几个ffmpeg中parser相关的几个函数使用问题
谁能悟出下面几个想关联的函数怎么一起使用 特别是av_parser_change、 struct AVCodecParserContext 、av_parser_next怎么意思呀????
typedef struct AVCodecParserContext {
void *priv_data;
struct AVCodecParser *parser;
int64_t frame_offset; /* offset of the current frame */
int64_t cur_offset; /* current offset
(incremented by each av_parser_parse()) */
int64_t next_frame_offset; /* offset of the next frame */
/* video info */
int pict_type; /* XXX: Put it back in AVCodecContext. */
/**
* This field is used for proper frame duration computation in lavf.
* It signals, how much longer the frame duration of the current frame
* is compared to normal frame duration.
*
* frame_duration = (1 + repeat_pict) * time_base
*
* It is used by codecs like H.264 to display telecined material.
*/
int repeat_pict; /* XXX: Put it back in AVCodecContext. */
int64_t pts; /* pts of the current frame */
int64_t dts; /* dts of the current frame */
/* private data */
int64_t last_pts;
int64_t last_dts;
int fetch_timestamp;
#define AV_PARSER_PTS_NB 4
int cur_frame_start_index;
int64_t cur_frame_offset[AV_PARSER_PTS_NB];
int64_t cur_frame_pts[AV_PARSER_PTS_NB];
int64_t cur_frame_dts[AV_PARSER_PTS_NB];
int flags;
#define PARSER_FLAG_COMPLETE_FRAMES 0x0001
#define PARSER_FLAG_ONCE 0x0002
/// Set if the parser has a valid file offset
#define PARSER_FLAG_FETCHED_OFFSET 0x0004
#define PARSER_FLAG_USE_CODEC_TS 0x1000
int64_t offset; ///< byte offset from starting packet start
int64_t cur_frame_end[AV_PARSER_PTS_NB];
/**
* Set by parser to 1 for key frames and 0 for non-key frames.
* It is initialized to -1, so if the parser doesn't set this flag,
* old-style fallback using AV_PICTURE_TYPE_I picture type as key frames
* will be used.
*/
int key_frame;
/**
* Time difference in stream time base units from the pts of this
* packet to the point at which the output from the decoder has converged
* independent from the availability of previous frames. That is, the
* frames are virtually identical no matter if decoding started from
* the very first frame or from this keyframe.
* Is AV_NOPTS_VALUE if unknown.
* This field is not the display duration of the current frame.
* This field has no meaning if the packet does not have AV_PKT_FLAG_KEY
* set.
*
* The purpose of this field is to allow seeking in streams that have no
* keyframes in the conventional sense. It corresponds to the
* recovery point SEI in H.264 and match_time_delta in NUT. It is also
* essential for some types of subtitle streams to ensure that all
* subtitles are correctly displayed after seeking.
*/
int64_t convergence_duration;
// Timestamp generation support:
/**
* Synchronization point for start of timestamp generation.
*
* Set to >0 for sync point, 0 for no sync point and <0 for undefined
* (default).
*
* For example, this corresponds to presence of H.264 buffering period
* SEI message.
*/
int dts_sync_point;
/**
* Offset of the current timestamp against last timestamp sync point in
* units of AVCodecContext.time_base.
*
* Set to INT_MIN when dts_sync_point unused. Otherwise, it must
* contain a valid timestamp offset.
*
* Note that the timestamp of sync point has usually a nonzero
* dts_ref_dts_delta, which refers to the previous sync point. Offset of
* the next frame after timestamp sync point will be usually 1.
*
* For example, this corresponds to H.264 cpb_removal_delay.
*/
int dts_ref_dts_delta;
/**
* Presentation delay of current frame in units of AVCodecContext.time_base.
*
* Set to INT_MIN when dts_sync_point unused. Otherwise, it must
* contain valid non-negative timestamp delta (presentation time of a frame
* must not lie in the past).
*
* This delay represents the difference between decoding and presentation
* time of the frame.
*
* For example, this corresponds to H.264 dpb_output_delay.
*/
int pts_dts_delta;
/**
* Position of the packet in file.
*
* Analogous to cur_frame_pts/dts
*/
int64_t cur_frame_pos[AV_PARSER_PTS_NB];
/**
* Byte position of currently parsed frame in stream.
*/
int64_t pos;
/**
* Previous frame byte position.
*/
int64_t last_pos;
/**
* Duration of the current frame.
* For audio, this is in units of 1 / AVCodecContext.sample_rate.
* For all other types, this is in units of AVCodecContext.time_base.
*/
int duration;
enum AVFieldOrder field_order;
/**
* Indicate whether a picture is coded as a frame, top field or bottom field.
*
* For example, H.264 field_pic_flag equal to 0 corresponds to
* AV_PICTURE_STRUCTURE_FRAME. An H.264 picture with field_pic_flag
* equal to 1 and bottom_field_flag equal to 0 corresponds to
* AV_PICTURE_STRUCTURE_TOP_FIELD.
*/
enum AVPictureStructure picture_structure;
} AVCodecParserContext;
typedef struct AVCodecParser {
int codec_ids[5]; /* several codec IDs are permitted */
int priv_data_size;
int (*parser_init)(AVCodecParserContext *s);
int (*parser_parse)(AVCodecParserContext *s,
AVCodecContext *avctx,
const uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size);
void (*parser_close)(AVCodecParserContext *s);
int (*split)(AVCodecContext *avctx, const uint8_t *buf, int buf_size);
struct AVCodecParser *next;
} AVCodecParser;
AVCodecParser *av_parser_next(AVCodecParser *c);
void av_register_codec_parser(AVCodecParser *parser);
AVCodecParserContext *av_parser_init(int codec_id);
/**
* Parse a packet.
*
* @param s parser context.
* @param avctx codec context.
* @param poutbuf set to pointer to parsed buffer or NULL if not yet finished.
* @param poutbuf_size set to size of parsed buffer or zero if not yet finished.
* @param buf input buffer.
* @param buf_size input length, to signal EOF, this should be 0 (so that the last frame can be output).
* @param pts input presentation timestamp.
* @param dts input decoding timestamp.
* @param pos input byte position in stream.
* @return the number of bytes of the input bitstream used.
*
* Example:
* @code
* while(in_len){
* len = av_parser_parse2(myparser, AVCodecContext, &data, &size,
* in_data, in_len,
* pts, dts, pos);
* in_data += len;
* in_len -= len;
*
* if(size)
* decode_frame(data, size);
* }
* @endcode
*/
int av_parser_parse2(AVCodecParserContext *s,
AVCodecContext *avctx,
uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size,
int64_t pts, int64_t dts,
int64_t pos);
/**
* @return 0 if the output buffer is a subset of the input, 1 if it is allocated and must be freed
* @deprecated use AVBitStreamFilter
*/
int av_parser_change(AVCodecParserContext *s,
AVCodecContext *avctx,
uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size, int keyframe);
void av_parser_close(AVCodecParserContext *s);
