alsa-lib: add iec958 patch to implement HDMI HBR formatting

Signed-off-by: Matthias Reichl <hias@horus.com>

packages/audio/alsa-lib/patches/alsa-lib-001-iec958-hbr.patch

@@ -0,0 +1,150 @@
+From 10ee8fad6ac9f66b90454dee0d6c798efd209a05 Mon Sep 17 00:00:00 2001
+From: Matthias Reichl <hias@horus.com>
+Date: Tue, 30 Jun 2020 12:45:54 +0200
+Subject: [PATCH] pcm_iec958: implement HDMI HBR audio formatting
+
+High bitrate compressed audio data like DTS HD or MAT is usually
+packed into 8-channel data. The HDMI specs state this has to be
+formatted as a single IEC958 stream, compared to normal multi-
+channel PCM data which has to be formatted as parallel IEC958 streams.
+
+As this single-stream formatting mode may break existing setups that
+expect non-PCM multichannel data to be formatted as parallel IEC958
+streams it needs to be explicitly selected by setting the hdmi_mode
+option to true.
+
+The single-stream formatting implementation is prepared to cope with
+arbitrary channel counts but only limited testing was done for channel
+counts other than 8.
+
+Signed-off-by: Matthias Reichl <hias@horus.com>
+---
+ src/pcm/pcm_iec958.c | 37 +++++++++++++++++++++++++++++++++----
+ 1 file changed, 33 insertions(+), 4 deletions(-)
+
+diff --git a/src/pcm/pcm_iec958.c b/src/pcm/pcm_iec958.c
+index 76d3ca7b..17ade957 100644
+--- a/src/pcm/pcm_iec958.c
++++ b/src/pcm/pcm_iec958.c
+@@ -63,6 +63,7 @@ struct snd_pcm_iec958 {
+ 	unsigned int byteswap;
+ 	unsigned char preamble[3];	/* B/M/W or Z/X/Y */
+ 	snd_pcm_fast_ops_t fops;
++	int hdmi_mode;
+ };
+ 
+ enum { PREAMBLE_Z, PREAMBLE_X, PREAMBLE_Y };
+@@ -193,6 +194,10 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec,
+ 	unsigned int channel;
+ 	int32_t sample = 0;
+ 	int counter = iec->counter;
++	int single_stream = iec->hdmi_mode &&
++			    (iec->status[0] & IEC958_AES0_NONAUDIO) &&
++			    (channels == 8);
++	int counter_step = single_stream ? ((channels + 1) >> 1) : 1;
+ 	for (channel = 0; channel < channels; ++channel) {
+ 		const char *src;
+ 		uint32_t *dst;
+@@ -205,7 +210,12 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec,
+ 		src_step = snd_pcm_channel_area_step(src_area);
+ 		dst_step = snd_pcm_channel_area_step(dst_area) / sizeof(uint32_t);
+ 		frames1 = frames;
+-		iec->counter = counter;
++
++		if (single_stream)
++			iec->counter = (counter + (channel >> 1)) % 192;
++		else
++			iec->counter = counter;
++
+ 		while (frames1-- > 0) {
+ 			goto *get;
+ #define GET32_END after
+@@ -217,9 +227,11 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec,
+ 			*dst = sample;
+ 			src += src_step;
+ 			dst += dst_step;
+-			iec->counter++;
++			iec->counter += counter_step;
+ 			iec->counter %= 192;
+ 		}
++		if (single_stream) /* set counter to ch0 value for next iteration */
++			iec->counter = (counter + frames * counter_step) % 192;
+ 	}
+ }
+ #endif /* DOC_HIDDEN */
+@@ -473,6 +485,7 @@ static const snd_pcm_ops_t snd_pcm_iec958_ops = {
+  * \param close_slave When set, the slave PCM handle is closed with copy PCM
+  * \param status_bits The IEC958 status bits
+  * \param preamble_vals The preamble byte values
++ * \param hdmi_mode When set, enable HDMI compliant formatting
+  * \retval zero on success otherwise a negative error code
+  * \warning Using of this function might be dangerous in the sense
+  *          of compatibility reasons. The prototype might be freely
+@@ -481,7 +494,8 @@ static const snd_pcm_ops_t snd_pcm_iec958_ops = {
+ int snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sformat,
+ 			snd_pcm_t *slave, int close_slave,
+ 			const unsigned char *status_bits,
+-			const unsigned char *preamble_vals)
++			const unsigned char *preamble_vals,
++		        int hdmi_mode)
+ {
+ 	snd_pcm_t *pcm;
+ 	snd_pcm_iec958_t *iec;
+@@ -519,6 +533,8 @@ int snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sfo
+ 
+ 	memcpy(iec->preamble, preamble_vals, 3);
+ 
++	iec->hdmi_mode = hdmi_mode;
++
+ 	err = snd_pcm_new(&pcm, SND_PCM_TYPE_IEC958, name, slave->stream, slave->mode);
+ 	if (err < 0) {
+ 		free(iec);
+@@ -566,9 +582,14 @@ pcm.name {
+ 	[preamble.z or preamble.b val]
+ 	[preamble.x or preamble.m val]
+ 	[preamble.y or preamble.w val]
++	[hdmi_mode true]
+ }
+ \endcode
+ 
++When <code>hdmi_mode</code> is true, 8-channel compressed data is
++formatted as 4 contiguous frames of a single IEC958 stream as required
++by the HDMI HBR specification.
++
+ \subsection pcm_plugins_iec958_funcref Function reference
+ 
+ <UL>
+@@ -605,6 +626,7 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name,
+ 	unsigned char preamble_vals[3] = {
+ 		0x08, 0x02, 0x04 /* Z, X, Y */
+ 	};
++	int hdmi_mode = 0;
+ 
+ 	snd_config_for_each(i, next, conf) {
+ 		snd_config_t *n = snd_config_iterator_entry(i);
+@@ -633,6 +655,13 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name,
+ 			preamble = n;
+ 			continue;
+ 		}
++		if (strcmp(id, "hdmi_mode") == 0) {
++			err = snd_config_get_bool(n);
++			if (err < 0)
++				continue;
++			hdmi_mode = err;
++			continue;
++		}
+ 		SNDERR("Unknown field %s", id);
+ 		return -EINVAL;
+ 	}
+@@ -707,7 +736,7 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name,
+ 		return err;
+ 	err = snd_pcm_iec958_open(pcmp, name, sformat, spcm, 1,
+ 				  status ? status_bits : NULL,
+-				  preamble_vals);
++				  preamble_vals, hdmi_mode);
+ 	if (err < 0)
+ 		snd_pcm_close(spcm);
+ 	return err;
+-- 
+2.20.1
+