obs-studio/plugins/decklink/audio-repack.c

#include "audio-repack.h"

#include <emmintrin.h>

int check_buffer(struct audio_repack *repack,
		uint32_t frame_count)
{
	const uint32_t new_size = frame_count * repack->base_dst_size
			+ repack->extra_dst_size;

	if (repack->packet_size < new_size) {
		repack->packet_buffer = brealloc(
				repack->packet_buffer, new_size);
		if (!repack->packet_buffer)
			return -1;

		repack->packet_size = new_size;
	}

	return 0;
}

/*
 * Swap channel 3 & 4, 5 & 7, 6 & 8 and squash arrays
 * 2.1:
 *
 * | FL | FR | LFE | emp | emp | emp |emp |emp |
 * |    |    |
 * | FL | FR | LFE |
 * 4.0 (quad):
 *
 * | FL | FR | BR | BL | emp | emp |emp |emp |
 * |    |         x    |
 * | FL | FR | BL | BC |
 *
 * 4.1:
 *
 * | FL | FR |LFE | FC | BC | emp |emp |emp |
 * |    |         x    |    |
 * | FL | FR | FC |LFE | BC |
 *
 * 5.1:
 *
 * | FL | FR |LFE | FC |(emp|emp)|(BL|BR)|
 * |    |         x              x
 * | FL | FR | FC |LFE | BL | BR |
 *
 * 7.1:
 *
 * | FL | FR |LFE | FC |( SL | SR )|(BL |BR )|
 * |    |         x              X
 * | FL | FR | FC |LFE |( BL | BR )|(SL |SR )|
 */

int repack_squash_swap(struct audio_repack *repack,
		const uint8_t *bsrc, uint32_t frame_count)
{
	if (check_buffer(repack, frame_count) < 0)
		return -1;

	int squash = repack->extra_dst_size;
	const __m128i *src = (__m128i *)bsrc;
	const __m128i *esrc = src + frame_count;
	uint16_t *dst = (uint16_t *)repack->packet_buffer;
	/* 2.1 audio does not require re-ordering but still needs squashing
	 * in order to avoid sampling issues.
	 */
	if (squash == 5) {
		while (src != esrc) {
			__m128i target = _mm_load_si128(src++);
			_mm_storeu_si128((__m128i *)dst, target);
			dst += 8 - squash;
		}
	} else {
		while (src != esrc) {
			__m128i target = _mm_load_si128(src++);
			__m128i buf = _mm_shufflelo_epi16(target, _MM_SHUFFLE(2, 3, 1, 0));
			__m128i buf2 = _mm_shufflehi_epi16(buf, _MM_SHUFFLE(1, 0, 3, 2));
			_mm_storeu_si128((__m128i *)dst, buf2);
			dst += 8 - squash;
		}
	}

	return 0;
}

int audio_repack_init(struct audio_repack *repack,
		audio_repack_mode_t repack_mode, uint8_t sample_bit)
{
	memset(repack, 0, sizeof(*repack));

	if (sample_bit != 16)
		return -1;

	switch (repack_mode) {
	case repack_mode_8to3ch_swap23:
		repack->base_src_size = 8 * (16 / 8);
		repack->base_dst_size = 3 * (16 / 8);
		repack->extra_dst_size = 5;
		repack->repack_func = &repack_squash_swap;
		break;
	case repack_mode_8to4ch_swap23:
		repack->base_src_size = 8 * (16 / 8);
		repack->base_dst_size = 4 * (16 / 8);
		repack->extra_dst_size = 4;
		repack->repack_func = &repack_squash_swap;
		break;

	case repack_mode_8to5ch_swap23:
		repack->base_src_size = 8 * (16 / 8);
		repack->base_dst_size = 5 * (16 / 8);
		repack->extra_dst_size = 3;
		repack->repack_func = &repack_squash_swap;
		break;

	case repack_mode_8to6ch_swap23:
		repack->base_src_size = 8 * (16 / 8);
		repack->base_dst_size = 6 * (16 / 8);
		repack->extra_dst_size = 2;
		repack->repack_func = &repack_squash_swap;
		break;

	case repack_mode_8ch_swap23_swap46_swap57:
		repack->base_src_size = 8 * (16 / 8);
		repack->base_dst_size = 8 * (16 / 8);
		repack->extra_dst_size = 0;
		repack->repack_func = &repack_squash_swap;
		break;

	default: return -1;
	}

	return 0;
}

void audio_repack_free(struct audio_repack *repack)
{
	if (repack->packet_buffer)
		bfree(repack->packet_buffer);

	memset(repack, 0, sizeof(*repack));
}