gecko/media/liboggz/include/oggz/oggz_seek.h

/*
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   Organisation (CSIRO) Australia

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*/

#ifndef __OGGZ_SEEK_H__
#define __OGGZ_SEEK_H__

/** \file
 * Seeking within files
 */

/** \defgroup seek_api Oggz Seek API
 *
 * Oggz can seek on multitrack, multicodec bitstreams.
 *
 * \section seek_time Time seeking
 *
 * Support is built-in for seeking to time positions in
 * <a href="http://www.celt-codec.org/">CELT</a>,
 * <a href="http://www.annodex.net/">CMML</a>.
 * <a href="http://flac.sourceforge.net/">FLAC</a>,
 * <a href="http://wiki.xiph.org/OggPCM">OggPCM</a>,
 * <a href="http://www.speex.org/">Speex</a>,
 * <a href="http://www.theora.org/">Theora</a>
 * and <a href="http://www.vorbis.com/">Vorbis</a>.
 * Oggz is also compatible with 
 * <a href="http://www.annodex.net/">Annodex</a> streams, and supports seeking
 * on all tracks described in an
 * <a href="http://wiki.xiph.org/OggSkeleton">Ogg Skeleton</a> track.
 *
 * You need to open the file with the OGGZ_AUTO flag set:
 *
 * - Create an OGGZ handle for reading with \a flags = OGGZ_READ | OGGZ_AUTO
 * - Read data, ensuring that you have received all b_o_s pages before
 *   attempting to seek.
 *
 * Oggz will silently parse known codec headers and associate metrics
 * appropriately; if you attempt to seek before you have received all
 * b_o_s pages, Oggz will not have had a chance to parse the codec headers
 * and associate metrics.
 * It is safe to seek once you have received a packet with \a b_o_s == 0;
 * see the \link basics Ogg basics \endlink section for more details.
 *
 * \note Oggz parses these codec headers internally, and so liboggz is \b not
 * linked to libspeex, libvorbis, libflac, libtheora, libcmml or libannodex.
 *
 * For other data streams, you will need to provide a metric function;
 * see the section on \link metric Using OggzMetrics \endlink for details
 * of setting up and seeking with metrics.
 *
 * \section seek_bytes Byte seeking
 *
 * oggz_seek() provides low-level seeking to byte positions.
 *
 * \section seek_info More detail
 *
 * For a full description of the seeking methods possible in Ogg, see
 * \link seek_semantics Semantics of seeking in Ogg bitstreams \endlink.
 *
 * \{
 */

/**
 * Query the current offset in milliseconds, or custom units as
 * specified by a Metric function you have provided.
 * \param oggz An OGGZ handle
 * \returns the offset in milliseconds, or custom units
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 * \retval OGGZ_ERR_INVALID Operation not suitable for this OGGZ
 */
ogg_int64_t oggz_tell_units (OGGZ * oggz);

/**
 * Seek to an offset in milliseconds, or custom units as specified
 * by a Metric function you have provided.
 * \param oggz An OGGZ handle
 * \param units A number of milliseconds, or custom units
 * \param whence As defined in <stdio.h>: SEEK_SET, SEEK_CUR or SEEK_END
 * \returns the new file offset, or -1 on failure.
 */
ogg_int64_t oggz_seek_units (OGGZ * oggz, ogg_int64_t units, int whence);

/**
 * Provide the exact stored granulepos (from the page header) if relevant to
 * the current packet, or a constructed granulepos if the stored granulepos
 * does not belong to this packet, or -1 if this codec does not have support
 * for granulepos interpolation
 * \param oggz An OGGZ handle
 * \returns the granulepos of the \a current packet (if available)
 */
ogg_int64_t
oggz_tell_granulepos (OGGZ * oggz);

/**
 * Query the file offset in bytes corresponding to the data read.
 * \param oggz An OGGZ handle
 * \returns The current offset of oggz.
 *
 * \note When reading, the value returned by oggz_tell() reflects the
 * data offset of the start of the most recent packet processed, so that
 * when called from an OggzReadPacket callback it reflects the byte
 * offset of the start of the packet. As Oggz may have internally read
 * ahead, this may differ from the current offset of the associated file
 * descriptor.
 */
oggz_off_t oggz_tell (OGGZ * oggz);

/**
 * Seek to a specific byte offset
 * \param oggz An OGGZ handle
 * \param offset a byte offset
 * \param whence As defined in <stdio.h>: SEEK_SET, SEEK_CUR or SEEK_END
 * \returns the new file offset, or -1 on failure.
 */
oggz_off_t oggz_seek (OGGZ * oggz, oggz_off_t offset, int whence);

#ifdef _UNIMPLEMENTED
long oggz_seek_packets (OGGZ * oggz, long serialno, long packets, int whence);
#endif

/** \}
 */

/** \defgroup seek_semantics Semantics of seeking in Ogg bitstreams
 *
 * \section seek_semantics_intro Introduction
 *
 *         [*** This line works around a bug in doxygen ***]
 *
 *         [*** This line works around a bug in doxygen ***]
 *
 * The seeking semantics of the Ogg file format were outlined by Monty in
 * <a href="http://web.archive.org/web/20031201054855/http://www.xiph.org/archives/theora-dev/200209/0040.html"> a 
 * post to theora-dev</a> in September 2002. Quoting from that post, we
 * have the following assumptions:
 *
 * - Ogg is not a non-linear format. ... It is a media transport format
 *   designed to do nothing more than deliver content, in a stream, and
 *   have all the pieces arrive on time and in sync.
 * - The Ogg layer does not know the specifics of the codec data it's
 *   multiplexing into a stream. It knows nothing beyond 'Oooo, packets!',
 *   that the packets belong to different buckets, that the packets go in
 *   order, and that packets have position markers. Ogg does not even have
 *   a concept of 'time'; it only knows about the sequentially increasing,
 *   unitless position markers. It is up to higher layers which have
 *   access to the codec APIs to assign and convert units of framing or
 *   time.
 *
 * (For more details on the structure of Ogg streams, see the
 * \link basics Ogg Basics \endlink section).
 *
 * For data such as media, for which it is possible to provide a mapping
 * such as 'time', Oggz can efficiently navigate through an Ogg stream
 * by use of an OggzMetric callback, thus allowing automatic seeking to
 * points in 'time'.
 *
 * For common codecs you can ask Oggz to set this for you automatically by
 * instantiating the OGGZ handle with the OGGZ_AUTO flag set. For others
 * you can specify a multiplier with oggz_set_metric_linear(), or a generic
 * non-linear metric with oggz_set_metric().
 *
 */

/** \defgroup metric Using OggzMetric
 *
 * \section metric_intro Introduction
 *
 * An OggzMetric is a helper function for Oggz's seeking mechanism.
 *
 * If every position in an Ogg stream can be described by a metric such as
 * time, then it is possible to define a function that, given a serialno and
 * granulepos, returns a measurement in units such as milliseconds. Oggz
 * will use this function repeatedly while seeking in order to navigate
 * through the Ogg stream.
 *
 * The meaning of the units is arbitrary, but must be consistent across all
 * logical bitstreams. This allows Oggz to seek accurately through Ogg
 * bitstreams containing multiple logical bitstreams such as tracks of media.
 *
 * \section setting How to set metrics
 *
 * You don't need to set metrics for Speex, Vorbis, FLAC, Theora, CMML or
 * Annodex.
 * These can be handled \link seek_api automatically \endlink by Oggz.
 *
 * For most others it is simply a matter of providing a "granulerate":
 * a frame or sampling rate, if each packet's granulepos represents a
 * sample number.
 *
 * - Set the \a granule_rate_numerator and \a granule_rate_denominator
 *   appropriately using oggz_set_granulerate()
 *
 * Some codecs use a "granuleshift" to divide a granulepos into two halves;
 * the first describing a dependency on a previous packet, the second
 * giving the offset since that packet. This is used to mark keyframes and
 * intermediate frames.
 *
 * - Set the \a granuleshift appropriately using oggz_set_granuleshift()
 *
 * \subsection custom Custom Metrics
 *
 * For streams with non-linear granulepos, you need to set a custom metric:
 *
 * - Implement an OggzMetric callback
 * - Set the OggzMetric callback using oggz_set_metric()
 *
 * \section using Seeking with OggzMetrics
 *
 * To seek, use oggz_seek_units(). Oggz will perform a ratio search
 * through the Ogg bitstream, using the OggzMetric callback to determine
 * its position relative to the desired unit.
 *
 * \note
 *
 * Many data streams begin with headers describing such things as codec
 * setup parameters. One of the assumptions Monty makes is:
 *
 * - Given pre-cached decode headers, a player may seek into a stream at
 *   any point and begin decode.
 *
 * Thus, the first action taken by applications dealing with such data is
 * to read in and cache the decode headers; thereafter the application can
 * safely seek to arbitrary points in the data.
 *
 * This impacts seeking because the portion of the bitstream containing
 * decode headers should not be considered part of the metric space. To
 * inform Oggz not to seek earlier than the end of the decode headers,
 * use oggz_set_data_start().
 *
 * \{
 */

/**
 * Retrieve the preroll of a logical bitstream.
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz
 * \returns The preroll of the specified logical bitstream.
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 * logical bitstream in \a oggz.
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 */
int oggz_get_preroll (OGGZ * oggz, long serialno);

/**
 * Specify the preroll of a logical bitstream.
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz to attach
 * this preroll to.
 * \param preroll The preroll
 * \returns 0 Success
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 * logical bitstream in \a oggz.
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 */
int oggz_set_preroll (OGGZ * oggz, long serialno, int preroll);

/**
 * Retrieve the granuleshift of a logical bitstream.
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz
 * \returns The granuleshift of the specified logical bitstream.
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 * logical bitstream in \a oggz.
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 */
int oggz_get_granuleshift (OGGZ * oggz, long serialno);

/**
 * Specify the granuleshift of a logical bitstream.
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz to attach
 * this granuleshift metric to. A value of -1 indicates that the metric should
 * be attached to all unattached logical bitstreams in \a oggz.
 * \param granuleshift The granuleshift
 * \returns 0 Success
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 * logical bitstream in \a oggz.
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 */
int oggz_set_granuleshift (OGGZ * oggz, long serialno, int granuleshift);

/**
 * Retrieve the granulerate of a logical bitstream.
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz
 * \param granulerate_n Return location for the granulerate numerator
 * \param granulerate_d Return location for the granulerate denominator
 * \returns 0 Success
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 * logical bitstream in \a oggz.
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 *
 */
int oggz_get_granulerate (OGGZ * oggz, long serialno,
			  ogg_int64_t * granulerate_n,
			  ogg_int64_t * granulerate_d);

/**
 * Specify the granulerate of a logical bitstream.
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz to attach
 * this linear metric to. A value of -1 indicates that the metric should
 * be attached to all unattached logical bitstreams in \a oggz.
 * \param granule_rate_numerator The numerator of the granule rate
 * \param granule_rate_denominator The denominator of the granule rate
 * \returns 0 Success
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 * logical bitstream in \a oggz.
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 */
int oggz_set_granulerate (OGGZ * oggz, long serialno,
			  ogg_int64_t granule_rate_numerator,
			  ogg_int64_t granule_rate_denominator);

/**
 * This is the signature of a function to correlate Ogg streams.
 * If every position in an Ogg stream can be described by a metric (eg. time)
 * then define this function that returns some arbitrary unit value.
 * This is the normal use of Oggz for media streams. The meaning of units is
 * arbitrary, but must be consistent across all logical bitstreams; for
 * example a conversion of the time offset of a given packet into nanoseconds
 * or a similar stream-specific subdivision may be appropriate.
 *
 * \param oggz An OGGZ handle
 * \param serialno Identifies a logical bitstream within \a oggz
 * \param granulepos A granulepos within the logical bitstream identified
 *                   by \a serialno
 * \param user_data Arbitrary data you wish to pass to your callback
 * \returns A conversion of the (serialno, granulepos) pair into a measure
 * in units which is consistent across all logical bitstreams within \a oggz
 */
typedef ogg_int64_t (*OggzMetric) (OGGZ * oggz, long serialno,
				   ogg_int64_t granulepos, void * user_data);

/**
 * Set the OggzMetric to use for an OGGZ handle
 *
 * \param oggz An OGGZ handle
 * \param serialno Identify the logical bitstream in \a oggz to attach
 *                 this metric to. A value of -1 indicates that this metric
 *                 should be attached to all unattached logical bitstreams
 *                 in \a oggz.
 * \param metric An OggzMetric callback
 * \param user_data arbitrary data to pass to the metric callback
 *
 * \returns 0 Success
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 *                               logical bitstream in \a oggz, and is not -1
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 *
 * \note Specifying values of \a serialno other than -1 allows you to pass
 *       logical bitstream specific user_data to the same metric.
 * \note Alternatively, you may use a different \a metric for each
 *       \a serialno, but all metrics used must return mutually consistent
 *       unit measurements.
 */
int oggz_set_metric (OGGZ * oggz, long serialno, OggzMetric metric,
		     void * user_data);

#ifdef _UNIMPLEMENTED
/** \defgroup order OggzOrder
 *
 * - A mechanism to aid seeking across non-metric spaces for which a partial
 *   order exists (ie. data that is not synchronised by a measure such as time,
 *   but is nevertheless somehow seekably structured), is also planned.
 *
 * \subsection OggzOrder
 *
 * Suppose there is a partial order < and a corresponding equivalence
 * relation = defined on the space of packets in the Ogg stream of 'OGGZ'.
 * An OggzOrder simply provides a comparison in terms of '<' and '=' for
 * ogg_packets against a target.
 *
 * To use OggzOrder:
 *
 * - Implement an OggzOrder callback
 * - Set the OggzOrder callback for an OGGZ handle with oggz_set_order()
 * - To seek, use oggz_seek_byorder(). Oggz will use a combination bisection
 *   search and scan of the Ogg bitstream, using the OggzOrder callback to
 *   match against the desired 'target'.
 *
 * Otherwise, for more general ogg streams for which a partial order can be
 * defined, define a function matching this specification.
 *
 * Parameters:
 *
 *     OGGZ: the OGGZ object
 *     op:  an ogg packet in the stream
 *     target: a user defined object
 *
 * Return values:
 *
 *    -1 , if 'op' would occur before the position represented by 'target'
 *     0 , if the position of 'op' is equivalent to that of 'target'
 *     1 , if 'op' would occur after the position represented by 'target'
 *     2 , if the relationship between 'op' and 'target' is undefined.
 *
 * Symbolically:
 *
 * Suppose there is a partial order < and a corresponding equivalence
 * relation = defined on the space of packets in the Ogg stream of 'OGGZ'.
 * Let p represent the position of the packet 'op', and t be the position
 * represented by 'target'.
 *
 * Then a function implementing OggzPacketOrder should return as follows:
 *
 *    -1 , p < t
 *     0 , p = t
 *     1 , t < p
 *     2 , otherwise
 *
 * Hacker's hint: if there are no circumstances in which you would return
 * a value of 2, there is a linear order; it may be possible to define a
 * Metric rather than an Order.
 *
 */
typedef int (*OggzOrder) (OGGZ * oggz, ogg_packet * op, void * target,
			 void * user_data);
/**
 * \retval 0 Success
 * \retval OGGZ_ERR_BAD_OGGZ \a oggz does not refer to an existing OGGZ
 * \retval OGGZ_ERR_INVALID Operation not suitable for this OGGZ
 * \retval OGGZ_ERR_BAD_SERIALNO \a serialno does not identify an existing
 *                               logical bitstream in \a oggz, and is not -1
 */
int oggz_set_order (OGGZ * oggz, long serialno, OggzOrder order,
		    void * user_data);

long oggz_seek_byorder (OGGZ * oggz, void * target);

#endif /* _UNIMPLEMENTED */

/**
 * Tell Oggz to remember the given offset as the start of data.
 * This informs the seeking mechanism that when seeking back to unit 0,
 * go to the given offset, not to the start of the file, which is usually
 * codec headers.
 * The usual usage is:
<pre>
    oggz_set_data_start (oggz, oggz_tell (oggz));
</pre>
 * \param oggz An OGGZ handle previously opened for reading
 * \param offset The offset of the start of data
 * \returns 0 on success, -1 on failure.
 */
int oggz_set_data_start (OGGZ * oggz, oggz_off_t offset);
/** \}
 */

#endif /* __OGGZ_SEEK_H__ */