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https://github.com/Divested-Mobile/DivestOS-Build.git
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168 lines
6.4 KiB
Diff
168 lines
6.4 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: ValdikSS <iam@valdikss.org.ru>
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Date: Fri, 21 Sep 2018 21:43:14 +0300
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Subject: [PATCH] Explicit SBC Dual Channel (SBC HD) support
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Overwhelming majority of Bluetooth audio devices have SBC maximum bitpool value
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limited to 53, which prevents bitrates higher than 328 kbit/s to be used with
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the most common 44.1 kHz Joint Stereo, 8 subbands, 16 blocks profile. This
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limitation could be circumvented on any existing device to achieve higher audio
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quality, by using Dual Channel mode.
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Dual Channel encodes channels separately, using the entire bitpool for each
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channel. Forcing the device to use Dual Channel instead of Joint Stereo almost
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doubles maximum possible bitrate for the same bitpool value.
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A2DP specification v1.2, which was active from 2007 to 2015, requires all
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decoders to work correctly with bitrates up to 512 kbps. Newer specification
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does not have the limit at all. It is assumed that most modern headphones with
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EDR support can handle any SBC profile with maximum bitpool value, regardless
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of resulting bitrate.
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This commit defines optimal Dual Channel bitrate profiles:
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EDR 2mbit/s - 452 kbit/s for 44.1 kHz, 492 kbit/s for 48 kHz (bitpool 38,
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4 audio frames, 10.7 ms, 6 wasted bytes per packet)
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EDR 3mbit/s - 551.3 kbit/s for 44.1 kHz, 600 kbit/s for 48 kHz (bitpool 47,
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5 audio frames, 13.4 ms, 4 wasted bytes per packet)
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With 452 kbit/s, SBC outperforms aptX, with 551.3 kbit/s, on par or close to
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aptX HD.
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SBC HD is disabled by default and should be activated by setting
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"persist.bt.sbc_hd_enabled" property:
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$ setprop persist.bt.sbc_hd_enabled 1
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Bitrate could be increased further with "persist.bt.sbc_hd_higher_kbps"
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property. If the property is set, the following EDR 2mbit/s profile is used:
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595.4 kbit/s for 44.1 kHz, 648 kbit/s for 48 kHz (bitpool 51, 3 audio frames,
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8.8 ms, 14 wasted bytes per packet)
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53 out of 57 tested headphones, receivers and automotive head units were able
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to correctly receive and decode high bitrate Dual Channel audio.
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Test: manual, with various headphones, receivers, and speakers
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Change-Id: If74d9d46461c67b8aef39d63430b2f0187c9e714
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---
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btif/co/bta_av_co.c | 21 ++++++++++++++++++++-
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btif/src/btif_media_task.c | 14 ++++++++++++++
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2 files changed, 34 insertions(+), 1 deletion(-)
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diff --git a/btif/co/bta_av_co.c b/btif/co/bta_av_co.c
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index 39a8ebfa7..f205ddacc 100644
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--- a/btif/co/bta_av_co.c
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+++ b/btif/co/bta_av_co.c
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@@ -43,6 +43,7 @@
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#include "btif_av_co.h"
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#include "btif_util.h"
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#include "osi/include/mutex.h"
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+#include "osi/include/properties.h"
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#include "bt_utils.h"
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#include "a2d_aptx.h"
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@@ -81,6 +82,7 @@
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#else
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#define BTA_AV_CO_SBC_MAX_BITPOOL 53
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#endif
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+#define A2DP_SBC_HD_ENABLE_PROP "persist.bt.sbc_hd_enabled"
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/* SCMS-T protect info */
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const UINT8 bta_av_co_cp_scmst[BTA_AV_CP_INFO_LEN] = "\x02\x02\x00";
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@@ -138,6 +140,18 @@ const tA2D_SBC_CIE btif_av_sbc_default_config =
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A2D_SBC_IE_MIN_BITPOOL /* min_bitpool */
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};
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+/* Alternative SBC codec configuration */
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+const tA2D_SBC_CIE btif_av_sbc_alt_config =
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+{
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+ BTIF_AV_SBC_DEFAULT_SAMP_FREQ, /* samp_freq */
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+ A2D_SBC_IE_CH_MD_DUAL, /* ch_mode */
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+ A2D_SBC_IE_BLOCKS_16, /* block_len */
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+ A2D_SBC_IE_SUBBAND_8, /* num_subbands */
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+ A2D_SBC_IE_ALLOC_MD_L, /* alloc_mthd */
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+ BTA_AV_CO_SBC_MAX_BITPOOL, /* max_bitpool */
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+ A2D_SBC_IE_MIN_BITPOOL /* min_bitpool */
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+};
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+
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const tA2D_APTX_CIE bta_av_co_aptx_caps =
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{
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A2D_APTX_VENDOR_ID,
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@@ -566,7 +580,10 @@ void bta_av_build_src_cfg (UINT8 *p_pref_cfg, UINT8 *p_src_cap)
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else if (src_cap.samp_freq & A2D_SBC_IE_SAMP_FREQ_44)
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pref_cap.samp_freq = A2D_SBC_IE_SAMP_FREQ_44;
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- if (src_cap.ch_mode & A2D_SBC_IE_CH_MD_JOINT)
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+ if (property_get_int32(A2DP_SBC_HD_ENABLE_PROP, 0)
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+ && (src_cap.ch_mode & A2D_SBC_IE_CH_MD_DUAL))
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+ pref_cap.ch_mode = A2D_SBC_IE_CH_MD_DUAL;
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+ else if (src_cap.ch_mode & A2D_SBC_IE_CH_MD_JOINT)
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pref_cap.ch_mode = A2D_SBC_IE_CH_MD_JOINT;
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else if (src_cap.ch_mode & A2D_SBC_IE_CH_MD_STEREO)
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pref_cap.ch_mode = A2D_SBC_IE_CH_MD_STEREO;
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@@ -2209,6 +2226,8 @@ BOOLEAN bta_av_co_audio_set_codec(const tBTIF_AV_MEDIA_FEEDINGS *p_feeding, tBTI
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new_cfg_sbc.id = BTIF_AV_CODEC_SBC;
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sbc_config = btif_av_sbc_default_config;
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+ if (property_get_int32(A2DP_SBC_HD_ENABLE_PROP, 0))
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+ sbc_config = btif_av_sbc_alt_config;
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if ((p_feeding->cfg.pcm.num_channel != 1) &&
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(p_feeding->cfg.pcm.num_channel != 2))
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{
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diff --git a/btif/src/btif_media_task.c b/btif/src/btif_media_task.c
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index cac0c2211..4c956bd3c 100644
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--- a/btif/src/btif_media_task.c
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+++ b/btif/src/btif_media_task.c
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@@ -59,6 +59,7 @@
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#include "osi/include/metrics.h"
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#include "osi/include/mutex.h"
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#include "osi/include/thread.h"
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+#include "osi/include/properties.h"
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#include "bt_utils.h"
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#include "a2d_api.h"
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#include "a2d_int.h"
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@@ -114,6 +115,8 @@ OI_INT16 pcmData[15*SBC_MAX_SAMPLES_PER_FRAME*SBC_MAX_CHANNELS];
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#include "bta_api.h"
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#endif
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+#define A2DP_SBC_HD_PROP "persist.bt.sbc_hd_higher_kbps"
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+
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/*****************************************************************************
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** Constants
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@@ -209,12 +212,16 @@ enum {
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#ifdef BTA_AV_SPLIT_A2DP_DEF_FREQ_48KHZ
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#define BTIF_A2DP_DEFAULT_BITRATE 496
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+#define BTIF_A2DP_3DH5_BITRATE 601
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+#define BTIF_A2DP_2DH5_ALT_BITRATE 649
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#ifndef BTIF_A2DP_NON_EDR_MAX_RATE
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#define BTIF_A2DP_NON_EDR_MAX_RATE 237
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#endif
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#else
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#define BTIF_A2DP_DEFAULT_BITRATE 455
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+#define BTIF_A2DP_3DH5_BITRATE 552
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+#define BTIF_A2DP_2DH5_ALT_BITRATE 596
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#ifndef BTIF_A2DP_NON_EDR_MAX_RATE
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#define BTIF_A2DP_NON_EDR_MAX_RATE 229
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@@ -232,6 +239,7 @@ enum {
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/* 2DH5 payload size of 679 bytes - (4 bytes L2CAP Header + 12 bytes AVDTP Header) */
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#define MAX_2MBPS_AVDTP_MTU 663
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+#define MIN_3MBPS_AVDTP_SAFE_MTU 800
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#define USEC_PER_SEC 1000000L
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#define TPUT_STATS_INTERVAL_US (3000*1000)
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@@ -1252,6 +1260,12 @@ static UINT16 btif_media_task_get_sbc_rate(void)
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{
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rate = BTIF_A2DP_NON_EDR_MAX_RATE;
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APPL_TRACE_DEBUG("non-edr a2dp sink detected, restrict rate to %d", rate);
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+ } else if (btif_av_peer_supports_3mbps()
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+ && btif_media_cb.TxAaMtuSize >= MIN_3MBPS_AVDTP_SAFE_MTU) {
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+ rate = BTIF_A2DP_3DH5_BITRATE;
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+ } else if (!btif_av_peer_supports_3mbps()
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+ && property_get_int32(A2DP_SBC_HD_PROP, 0)) {
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+ rate = BTIF_A2DP_2DH5_ALT_BITRATE;
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}
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return rate;
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