FFmpeg Structure and function Introduction (II.) usefully

1 Avcodec_find_decoder ()

/**

* Find a registered decoder with a matching codec ID.

*

* @param ID Codecid of the requested decoder

* @return A Decoder If one was found, NULL otherwise.

*/

Avcodec *avcodec_find_decoder (enum codecid ID);

Find a registered audio and video decoder with code ID

Introduction of #include "libavcodec/avcodec.h"

Implementation in: \FFMPEG\LIBAVCODEC\UTILS.C

Before locating the decoder, you must first call Av_register_all to register all supported decoders

Lookup successfully Returns the decoder pointer, otherwise NULL is returned

The audio and video decoder is stored in a linked list, and during the lookup process, the function iterates through the list, looking for the decoder by comparing its ID.

2 avcodec_find_decoder_by_name ()

/**

* Find a registered decoder with the specified name.

*

* @param name Name of the requested decoder

* @return A Decoder If one was found, NULL otherwise.

*/

Avcodec *avcodec_find_decoder_by_name (const char *name);

Find a registered audio and video decoder with a specified name

Introduction of #include "libavcodec/avcodec.h"

Implementation in: \FFMPEG\LIBAVCODEC\UTILS.C

Before locating the decoder, you must first call Av_register_all to register all supported decoders

Lookup successfully Returns the decoder pointer, otherwise NULL is returned

The audio and video decoder is stored in a linked list, and during the lookup process, the function iterates through the list, looking for the decoder by comparing its name.

3 Avcodec_find_encoder ()

/**

* Find a registered encoder with a matching codec ID.

*

* @param ID Codecid of the requested encoder

* @return An encoder If one is found, NULL otherwise.

*/

Avcodec *avcodec_find_encoder (enum codecid ID);

Find a registered audio and video encoder with code ID

Introduced #include "libavcodec/avcodec.h"//implemented in: \FFMPEG\LIBAVCODEC\UTILS.C

Before you can find an encoder, you must first call Av_register_all to register all supported Encoders

Lookup succeeded in returning encoder pointer, otherwise NULL is returned

Audio and video encoders are stored in a linked list, and during the lookup process, the function iterates through the list, looking for the ID of the encoder by comparing it

4 avcodec_find_encoder_by_name ()

/**

* Find a registered encoder with the specified name.

*

* @param name Name of the requested encoder

* @return An encoder If one is found, NULL otherwise.

*/

Avcodec *avcodec_find_encoder_by_name (const char *name);

Find a registered audio and video encoder with a specified name

Introduced #include "libavcodec/avcodec.h"//implemented in: \FFMPEG\LIBAVCODEC\UTILS.C

Before you can find an encoder, you must first call Av_register_all to register all supported Encoders

Lookup succeeded in returning encoder pointer, otherwise NULL is returned

Audio and video encoders are stored in a linked list, and during the lookup process, the function traverses the list from beginning to end, by comparing the name of the encoder to find

5 Avcodec_open ()

/**

* Initialize the Avcodeccontext to use the given avcodec. Prior to using this

* Function The context has to be allocated.

*

* The Functions Avcodec_find_decoder_by_name (), Avcodec_find_encoder_by_name (),

* Avcodec_find_decoder () and Avcodec_find_encoder () provide an easy to

* Retrieving a codec.

*

* @warning This function was not thread safe!

*

* @code

* Avcodec_register_all ();

* codec = Avcodec_find_decoder (codec_id_h264);

* IF (!CODEC)

* EXIT (1);

*

* context = Avcodec_alloc_context ();

*

* IF (Avcodec_open (context, codec) < 0)

* EXIT (1);

* @endcode

*

* @param avctx the context which would be set up to use the given codec.

* @param codec the codec to use within the context.

* @return Zero on success, a negative value on error

* @see Avcodec_alloc_context, Avcodec_find_decoder, Avcodec_find_encoder, Avcodec_close

*/

int Avcodec_open (Avcodeccontext *avctx, Avcodec *codec);

Initializes the avcodeccontext with the given Avcodec

Introduction of # include "Libavcodec/avcodec.h"

Method: Avcodec_find_decoder_by_name (), Avcodec_find_encoder_by_name (), Avcodec_find_decoder () and Avcodec_find_ Encoder () provides a quick way to get a codec

This method is used in both encoding and decoding.

Return 0 o'clock successful, open as output when the parameter setting is incorrect, the call fails 6 Av_guess_format ()

/**

* Return the output format in the list of registered output formats

* Which best matches the provided parameters, or return NULL if

* There is no match.

*

* @param short_name If non-null checks if short_name matches with the

* Names of the registered formats

* @param filename If non-null checks if filename terminates with the

* Extensions of the registered formats

* @param mime_type If non-null checks if Mime_type matches with the

* MIME type of the registered formats

*/

Avoutputformat *av_guess_format (const char *short_name,

const Char *filename,

const char *mime_type);

Returns the most appropriate output format that has been registered

Introduction of # include "Libavformat/avformat.h"

Can be obtained through the const char *short_name, such as "MPEG"

can also be obtained through the const char *filename, such as "E:\a.mp4"

7 Av_new_stream ()

/**

* Add a new stream to a media file.

*

* Can only is called in the Read_header () function. IF the flag

* Avfmtctx_noheader is in the format context and then new streams

* Can is added in Read_packet too.

*

* @param s media file handle

* @param ID file-format-dependent stream ID

*/

Avstream *av_new_stream (avformatcontext *s, int id);

Adds a stream to the media file, typically adding a stream of audio and video to the media file container as output

Introduction of #include "Libavformat/avformat.h"

When you open the source file again, the user typically does not need to call the method directly 8 Dump_format ()

#if Ff_api_dump_format

/**

* @deprecated deprecated in favor of Av_dump_format ().

*/

attribute_deprecated void Dump_format (Avformatcontext *ic,

int index,

const Char *url,

int is_output);

#endif//The function is to check whether the parameters set in the initialization process conform to specifications//In some versions av_ Dump_format 9 av_set_parameters ()

#if ff_api_format_parameters

/**

* @deprecated Pass the options to Avformat_write_header directly.

*/

attribute_deprecated int av_set_parameters (Avformatcontext *s, avformatparameters *ap); #endif//Set initialization parameters//Disapprove of skipping this method, call Avformat_write_header/av_write_header Av_write_header () directly

#if ff_api_format_parameters

/**

* Allocate the stream private data and write the stream header to an

* Output media file.

* @note: This sets stream time-bases, if possible to stream->codec->time_base

* But for some formats it might also is some other time base

*

* @param s media file handle

* @return 0 if OK, averror_xxx on Error

*

* @deprecated use Avformat_write_header.

*/

attribute_deprecated int Av_write_header (Avformatcontext *s);

#endif//write the stream header information to the media file//Return 0 success