Add multichannel USB handshaking with AudioFlinger
The number of channels can be "forced" using k_force_channels.
If the channel count proposed by AudioFlinger is not permitted
by the device, it is emulated.
Change-Id: Ib20e680c8f95adb84616a4fe52977f659cf4d6ca
diff --git a/modules/usbaudio/audio_hw.c b/modules/usbaudio/audio_hw.c
index 4a946e7..1ef2588 100644
--- a/modules/usbaudio/audio_hw.c
+++ b/modules/usbaudio/audio_hw.c
@@ -38,6 +38,17 @@
#include <audio_utils/channels.h>
+/* FOR TESTING:
+ * Set k_force_channels to force the number of channels to present to AudioFlinger.
+ * 0 disables (this is default: present the device channels to AudioFlinger).
+ * 2 forces to legacy stereo mode.
+ *
+ * Others values can be tried (up to 8).
+ * TODO: AudioFlinger cannot support more than 8 active output channels
+ * at this time, so limiting logic needs to be put here or communicated from above.
+ */
+static const unsigned k_force_channels = 0;
+
#include "alsa_device_profile.h"
#include "alsa_device_proxy.h"
#include "logging.h"
@@ -69,6 +80,11 @@
alsa_device_profile * profile;
alsa_device_proxy proxy; /* state of the stream */
+ unsigned hal_channel_count; /* channel count exposed to AudioFlinger.
+ * This may differ from the device channel count when
+ * the device is not compatible with AudioFlinger
+ * capabilities, e.g. exposes too many channels or
+ * too few channels. */
void * conversion_buffer; /* any conversions are put into here
* they could come from here too if
* there was a previous conversion */
@@ -243,18 +259,8 @@
static uint32_t out_get_channels(const struct audio_stream *stream)
{
- /*
- * alsa_device_profile * profile = ((struct stream_out*)stream)->profile;
- * unsigned channel_count = profile_get_channel_count(profile);
- * uint32_t channel_mask = audio_channel_out_mask_from_count(channel_count);
- * ALOGV("out_get_channels() = 0x%X count:%d", channel_mask, channel_count);
- * return channel_mask;
- */
-
- /* Always Stereo for now. We will do *some* conversions in this HAL.
- * TODO When AudioPolicyManager & AudioFlinger supports arbitrary channels
- * rewrite this to return the ACTUAL channel format */
- return AUDIO_CHANNEL_OUT_STEREO;
+ const struct stream_out *out = (const struct stream_out*)stream;
+ return audio_channel_out_mask_from_count(out->hal_channel_count);
}
static audio_format_t out_get_format(const struct audio_stream *stream)
@@ -387,39 +393,27 @@
out->standby = false;
}
- alsa_device_profile* profile = out->profile;
alsa_device_proxy* proxy = &out->proxy;
-
- /*
- * Setup conversion buffer
- * compute maximum potential buffer size.
- * * 2 for stereo -> quad conversion
- * * 3/2 for 16bit -> 24 bit conversion
- */
- size_t required_conversion_buffer_size = (bytes * 3 * 2) / 2;
- if (required_conversion_buffer_size > out->conversion_buffer_size) {
- /* TODO Remove this when AudioPolicyManger/AudioFlinger support arbitrary formats
- (and do these conversions themselves) */
- out->conversion_buffer_size = required_conversion_buffer_size;
- out->conversion_buffer = realloc(out->conversion_buffer, out->conversion_buffer_size);
- }
-
const void * write_buff = buffer;
int num_write_buff_bytes = bytes;
-
- /*
- * Num Channels conversion
- */
- int num_device_channels = proxy_get_channel_count(proxy);
- int num_req_channels = 2; /* always for now */
-
+ const int num_device_channels = proxy_get_channel_count(proxy); /* what we told alsa */
+ const int num_req_channels = out->hal_channel_count; /* what we told AudioFlinger */
if (num_device_channels != num_req_channels) {
- audio_format_t audio_format = out_get_format(&(out->stream.common));
- unsigned sample_size_in_bytes = audio_bytes_per_sample(audio_format);
+ /* allocate buffer */
+ const size_t required_conversion_buffer_size =
+ bytes * num_device_channels / num_req_channels;
+ if (required_conversion_buffer_size > out->conversion_buffer_size) {
+ out->conversion_buffer_size = required_conversion_buffer_size;
+ out->conversion_buffer = realloc(out->conversion_buffer,
+ out->conversion_buffer_size);
+ }
+ /* convert data */
+ const audio_format_t audio_format = out_get_format(&(out->stream.common));
+ const unsigned sample_size_in_bytes = audio_bytes_per_sample(audio_format);
num_write_buff_bytes =
- adjust_channels(write_buff, num_req_channels,
- out->conversion_buffer, num_device_channels,
- sample_size_in_bytes, num_write_buff_bytes);
+ adjust_channels(write_buff, num_req_channels,
+ out->conversion_buffer, num_device_channels,
+ sample_size_in_bytes, num_write_buff_bytes);
write_buff = out->conversion_buffer;
}
@@ -541,33 +535,18 @@
}
/* Channels */
- if (config->channel_mask == AUDIO_CHANNEL_NONE) {
- /* This will be needed when the framework supports non-stereo output */
- /* config->channel_mask =
- * audio_channel_out_mask_from_count(profile_get_default_channel_count(out->profile));
- */
- proxy_config.channels = profile_get_default_channel_count(out->profile);
- config->channel_mask = AUDIO_CHANNEL_OUT_STEREO;
- } else {
- /* This will be needed when the framework supports non-stereo output */
- /*
- * unsigned channel_count = audio_channel_count_from_out_mask(config->channel_mask);
- * if (profile_is_channel_count_valid(out->profile, channel_count)) {
- * proxy_set_channel_count(out->proxy, channel_count);
- * } else {
- * config->channel_mask =
- * audio_channel_out_mask_from_count(proxy_get_channel_count(out->proxy));
- * ret = -EINVAL;
- * }
- */
- if (config->channel_mask != AUDIO_CHANNEL_OUT_STEREO) {
- proxy_config.channels = profile_get_default_channel_count(out->profile);
- config->channel_mask = AUDIO_CHANNEL_OUT_STEREO;
- ret = -EINVAL;
- } else {
- proxy_config.channels = profile_get_default_channel_count(out->profile);
- }
+ unsigned proposed_channel_count = profile_get_default_channel_count(out->profile);
+ if (k_force_channels) {
+ proposed_channel_count = k_force_channels;
+ } else if (config->channel_mask != AUDIO_CHANNEL_NONE) {
+ proposed_channel_count = audio_channel_count_from_out_mask(config->channel_mask);
}
+ /* we can expose any channel count mask, and emulate internally. */
+ config->channel_mask = audio_channel_out_mask_from_count(proposed_channel_count);
+ out->hal_channel_count = proposed_channel_count;
+ /* no validity checks are needed as proxy_prepare() forces channel_count to be valid.
+ * and we emulate any channel count discrepancies in out_write(). */
+ proxy_config.channels = proposed_channel_count;
proxy_prepare(&out->proxy, out->profile, &proxy_config);