bluetooth: split BT codec from A2DP SEP configuration api

Common API for all bluetooth codecs is now pa_bt_codec.
API to negotiate and configure A2DP SEP over Bluez is now pa_a2dp_endpoint_conf.

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/507>

src/modules/bluetooth/bt-codec-api.h

@@ -0,0 +1,67 @@
+#pragma once
+
+/***
+  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/>.
+***/
+
+#include <pulsecore/core.h>
+
+typedef struct pa_bt_codec {
+    /* Unique name of the codec, lowercase and without whitespaces, used for
+     * constructing identifier, D-Bus paths, ... */
+    const char *name;
+    /* Human readable codec description */
+    const char *description;
+
+    /* Initialize codec, returns codec info data and set sample_spec,
+     * for_encoding is true when codec_info is used for encoding,
+     * for_backchannel is true when codec_info is used for backchannel */
+    void *(*init)(bool for_encoding, bool for_backchannel, const uint8_t *config_buffer, uint8_t config_size, pa_sample_spec *sample_spec, pa_core *core);
+    /* Deinitialize and release codec info data in codec_info */
+    void (*deinit)(void *codec_info);
+    /* Reset internal state of codec info data in codec_info, returns
+     * a negative value on failure */
+    int (*reset)(void *codec_info);
+
+    /* Get read block size for codec, it is minimal size of buffer
+     * needed to decode read_link_mtu bytes of encoded data */
+    size_t (*get_read_block_size)(void *codec_info, size_t read_link_mtu);
+    /* Get write block size for codec, it is maximal size of buffer
+     * which can produce at most write_link_mtu bytes of encoded data */
+    size_t (*get_write_block_size)(void *codec_info, size_t write_link_mtu);
+    /* Get encoded block size for codec to hold one encoded frame.
+     * Note HFP mSBC codec encoded block may not fit into one MTU and is sent out in chunks. */
+    size_t (*get_encoded_block_size)(void *codec_info, size_t input_size);
+
+    /* Reduce encoder bitrate for codec, returns new write block size or zero
+     * if not changed, called when socket is not accepting encoded data fast
+     * enough */
+    size_t (*reduce_encoder_bitrate)(void *codec_info, size_t write_link_mtu);
+
+    /* Increase encoder bitrate for codec, returns new write block size or zero
+     * if not changed, called periodically when socket is keeping up with
+     * encoded data */
+    size_t (*increase_encoder_bitrate)(void *codec_info, size_t write_link_mtu);
+
+    /* Encode input_buffer of input_size to output_buffer of output_size,
+     * returns size of filled ouput_buffer and set processed to size of
+     * processed input_buffer */
+    size_t (*encode_buffer)(void *codec_info, uint32_t timestamp, const uint8_t *input_buffer, size_t input_size, uint8_t *output_buffer, size_t output_size, size_t *processed);
+    /* Decode input_buffer of input_size to output_buffer of output_size,
+     * returns size of filled ouput_buffer and set processed to size of
+     * processed input_buffer */
+    size_t (*decode_buffer)(void *codec_info, const uint8_t *input_buffer, size_t input_size, uint8_t *output_buffer, size_t output_size, size_t *processed);
+} pa_bt_codec;