[pulseaudio-discuss] [PATCH 1/2] alsa: Use alsa-lib's channel mapping API to select the best channel map
David Henningsson
david.henningsson at canonical.com
Tue Oct 22 22:13:55 CEST 2013
Recently ALSA added the channel mapping API. Here we use it to set
the right channel map if ALSA gives us several maps to choose from,
and skip the PCM completely if no map fit.
Signed-off-by: David Henningsson <david.henningsson at canonical.com>
---
src/modules/alsa/alsa-sink.c | 6 ++
src/modules/alsa/alsa-source.c | 6 ++
src/modules/alsa/alsa-util.c | 142 +++++++++++++++++++++++++++++++++++++++++
src/modules/alsa/alsa-util.h | 2 +
4 files changed, 156 insertions(+)
diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
index e10e14e..e101d48 100644
--- a/src/modules/alsa/alsa-sink.c
+++ b/src/modules/alsa/alsa-sink.c
@@ -1111,6 +1111,9 @@ static int unsuspend(struct userdata *u) {
goto fail;
}
+ if (pa_alsa_set_channel_map(u->pcm_handle, &u->sink->channel_map) < 0)
+ goto fail;
+
if (update_sw_params(u) < 0)
goto fail;
@@ -2243,6 +2246,9 @@ pa_sink *pa_alsa_sink_new(pa_module *m, pa_modargs *ma, const char*driver, pa_ca
goto fail;
}
+ if (pa_alsa_set_channel_map(u->pcm_handle, &map) < 0)
+ goto fail;
+
/* ALSA might tweak the sample spec, so recalculate the frame size */
frame_size = pa_frame_size(&ss);
diff --git a/src/modules/alsa/alsa-source.c b/src/modules/alsa/alsa-source.c
index 2e93e0f..41e6601 100644
--- a/src/modules/alsa/alsa-source.c
+++ b/src/modules/alsa/alsa-source.c
@@ -995,6 +995,9 @@ static int unsuspend(struct userdata *u) {
goto fail;
}
+ if (pa_alsa_set_channel_map(u->pcm_handle, &u->source->channel_map) < 0)
+ goto fail;
+
if (update_sw_params(u) < 0)
goto fail;
@@ -1942,6 +1945,9 @@ pa_source *pa_alsa_source_new(pa_module *m, pa_modargs *ma, const char*driver, p
goto fail;
}
+ if (pa_alsa_set_channel_map(u->pcm_handle, &map) < 0)
+ goto fail;
+
/* ALSA might tweak the sample spec, so recalculate the frame size */
frame_size = pa_frame_size(&ss);
diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c
index 75f5858..0baf54d 100644
--- a/src/modules/alsa/alsa-util.c
+++ b/src/modules/alsa/alsa-util.c
@@ -478,6 +478,143 @@ int pa_alsa_set_sw_params(snd_pcm_t *pcm, snd_pcm_uframes_t avail_min, bool peri
return 0;
}
+#if (SND_LIB_VERSION >= ((1<<16)|(0<<8)|27)) /* API additions in 1.0.27 */
+
+static const int chmap_channel_ids[PA_CHANNEL_POSITION_MAX] = {
+ [PA_CHANNEL_POSITION_MONO] = SND_CHMAP_MONO,
+
+ [PA_CHANNEL_POSITION_FRONT_CENTER] = SND_CHMAP_FC,
+ [PA_CHANNEL_POSITION_FRONT_LEFT] = SND_CHMAP_FL,
+ [PA_CHANNEL_POSITION_FRONT_RIGHT] = SND_CHMAP_FR,
+
+ [PA_CHANNEL_POSITION_REAR_CENTER] = SND_CHMAP_RC,
+ [PA_CHANNEL_POSITION_REAR_LEFT] = SND_CHMAP_RL,
+ [PA_CHANNEL_POSITION_REAR_RIGHT] = SND_CHMAP_RR,
+
+ [PA_CHANNEL_POSITION_LFE] = SND_CHMAP_LFE,
+
+ [PA_CHANNEL_POSITION_FRONT_LEFT_OF_CENTER] = SND_CHMAP_FLC,
+ [PA_CHANNEL_POSITION_FRONT_RIGHT_OF_CENTER] = SND_CHMAP_FRC,
+
+ [PA_CHANNEL_POSITION_SIDE_LEFT] = SND_CHMAP_SL,
+ [PA_CHANNEL_POSITION_SIDE_RIGHT] = SND_CHMAP_SR,
+
+ [PA_CHANNEL_POSITION_TOP_CENTER] = SND_CHMAP_TC,
+
+ [PA_CHANNEL_POSITION_TOP_FRONT_CENTER] = SND_CHMAP_TFC,
+ [PA_CHANNEL_POSITION_TOP_FRONT_LEFT] = SND_CHMAP_TFL,
+ [PA_CHANNEL_POSITION_TOP_FRONT_RIGHT] = SND_CHMAP_TFR,
+
+ [PA_CHANNEL_POSITION_TOP_REAR_CENTER] = SND_CHMAP_TRC,
+ [PA_CHANNEL_POSITION_TOP_REAR_LEFT] = SND_CHMAP_TRL,
+ [PA_CHANNEL_POSITION_TOP_REAR_RIGHT] = SND_CHMAP_TRR
+};
+
+int pa_alsa_set_channel_map(snd_pcm_t *pcm, pa_channel_map *map) {
+ snd_pcm_chmap_t *chmap;
+ unsigned int i;
+ int err;
+ char buf[512] = "";
+
+ chmap = alloca(sizeof(unsigned int) * (map->channels + 1));
+ chmap->channels = map->channels;
+ for (i = 0; i < map->channels; i++)
+ chmap->pos[i] = chmap_channel_ids[map->map[i]];
+
+ if (snd_pcm_chmap_print(chmap, sizeof(buf), buf) < 0)
+ return -1;
+ pa_log_debug("Setting channel map to %s", buf);
+
+ if ((err = snd_pcm_set_chmap(pcm, chmap)) < 0) {
+ if (err == -ENXIO)
+ return 0; /* snd_pcm_set_chmap returns -ENXIO if device does not support channel maps at all */
+ pa_log_warn("Unable to set channel map: %s\n", pa_alsa_strerror(err));
+ return -1;
+ }
+ return 0;
+}
+
+
+static int is_chmap_compatible(snd_pcm_chmap_query_t *c, pa_channel_map *map) {
+ unsigned int i;
+ bool needsmove = false;
+ char cm[PA_CHANNEL_MAP_SNPRINT_MAX];
+ char buf[512] = "";
+
+ pa_assert(c);
+ pa_assert(map);
+
+ pa_channel_map_snprint(cm, sizeof(cm), map);
+ if (snd_pcm_chmap_print(&c->map, sizeof(buf), buf) < 0)
+ return -1;
+
+ pa_log_debug("Checking ALSA channel map type %s, %s against PA map %s",
+ snd_pcm_chmap_type_name(c->type), buf, cm);
+
+ if (c->map.channels != map->channels)
+ needsmove = true;
+
+ for (i = 0; i < map->channels; i++) {
+ unsigned int j;
+ bool found = false;
+ unsigned int m = chmap_channel_ids[map->map[i]];
+ if (c->map.channels > i && m == c->map.pos[i])
+ continue; /* Great, it's where we want it! */
+ for (j = 0; j < c->map.channels; j++)
+ if (m == c->map.pos[j]) {
+ found = true;
+ if (c->type != SND_CHMAP_TYPE_VAR)
+ needsmove = true;
+ break;
+ }
+ if (!found)
+ return -1;
+ }
+
+ return needsmove ? 1 : 2;
+}
+
+static int query_chmap_for_pcm(snd_pcm_t *pcm, pa_channel_map *map) {
+
+ snd_pcm_chmap_query_t **i, **avail;
+ int bestscore = 0;
+
+ avail = snd_pcm_query_chmaps(pcm);
+ if (avail == NULL) {
+ pa_log_debug("This device does not support ALSA channel mapping API.");
+ return 0;
+ }
+
+ for (i = avail; *i != NULL; i++) {
+ int score = is_chmap_compatible(*i, map);
+ if (score > bestscore)
+ bestscore = score;
+ }
+
+ snd_pcm_free_chmaps(avail);
+
+ if (bestscore < 2) {
+ /* TODO: If we find all channels but not in the right order, we can update
+ our own channel map to match. We haven't implemented that yet. */
+ pa_log_debug("Did not find a compatible channel map, skipping.");
+ return -1;
+ }
+
+ return 0;
+}
+
+#else
+
+static int query_chmap_for_pcm(snd_pcm_t *pcm, pa_channel_map *map) {
+ return 0;
+}
+
+int pa_alsa_set_chmap(snd_pcm_t *pcm, pa_channel_map *map) {
+ return 0;
+}
+
+#endif
+
snd_pcm_t *pa_alsa_open_by_device_id_auto(
const char *dev_id,
char **dev,
@@ -714,6 +851,11 @@ snd_pcm_t *pa_alsa_open_by_device_string(
goto fail;
}
+ if (query_chmap_for_pcm(pcm_handle, map) < 0) {
+ snd_pcm_close(pcm_handle);
+ goto fail;
+ }
+
if (dev)
*dev = d;
else
diff --git a/src/modules/alsa/alsa-util.h b/src/modules/alsa/alsa-util.h
index 0e3ae69..2175985 100644
--- a/src/modules/alsa/alsa-util.h
+++ b/src/modules/alsa/alsa-util.h
@@ -108,6 +108,8 @@ snd_pcm_t *pa_alsa_open_by_template(
bool *use_tsched, /* modified at return */
bool require_exact_channel_number);
+int pa_alsa_set_channel_map(snd_pcm_t *pcm, pa_channel_map *map);
+
void pa_alsa_dump(pa_log_level_t level, snd_pcm_t *pcm);
void pa_alsa_dump_status(snd_pcm_t *pcm);
--
1.8.3.2
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