FFmpeg codec usage Summary

 

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Video coding and decoding Technology
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FFmpeg provides many encoder and decoder. For details, see the enumerated variable codecid in avcodec. h.

 

Macro definition

# Define register_encoder (x, x ){/
Extern avcodec x ##_ encoder ;/
If (# x ###_ encoder) avcodec_register (& X ##_ encoder );}

 

# Define register_decoder (x, x ){/
Extern avcodec x ##_ decoder ;/
If (# codec_id _ # X #) avcodec_register (& X ##_ decoder );}

 

For example:

Register_decoder (h264, h264 );

It is equivalent to extern avcodec hsf-_decoder;

If (codec_id_h264)

Avcodec_register (& hsf-_decoder );

 

The actual functions of these three lines of code are as follows:

Avcodec codec;

Codec = & hsf-_decoder;

 

After codec is configured,

Define the global variable avcodeccontext * avctx;

Then avctx-> codec = codec;

 

In the future, you can call common APIs:

Avctx-> codec-> init Initialization

Avctx-> codec-> decode Decoding

Or avctx-> codec-> encode Encoding

Avctx-> codec-> close

Encoding or decoding

 

Codec is a struct and is defined as follows:

Typedef struct avcodec {
Const char * Name;
Enum codectype type;
Enum codecid ID;
Int priv_data_size;
INT (* init) (avcodeccontext *); // initialize the Function
INT (* encode) (avcodeccontext *, uint8_t * Buf, int buf_size, void * data );
// Encoding function
INT (* close) (avcodeccontext *); // close the Function
INT (* decode) (avcodeccontext *, void * outdata, int * outdata_size, avpacket * avpkt );
// Decoding function

For different codec, the three APIs correspond to different functions.

For codec_id_h264, hsf-_decoder is defined

 

Avcodec hsf-_decoder = {
"H264 ",
Codec_type_video,
Codec_id_h264,
Sizeof (hsf-context ),
Decode_init,
Null,
Decode_end,
Decode_frame,

}

The definition of codec_id_h263 and h263_decoder is as follows:

Avcodec h263_decoder = {
"H263 ",
Codec_type_video,
Codec_id_h263,
Sizeof (mpegenccontext ),
Ff_h263_decode_init,
Null,
Ff_h263_decode_end,
Ff_h263_decode_frame,
Codec_cap_draw_horiz_band | codec_cap_dr1 | codec_cap_truncated | codec_cap_delay,
//. Flush = ff_mpeg_flush,
//. Long_name = null_if_config_small ("H.263/H.263-1996, H.263 +/H.263-1998/H.263 Version 2 "),
//. Pix_fmts = ff_hwaccel_pixfmt_list_420,
};

 

The definition of codec_id_mpeg4 and mpeg4_decoder is as follows:

Avcodec mpeg4_decoder = {
"MPEG4 ",
Codec_type_video,
Codec_id_mpeg4,
Sizeof (mpegenccontext ),
Ff_h263_decode_init,
Null,
Ff_h263_decode_end,
Ff_h263_decode_frame,
Codec_cap_draw_horiz_band | codec_cap_dr1 | codec_cap_truncated | codec_cap_delay,
//. Flush = ff_mpeg_flush,
//. Long_name = null_if_config_small ("MPEG-4 Part 2 "),
//. Pix_fmts = ff_hwaccel_pixfmt_list_420,
};