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ALSA: hda: HDMI channel allocations for audio infoframe
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To play a 3+ channels LPCM/DSD stream via HDMI,

	- HDMI sink must tell HDMI source about its speaker placements
	  (via ELD, speaker-allocation field)
	- HDMI source must tell the HDMI sink about channel allocation
	  (via audio infoframe, channel-allocation field)

(related docs: HDMI 1.3a spec section 7.4, CEA-861-D section 7.5.3 and 6.6)

This patch attempts to set the CA(channel-allocation) byte in the audio infoframe
according to
	- the number of channels in the current stream
	- the speakers attached to the HDMI sink

A channel_allocations[] line must meet the following two criteria to be
considered as a valid candidate for CA:
	1) its number of allocated channels = substream->runtime->channels
	2) its speakers are a subset of the available ones on the sink side

If there are multiple candidates, the first one is selected.  This simple
policy shall cheat the sink into playing music, but may direct data to the
wrong speakers.

Signed-off-by: Wu Fengguang <wfg@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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Wu Fengguang authored and Takashi Iwai committed Nov 19, 2008
1 parent 903b21d commit 698544d
Showing 1 changed file with 205 additions and 0 deletions.
205 changes: 205 additions & 0 deletions sound/pci/hda/patch_intelhdmi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,132 @@ struct hdmi_audio_infoframe {
u8 reserved[5]; /* PB6 - PB10 */
};

/*
* CEA speaker placement:
*
* FLH FCH FRH
* FLW FL FLC FC FRC FR FRW
*
* LFE
* TC
*
* RL RLC RC RRC RR
*
* The Left/Right Surround channel _notions_ LS/RS in SMPTE 320M corresponds to
* CEA RL/RR; The SMPTE channel _assignment_ C/LFE is swapped to CEA LFE/FC.
*/
enum cea_speaker_placement {
FL = (1 << 0), /* Front Left */
FC = (1 << 1), /* Front Center */
FR = (1 << 2), /* Front Right */
FLC = (1 << 3), /* Front Left Center */
FRC = (1 << 4), /* Front Right Center */
RL = (1 << 5), /* Rear Left */
RC = (1 << 6), /* Rear Center */
RR = (1 << 7), /* Rear Right */
RLC = (1 << 8), /* Rear Left Center */
RRC = (1 << 9), /* Rear Right Center */
LFE = (1 << 10), /* Low Frequency Effect */
FLW = (1 << 11), /* Front Left Wide */
FRW = (1 << 12), /* Front Right Wide */
FLH = (1 << 13), /* Front Left High */
FCH = (1 << 14), /* Front Center High */
FRH = (1 << 15), /* Front Right High */
TC = (1 << 16), /* Top Center */
};

/*
* ELD SA bits in the CEA Speaker Allocation data block
*/
static int eld_speaker_allocation_bits[] = {
[0] = FL | FR,
[1] = LFE,
[2] = FC,
[3] = RL | RR,
[4] = RC,
[5] = FLC | FRC,
[6] = RLC | RRC,
/* the following are not defined in ELD yet */
[7] = FLW | FRW,
[8] = FLH | FRH,
[9] = TC,
[10] = FCH,
};

struct cea_channel_speaker_allocation {
int ca_index;
int speakers[8];

/* derived values, just for convenience */
int channels;
int spk_mask;
};

/*
* This is an ordered list!
*
* The preceding ones have better chances to be selected by
* hdmi_setup_channel_allocation().
*/
static struct cea_channel_speaker_allocation channel_allocations[] = {
/* channel: 8 7 6 5 4 3 2 1 */
{ .ca_index = 0x00, .speakers = { 0, 0, 0, 0, 0, 0, FR, FL } },
/* 2.1 */
{ .ca_index = 0x01, .speakers = { 0, 0, 0, 0, 0, LFE, FR, FL } },
/* dolby surround */
{ .ca_index = 0x02, .speakers = { 0, 0, 0, 0, FC, 0, FR, FL } },
{ .ca_index = 0x03, .speakers = { 0, 0, 0, 0, FC, LFE, FR, FL } },
{ .ca_index = 0x04, .speakers = { 0, 0, 0, RC, 0, 0, FR, FL } },
{ .ca_index = 0x05, .speakers = { 0, 0, 0, RC, 0, LFE, FR, FL } },
{ .ca_index = 0x06, .speakers = { 0, 0, 0, RC, FC, 0, FR, FL } },
{ .ca_index = 0x07, .speakers = { 0, 0, 0, RC, FC, LFE, FR, FL } },
{ .ca_index = 0x08, .speakers = { 0, 0, RR, RL, 0, 0, FR, FL } },
{ .ca_index = 0x09, .speakers = { 0, 0, RR, RL, 0, LFE, FR, FL } },
{ .ca_index = 0x0a, .speakers = { 0, 0, RR, RL, FC, 0, FR, FL } },
/* 5.1 */
{ .ca_index = 0x0b, .speakers = { 0, 0, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x0c, .speakers = { 0, RC, RR, RL, 0, 0, FR, FL } },
{ .ca_index = 0x0d, .speakers = { 0, RC, RR, RL, 0, LFE, FR, FL } },
{ .ca_index = 0x0e, .speakers = { 0, RC, RR, RL, FC, 0, FR, FL } },
/* 6.1 */
{ .ca_index = 0x0f, .speakers = { 0, RC, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x10, .speakers = { RRC, RLC, RR, RL, 0, 0, FR, FL } },
{ .ca_index = 0x11, .speakers = { RRC, RLC, RR, RL, 0, LFE, FR, FL } },
{ .ca_index = 0x12, .speakers = { RRC, RLC, RR, RL, FC, 0, FR, FL } },
/* 7.1 */
{ .ca_index = 0x13, .speakers = { RRC, RLC, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x14, .speakers = { FRC, FLC, 0, 0, 0, 0, FR, FL } },
{ .ca_index = 0x15, .speakers = { FRC, FLC, 0, 0, 0, LFE, FR, FL } },
{ .ca_index = 0x16, .speakers = { FRC, FLC, 0, 0, FC, 0, FR, FL } },
{ .ca_index = 0x17, .speakers = { FRC, FLC, 0, 0, FC, LFE, FR, FL } },
{ .ca_index = 0x18, .speakers = { FRC, FLC, 0, RC, 0, 0, FR, FL } },
{ .ca_index = 0x19, .speakers = { FRC, FLC, 0, RC, 0, LFE, FR, FL } },
{ .ca_index = 0x1a, .speakers = { FRC, FLC, 0, RC, FC, 0, FR, FL } },
{ .ca_index = 0x1b, .speakers = { FRC, FLC, 0, RC, FC, LFE, FR, FL } },
{ .ca_index = 0x1c, .speakers = { FRC, FLC, RR, RL, 0, 0, FR, FL } },
{ .ca_index = 0x1d, .speakers = { FRC, FLC, RR, RL, 0, LFE, FR, FL } },
{ .ca_index = 0x1e, .speakers = { FRC, FLC, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x1f, .speakers = { FRC, FLC, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x20, .speakers = { 0, FCH, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x21, .speakers = { 0, FCH, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x22, .speakers = { TC, 0, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x23, .speakers = { TC, 0, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x24, .speakers = { FRH, FLH, RR, RL, 0, 0, FR, FL } },
{ .ca_index = 0x25, .speakers = { FRH, FLH, RR, RL, 0, LFE, FR, FL } },
{ .ca_index = 0x26, .speakers = { FRW, FLW, RR, RL, 0, 0, FR, FL } },
{ .ca_index = 0x27, .speakers = { FRW, FLW, RR, RL, 0, LFE, FR, FL } },
{ .ca_index = 0x28, .speakers = { TC, RC, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x29, .speakers = { TC, RC, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x2a, .speakers = { FCH, RC, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x2b, .speakers = { FCH, RC, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x2c, .speakers = { TC, FCH, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x2d, .speakers = { TC, FCH, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x2e, .speakers = { FRH, FLH, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x2f, .speakers = { FRH, FLH, RR, RL, FC, LFE, FR, FL } },
{ .ca_index = 0x30, .speakers = { FRW, FLW, RR, RL, FC, 0, FR, FL } },
{ .ca_index = 0x31, .speakers = { FRW, FLW, RR, RL, FC, LFE, FR, FL } },
};

/*
* HDMI routines
*/
Expand Down Expand Up @@ -260,6 +386,81 @@ static void hdmi_fill_audio_infoframe(struct hda_codec *codec,
hdmi_write_dip_byte(codec, PIN_NID, params[i]);
}

/*
* Compute derived values in channel_allocations[].
*/
static void init_channel_allocations(void)
{
int i, j;
struct cea_channel_speaker_allocation *p;

for (i = 0; i < ARRAY_SIZE(channel_allocations); i++) {
p = channel_allocations + i;
p->channels = 0;
p->spk_mask = 0;
for (j = 0; j < ARRAY_SIZE(p->speakers); j++)
if (p->speakers[j]) {
p->channels++;
p->spk_mask |= p->speakers[j];
}
}
}

/*
* The transformation takes two steps:
*
* eld->spk_alloc => (eld_speaker_allocation_bits[]) => spk_mask
* spk_mask => (channel_allocations[]) => ai->CA
*
* TODO: it could select the wrong CA from multiple candidates.
*/
static int hdmi_setup_channel_allocation(struct hda_codec *codec,
struct hdmi_audio_infoframe *ai)
{
struct intel_hdmi_spec *spec = codec->spec;
struct sink_eld *eld = &spec->sink;
int i;
int spk_mask = 0;
int channels = 1 + (ai->CC02_CT47 & 0x7);
char buf[SND_PRINT_CHANNEL_ALLOCATION_ADVISED_BUFSIZE];

/*
* CA defaults to 0 for basic stereo audio
*/
if (!eld->eld_ver)
return 0;
if (!eld->spk_alloc)
return 0;
if (channels <= 2)
return 0;

/*
* expand ELD's speaker allocation mask
*
* ELD tells the speaker mask in a compact(paired) form,
* expand ELD's notions to match the ones used by audio infoframe.
*/
for (i = 0; i < ARRAY_SIZE(eld_speaker_allocation_bits); i++) {
if (eld->spk_alloc & (1 << i))
spk_mask |= eld_speaker_allocation_bits[i];
}

/* search for the first working match in the CA table */
for (i = 0; i < ARRAY_SIZE(channel_allocations); i++) {
if (channels == channel_allocations[i].channels &&
(spk_mask & channel_allocations[i].spk_mask) ==
channel_allocations[i].spk_mask) {
ai->CA = channel_allocations[i].ca_index;
return 0;
}
}

snd_print_channel_allocation(eld->spk_alloc, buf, sizeof(buf));
snd_printd(KERN_INFO "failed to setup channel allocation: %d of %s\n",
channels, buf);
return -1;
}

static void hdmi_setup_audio_infoframe(struct hda_codec *codec,
struct snd_pcm_substream *substream)
{
Expand All @@ -270,6 +471,8 @@ static void hdmi_setup_audio_infoframe(struct hda_codec *codec,
.CC02_CT47 = substream->runtime->channels - 1,
};

hdmi_setup_channel_allocation(codec, &ai);

hdmi_fill_audio_infoframe(codec, &ai);
}

Expand Down Expand Up @@ -455,6 +658,8 @@ static int patch_intel_hdmi(struct hda_codec *codec)

snd_hda_eld_proc_new(codec, &spec->sink);

init_channel_allocations();

return 0;
}

Expand Down

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