[v8,07/12] bluetooth: Add A2DP aptX and aptX HD codecs support

Submitted by Pali Rohár on April 6, 2019, 9:16 a.m.

Details

Message ID 20190406091607.29092-8-pali.rohar@gmail.com
State Superseded
Headers show
Series "New API for Bluetooth A2DP codecs" ( rev: 57 56 55 54 53 52 51 50 49 48 47 46 ) in PulseAudio

Not browsing as part of any series.

Commit Message

Pali Rohár April 6, 2019, 9:16 a.m.
This patch provides support for aptX and aptX HD codecs in bluetooth A2DP
profile. It uses open source LGPLv2.1+ licensed libopenaptx library which
can be found at https://github.com/pali/libopenaptx.

aptX for s24 stereo samples provides fixed 6:1 compression ratio and
bitrate 352.8 kbit/s, aptX HD provides fixed 4:1 compression ratio and
bitrate 529.2 kbit/s.

According to soundexpert research, aptX codec used in bluetooth A2DP is no
better than SBC High Quality settings. And you cannot hear difference
between aptX and SBC High Quality, aptX is just a copper-less overpriced
audio cable.

aptX HD is high-bitrate version of aptX. It has clearly noticeable increase
in sound quality (not dramatic though taking into account the increase in
bitrate).

http://soundexpert.org/news/-/blogs/audio-quality-of-bluetooth-aptx
---
 configure.ac                            |  36 +++
 src/Makefile.am                         |   6 +
 src/modules/bluetooth/a2dp-codec-aptx.c | 445 ++++++++++++++++++++++++++++++++
 src/modules/bluetooth/a2dp-codec-util.c |   8 +
 4 files changed, 495 insertions(+)
 create mode 100644 src/modules/bluetooth/a2dp-codec-aptx.c

Patch hide | download patch | download mbox

diff --git a/configure.ac b/configure.ac
index c004bd70d..471a4c687 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1106,6 +1106,40 @@  AC_SUBST(HAVE_BLUEZ_5_NATIVE_HEADSET)
 AM_CONDITIONAL([HAVE_BLUEZ_5_NATIVE_HEADSET], [test "x$HAVE_BLUEZ_5_NATIVE_HEADSET" = x1])
 AS_IF([test "x$HAVE_BLUEZ_5_NATIVE_HEADSET" = "x1"], AC_DEFINE([HAVE_BLUEZ_5_NATIVE_HEADSET], 1, [Bluez 5 native headset backend enabled]))
 
+#### Bluetooth A2DP aptX codec (optional) ###
+
+AC_ARG_ENABLE([aptx],
+    AS_HELP_STRING([--disable-aptx],[Disable optional bluetooth A2DP aptX and aptX HD codecs support (via libopenaptx)]))
+AC_ARG_VAR([OPENAPTX_CPPFLAGS], [C preprocessor flags for openaptx])
+AC_ARG_VAR([OPENAPTX_LDFLAGS], [linker flags for openaptx])
+
+CPPFLAGS_SAVE="$CPPFLAGS"
+LDFLAGS_SAVE="$LDFLAGS"
+LIBS_SAVE="$LIBS"
+
+CPPFLAGS="$CPPFLAGS $OPENAPTX_CPPFLAGS"
+LDFLAGS="$LDFLAGS $OPENAPTX_LDFLAGS"
+
+AS_IF([test "x$HAVE_BLUEZ_5" = "x1" && test "x$enable_aptx" != "xno"],
+    [AC_CHECK_HEADER([openaptx.h],
+        [AC_SEARCH_LIBS([aptx_init], [openaptx],
+            [HAVE_OPENAPTX=1; AS_IF([test "x$ac_cv_search_aptx_init" != "xnone required"], [OPENAPTX_LDFLAGS="$OPENAPTX_LDFLAGS $ac_cv_search_aptx_init"])],
+            [HAVE_OPENAPTX=0])],
+        [HAVE_OPENAPTX=0])])
+
+CPPFLAGS="$CPPFLAGS_SAVE"
+LDFLAGS="$LDFLAGS_SAVE"
+LIBS="$LIBS_SAVE"
+
+AS_IF([test "x$HAVE_BLUEZ_5" = "x1" && test "x$enable_aptx" = "xyes" && test "x$HAVE_OPENAPTX" = "x0"],
+    [AC_MSG_ERROR([*** libopenaptx from https://github.com/pali/libopenaptx not found])])
+
+AC_SUBST(OPENAPTX_CPPFLAGS)
+AC_SUBST(OPENAPTX_LDFLAGS)
+AC_SUBST(HAVE_OPENAPTX)
+AM_CONDITIONAL([HAVE_OPENAPTX], [test "x$HAVE_OPENAPTX" = "x1"])
+AS_IF([test "x$HAVE_OPENAPTX" = "x1"], AC_DEFINE([HAVE_OPENAPTX], 1, [Have openaptx codec library]))
+
 #### UDEV support (optional) ####
 
 AC_ARG_ENABLE([udev],
@@ -1591,6 +1625,7 @@  AS_IF([test "x$HAVE_SYSTEMD_JOURNAL" = "x1"], ENABLE_SYSTEMD_JOURNAL=yes, ENABLE
 AS_IF([test "x$HAVE_BLUEZ_5" = "x1"], ENABLE_BLUEZ_5=yes, ENABLE_BLUEZ_5=no)
 AS_IF([test "x$HAVE_BLUEZ_5_OFONO_HEADSET" = "x1"], ENABLE_BLUEZ_5_OFONO_HEADSET=yes, ENABLE_BLUEZ_5_OFONO_HEADSET=no)
 AS_IF([test "x$HAVE_BLUEZ_5_NATIVE_HEADSET" = "x1"], ENABLE_BLUEZ_5_NATIVE_HEADSET=yes, ENABLE_BLUEZ_5_NATIVE_HEADSET=no)
+AS_IF([test "x$HAVE_OPENAPTX" = "x1"], ENABLE_APTX=yes, ENABLE_APTX=no)
 AS_IF([test "x$HAVE_HAL_COMPAT" = "x1"], ENABLE_HAL_COMPAT=yes, ENABLE_HAL_COMPAT=no)
 AS_IF([test "x$HAVE_TCPWRAP" = "x1"], ENABLE_TCPWRAP=yes, ENABLE_TCPWRAP=no)
 AS_IF([test "x$HAVE_LIBSAMPLERATE" = "x1"], ENABLE_LIBSAMPLERATE="yes (DEPRECATED)", ENABLE_LIBSAMPLERATE=no)
@@ -1649,6 +1684,7 @@  echo "
       Enable BlueZ 5:              ${ENABLE_BLUEZ_5}
         Enable ofono headsets:     ${ENABLE_BLUEZ_5_OFONO_HEADSET}
         Enable native headsets:    ${ENABLE_BLUEZ_5_NATIVE_HEADSET}
+        Enable aptX+aptXHD codecs: ${ENABLE_APTX}
     Enable udev:                   ${ENABLE_UDEV}
       Enable HAL->udev compat:     ${ENABLE_HAL_COMPAT}
     Enable systemd
diff --git a/src/Makefile.am b/src/Makefile.am
index 5ef870e32..a303578bb 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -2154,6 +2154,12 @@  libbluez5_util_la_SOURCES += modules/bluetooth/a2dp-codec-sbc.c
 libbluez5_util_la_LIBADD += $(SBC_LIBS)
 libbluez5_util_la_CFLAGS += $(SBC_CFLAGS)
 
+if HAVE_OPENAPTX
+libbluez5_util_la_SOURCES += modules/bluetooth/a2dp-codec-aptx.c
+libbluez5_util_la_CPPFLAGS += $(OPENAPTX_CPPFLAGS)
+libbluez5_util_la_LDFLAGS += $(OPENAPTX_LDFLAGS)
+endif
+
 module_bluez5_discover_la_SOURCES = modules/bluetooth/module-bluez5-discover.c
 module_bluez5_discover_la_LDFLAGS = $(MODULE_LDFLAGS)
 module_bluez5_discover_la_LIBADD = $(MODULE_LIBADD) $(DBUS_LIBS) libbluez5-util.la
diff --git a/src/modules/bluetooth/a2dp-codec-aptx.c b/src/modules/bluetooth/a2dp-codec-aptx.c
new file mode 100644
index 000000000..0d966e6f3
--- /dev/null
+++ b/src/modules/bluetooth/a2dp-codec-aptx.c
@@ -0,0 +1,445 @@ 
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2018-2019 Pali Rohár <pali.rohar@gmail.com>
+
+  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/>.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <pulsecore/log.h>
+#include <pulsecore/macro.h>
+#include <pulsecore/once.h>
+#include <pulse/sample.h>
+
+#include <openaptx.h>
+
+#include "a2dp-codecs.h"
+#include "a2dp-codec-api.h"
+
+static bool can_accept_capabilities_common(const a2dp_aptx_t *capabilities, uint32_t vendor_id, uint16_t codec_id) {
+    if (!(capabilities->frequency & (APTX_SAMPLING_FREQ_16000 | APTX_SAMPLING_FREQ_32000 |
+                                     APTX_SAMPLING_FREQ_44100 | APTX_SAMPLING_FREQ_48000)))
+        return false;
+
+    if (A2DP_GET_VENDOR_ID(capabilities->info) != vendor_id || A2DP_GET_CODEC_ID(capabilities->info) != codec_id)
+        return false;
+
+    if (!(capabilities->channel_mode & APTX_CHANNEL_MODE_STEREO))
+        return false;
+
+    return true;
+}
+
+static bool can_accept_capabilities(const uint8_t *capabilities_buffer, uint8_t capabilities_size, bool for_encoding) {
+    const a2dp_aptx_t *capabilities = (const a2dp_aptx_t *) capabilities_buffer;
+
+    if (capabilities_size != sizeof(*capabilities))
+        return false;
+
+    return can_accept_capabilities_common(capabilities, APTX_VENDOR_ID, APTX_CODEC_ID);
+}
+
+static bool can_accept_capabilities_hd(const uint8_t *capabilities_buffer, uint8_t capabilities_size, bool for_encoding) {
+    const a2dp_aptx_hd_t *capabilities = (const a2dp_aptx_hd_t *) capabilities_buffer;
+
+    if (capabilities_size != sizeof(*capabilities))
+        return false;
+
+    return can_accept_capabilities_common(&capabilities->aptx, APTX_HD_VENDOR_ID, APTX_HD_CODEC_ID);
+}
+
+static const char *choose_remote_endpoint_common(bool (*can_accept_capabilities_func)(const uint8_t *, uint8_t, bool), const pa_hashmap *capabilities_hashmap, bool for_encoding) {
+    const pa_a2dp_codec_capabilities *a2dp_capabilities;
+    const char *key;
+    void *state;
+
+    /* There is no preference, just choose random valid entry */
+    PA_HASHMAP_FOREACH_KV(key, a2dp_capabilities, capabilities_hashmap, state) {
+        if (can_accept_capabilities_func(a2dp_capabilities->buffer, a2dp_capabilities->size, for_encoding))
+            return key;
+    }
+
+    return NULL;
+}
+
+static const char *choose_remote_endpoint(const pa_hashmap *capabilities_hashmap, const pa_sample_spec *default_sample_spec, bool for_encoding) {
+    return choose_remote_endpoint_common(can_accept_capabilities, capabilities_hashmap, for_encoding);
+}
+
+static const char *choose_remote_endpoint_hd(const pa_hashmap *capabilities_hashmap, const pa_sample_spec *default_sample_spec, bool for_encoding) {
+    return choose_remote_endpoint_common(can_accept_capabilities_hd, capabilities_hashmap, for_encoding);
+}
+
+static void fill_capabilities_common(a2dp_aptx_t *capabilities, uint32_t vendor_id, uint16_t codec_id) {
+    capabilities->info = A2DP_SET_VENDOR_ID_CODEC_ID(vendor_id, codec_id);
+    capabilities->channel_mode = APTX_CHANNEL_MODE_STEREO;
+    capabilities->frequency = APTX_SAMPLING_FREQ_16000 | APTX_SAMPLING_FREQ_32000 |
+                              APTX_SAMPLING_FREQ_44100 | APTX_SAMPLING_FREQ_48000;
+}
+
+static uint8_t fill_capabilities(uint8_t capabilities_buffer[MAX_A2DP_CAPS_SIZE]) {
+    a2dp_aptx_t *capabilities = (a2dp_aptx_t *) capabilities_buffer;
+
+    pa_zero(*capabilities);
+    fill_capabilities_common(capabilities, APTX_VENDOR_ID, APTX_CODEC_ID);
+    return sizeof(*capabilities);
+}
+
+static uint8_t fill_capabilities_hd(uint8_t capabilities_buffer[MAX_A2DP_CAPS_SIZE]) {
+    a2dp_aptx_hd_t *capabilities = (a2dp_aptx_hd_t *) capabilities_buffer;
+
+    pa_zero(*capabilities);
+    fill_capabilities_common(&capabilities->aptx, APTX_HD_VENDOR_ID, APTX_HD_CODEC_ID);
+    return sizeof(*capabilities);
+}
+
+static bool is_configuration_valid_common(const a2dp_aptx_t *config, uint32_t vendor_id, uint16_t codec_id) {
+    if (A2DP_GET_VENDOR_ID(config->info) != vendor_id || A2DP_GET_CODEC_ID(config->info) != codec_id) {
+        pa_log_error("Invalid vendor codec information in configuration");
+        return false;
+    }
+
+    if (config->frequency != APTX_SAMPLING_FREQ_16000 && config->frequency != APTX_SAMPLING_FREQ_32000 &&
+        config->frequency != APTX_SAMPLING_FREQ_44100 && config->frequency != APTX_SAMPLING_FREQ_48000) {
+        pa_log_error("Invalid sampling frequency in configuration");
+        return false;
+    }
+
+    if (config->channel_mode != APTX_CHANNEL_MODE_STEREO) {
+        pa_log_error("Invalid channel mode in configuration");
+        return false;
+    }
+
+    return true;
+}
+
+static bool is_configuration_valid(const uint8_t *config_buffer, uint8_t config_size) {
+    const a2dp_aptx_t *config = (const a2dp_aptx_t *) config_buffer;
+
+    if (config_size != sizeof(*config)) {
+        pa_log_error("Invalid size of config buffer");
+        return false;
+    }
+
+    return is_configuration_valid_common(config, APTX_VENDOR_ID, APTX_CODEC_ID);
+}
+
+static bool is_configuration_valid_hd(const uint8_t *config_buffer, uint8_t config_size) {
+    const a2dp_aptx_hd_t *config = (const a2dp_aptx_hd_t *) config_buffer;
+
+    if (config_size != sizeof(*config)) {
+        pa_log_error("Invalid size of config buffer");
+        return false;
+    }
+
+    return is_configuration_valid_common(&config->aptx, APTX_HD_VENDOR_ID, APTX_HD_CODEC_ID);
+}
+
+static bool fill_preferred_configuration_common(const pa_sample_spec *default_sample_spec, const a2dp_aptx_t *capabilities, a2dp_aptx_t *config, uint32_t vendor_id, uint16_t codec_id) {
+    int i;
+
+    static const struct {
+        uint32_t rate;
+        uint8_t cap;
+    } freq_table[] = {
+        { 16000U, APTX_SAMPLING_FREQ_16000 },
+        { 32000U, APTX_SAMPLING_FREQ_32000 },
+        { 44100U, APTX_SAMPLING_FREQ_44100 },
+        { 48000U, APTX_SAMPLING_FREQ_48000 }
+    };
+
+    if (A2DP_GET_VENDOR_ID(capabilities->info) != vendor_id || A2DP_GET_CODEC_ID(capabilities->info) != codec_id) {
+        pa_log_error("No supported vendor codec information");
+        return false;
+    }
+
+    config->info = A2DP_SET_VENDOR_ID_CODEC_ID(vendor_id, codec_id);
+
+    if (!(capabilities->channel_mode & APTX_CHANNEL_MODE_STEREO)) {
+        pa_log_error("No supported channel modes");
+        return false;
+    }
+
+    config->channel_mode = APTX_CHANNEL_MODE_STEREO;
+
+    /* Find the lowest freq that is at least as high as the requested sampling rate */
+    for (i = 0; (unsigned) i < PA_ELEMENTSOF(freq_table); i++) {
+        if (freq_table[i].rate >= default_sample_spec->rate && (capabilities->frequency & freq_table[i].cap)) {
+            config->frequency = freq_table[i].cap;
+            break;
+        }
+    }
+
+    if ((unsigned) i == PA_ELEMENTSOF(freq_table)) {
+        for (--i; i >= 0; i--) {
+            if (capabilities->frequency & freq_table[i].cap) {
+                config->frequency = freq_table[i].cap;
+                break;
+            }
+        }
+
+        if (i < 0) {
+            pa_log_error("Not suitable sample rate");
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static uint8_t fill_preferred_configuration(const pa_sample_spec *default_sample_spec, const uint8_t *capabilities_buffer, uint8_t capabilities_size, uint8_t config_buffer[MAX_A2DP_CAPS_SIZE]) {
+    a2dp_aptx_t *config = (a2dp_aptx_t *) config_buffer;
+    const a2dp_aptx_t *capabilities = (const a2dp_aptx_t *) capabilities_buffer;
+
+    if (capabilities_size != sizeof(*capabilities)) {
+        pa_log_error("Invalid size of capabilities buffer");
+        return 0;
+    }
+
+    pa_zero(*config);
+
+    if (!fill_preferred_configuration_common(default_sample_spec, capabilities, config, APTX_VENDOR_ID, APTX_CODEC_ID))
+        return 0;
+
+    return sizeof(*config);
+}
+
+static uint8_t fill_preferred_configuration_hd(const pa_sample_spec *default_sample_spec, const uint8_t *capabilities_buffer, uint8_t capabilities_size, uint8_t config_buffer[MAX_A2DP_CAPS_SIZE]) {
+    a2dp_aptx_hd_t *config = (a2dp_aptx_hd_t *) config_buffer;
+    const a2dp_aptx_hd_t *capabilities = (const a2dp_aptx_hd_t *) capabilities_buffer;
+
+    if (capabilities_size != sizeof(*capabilities)) {
+        pa_log_error("Invalid size of capabilities buffer");
+        return 0;
+    }
+
+    pa_zero(*config);
+
+    if (!fill_preferred_configuration_common(default_sample_spec, &capabilities->aptx, &config->aptx, APTX_HD_VENDOR_ID, APTX_HD_CODEC_ID))
+        return 0;
+
+    return sizeof(*config);
+}
+
+static void *init_common(const a2dp_aptx_t *config, pa_sample_spec *sample_spec, int hd) {
+    struct aptx_context *aptx_c;
+
+    aptx_c = aptx_init(hd);
+    if (!aptx_c) {
+        pa_log_error("libopenaptx initialization failed");
+        return NULL;
+    }
+
+    sample_spec->format = PA_SAMPLE_S24LE;
+
+    switch (config->frequency) {
+        case APTX_SAMPLING_FREQ_16000:
+            sample_spec->rate = 16000U;
+            break;
+        case APTX_SAMPLING_FREQ_32000:
+            sample_spec->rate = 32000U;
+            break;
+        case APTX_SAMPLING_FREQ_44100:
+            sample_spec->rate = 44100U;
+            break;
+        case APTX_SAMPLING_FREQ_48000:
+            sample_spec->rate = 48000U;
+            break;
+        default:
+            pa_assert_not_reached();
+    }
+
+    switch (config->channel_mode) {
+        case APTX_CHANNEL_MODE_STEREO:
+            sample_spec->channels = 2;
+            break;
+        default:
+            pa_assert_not_reached();
+    }
+
+    PA_ONCE_BEGIN {
+#if OPENAPTX_MAJOR == 0 && OPENAPTX_MINOR == 0 && OPENAPTX_PATCH == 0
+        /* libopenaptx version 0.0.0 does not export version global variables */
+        const int aptx_major = OPENAPTX_MAJOR;
+        const int aptx_minor = OPENAPTX_MINOR;
+        const int aptx_patch = OPENAPTX_PATCH;
+#endif
+        pa_log_debug("Using aptX codec implementation: libopenaptx %d.%d.%d from https://github.com/pali/libopenaptx", aptx_major, aptx_minor, aptx_patch);
+    } PA_ONCE_END;
+
+    return aptx_c;
+}
+
+static void *init(bool for_encoding, bool for_backchannel, const uint8_t *config_buffer, uint8_t config_size, pa_sample_spec *sample_spec) {
+    const a2dp_aptx_t *config = (const a2dp_aptx_t *) config_buffer;
+
+    pa_assert(config_size == sizeof(*config));
+    pa_assert(!for_backchannel);
+
+    return init_common(config, sample_spec, 0);
+}
+
+static void *init_hd(bool for_encoding, bool for_backchannel, const uint8_t *config_buffer, uint8_t config_size, pa_sample_spec *sample_spec) {
+    const a2dp_aptx_hd_t *config = (const a2dp_aptx_hd_t *) config_buffer;
+
+    pa_assert(config_size == sizeof(*config));
+    pa_assert(!for_backchannel);
+
+    return init_common(&config->aptx, sample_spec, 1);
+}
+
+static void deinit(void *codec_info) {
+    struct aptx_context *aptx_c = (struct aptx_context *) codec_info;
+
+    aptx_finish(aptx_c);
+}
+
+static void reset(void *codec_info) {
+    struct aptx_context *aptx_c = (struct aptx_context *) codec_info;
+
+    aptx_reset(aptx_c);
+}
+
+static size_t get_block_size(void *codec_info, size_t link_mtu) {
+    /* aptX compression ratio is 6:1 and we need to process 4 aptX bytes at once */
+    return (link_mtu/4) * 4*6;
+}
+
+static size_t get_block_size_hd(void *codec_info, size_t link_mtu) {
+    /* aptX HD compression ratio is 4:1 and we need to process 4 aptX HD bytes at once */
+    return (link_mtu/4) * 4*4;
+}
+
+static size_t reduce_encoder_bitrate(void *codec_info, size_t write_link_mtu) {
+    return 0;
+}
+
+static 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) {
+    struct aptx_context *aptx_c = (struct aptx_context *) codec_info;
+    uint8_t *d;
+    const uint8_t *p;
+    size_t to_write, to_encode;
+
+    p = input_buffer;
+    to_encode = input_size;
+
+    d = output_buffer;
+    to_write = output_size;
+
+    while (PA_LIKELY(to_encode > 0 && to_write > 0)) {
+        size_t written;
+        size_t encoded;
+        encoded = aptx_encode(aptx_c, p, to_encode, d, to_write, &written);
+
+        if (PA_UNLIKELY(encoded == 0)) {
+            pa_log_error("aptX encoding error");
+            *processed = p - input_buffer;
+            return 0;
+        }
+
+        pa_assert_fp((size_t) encoded <= to_encode);
+        pa_assert_fp((size_t) written <= to_write);
+
+        p += encoded;
+        to_encode -= encoded;
+
+        d += written;
+        to_write -= written;
+    }
+
+    *processed = p - input_buffer;
+    return d - output_buffer;
+}
+
+static 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) {
+    struct aptx_context *aptx_c = (struct aptx_context *) codec_info;
+
+    const uint8_t *p;
+    uint8_t *d;
+    size_t to_write, to_decode;
+
+    p = input_buffer;
+    to_decode = input_size;
+
+    d = output_buffer;
+    to_write = output_size;
+
+    while (PA_LIKELY(to_decode > 0)) {
+        size_t written;
+        size_t decoded;
+
+        decoded = aptx_decode(aptx_c, p, to_decode, d, to_write, &written);
+
+        if (PA_UNLIKELY(decoded == 0)) {
+            pa_log_error("aptX decoding error");
+            *processed = p - input_buffer;
+            return 0;
+        }
+
+        pa_assert_fp((size_t) decoded <= to_decode);
+
+        p += decoded;
+        to_decode -= decoded;
+
+        d += written;
+        to_write -= written;
+    }
+
+    *processed = p - input_buffer;
+    return d - output_buffer;
+}
+
+const pa_a2dp_codec pa_a2dp_codec_aptx = {
+    .name = "aptx",
+    .description = "aptX",
+    .id = { A2DP_CODEC_VENDOR, APTX_VENDOR_ID, APTX_CODEC_ID },
+    .support_backchannel = false,
+    .can_accept_capabilities = can_accept_capabilities,
+    .choose_remote_endpoint = choose_remote_endpoint,
+    .fill_capabilities = fill_capabilities,
+    .is_configuration_valid = is_configuration_valid,
+    .fill_preferred_configuration = fill_preferred_configuration,
+    .init = init,
+    .deinit = deinit,
+    .reset = reset,
+    .get_read_block_size = get_block_size,
+    .get_write_block_size = get_block_size,
+    .reduce_encoder_bitrate = reduce_encoder_bitrate,
+    .encode_buffer = encode_buffer,
+    .decode_buffer = decode_buffer,
+};
+
+const pa_a2dp_codec pa_a2dp_codec_aptx_hd = {
+    .name = "aptx_hd",
+    .description = "aptX HD",
+    .id = { A2DP_CODEC_VENDOR, APTX_HD_VENDOR_ID, APTX_HD_CODEC_ID },
+    .support_backchannel = false,
+    .can_accept_capabilities = can_accept_capabilities_hd,
+    .choose_remote_endpoint = choose_remote_endpoint_hd,
+    .fill_capabilities = fill_capabilities_hd,
+    .is_configuration_valid = is_configuration_valid_hd,
+    .fill_preferred_configuration = fill_preferred_configuration_hd,
+    .init = init_hd,
+    .deinit = deinit,
+    .reset = reset,
+    .get_read_block_size = get_block_size_hd,
+    .get_write_block_size = get_block_size_hd,
+    .reduce_encoder_bitrate = reduce_encoder_bitrate,
+    .encode_buffer = encode_buffer,
+    .decode_buffer = decode_buffer,
+};
diff --git a/src/modules/bluetooth/a2dp-codec-util.c b/src/modules/bluetooth/a2dp-codec-util.c
index 94d01e7bd..363fcc387 100644
--- a/src/modules/bluetooth/a2dp-codec-util.c
+++ b/src/modules/bluetooth/a2dp-codec-util.c
@@ -27,11 +27,19 @@ 
 #include "a2dp-codec-util.h"
 
 extern const pa_a2dp_codec pa_a2dp_codec_sbc;
+#ifdef HAVE_OPENAPTX
+extern const pa_a2dp_codec pa_a2dp_codec_aptx;
+extern const pa_a2dp_codec pa_a2dp_codec_aptx_hd;
+#endif
 
 /* This is list of supported codecs. Their order is important.
  * Codec with higher index has higher priority. */
 const pa_a2dp_codec *pa_a2dp_codecs[] = {
     &pa_a2dp_codec_sbc,
+#ifdef HAVE_OPENAPTX
+    &pa_a2dp_codec_aptx,
+    &pa_a2dp_codec_aptx_hd,
+#endif
 };
 
 unsigned int pa_bluetooth_a2dp_codec_count(void) {

Comments

On Sat, 2019-04-06 at 11:16 +0200, Pali Rohár wrote:
> This patch provides support for aptX and aptX HD codecs in bluetooth A2DP
> profile. It uses open source LGPLv2.1+ licensed libopenaptx library which
> can be found at https://github.com/pali/libopenaptx.
> 
> aptX for s24 stereo samples provides fixed 6:1 compression ratio and
> bitrate 352.8 kbit/s, aptX HD provides fixed 4:1 compression ratio and
> bitrate 529.2 kbit/s.
> 
> According to soundexpert research, aptX codec used in bluetooth A2DP is no
> better than SBC High Quality settings. And you cannot hear difference
> between aptX and SBC High Quality, aptX is just a copper-less overpriced
> audio cable.
> 
> aptX HD is high-bitrate version of aptX. It has clearly noticeable increase
> in sound quality (not dramatic though taking into account the increase in
> bitrate).
> 
> http://soundexpert.org/news/-/blogs/audio-quality-of-bluetooth-aptx
> ---
>  configure.ac                            |  36 +++
>  src/Makefile.am                         |   6 +
>  src/modules/bluetooth/a2dp-codec-aptx.c | 445 ++++++++++++++++++++++++++++++++
>  src/modules/bluetooth/a2dp-codec-util.c |   8 +
>  4 files changed, 495 insertions(+)
>  create mode 100644 src/modules/bluetooth/a2dp-codec-aptx.c

> +static bool can_accept_capabilities_common(const a2dp_aptx_t *capabilities, uint32_t vendor_id, uint16_t codec_id) {
> +    if (!(capabilities->frequency & (APTX_SAMPLING_FREQ_16000 | APTX_SAMPLING_FREQ_32000 |
> +                                     APTX_SAMPLING_FREQ_44100 | APTX_SAMPLING_FREQ_48000)))
> +        return false;
> +
> +    if (A2DP_GET_VENDOR_ID(capabilities->info) != vendor_id || A2DP_GET_CODEC_ID(capabilities->info) != codec_id)
> +        return false;
> +
> +    if (!(capabilities->channel_mode & APTX_CHANNEL_MODE_STEREO))

Why is mono support not implemented? Is it a limitation of libopenaptx?
It's not a big shortcoming, but it would be nice to support mono too.

> +static 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) {
> +    struct aptx_context *aptx_c = (struct aptx_context *) codec_info;
> +
> +    const uint8_t *p;
> +    uint8_t *d;
> +    size_t to_write, to_decode;
> +
> +    p = input_buffer;
> +    to_decode = input_size;
> +
> +    d = output_buffer;
> +    to_write = output_size;
> +
> +    while (PA_LIKELY(to_decode > 0)) {

Is it intentional that encode_buffer() checks both to_encode and
to_write in the while loop condition, but decode_buffer() only checks
to_decode? If so, why does encode_buffer() need to be extra careful but
decode_buffer() doesn't?

On Fri, 2019-04-19 at 12:52 +0200, Pali Rohár wrote:
> On Friday 19 April 2019 11:41:22 Tanu Kaskinen wrote:
> > On Sat, 2019-04-06 at 11:16 +0200, Pali Rohár wrote:
> > > +static 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) {
> > > +    struct aptx_context *aptx_c = (struct aptx_context *) codec_info;
> > > +
> > > +    const uint8_t *p;
> > > +    uint8_t *d;
> > > +    size_t to_write, to_decode;
> > > +
> > > +    p = input_buffer;
> > > +    to_decode = input_size;
> > > +
> > > +    d = output_buffer;
> > > +    to_write = output_size;
> > > +
> > > +    while (PA_LIKELY(to_decode > 0)) {
> > 
> > Is it intentional that encode_buffer() checks both to_encode and
> > to_write in the while loop condition, but decode_buffer() only checks
> > to_decode? If so, why does encode_buffer() need to be extra careful but
> > decode_buffer() doesn't?
> 
> These checks are similar/same as in SBC codec code. And SBC code was
> there prior to my work. So personally I do not know.

Ok, let's find out if this code needs changing.

The output buffer size when decoding is determined by
get_read_block_size(), which returns a value corresponding to the read
MTU (the MTU is in the compressed domain, the block size is in the
uncompressed domain).

The input buffer size is potentially up to twice the read MTU.

It doesn't seem impossible that the socket could have more data queued
than just one MTU. Therefore this doesn't seem safe, because
decode_buffer() may overrun the output buffer. The solution isn't to
check to_write, however, because that would lead to some audio getting
dropped. I think the input buffer size should be limited to roughly one
MTU just like the output buffer size is limited to roughly one MTU. The
exact logic is codec dependent, so the codec implementation should
decide both the input and output buffer sizes, and it should be ensured
that the output buffer is big enough to fully decode a full input
buffer.