avcodec.h

 * @warning The input buffer must be \c FF_INPUT_BUFFER_PADDING_SIZE larger than
 * the actual read bytes because some optimized bitstream readers read 32 or 64
 * bits at once and could read over the end.
 *
 * @warning The end of the input buffer \p buf should be set to 0 to ensure that
 * no overreading happens for damaged MPEG streams.
 *
 * @note You might have to align the input buffer \p buf and output buffer \p
 * samples. The alignment requirements depend on the CPU: on some CPUs it isn't
 * necessary at all, on others it won't work at all if not aligned and on others
 * it will work but it will have an impact on performance. In practice, the
 * bitstream should have 4 byte alignment at minimum and all sample data should
 * be 16 byte aligned unless the CPU doesn't need it (AltiVec and SSE do). If
 * the linesize is not a multiple of 16 then there's no sense in aligning the
 * start of the buffer to 16.
 *
 * @note Some codecs have a delay between input and output, these need to be
 * feeded with buf=NULL, buf_size=0 at the end to return the remaining frames.
 *
 * @param avctx the codec context
 * @param[out] picture The AVFrame in which the decoded video frame will be stored.
 * @param[in] buf the input buffer
 * @param[in] buf_size the size of the input buffer in bytes
 * @param[in,out] got_picture_ptr Zero if no frame could be decompressed, otherwise, it is nonzero.
 * @return On error a negative value is returned, otherwise the number of bytes
 * used or zero if no frame could be decompressed.
 */
int avcodec_decode_video(AVCodecContext *avctx, AVFrame *picture,
                         int *got_picture_ptr,
                         const uint8_t *buf, int buf_size);

/* Decode a subtitle message. Return -1 if error, otherwise return the
 * number of bytes used. If no subtitle could be decompressed,
 * got_sub_ptr is zero. Otherwise, the subtitle is stored in *sub. */
int avcodec_decode_subtitle(AVCodecContext *avctx, AVSubtitle *sub,
                            int *got_sub_ptr,
                            const uint8_t *buf, int buf_size);
int avcodec_parse_frame(AVCodecContext *avctx, uint8_t **pdata,
                        int *data_size_ptr,
                        uint8_t *buf, int buf_size);

/**
 * Encodes an audio frame from \p samples into \p buf.
 * The avcodec_encode_audio() function encodes an audio frame from the input
 * buffer \p samples. To encode it, it makes use of the audio codec which was
 * coupled with \p avctx using avcodec_open(). The resulting encoded frame is
 * stored in output buffer \p buf.
 *
 * @note The output buffer should be at least \c FF_MIN_BUFFER_SIZE bytes large.
 *
 * @param avctx the codec context
 * @param[out] buf the output buffer
 * @param[in] buf_size the output buffer size
 * @param[in] samples the input buffer containing the samples
 * The number of samples read from this buffer is frame_size*channels,
 * both of which are defined in \p avctx.
 * For PCM audio the number of samples read from \p samples is equal to
 * \p buf_size * input_sample_size / output_sample_size.
 * @return On error a negative value is returned, on success zero or the number
 * of bytes used to encode the data read from the input buffer.
 */
int avcodec_encode_audio(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                         const short *samples);

/**
 * Encodes a video frame from \p pict into \p buf.
 * The avcodec_encode_video() function encodes a video frame from the input
 * \p pict. To encode it, it makes use of the video codec which was coupled with
 * \p avctx using avcodec_open(). The resulting encoded bytes representing the
 * frame are stored in the output buffer \p buf. The input picture should be
 * stored using a specific format, namely \c avctx.pix_fmt.
 *
 * @param avctx the codec context
 * @param[out] buf the output buffer for the bitstream of encoded frame
 * @param[in] buf_size the size of the output buffer in bytes
 * @param[in] pict the input picture to encode
 * @return On error a negative value is returned, on success zero or the number
 * of bytes used from the output buffer.
 */
int avcodec_encode_video(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                         const AVFrame *pict);
int avcodec_encode_subtitle(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                            const AVSubtitle *sub);

int avcodec_close(AVCodecContext *avctx);

/**
 * Register all the codecs, parsers and bitstream filters which were enabled at
 * configuration time. If you do not call this function you can select exactly
 * which formats you want to support, by using the individual registration
 * functions.
 *
 * @see avcodec_register
 * @see av_register_codec_parser
 * @see av_register_bitstream_filter
 */
void avcodec_register_all(void);

/**
 * Flush buffers, should be called when seeking or when switching to a different stream.
 */
void avcodec_flush_buffers(AVCodecContext *avctx);

void avcodec_default_free_buffers(AVCodecContext *s);

/* misc useful functions */

/**
 * Returns a single letter to describe the given picture type \p pict_type.
 *
 * @param[in] pict_type the picture type
 * @return A single character representing the picture type.
 */
char av_get_pict_type_char(int pict_type);

/**
 * Returns codec bits per sample.
 *
 * @param[in] codec_id the codec
 * @return Number of bits per sample or zero if unknown for the given codec.
 */
int av_get_bits_per_sample(enum CodecID codec_id);

/**
 * Returns sample format bits per sample.
 *
 * @param[in] sample_fmt the sample format
 * @return Number of bits per sample or zero if unknown for the given sample format.
 */
int av_get_bits_per_sample_format(enum SampleFormat sample_fmt);

/* frame parsing */
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

    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 FF_I_TYPE 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.
     *
     * 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;
} 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);

#if LIBAVCODEC_VERSION_MAJOR < 53
attribute_deprecated
int av_parser_parse(AVCodecParserContext *s,
                    AVCodecContext *avctx,
                    uint8_t **poutbuf, int *poutbuf_size,
                    const uint8_t *buf, int buf_size,
                    int64_t pts, int64_t dts);
#endif

/**
 * 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);

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);


typedef struct AVBitStreamFilterContext {
    void *priv_data;
    struct AVBitStreamFilter *filter;
    AVCodecParserContext *parser;
    struct AVBitStreamFilterContext *next;
} AVBitStreamFilterContext;


typedef struct AVBitStreamFilter {
    const char *name;
    int priv_data_size;
    int (*filter)(AVBitStreamFilterContext *bsfc,
                  AVCodecContext *avctx, const char *args,
                  uint8_t **poutbuf, int *poutbuf_size,
                  const uint8_t *buf, int buf_size, int keyframe);
    void (*close)(AVBitStreamFilterContext *bsfc);
    struct AVBitStreamFilter *next;
} AVBitStreamFilter;

void av_register_bitstream_filter(AVBitStreamFilter *bsf);
AVBitStreamFilterContext *av_bitstream_filter_init(const char *name);
int av_bitstream_filter_filter(AVBitStreamFilterContext *bsfc,
                               AVCodecContext *avctx, const char *args,
                               uint8_t **poutbuf, int *poutbuf_size,
                               const uint8_t *buf, int buf_size, int keyframe);
void av_bitstream_filter_close(AVBitStreamFilterContext *bsf);

AVBitStreamFilter *av_bitstream_filter_next(AVBitStreamFilter *f);

/* memory */

/**
 * Reallocates the given block if it is not large enough, otherwise it
 * does nothing.
 *
 * @see av_realloc
 */
void *av_fast_realloc(void *ptr, unsigned int *size, unsigned int min_size);

/**
 * Copy image 'src' to 'dst'.
 */
void av_picture_copy(AVPicture *dst, const AVPicture *src,
              int pix_fmt, int width, int height);

/**
 * Crop image top and left side.
 */
int av_picture_crop(AVPicture *dst, const AVPicture *src,
             int pix_fmt, int top_band, int left_band);

/**
 * Pad image.
 */
int av_picture_pad(AVPicture *dst, const AVPicture *src, int height, int width, int pix_fmt,
            int padtop, int padbottom, int padleft, int padright, int *color);

unsigned int av_xiphlacing(unsigned char *s, unsigned int v);

/**
 * Parses \p str and put in \p width_ptr and \p height_ptr the detected values.
 *
 * @return 0 in case of a successful parsing, a negative value otherwise
 * @param[in] str the string to parse: it has to be a string in the format
 * <width>x<height> or a valid video frame size abbreviation.
 * @param[in,out] width_ptr pointer to the variable which will contain the detected
 * frame width value
 * @param[in,out] height_ptr pointer to the variable which will contain the detected
 * frame height value
 */
int av_parse_video_frame_size(int *width_ptr, int *height_ptr, const char *str);

/**
 * Parses \p str and put in \p frame_rate the detected values.
 *
 * @return 0 in case of a successful parsing, a negative value otherwise
 * @param[in] str the string to parse: it has to be a string in the format
 * <frame_rate_num>/<frame_rate_den>, a float number or a valid video rate abbreviation
 * @param[in,out] frame_rate pointer to the AVRational which will contain the detected
 * frame rate
 */
int av_parse_video_frame_rate(AVRational *frame_rate, const char *str);

/* error handling */
#if EINVAL > 0
#define AVERROR(e) (-(e)) /**< Returns a negative error code from a POSIX error code, to return from library functions. */
#define AVUNERROR(e) (-(e)) /**< Returns a POSIX error code from a library function error return value. */
#else
/* Some platforms have E* and errno already negated. */
#define AVERROR(e) (e)
#define AVUNERROR(e) (e)
#endif
#define AVERROR_UNKNOWN     AVERROR(EINVAL)  /**< unknown error */
#define AVERROR_IO          AVERROR(EIO)     /**< I/O error */
#define AVERROR_NUMEXPECTED AVERROR(EDOM)    /**< Number syntax expected in filename. */
#define AVERROR_INVALIDDATA AVERROR(EINVAL)  /**< invalid data found */
#define AVERROR_NOMEM       AVERROR(ENOMEM)  /**< not enough memory */
#define AVERROR_NOFMT       AVERROR(EILSEQ)  /**< unknown format */
#define AVERROR_NOTSUPP     AVERROR(ENOSYS)  /**< Operation not supported. */
#define AVERROR_NOENT       AVERROR(ENOENT)  /**< No such file or directory. */
#define AVERROR_EOF         AVERROR(EPIPE)   /**< End of file. */
#define AVERROR_PATCHWELCOME    -MKTAG('P','A','W','E') /**< Not yet implemented in FFmpeg. Patches welcome. */

/**
 * Registers the hardware accelerator \p hwaccel.
 */
void av_register_hwaccel(AVHWAccel *hwaccel);

/**
 * If hwaccel is NULL, returns the first registered hardware accelerator,
 * if hwaccel is non-NULL, returns the next registered hardware accelerator
 * after hwaccel, or NULL if hwaccel is the last one.
 */
AVHWAccel *av_hwaccel_next(AVHWAccel *hwaccel);

#endif /* AVCODEC_AVCODEC_H */