[pulseaudio-discuss] [PATCH v15 03/10] bluetooth: Change codec API for choosing remote endpoint
Pali Rohár
pali.rohar at gmail.com
Wed Apr 15 19:04:39 UTC 2020
Current codec API for choosing remote endpoint was not suitable for
implementing fallback to another endpoint when first chosen one was not
possible to establish.
To overcome this problem change codec API to rather provide generic method
for comparing two endpoints by their capabilities. Return value is standard
value what comparator function returns (-1, 0, 1). It can be used e.g. for
searching the best remote endpoint (like did previous API method) or
creating a full list of all endpoints in preferred order (e.g. by sorting
function).
Currently this method is not used (neither old choose remote endpoint).
It is used by code for switching A2DP codec which is in next patches.
---
src/modules/bluetooth/a2dp-codec-api.h | 21 ++--
src/modules/bluetooth/a2dp-codec-sbc.c | 157 +++++++++++++++++++++++--
2 files changed, 157 insertions(+), 21 deletions(-)
diff --git a/src/modules/bluetooth/a2dp-codec-api.h b/src/modules/bluetooth/a2dp-codec-api.h
index a3123f4ca..6ee722e37 100644
--- a/src/modules/bluetooth/a2dp-codec-api.h
+++ b/src/modules/bluetooth/a2dp-codec-api.h
@@ -24,11 +24,6 @@
#define MAX_A2DP_CAPS_SIZE 254
-typedef struct pa_a2dp_codec_capabilities {
- uint8_t size;
- uint8_t buffer[]; /* max size is 254 bytes */
-} pa_a2dp_codec_capabilities;
-
typedef struct pa_a2dp_codec_id {
uint8_t codec_id;
uint32_t vendor_id;
@@ -51,11 +46,17 @@ typedef struct pa_a2dp_codec {
/* Returns true if codec accepts capabilities, for_encoding is true when
* capabilities are used for encoding */
bool (*can_accept_capabilities)(const uint8_t *capabilities_buffer, uint8_t capabilities_size, bool for_encoding);
- /* Choose remote endpoint based on capabilities from hash map
- * (const char *endpoint -> const pa_a2dp_codec_capabilities *capability)
- * and returns corresponding endpoint key (or NULL when there is no valid),
- * for_encoder is true when capabilities hash map is used for encoding */
- const char *(*choose_remote_endpoint)(const pa_hashmap *capabilities_hashmap, const pa_sample_spec *default_sample_spec, bool for_encoding);
+ /* Comparator function for sorting endpoints, based on endpoint capabilities
+ * and default sample spec, this function should return:
+ * -1 if first endpoint is preferred;
+ * 1 if second endpoint is preferred;
+ * 0 if both endpoints have same priority;
+ * for_encoding is true when endpoints are used for encoding,
+ * only endpoints which passed can_accept_capabilities() are compared,
+ * remote endpoints are tried from most preferred to less preferred,
+ * endpoint which better fits for default sample spec should be more
+ * preferred than other endpoints */
+ int (*cmp_endpoints)(const uint8_t *capabilities1_buffer, uint8_t capabilities1_size, const uint8_t *capabilities2_buffer, uint8_t capabilities2_size, const pa_sample_spec *default_sample_spec, bool for_encoding);
/* Fill codec capabilities, returns size of filled buffer */
uint8_t (*fill_capabilities)(uint8_t capabilities_buffer[MAX_A2DP_CAPS_SIZE]);
/* Validate codec configuration, returns true on success */
diff --git a/src/modules/bluetooth/a2dp-codec-sbc.c b/src/modules/bluetooth/a2dp-codec-sbc.c
index 89c647fbe..ba47fa066 100644
--- a/src/modules/bluetooth/a2dp-codec-sbc.c
+++ b/src/modules/bluetooth/a2dp-codec-sbc.c
@@ -77,18 +77,153 @@ static bool can_accept_capabilities(const uint8_t *capabilities_buffer, uint8_t
return true;
}
-static const char *choose_remote_endpoint(const pa_hashmap *capabilities_hashmap, const pa_sample_spec *default_sample_spec, 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(a2dp_capabilities->buffer, a2dp_capabilities->size, for_encoding))
- return key;
+static int cmp_endpoints_by_channels(const a2dp_sbc_t *capabilities1, const a2dp_sbc_t *capabilities2, const pa_sample_spec *default_sample_spec, bool for_encoding) {
+ /* Prefer enpoint which number of channels is near to default sample channel number */
+ if (default_sample_spec->channels < 2) {
+ if ((capabilities1->channel_mode & SBC_CHANNEL_MODE_MONO) && !(capabilities2->channel_mode & SBC_CHANNEL_MODE_MONO))
+ return -1;
+ if (!(capabilities1->channel_mode & SBC_CHANNEL_MODE_MONO) && (capabilities2->channel_mode & SBC_CHANNEL_MODE_MONO))
+ return 1;
+ } else {
+ if ((capabilities1->channel_mode & (SBC_CHANNEL_MODE_DUAL_CHANNEL|SBC_CHANNEL_MODE_STEREO|SBC_CHANNEL_MODE_JOINT_STEREO)) &&
+ !(capabilities2->channel_mode & (SBC_CHANNEL_MODE_DUAL_CHANNEL|SBC_CHANNEL_MODE_STEREO|SBC_CHANNEL_MODE_JOINT_STEREO)))
+ return -1;
+ if (!(capabilities1->channel_mode & (SBC_CHANNEL_MODE_DUAL_CHANNEL|SBC_CHANNEL_MODE_STEREO|SBC_CHANNEL_MODE_JOINT_STEREO)) &&
+ (capabilities2->channel_mode & (SBC_CHANNEL_MODE_DUAL_CHANNEL|SBC_CHANNEL_MODE_STEREO|SBC_CHANNEL_MODE_JOINT_STEREO)))
+ return 1;
}
- return NULL;
+ return 0;
+}
+
+static int cmp_endpoints_by_freq(const a2dp_sbc_t *capabilities1, const a2dp_sbc_t *capabilities2, const pa_sample_spec *default_sample_spec, bool for_encoding) {
+ uint32_t freq1 = 0;
+ uint32_t freq2 = 0;
+ int i;
+
+ static const struct {
+ uint32_t rate;
+ uint8_t cap;
+ } freq_table[] = {
+ { 16000U, SBC_SAMPLING_FREQ_16000 },
+ { 32000U, SBC_SAMPLING_FREQ_32000 },
+ { 44100U, SBC_SAMPLING_FREQ_44100 },
+ { 48000U, SBC_SAMPLING_FREQ_48000 }
+ };
+
+ /* 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 (!freq1 && freq_table[i].rate >= default_sample_spec->rate && (capabilities1->frequency & freq_table[i].cap))
+ freq1 = freq_table[i].rate;
+ if (!freq2 && freq_table[i].rate >= default_sample_spec->rate && (capabilities2->frequency & freq_table[i].cap))
+ freq2 = freq_table[i].rate;
+ if (freq1 && freq2)
+ break;
+ }
+
+ /* Prefer endpoint which frequency is near to default sample rate */
+ if (freq1 && freq2) {
+ if (freq1 < freq2)
+ return -1;
+ if (freq1 > freq2)
+ return 1;
+ } else if (freq1) {
+ return freq1;
+ } else if (freq2) {
+ return freq2;
+ } else {
+ for (i = PA_ELEMENTSOF(freq_table)-1; i >= 0; i--) {
+ if (capabilities1->frequency & freq_table[i].cap)
+ freq1 = freq_table[i].rate;
+ if (capabilities2->frequency & freq_table[i].cap)
+ freq2 = freq_table[i].rate;
+ if (freq1 && freq2)
+ break;
+ }
+ pa_assert(i >= 0);
+
+ if (freq1 > freq2)
+ return -1;
+ if (freq2 < freq1)
+ return 1;
+ }
+
+ return 0;
+}
+
+static int cmp_endpoints(const uint8_t *capabilities1_buffer, uint8_t capabilities1_size, const uint8_t *capabilities2_buffer, uint8_t capabilities2_size, const pa_sample_spec *default_sample_spec, bool for_encoding) {
+ const a2dp_sbc_t *capabilities1 = (const a2dp_sbc_t *) capabilities1_buffer;
+ const a2dp_sbc_t *capabilities2 = (const a2dp_sbc_t *) capabilities2_buffer;
+ uint8_t max1_bitpool, max2_bitpool, min1_bitpool, min2_bitpool;
+ uint8_t capabilities1_range, capabilities2_range;
+ uint8_t unusable1_range, unusable2_range;
+ int cmp;
+
+ pa_assert(capabilities1_size == sizeof(a2dp_sbc_t));
+ pa_assert(capabilities2_size == sizeof(a2dp_sbc_t));
+
+ /* For mono outputs prefer endpoint with mono capability and for other outputs prefer non-mono capabilities */
+ cmp = cmp_endpoints_by_channels(capabilities1, capabilities2, default_sample_spec, for_encoding);
+ if (cmp != 0)
+ return cmp;
+
+ /* For sample rate above 44.1kHz when at least one endpoint does not support frequency suitable for 44.1kHz, use preference based on frequency */
+ if (default_sample_spec->rate >= 44100 &&
+ !((capabilities1->frequency & (SBC_SAMPLING_FREQ_44100|SBC_SAMPLING_FREQ_48000)) &&
+ (capabilities2->frequency & (SBC_SAMPLING_FREQ_44100|SBC_SAMPLING_FREQ_48000)))) {
+ cmp = cmp_endpoints_by_freq(capabilities1, capabilities2, default_sample_spec, for_encoding);
+ if (cmp != 0)
+ return cmp;
+ }
+
+ /* Calculate usable bitpool range compatible with both remote capabilities and capabilities from auto sbc quality */
+ max1_bitpool = PA_MIN(capabilities1->max_bitpool, SBC_BITPOOL_HQ_JOINT_STEREO_44100);
+ max2_bitpool = PA_MIN(capabilities2->max_bitpool, SBC_BITPOOL_HQ_JOINT_STEREO_44100);
+ min1_bitpool = PA_MAX(capabilities1->min_bitpool, SBC_MIN_BITPOOL);
+ min2_bitpool = PA_MAX(capabilities2->min_bitpool, SBC_MIN_BITPOOL);
+ capabilities1_range = max1_bitpool - min1_bitpool;
+ capabilities2_range = max2_bitpool - min2_bitpool;
+
+ /* Prefer endpoint with larger usable bitpool range compatible with both sides */
+ if (capabilities1_range > capabilities2_range)
+ return -1;
+ if (capabilities1_range < capabilities2_range)
+ return 1;
+
+ /* Calculate unusable bitpool range which is not not compatible with both sides */
+ unusable1_range = PA_MAX(capabilities1->max_bitpool, SBC_BITPOOL_HQ_JOINT_STEREO_44100) - PA_MIN(capabilities1->min_bitpool, SBC_MIN_BITPOOL) - capabilities1_range;
+ unusable2_range = PA_MAX(capabilities2->max_bitpool, SBC_BITPOOL_HQ_JOINT_STEREO_44100) - PA_MIN(capabilities2->min_bitpool, SBC_MIN_BITPOOL) - capabilities2_range;
+
+ /* Prefer endpoint with smaller unusable bitpool range */
+ if (unusable1_range > unusable2_range)
+ return -1;
+ if (unusable1_range < unusable2_range)
+ return 1;
+
+ /* Prefer endpoint with higher maximal bitpool value compatible with boot sides */
+ if (max1_bitpool > max2_bitpool)
+ return -1;
+ if (max1_bitpool < max2_bitpool)
+ return 1;
+
+ /* Prefer endpoint with larger bitpool range */
+ if (capabilities1->max_bitpool - capabilities1->min_bitpool > capabilities2->max_bitpool - capabilities2->min_bitpool)
+ return -1;
+ if (capabilities1->max_bitpool - capabilities1->min_bitpool < capabilities2->max_bitpool - capabilities2->min_bitpool)
+ return 1;
+
+ /* Prefer endpoint with higher maximal bitpool value */
+ if (capabilities1->max_bitpool > capabilities2->max_bitpool)
+ return -1;
+ if (capabilities1->max_bitpool < capabilities2->max_bitpool)
+ return 1;
+
+ /* Last preference is by frequency */
+ cmp = cmp_endpoints_by_freq(capabilities1, capabilities2, default_sample_spec, for_encoding);
+ if (cmp != 0)
+ return cmp;
+
+ return 0;
}
static uint8_t fill_capabilities(uint8_t capabilities_buffer[MAX_A2DP_CAPS_SIZE]) {
@@ -667,7 +802,7 @@ const pa_a2dp_codec pa_a2dp_codec_sbc = {
.id = { A2DP_CODEC_SBC, 0, 0 },
.support_backchannel = false,
.can_accept_capabilities = can_accept_capabilities,
- .choose_remote_endpoint = choose_remote_endpoint,
+ .cmp_endpoints = cmp_endpoints,
.fill_capabilities = fill_capabilities,
.is_configuration_valid = is_configuration_valid,
.fill_preferred_configuration = fill_preferred_configuration,
--
2.20.1
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