video frame width and height (1920x1080,1280x720 ... ）
int nb_samples: One avframe of audio may contain multiple audio frames, where the tag contains several
int format: Decoded raw data type (Yuv420,yuv422,rgb24 ... ）
int Key_frame: Whether it is a keyframe
Enum Avpicturetype Pict_type: Frame type (i,b,p ... ）
Avrational Sample_aspect_ratio: Aspect ratio (16:9,4:3 ...)
int64_t pts: Displaying timestamps
int Coded_picture_number: Encode frame number
int Display_picture_number: Display frame number
int8_t *QSCALE_TABLE:QP Table
uint8_t *mbskip_table: Skip macro Block table
int16_t (*motion_val[2]) [2]: Motion vector table
uint32_t *MB_TYPE: Macro block Type table
Short *DCT_COEFF:DCT coefficient, this one has not been extracted
int8_t *ref_index[2]: Motion Estimation reference frame list (it seems that this relatively new standard will involve multiple reference frames)
int Interlaced_frame: Whether it is an interlaced scan
uint8_t MOTION_SUBSAMPLE_LOG2: The number of motion vectors sampled in a macro block, take log

Avformatcontext (located in avformat.h) is a data structure that runs through the constant, and many functions use it as a parameter.
It is the structure of ffmpeg encapsulation (Flv,mp4,rmvb,avi) function.
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Here are a few of the main variables (consider the case of decoding here):
struct Avinputformat *iformat: Encapsulation format for input data
Aviocontext *PB: Caching of input data
unsigned int nb_streams: The number of video audio streams
Avstream **streams: Video audio streaming
Char filename[1024]: file name
int64_t Duration: Duration (in microseconds us, converted to seconds, divided by 1000000)
int bit_rate: Bit rate (unit bps, converted to kbps needs to be divided by 1000)
Avdictionary *metadata: Meta data

Many of the parameters in Avcodeccontext (located in avcodec.h) are used when encoding
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Here are some key variables to look at (just consider decoding here).
Enum Avmediatype Codec_type: Type of codec (video, audio ...) ）
struct AVCODEC *codec: Decoder avcodec Used (H.264,MPEG2 ... ）
int bit_rate: Average bit rate
uint8_t *extradata; int Extradata_size: Additional information for a specific encoder (for example, storage Sps,pps, etc. for a. h decoder)
Avrational time_base: Depending on the parameter, the PTS can be converted to the actual time in seconds s
int width, Height: If it's a video, it represents width and height.
int refs: The number of reference frames for motion estimation (there will be multiple frames in H. MPEG2, this kind of general will not be)
int sample_rate: Sample rate (audio)
int channels: Number of channels (audio)
Enum Avsampleformat sample_fmt: Sampling format
int profile: Type (inside H. I, other coding standards should also have)
int level: (and profile difference not too much)

Aviocontext (located at avio.h) is the structure of ffmpeg management input and output data.
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The following variables are more important in Aviocontext:
unsigned char *buffer: Cache start Location
int buffer_size: Cache size (default 32768)
unsigned char *buf_ptr: Where the current pointer is read
unsigned char *buf_end: where the cache ends
void *opaque:urlcontext Structural Body

Avcodec (located at avcodec.h) is the structure that stores codec information.
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Here are some of the most important variables:
const CHAR *name: The name of the codec, relatively short
const CHAR *long_name: Codec name, full length, longer
Enum Avmediatype Type: Indicates the type, whether it is video, audio, or subtitles
Enum Avcodecid Id:id, not repeating
Const avrational *supported_framerates: Supported frame rate (video only)
const enum Avpixelformat *PIX_FMTS: Supported pixel format (video only)
const INT *SUPPORTED_SAMPLERATES: Supported sample rate (audio only)
const enum Avsampleformat *SAMPLE_FMTS: Supported sampling format (audio only)
Const uint64_t *channel_layouts: Number of channels supported (audio only)
int priv_data_size: size of private data

Avstream (located in avformat.h) is the structure that stores each video/audio stream information.
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The important variables are as follows:
int index: Identifies the video/audio stream
Avcodeccontext *codec: Avcodeccontext that points to the video/audio stream (they are one by one corresponding relationships)
Avrational time_base: Timing. This value can be used to convert Pts,dts into real time. FFmpeg also has this field in other structures,
But according to my experience, only the Time_base in Avstream is available. Pts*time_base= Real time.
int64_t Duration: The video/audio stream length
Avdictionary *metadata: Meta data information
Avrational Avg_frame_rate: Frame rate (Note: This is very important for video)
Avpacket Attached_pic: The accompanying picture. For example, some of the album art included with MP3,AAC audio files.

Avpacket (located in avcodec.h) is a structure that stores information about compressed encoded data.
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The important variables are the following:
uint8_t *data: Compresses the encoded data.
For example, for H. Data for 1 Avpacket usually corresponds to a nal.
Note: Here is just the correspondence, not the exact same. There is a slight difference between them: using the FFmpeg class library to isolate the H. D stream in a multimedia file
Therefore, when using ffmpeg for AV processing, it is often possible to write the resulting avpacket data directly into a file, resulting in audio-visual stream files.
The size of the int size:data
int64_t pts: Displaying timestamps
int64_t DTS: Decoding timestamps
int Stream_index: Identifies the video/audio stream to which the avpacket belongs.

FFmpeg key structural bodies