[alsa-devel] [PATCH 11/11] ALSA: digi00x: apply double-oh-three algorithm to multiplex PCM samples
Takashi Sakamoto
o-takashi at sakamocchi.jp
Sun Mar 29 17:05:31 CEST 2015
Digi 002/003 family uses own way to multiplex PCM samples into data
blocks of CIP payload for received stream, thus AMDTP-conformant
implementation causes noisy sound.
This commit applies double-oh-three algorithm, which discovered by Robin
Gareus and Damien Zammit in 2012.
Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
sound/firewire/digi00x/digi00x-pcm.c | 9 +-
sound/firewire/digi00x/digi00x-protocol.c | 143 ++++++++++++++++++++++++++++++
sound/firewire/digi00x/digi00x.h | 21 +++++
3 files changed, 170 insertions(+), 3 deletions(-)
diff --git a/sound/firewire/digi00x/digi00x-pcm.c b/sound/firewire/digi00x/digi00x-pcm.c
index a050d67..9b54ab7 100644
--- a/sound/firewire/digi00x/digi00x-pcm.c
+++ b/sound/firewire/digi00x/digi00x-pcm.c
@@ -179,8 +179,9 @@ static int pcm_playback_hw_params(struct snd_pcm_substream *substream,
dg00x->playback_substreams++;
mutex_unlock(&dg00x->mutex);
}
- amdtp_stream_set_pcm_format(&dg00x->rx_stream,
- params_format(hw_params));
+ /* Apply double-oh-three algorism. */
+ snd_dg00x_protocol_set_pcm_function(&dg00x->rx_stream,
+ params_format(hw_params));
return snd_pcm_lib_alloc_vmalloc_buffer(substream,
params_buffer_bytes(hw_params));
}
@@ -241,8 +242,10 @@ static int pcm_playback_prepare(struct snd_pcm_substream *substream)
mutex_lock(&dg00x->mutex);
err = snd_dg00x_stream_start_duplex(dg00x, runtime->rate);
- if (err >= 0)
+ if (err >= 0) {
amdtp_stream_pcm_prepare(&dg00x->rx_stream);
+ snd_dg00x_protocol_init_state(&dg00x->state);
+ }
mutex_unlock(&dg00x->mutex);
diff --git a/sound/firewire/digi00x/digi00x-protocol.c b/sound/firewire/digi00x/digi00x-protocol.c
index 9104691..19c4d8b 100644
--- a/sound/firewire/digi00x/digi00x-protocol.c
+++ b/sound/firewire/digi00x/digi00x-protocol.c
@@ -2,12 +2,136 @@
* digi00x-protocol.c - a part of driver for Digidesign Digi 002/003 family
*
* Copyright (c) 2014-2015 Takashi Sakamoto
+ * Copyright (C) 2012 Robin Gareus <robin at gareus.org>
+ * Copyright (C) 2012 Damien Zammit <damien at zamaudio.com>
*
* Licensed under the terms of the GNU General Public License, version 2.
*/
+#include <sound/asound.h>
#include "digi00x.h"
+#define BYTE_PER_SAMPLE (4)
+#define MAGIC_DOT_BYTE (2)
+
+#define MAGIC_BYTE_OFF(x) (((x) * BYTE_PER_SAMPLE) + MAGIC_DOT_BYTE)
+
+/*
+ * double-oh-three look up table
+ *
+ * @param idx index byte (audio-sample data) 0x00..0xff
+ * @param off channel offset shift
+ * @return salt to XOR with given data
+ */
+static const __u8 dot_scrt(const __u8 idx, const unsigned int off)
+{
+ /*
+ * the length of the added pattern only depends on the lower nibble
+ * of the last non-zero data
+ */
+ static const __u8 len[16] = {0, 1, 3, 5, 7, 9, 11, 13, 14,
+ 12, 10, 8, 6, 4, 2, 0};
+
+ /*
+ * the lower nibble of the salt. Interleaved sequence.
+ * this is walked backwards according to len[]
+ */
+ static const __u8 nib[15] = {0x8, 0x7, 0x9, 0x6, 0xa, 0x5, 0xb, 0x4,
+ 0xc, 0x3, 0xd, 0x2, 0xe, 0x1, 0xf};
+
+ /* circular list for the salt's hi nibble. */
+ static const __u8 hir[15] = {0x0, 0x6, 0xf, 0x8, 0x7, 0x5, 0x3, 0x4,
+ 0xc, 0xd, 0xe, 0x1, 0x2, 0xb, 0xa};
+
+ /*
+ * start offset for upper nibble mapping.
+ * note: 9 is /special/. In the case where the high nibble == 0x9,
+ * hir[] is not used and - coincidentally - the salt's hi nibble is
+ * 0x09 regardless of the offset.
+ */
+ static const __u8 hio[16] = {0, 11, 12, 6, 7, 5, 1, 4,
+ 3, 0x00, 14, 13, 8, 9, 10, 2};
+
+ const __u8 ln = idx & 0xf;
+ const __u8 hn = (idx >> 4) & 0xf;
+ const __u8 hr = (hn == 0x9) ? 0x9 : hir[(hio[hn] + off) % 15];
+
+ if (len[ln] < off)
+ return 0x00;
+
+ return ((nib[14 + off - len[ln]]) | (hr << 4));
+}
+
+static void dot_encode_step(struct dot_state *state, __be32 *const buffer)
+{
+ __u8 * const data = (__u8 *) buffer;
+
+ if (data[MAGIC_DOT_BYTE] != 0x00) {
+ state->off = 0;
+ state->idx = data[MAGIC_DOT_BYTE] ^ state->carry;
+ }
+ data[MAGIC_DOT_BYTE] ^= state->carry;
+ state->carry = dot_scrt(state->idx, ++(state->off));
+}
+
+static void write_pcm_s16(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
+ __be32 *buffer, unsigned int frames)
+{
+ struct snd_dg00x *dg00x =
+ container_of(s, struct snd_dg00x, rx_stream);
+ struct snd_pcm_runtime *runtime = pcm->runtime;
+ unsigned int channels, remaining_frames, i, c;
+ const u16 *src;
+
+ channels = s->pcm_channels;
+ src = (void *)runtime->dma_area +
+ frames_to_bytes(runtime, s->pcm_buffer_pointer);
+ remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
+
+ for (i = 0; i < frames; ++i) {
+ for (c = 0; c < channels; ++c) {
+ buffer[s->pcm_positions[c]] =
+ cpu_to_be32((*src << 8) | 0x40000000);
+ dot_encode_step(&dg00x->state,
+ &buffer[s->pcm_positions[c]]);
+ src++;
+ }
+
+ buffer += s->data_block_quadlets;
+ if (--remaining_frames == 0)
+ src = (void *)runtime->dma_area;
+ }
+}
+
+static void write_pcm_s32(struct amdtp_stream *s, struct snd_pcm_substream *pcm,
+ __be32 *buffer, unsigned int frames)
+{
+ struct snd_dg00x *dg00x =
+ container_of(s, struct snd_dg00x, rx_stream);
+ struct snd_pcm_runtime *runtime = pcm->runtime;
+ unsigned int channels, remaining_frames, i, c;
+ const u32 *src;
+
+ channels = s->pcm_channels;
+ src = (void *)runtime->dma_area +
+ frames_to_bytes(runtime, s->pcm_buffer_pointer);
+ remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
+
+ for (i = 0; i < frames; ++i) {
+ for (c = 0; c < channels; ++c) {
+ buffer[s->pcm_positions[c]] =
+ cpu_to_be32((*src >> 8) | 0x40000000);
+ dot_encode_step(&dg00x->state,
+ &buffer[s->pcm_positions[c]]);
+ src++;
+ }
+
+ buffer += s->data_block_quadlets;
+ if (--remaining_frames == 0)
+ src = (void *)runtime->dma_area;
+ }
+}
+
static void fill_midi(struct amdtp_stream *s, __be32 *buffer,
unsigned int frames)
{
@@ -56,6 +180,25 @@ static void pull_midi(struct amdtp_stream *s, __be32 *buffer,
}
}
+void snd_dg00x_protocol_set_pcm_function(struct amdtp_stream *s,
+ snd_pcm_format_t format)
+{
+ if (WARN_ON(amdtp_stream_pcm_running(s)))
+ return;
+
+ switch (format) {
+ default:
+ WARN_ON(1);
+ /* fall through */
+ case SNDRV_PCM_FORMAT_S16:
+ s->transfer_samples = write_pcm_s16;
+ break;
+ case SNDRV_PCM_FORMAT_S32:
+ s->transfer_samples = write_pcm_s32;
+ break;
+ }
+}
+
/* Use own way to multiplex MIDI messages for data channels. */
void snd_dg00x_protocol_set_midi_function(struct snd_dg00x *dg00x)
{
diff --git a/sound/firewire/digi00x/digi00x.h b/sound/firewire/digi00x/digi00x.h
index b9d072c..96f9dea 100644
--- a/sound/firewire/digi00x/digi00x.h
+++ b/sound/firewire/digi00x/digi00x.h
@@ -33,6 +33,16 @@
#include "../iso-resources.h"
#include "../amdtp.h"
+/*
+ * The double-oh-three algorithm was discovered by Robin Gareus and Damien
+ * Zammit in 2012, with reverse-engineering for Digi 003 Rack.
+ */
+struct dot_state {
+ __u8 carry;
+ __u8 idx;
+ unsigned int off;
+};
+
struct snd_dg00x {
struct snd_card *card;
struct fw_unit *unit;
@@ -44,6 +54,7 @@ struct snd_dg00x {
struct amdtp_stream tx_stream;
struct fw_iso_resources tx_resources;
+ struct dot_state state;
struct amdtp_stream rx_stream;
struct fw_iso_resources rx_resources;
@@ -112,6 +123,16 @@ enum snd_dg00x_optical_mode {
SND_DG00X_OPT_IFACE_MODE_COUNT,
};
+/* Initialize dot status. */
+static inline void snd_dg00x_protocol_init_state(struct dot_state *state)
+{
+ state->carry = 0x00;
+ state->idx = 0x00;
+ state->off = 0;
+}
+
+void snd_dg00x_protocol_set_pcm_function(struct amdtp_stream *s,
+ snd_pcm_format_t format);
void snd_dg00x_protocol_set_midi_function(struct snd_dg00x *dg00x);
void snd_dg00x_protocol_queue_midi_message(struct snd_dg00x *dg00x);
int snd_dg00x_protocol_add_instance(struct snd_dg00x *dg00x);
--
2.1.0
More information about the Alsa-devel
mailing list