From 81208d78acb260c7c2e6debc765042dd5e98f862 Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Tue, 20 Mar 2012 01:01:12 +0100 Subject: pcm_dsd: implement DSD to 24 bit USB conversion Implements the dCS suggested standard: http://www.dcsltd.co.uk/page/assets/DSDoverUSB.pdf --- src/pcm_dsd_usb.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 src/pcm_dsd_usb.c (limited to 'src/pcm_dsd_usb.c') diff --git a/src/pcm_dsd_usb.c b/src/pcm_dsd_usb.c new file mode 100644 index 00000000..976420c0 --- /dev/null +++ b/src/pcm_dsd_usb.c @@ -0,0 +1,74 @@ +/* + * Copyright (C) 2003-2012 The Music Player Daemon Project + * http://www.musicpd.org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include "config.h" +#include "pcm_dsd_usb.h" +#include "pcm_buffer.h" +#include "audio_format.h" + +G_GNUC_CONST +static inline uint32_t +pcm_two_dsd_to_usb(uint8_t a, uint8_t b) +{ + return 0xffaa0000 | (a << 8) | b; +} + +const uint32_t * +pcm_dsd_to_usb(struct pcm_buffer *buffer, unsigned channels, + const uint8_t *src, size_t src_size, + size_t *dest_size_r) +{ + assert(buffer != NULL); + assert(audio_valid_channel_count(channels)); + assert(src != NULL); + assert(src_size > 0); + assert(src_size % channels == 0); + + const unsigned num_src_samples = src_size; + const unsigned num_src_frames = num_src_samples / channels; + + /* this rounds down and discards the last odd frame; not + elegant, but good enough for now */ + const unsigned num_frames = num_src_frames / 2; + const unsigned num_samples = num_frames * channels; + + const size_t dest_size = num_samples * 4; + *dest_size_r = dest_size; + uint32_t *const dest0 = pcm_buffer_get(buffer, dest_size), + *dest = dest0; + + for (unsigned i = num_frames; i > 0; --i) { + for (unsigned c = channels; c > 0; --c) { + /* each 24 bit sample has 16 DSD sample bits + plus the magic 0xaa marker */ + + *dest++ = pcm_two_dsd_to_usb(src[0], src[channels]); + + /* seek the source pointer to the next + channel */ + ++src; + } + + /* skip the second byte of each channel, because we + have already copied it */ + src += channels; + } + + return dest0; +} -- cgit v1.2.3