pcm_export: add option "pack"

Converts padded 24 bit samples to packed 24 bit samples.  Will replace
the packed S24 sample format, which is not used internally.

src/output/alsa_output_plugin.c

@@ -525,7 +525,7 @@ configure_hw:
 	ad->period_position = 0;
 
 	pcm_export_open(&ad->export, audio_format->format,
-			reverse_endian);
+			false, reverse_endian);
 
 	return true;
 

src/output/oss_output_plugin.c

@@ -536,6 +536,7 @@ oss_probe_sample_format(int fd, enum sample_format sample_format,
 
 #ifdef AFMT_S24_PACKED
 	pcm_export_open(export, sample_format,
+			false,
 			oss_format == AFMT_S24_PACKED &&
 			G_BYTE_ORDER != G_LITTLE_ENDIAN);
 #endif

src/pcm_export.c

@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "pcm_export.h"
+#include "pcm_pack.h"
 #include "util/byte_reverse.h"
 
 void
@@ -35,11 +36,15 @@ void pcm_export_deinit(struct pcm_export_state *state)
 void
 pcm_export_open(struct pcm_export_state *state,
 		enum sample_format sample_format,
-		bool reverse_endian)
+		bool pack, bool reverse_endian)
 {
+	state->pack24 = pack && sample_format == SAMPLE_FORMAT_S24_P32;
+
 	state->reverse_endian = 0;
 	if (reverse_endian) {
-		size_t sample_size = sample_format_size(sample_format);
+		size_t sample_size = state->pack24
+			? 3
+			: sample_format_size(sample_format);
 		assert(sample_size <= 0xff);
 
 		if (sample_size > 1)
@@ -51,6 +56,23 @@ const void *
 pcm_export(struct pcm_export_state *state, const void *data, size_t size,
 	   size_t *dest_size_r)
 {
+	if (state->pack24) {
+		assert(size % 4 == 0);
+
+		const size_t num_samples = size / 4;
+		const size_t dest_size = num_samples * 3;
+
+		const uint8_t *src8 = data, *src_end8 = src8 + size;
+		uint8_t *dest = pcm_buffer_get(&state->pack_buffer, dest_size);
+		assert(dest != NULL);
+
+		pcm_pack_24(dest, (const int32_t *)src8,
+			    (const int32_t *)src_end8);
+
+		data = dest;
+		size = dest_size;
+	}
+
 	if (state->reverse_endian > 0) {
 		assert(state->reverse_endian >= 2);
 

src/pcm_export.h

@@ -34,6 +34,13 @@ struct audio_format;
  * representation which are not supported by the pcm_convert library.
  */
 struct pcm_export_state {
+	/**
+	 * The buffer used to pack samples, removing padding.
+	 *
+	 * @see #reverse_endian
+	 */
+	struct pcm_buffer pack_buffer;
+
 	/**
 	 * The buffer used to reverse the byte order.
 	 *
@@ -41,6 +48,11 @@ struct pcm_export_state {
 	 */
 	struct pcm_buffer reverse_buffer;
 
+	/**
+	 * Pack 24 bit samples?
+	 */
+	bool pack24;
+
 	/**
 	 * Export the samples in reverse byte order?  A non-zero value
 	 * means the option is enabled and represents the size of each
@@ -72,7 +84,7 @@ pcm_export_deinit(struct pcm_export_state *state);
 void
 pcm_export_open(struct pcm_export_state *state,
 		enum sample_format sample_format,
-		bool reverse_endian);
+		bool pack, bool reverse_endian);
 
 /**
  * Export a PCM buffer.