Hi, I created a new module-plugin-sink and a small amplifier demo plugin based on the attached header file. I did not (yet) drop max_latency, disable_rewind and rewind_filter() because I am still waiting for more feedback on the specification. I made it however more clear (using Alexander's wording) that this should only be used if "real" rewinding is possible. Regards Georg
/*** This file is part of PulseAudio. PulseAudio is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. PulseAudio 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 Lesser General Public License along with PulseAudio; if not, see <http://www.gnu.org/licenses/>. ***/ typedef struct filter_plugin { const char *name; /* Name of the filter */ unsigned input_channels; /* Number of audio input channels, 0 if variable */ unsigned output_channels; /* Number of audio output channels, 0 if variable */ const char *desc_head; /* Leading part of description string */ const char *filter_type; /* Name for the type of filter */ size_t max_chunk_size; /* Maximum chunk size in bytes that the filter will * accept, 0 for default */ size_t fixed_block_size; /* Block size in frames for fixed block size filters, * 0 if block size is variable */ uint64_t max_latency; /* Maximum latency allowed for the sink, 0 if unused */ bool disable_rewind; /* True when rewinding is disabled */ /* Callback to rewind the filter when pulseaudio requests it. May be NULL. * Amount indicates the number of bytes to roll back. The filter state must * not be reset, but seamlessly restored to the specified point in the past * (which is the filter's responsibility to keep). * If it is not possible to do so, the best option is to disable rewinding * completely and limit the latency. */ void (*rewind_filter)(void *filter_handle, size_t amount); /* Callback to process a chunk of data by the filter. May be NULL */ void (*process_chunk)(float *src, float *dst, unsigned count, void *filter_handle); /* Callback to retrieve additional latency caused by the filter. May be NULL */ uint64_t (*get_extra_latency)(void *filter_handle); /* Initializes a new filter instance and returns a handle to it. */ void *(*create_filter)(unsigned input_channels, unsigned output_channels, unsigned sample_rate); /* Deletes filter instance. */ void (*delete_filter)(void *filter_handle); /* Activates filter. Returns 0 on success and a negative errror code on failure. * May be NULL. */ int (*activate_filter)(void *filter_handle); /* Deactivates filter. May be NULL. */ void (*deactivate_filter)(void *filter_handle); /* If set, this function is called in thread context when an update of the * filter parameters is requested, may be NULL. The function must replace * the currently used parameter structure by the new structure and return * a pointer to the old structure so that it can be freed in the main thread * using parameter_free(). If the old structure can be re-used, the function * may return NULL. */ void *(*update_filter_parameters)(void *parameters, void *filter_handle); /* Frees a parameter structure. May only be NULL, if update_filter_parameters() * is also NULL or if update_filter_parameters() always returns NULL. */ void (*parameter_free)(void *parameters); /* The following functions can be provided to set and get parameters. The parameter * structure is defined by the filter and should contain all parameters that are * configurable by the user. The library code makes no assumption on the contents * of the structure but only passes references. The library implements a message * handler which supports the following messages that use the functions below: * parameter-get - Retrieve a single parameter. * parameter-set - Set a single parameter. * parameter-get-all - Retrieve all parameters as a list in message format. * parameter-set-all - Set all parameters simultaneously. * parameter-get-description - Returns a filter description and a list that describes * all parameters. Example of the list element format: * {{Identifier}{Type}{default}{min}{max}} * The last message can be used to get information about the filter or to implement * a filter control GUI that is independent of the filter type. * If filter_message_handler() is defined, all other messages are passed on to the * filter. The get functions are expected to return a string in the message handler * format while the set functions receive plain strings. On failure, all get/set * functions will return NULL. */ /* Get the value of the parameter described by identifier. The value shall be returned * as a string enclosed in double curly braces. The identifier may be any string that * the filter recognizes like a name or index, depending of the implementation of this * function. */ char *(*parameter_get)(const char *identifier, void *filter_handle); /* Sets the value of the parameter described by identifier. The value is expected as * a string. The identifier may be any string that the filter recognizes like a name * or index. Returns a parameter structure filled with all current parameter values, * reflecting the updated parameter, so that the structure can be passed to * update_filter_parameters(). update_filter_parameters() will replace the current * parameter set with the new structure. */ void *(*parameter_set)(const char *identifier, const char *value, void *filter_handle); /* Returns a list of the values of all filter parameters. Each parameter must be enclosed * in curly braces and there must be braces around the whole list. */ char *(*parameter_get_all)(void *filter_handle); /* Expects an array of all filter parameter values as strings and returns a parameter * structure that can be passed to update_filter_parameters(). See set_parameter(). * If all_params is NULL, the function should return a default set of parameters. */ void *(*parameter_set_all)(const char **all_params, int param_count, void *filter_handle); /* Returns a parameter description string as described above. */ char *(*parameter_get_description)(void *filter_handle); /* Handler for additional messages. */ int (*filter_message_handler)(const char *message, char *message_parameters, char **response, void *filter_handle); } filter_plugin; /* Datatype corresponding to the get_Filter_Info() function. */ typedef const struct filter_plugin *(*Filter_Info_Function)(unsigned long Index);
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