toxcore/toxav/toxav.h

739 lines
25 KiB
C

/* toxav.h
*
* Copyright (C) 2013-2015 Tox project All Rights Reserved.
*
* This file is part of Tox.
*
* Tox is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Tox is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Tox. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef TOXAV_H
#define TOXAV_H
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif
/** \page av Public audio/video API for Tox clients.
*
* This API can handle multiple calls. Each call has its state, in very rare
* occasions the library can change the state of the call without apps knowledge.
*
*/
/** \subsection events Events and callbacks
*
* As in Core API, events are handled by callbacks. One callback can be
* registered per event. All events have a callback function type named
* `toxav_{event}_cb` and a function to register it named `toxav_callback_{event}`.
* Passing a NULL callback will result in no callback being registered for that
* event. Only one callback per event can be registered, so if a client needs
* multiple event listeners, it needs to implement the dispatch functionality
* itself. Unlike Core API, lack of some event handlers will cause the the
* library to drop calls before they are started. Hanging up call from a
* callback causes undefined behaviour.
*
*/
/** \subsection threading Threading implications
*
* Unlike the Core API, this API is fully thread-safe. The library will ensure
* the proper synchronization of parallel calls.
*
* A common way to run ToxAV (multiple or single instance) is to have a thread,
* separate from tox instance thread, running a simple toxav_iterate loop,
* sleeping for toxav_iteration_interval * milliseconds on each iteration.
*
* An important thing to note is that events are triggered from both tox and
* toxav thread (see above). Audio and video receive frame events are triggered
* from toxav thread while all the other events are triggered from tox thread.
*
* Tox thread has priority with mutex mechanisms. Any api function can
* fail if mutexes are held by tox thread in which case they will set SYNC
* error code.
*/
/**
* External Tox type.
*/
#ifndef TOX_DEFINED
#define TOX_DEFINED
typedef struct Tox Tox;
#endif /* TOX_DEFINED */
/**
* ToxAV.
*/
/**
* The ToxAV instance type. Each ToxAV instance can be bound to only one Tox
* instance, and Tox instance can have only one ToxAV instance. One must make
* sure to close ToxAV instance prior closing Tox instance otherwise undefined
* behaviour occurs. Upon closing of ToxAV instance, all active calls will be
* forcibly terminated without notifying peers.
*
*/
#ifndef TOXAV_DEFINED
#define TOXAV_DEFINED
typedef struct ToxAV ToxAV;
#endif /* TOXAV_DEFINED */
/*******************************************************************************
*
* :: API version
*
******************************************************************************/
/**
* The major version number. Incremented when the API or ABI changes in an
* incompatible way.
*/
#define TOXAV_VERSION_MAJOR 0u
/**
* The minor version number. Incremented when functionality is added without
* breaking the API or ABI. Set to 0 when the major version number is
* incremented.
*/
#define TOXAV_VERSION_MINOR 0u
/**
* The patch or revision number. Incremented when bugfixes are applied without
* changing any functionality or API or ABI.
*/
#define TOXAV_VERSION_PATCH 0u
/**
* A macro to check at preprocessing time whether the client code is compatible
* with the installed version of ToxAV.
*/
#define TOXAV_VERSION_IS_API_COMPATIBLE(MAJOR, MINOR, PATCH) \
(TOXAV_VERSION_MAJOR == MAJOR && \
(TOXAV_VERSION_MINOR > MINOR || \
(TOXAV_VERSION_MINOR == MINOR && \
TOXAV_VERSION_PATCH >= PATCH)))
/**
* A macro to make compilation fail if the client code is not compatible with
* the installed version of ToxAV.
*/
#define TOXAV_VERSION_REQUIRE(MAJOR, MINOR, PATCH) \
typedef char toxav_required_version[TOXAV_IS_COMPATIBLE(MAJOR, MINOR, PATCH) ? 1 : -1]
/**
* A convenience macro to call toxav_version_is_compatible with the currently
* compiling API version.
*/
#define TOXAV_VERSION_IS_ABI_COMPATIBLE() \
toxav_version_is_compatible(TOXAV_VERSION_MAJOR, TOXAV_VERSION_MINOR, TOXAV_VERSION_PATCH)
/**
* Return the major version number of the library. Can be used to display the
* ToxAV library version or to check whether the client is compatible with the
* dynamically linked version of ToxAV.
*/
uint32_t toxav_version_major(void);
/**
* Return the minor version number of the library.
*/
uint32_t toxav_version_minor(void);
/**
* Return the patch number of the library.
*/
uint32_t toxav_version_patch(void);
/**
* Return whether the compiled library version is compatible with the passed
* version numbers.
*/
bool toxav_version_is_compatible(uint32_t major, uint32_t minor, uint32_t patch);
/*******************************************************************************
*
* :: Creation and destruction
*
******************************************************************************/
typedef enum TOXAV_ERR_NEW {
/**
* The function returned successfully.
*/
TOXAV_ERR_NEW_OK,
/**
* One of the arguments to the function was NULL when it was not expected.
*/
TOXAV_ERR_NEW_NULL,
/**
* Memory allocation failure while trying to allocate structures required for
* the A/V session.
*/
TOXAV_ERR_NEW_MALLOC,
/**
* Attempted to create a second session for the same Tox instance.
*/
TOXAV_ERR_NEW_MULTIPLE,
} TOXAV_ERR_NEW;
/**
* Start new A/V session. There can only be only one session per Tox instance.
*/
ToxAV *toxav_new(Tox *tox, TOXAV_ERR_NEW *error);
/**
* Releases all resources associated with the A/V session.
*
* If any calls were ongoing, these will be forcibly terminated without
* notifying peers. After calling this function, no other functions may be
* called and the av pointer becomes invalid.
*/
void toxav_kill(ToxAV *toxAV);
/**
* Returns the Tox instance the A/V object was created for.
*/
Tox *toxav_get_tox(const ToxAV *toxAV);
/*******************************************************************************
*
* :: A/V event loop
*
******************************************************************************/
/**
* Returns the interval in milliseconds when the next toxav_iterate call should
* be. If no call is active at the moment, this function returns 200.
*/
uint32_t toxav_iteration_interval(const ToxAV *toxAV);
/**
* Main loop for the session. This function needs to be called in intervals of
* toxav_iteration_interval() milliseconds. It is best called in the separate
* thread from tox_iterate.
*/
void toxav_iterate(ToxAV *toxAV);
/*******************************************************************************
*
* :: Call setup
*
******************************************************************************/
typedef enum TOXAV_ERR_CALL {
/**
* The function returned successfully.
*/
TOXAV_ERR_CALL_OK,
/**
* A resource allocation error occurred while trying to create the structures
* required for the call.
*/
TOXAV_ERR_CALL_MALLOC,
/**
* Synchronization error occurred.
*/
TOXAV_ERR_CALL_SYNC,
/**
* The friend number did not designate a valid friend.
*/
TOXAV_ERR_CALL_FRIEND_NOT_FOUND,
/**
* The friend was valid, but not currently connected.
*/
TOXAV_ERR_CALL_FRIEND_NOT_CONNECTED,
/**
* Attempted to call a friend while already in an audio or video call with
* them.
*/
TOXAV_ERR_CALL_FRIEND_ALREADY_IN_CALL,
/**
* Audio or video bit rate is invalid.
*/
TOXAV_ERR_CALL_INVALID_BIT_RATE,
} TOXAV_ERR_CALL;
/**
* Call a friend. This will start ringing the friend.
*
* It is the client's responsibility to stop ringing after a certain timeout,
* if such behaviour is desired. If the client does not stop ringing, the
* library will not stop until the friend is disconnected. Audio and video
* receiving are both enabled by default.
*
* @param friend_number The friend number of the friend that should be called.
* @param audio_bit_rate Audio bit rate in Kb/sec. Set this to 0 to disable
* audio sending.
* @param video_bit_rate Video bit rate in Kb/sec. Set this to 0 to disable
* video sending.
*/
bool toxav_call(ToxAV *toxAV, uint32_t friend_number, uint32_t audio_bit_rate,
uint32_t video_bit_rate, TOXAV_ERR_CALL *error);
/**
* The function type for the call callback.
*
* @param friend_number The friend number from which the call is incoming.
* @param audio_enabled True if friend is sending audio.
* @param video_enabled True if friend is sending video.
*/
typedef void toxav_call_cb(ToxAV *toxAV, uint32_t friend_number, bool audio_enabled,
bool video_enabled, void *user_data);
/**
* Set the callback for the `call` event. Pass NULL to unset.
*
*/
void toxav_callback_call(ToxAV *toxAV, toxav_call_cb *callback, void *user_data);
typedef enum TOXAV_ERR_ANSWER {
/**
* The function returned successfully.
*/
TOXAV_ERR_ANSWER_OK,
/**
* Synchronization error occurred.
*/
TOXAV_ERR_ANSWER_SYNC,
/**
* Failed to initialize codecs for call session. Note that codec initiation
* will fail if there is no receive callback registered for either audio or
* video.
*/
TOXAV_ERR_ANSWER_CODEC_INITIALIZATION,
/**
* The friend number did not designate a valid friend.
*/
TOXAV_ERR_ANSWER_FRIEND_NOT_FOUND,
/**
* The friend was valid, but they are not currently trying to initiate a call.
* This is also returned if this client is already in a call with the friend.
*/
TOXAV_ERR_ANSWER_FRIEND_NOT_CALLING,
/**
* Audio or video bit rate is invalid.
*/
TOXAV_ERR_ANSWER_INVALID_BIT_RATE,
} TOXAV_ERR_ANSWER;
/**
* Accept an incoming call.
*
* If answering fails for any reason, the call will still be pending and it is
* possible to try and answer it later. Audio and video receiving are both
* enabled by default.
*
* @param friend_number The friend number of the friend that is calling.
* @param audio_bit_rate Audio bit rate in Kb/sec. Set this to 0 to disable
* audio sending.
* @param video_bit_rate Video bit rate in Kb/sec. Set this to 0 to disable
* video sending.
*/
bool toxav_answer(ToxAV *toxAV, uint32_t friend_number, uint32_t audio_bit_rate, uint32_t video_bit_rate, TOXAV_ERR_ANSWER *error);
/*******************************************************************************
*
* :: Call state graph
*
******************************************************************************/
enum TOXAV_FRIEND_CALL_STATE {
/**
* Set by the AV core if an error occurred on the remote end or if friend
* timed out. This is the final state after which no more state
* transitions can occur for the call. This call state will never be triggered
* in combination with other call states.
*/
TOXAV_FRIEND_CALL_STATE_ERROR = 1,
/**
* The call has finished. This is the final state after which no more state
* transitions can occur for the call. This call state will never be
* triggered in combination with other call states.
*/
TOXAV_FRIEND_CALL_STATE_FINISHED = 2,
/**
* The flag that marks that friend is sending audio.
*/
TOXAV_FRIEND_CALL_STATE_SENDING_A = 4,
/**
* The flag that marks that friend is sending video.
*/
TOXAV_FRIEND_CALL_STATE_SENDING_V = 8,
/**
* The flag that marks that friend is receiving audio.
*/
TOXAV_FRIEND_CALL_STATE_ACCEPTING_A = 16,
/**
* The flag that marks that friend is receiving video.
*/
TOXAV_FRIEND_CALL_STATE_ACCEPTING_V = 32,
};
/**
* The function type for the call_state callback.
*
* @param friend_number The friend number for which the call state changed.
* @param state The bitmask of the new call state which is guaranteed to be
* different than the previous state. The state is set to 0 when the call is
* paused. The bitmask represents all the activities currently performed by the
* friend.
*/
typedef void toxav_call_state_cb(ToxAV *toxAV, uint32_t friend_number, uint32_t state, void *user_data);
/**
* Set the callback for the `call_state` event. Pass NULL to unset.
*
*/
void toxav_callback_call_state(ToxAV *toxAV, toxav_call_state_cb *callback, void *user_data);
/*******************************************************************************
*
* :: Call control
*
******************************************************************************/
typedef enum TOXAV_CALL_CONTROL {
/**
* Resume a previously paused call. Only valid if the pause was caused by this
* client, if not, this control is ignored. Not valid before the call is accepted.
*/
TOXAV_CALL_CONTROL_RESUME,
/**
* Put a call on hold. Not valid before the call is accepted.
*/
TOXAV_CALL_CONTROL_PAUSE,
/**
* Reject a call if it was not answered, yet. Cancel a call after it was
* answered.
*/
TOXAV_CALL_CONTROL_CANCEL,
/**
* Request that the friend stops sending audio. Regardless of the friend's
* compliance, this will cause the audio_receive_frame event to stop being
* triggered on receiving an audio frame from the friend.
*/
TOXAV_CALL_CONTROL_MUTE_AUDIO,
/**
* Calling this control will notify client to start sending audio again.
*/
TOXAV_CALL_CONTROL_UNMUTE_AUDIO,
/**
* Request that the friend stops sending video. Regardless of the friend's
* compliance, this will cause the video_receive_frame event to stop being
* triggered on receiving a video frame from the friend.
*/
TOXAV_CALL_CONTROL_HIDE_VIDEO,
/**
* Calling this control will notify client to start sending video again.
*/
TOXAV_CALL_CONTROL_SHOW_VIDEO,
} TOXAV_CALL_CONTROL;
typedef enum TOXAV_ERR_CALL_CONTROL {
/**
* The function returned successfully.
*/
TOXAV_ERR_CALL_CONTROL_OK,
/**
* Synchronization error occurred.
*/
TOXAV_ERR_CALL_CONTROL_SYNC,
/**
* The friend_number passed did not designate a valid friend.
*/
TOXAV_ERR_CALL_CONTROL_FRIEND_NOT_FOUND,
/**
* This client is currently not in a call with the friend. Before the call is
* answered, only CANCEL is a valid control.
*/
TOXAV_ERR_CALL_CONTROL_FRIEND_NOT_IN_CALL,
/**
* Happens if user tried to pause an already paused call or if trying to
* resume a call that is not paused.
*/
TOXAV_ERR_CALL_CONTROL_INVALID_TRANSITION,
} TOXAV_ERR_CALL_CONTROL;
/**
* Sends a call control command to a friend.
*
* @param friend_number The friend number of the friend this client is in a call
* with.
* @param control The control command to send.
*
* @return true on success.
*/
bool toxav_call_control(ToxAV *toxAV, uint32_t friend_number, TOXAV_CALL_CONTROL control, TOXAV_ERR_CALL_CONTROL *error);
/*******************************************************************************
*
* :: Controlling bit rates
*
******************************************************************************/
typedef enum TOXAV_ERR_BIT_RATE_SET {
/**
* The function returned successfully.
*/
TOXAV_ERR_BIT_RATE_SET_OK,
/**
* Synchronization error occurred.
*/
TOXAV_ERR_BIT_RATE_SET_SYNC,
/**
* The audio bit rate passed was not one of the supported values.
*/
TOXAV_ERR_BIT_RATE_SET_INVALID_AUDIO_BIT_RATE,
/**
* The video bit rate passed was not one of the supported values.
*/
TOXAV_ERR_BIT_RATE_SET_INVALID_VIDEO_BIT_RATE,
/**
* The friend_number passed did not designate a valid friend.
*/
TOXAV_ERR_BIT_RATE_SET_FRIEND_NOT_FOUND,
/**
* This client is currently not in a call with the friend.
*/
TOXAV_ERR_BIT_RATE_SET_FRIEND_NOT_IN_CALL,
} TOXAV_ERR_BIT_RATE_SET;
/**
* Set the bit rate to be used in subsequent audio/video frames.
*
* @param friend_number The friend number of the friend for which to set the
* bit rate.
* @param audio_bit_rate The new audio bit rate in Kb/sec. Set to 0 to disable
* audio sending. Set to -1 to leave unchanged.
* @param video_bit_rate The new video bit rate in Kb/sec. Set to 0 to disable
* video sending. Set to -1 to leave unchanged.
*
*/
bool toxav_bit_rate_set(ToxAV *toxAV, uint32_t friend_number, int32_t audio_bit_rate,
int32_t video_bit_rate, TOXAV_ERR_BIT_RATE_SET *error);
/**
* The function type for the bit_rate_status callback. The event is triggered
* when the network becomes too saturated for current bit rates at which
* point core suggests new bit rates.
*
* @param friend_number The friend number of the friend for which to set the
* bit rate.
* @param audio_bit_rate Suggested maximum audio bit rate in Kb/sec.
* @param video_bit_rate Suggested maximum video bit rate in Kb/sec.
*/
typedef void toxav_bit_rate_status_cb(ToxAV *toxAV, uint32_t friend_number, uint32_t audio_bit_rate, uint32_t video_bit_rate, void *user_data);
/**
* Set the callback for the `bit_rate_status` event. Pass NULL to unset.
*
*/
void toxav_callback_bit_rate_status(ToxAV *toxAV, toxav_bit_rate_status_cb *callback, void *user_data);
/*******************************************************************************
*
* :: A/V sending
*
******************************************************************************/
typedef enum TOXAV_ERR_SEND_FRAME {
/**
* The function returned successfully.
*/
TOXAV_ERR_SEND_FRAME_OK,
/**
* In case of video, one of Y, U, or V was NULL. In case of audio, the samples
* data pointer was NULL.
*/
TOXAV_ERR_SEND_FRAME_NULL,
/**
* The friend_number passed did not designate a valid friend.
*/
TOXAV_ERR_SEND_FRAME_FRIEND_NOT_FOUND,
/**
* This client is currently not in a call with the friend.
*/
TOXAV_ERR_SEND_FRAME_FRIEND_NOT_IN_CALL,
/**
* Synchronization error occurred.
*/
TOXAV_ERR_SEND_FRAME_SYNC,
/**
* One of the frame parameters was invalid. E.g. the resolution may be too
* small or too large, or the audio sampling rate may be unsupported.
*/
TOXAV_ERR_SEND_FRAME_INVALID,
/**
* Either friend turned off audio or video receiving or we turned off sending
* for the said payload.
*/
TOXAV_ERR_SEND_FRAME_PAYLOAD_TYPE_DISABLED,
/**
* Failed to push frame through rtp interface.
*/
TOXAV_ERR_SEND_FRAME_RTP_FAILED,
} TOXAV_ERR_SEND_FRAME;
/**
* Send an audio frame to a friend.
*
* The expected format of the PCM data is: [s1c1][s1c2][...][s2c1][s2c2][...]...
* Meaning: sample 1 for channel 1, sample 1 for channel 2, ...
* For mono audio, this has no meaning, every sample is subsequent. For stereo,
* this means the expected format is LRLRLR... with samples for left and right
* alternating.
*
* @param friend_number The friend number of the friend to which to send an
* audio frame.
* @param pcm An array of audio samples. The size of this array must be
* sample_count * channels.
* @param sample_count Number of samples in this frame. Valid numbers here are
* ((sample rate) * (audio length) / 1000), where audio length can be
* 2.5, 5, 10, 20, 40 or 60 millseconds.
* @param channels Number of audio channels. Supported values are 1 and 2.
* @param sampling_rate Audio sampling rate used in this frame. Valid sampling
* rates are 8000, 12000, 16000, 24000, or 48000.
*/
bool toxav_audio_send_frame(ToxAV *toxAV, uint32_t friend_number, const int16_t *pcm,
size_t sample_count, uint8_t channels, uint32_t sampling_rate,
TOXAV_ERR_SEND_FRAME *error);
/**
* Send a video frame to a friend.
*
* Y - plane should be of size: height * width
* U - plane should be of size: (height/2) * (width/2)
* V - plane should be of size: (height/2) * (width/2)
*
* @param friend_number The friend number of the friend to which to send a video
* frame.
* @param width Width of the frame in pixels.
* @param height Height of the frame in pixels.
* @param y Y (Luminance) plane data.
* @param u U (Chroma) plane data.
* @param v V (Chroma) plane data.
*/
bool toxav_video_send_frame(ToxAV *toxAV, uint32_t friend_number, uint16_t width,
uint16_t height, const uint8_t *y, const uint8_t *u, const uint8_t *v,
TOXAV_ERR_SEND_FRAME *error);
/*******************************************************************************
*
* :: A/V receiving
*
******************************************************************************/
/**
* The function type for the audio_receive_frame callback. The callback can be
* called multiple times per single iteration depending on the amount of queued
* frames in the buffer. The received format is the same as in send function.
*
* @param friend_number The friend number of the friend who sent an audio frame.
* @param pcm An array of audio samples (sample_count * channels elements).
* @param sample_count The number of audio samples per channel in the PCM array.
* @param channels Number of audio channels.
* @param sampling_rate Sampling rate used in this frame.
*
*/
typedef void toxav_audio_receive_frame_cb(ToxAV *toxAV, uint32_t friend_number, const int16_t *pcm,
size_t sample_count, uint8_t channels, uint32_t sampling_rate,
void *user_data);
/**
* Set the callback for the `audio_receive_frame` event. Pass NULL to unset.
*
*/
void toxav_callback_audio_receive_frame(ToxAV *toxAV, toxav_audio_receive_frame_cb *callback, void *user_data);
/**
* The function type for the video_receive_frame callback.
*
* @param friend_number The friend number of the friend who sent a video frame.
* @param width Width of the frame in pixels.
* @param height Height of the frame in pixels.
* @param y
* @param u
* @param v Plane data.
* The size of plane data is derived from width and height where
* Y = MAX(width, abs(ystride)) * height,
* U = MAX(width/2, abs(ustride)) * (height/2) and
* V = MAX(width/2, abs(vstride)) * (height/2).
* @param ystride
* @param ustride
* @param vstride Strides data. Strides represent padding for each plane
* that may or may not be present. You must handle strides in
* your image processing code. Strides are negative if the
* image is bottom-up hence why you MUST abs() it when
* calculating plane buffer size.
*/
typedef void toxav_video_receive_frame_cb(ToxAV *toxAV, uint32_t friend_number, uint16_t width,
uint16_t height, const uint8_t *y, const uint8_t *u, const uint8_t *v,
int32_t ystride, int32_t ustride, int32_t vstride, void *user_data);
/**
* Set the callback for the `video_receive_frame` event. Pass NULL to unset.
*
*/
void toxav_callback_video_receive_frame(ToxAV *toxAV, toxav_video_receive_frame_cb *callback, void *user_data);
/**
* NOTE Compatibility with old toxav group calls TODO remove
*/
/* Create a new toxav group.
*
* return group number on success.
* return -1 on failure.
*
* Audio data callback format:
* audio_callback(Tox *tox, int groupnumber, int peernumber, const int16_t *pcm, unsigned int samples, uint8_t channels, unsigned int sample_rate, void *userdata)
*
* Note that total size of pcm in bytes is equal to (samples * channels * sizeof(int16_t)).
*/
int toxav_add_av_groupchat(Tox *tox, void (*audio_callback)(void*, int, int, const int16_t *, unsigned int, uint8_t,
unsigned int, void *), void *userdata);
/* Join a AV group (you need to have been invited first.)
*
* returns group number on success
* returns -1 on failure.
*
* Audio data callback format (same as the one for toxav_add_av_groupchat()):
* audio_callback(Tox *tox, int groupnumber, int peernumber, const int16_t *pcm, unsigned int samples, uint8_t channels, unsigned int sample_rate, void *userdata)
*
* Note that total size of pcm in bytes is equal to (samples * channels * sizeof(int16_t)).
*/
int toxav_join_av_groupchat(Tox *tox, int32_t friendnumber, const uint8_t *data, uint16_t length,
void (*audio_callback)(void*, int, int, const int16_t *, unsigned int, uint8_t, unsigned int, void *), void *userdata);
/* Send audio to the group chat.
*
* return 0 on success.
* return -1 on failure.
*
* Note that total size of pcm in bytes is equal to (samples * channels * sizeof(int16_t)).
*
* Valid number of samples are ((sample rate) * (audio length (Valid ones are: 2.5, 5, 10, 20, 40 or 60 ms)) / 1000)
* Valid number of channels are 1 or 2.
* Valid sample rates are 8000, 12000, 16000, 24000, or 48000.
*
* Recommended values are: samples = 960, channels = 1, sample_rate = 48000
*/
int toxav_group_send_audio(Tox *tox, int groupnumber, const int16_t *pcm, unsigned int samples, uint8_t channels,
unsigned int sample_rate);
#ifdef __cplusplus
}
#endif
#endif /* TOXAV_H */