implemented conversion between streams with different channel masks

1 files changed, 90 insertions, 0 deletions

diff --git a/premix.c b/premix.c
new file mode 100644
index 00000000..36fd4147
--- /dev/null
+++ b/premix.c
@@ -0,0 +1,90 @@
+/*
+    DeaDBeeF - ultimate music player for GNU/Linux systems with X11
+    Copyright (C) 2009-2010 Alexey Yakovenko <waker@users.sourceforge.net>
+
+    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 <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include "deadbeef.h"
+#include "premix.h"
+
+#define trace(...) { fprintf(stderr, __VA_ARGS__); }
+//#define trace(fmt,...)
+
+void
+pcm_write_sample (const ddb_waveformat_t * restrict inputfmt, const char * restrict input, const ddb_waveformat_t * restrict outputfmt, char * restrict output) {
+    memcpy (output, input, 2);
+}
+
+int
+pcm_convert (const ddb_waveformat_t * restrict inputfmt, const char * restrict input, const ddb_waveformat_t * restrict outputfmt, char * restrict output, int inputsize) {
+    // calculate output size
+    int inputsamplesize = (inputfmt->bps >> 3) * inputfmt->channels;
+    int outputsamplesize = (outputfmt->bps >> 3) * outputfmt->channels;
+    int nsamples = inputsize / inputsamplesize;
+
+    uint32_t outchannels = 0;
+
+    if (output) {
+        // build channelmap
+        int channelmap[32] = {-1};
+        uint32_t inputbitmask = 1;
+        for (int i = 0; i < inputfmt->channels; i++) {
+            // find next input channel
+            while (inputbitmask < 0x80000000 && !(inputfmt->channelmask & inputbitmask)) {
+                inputbitmask <<= 1;
+            }
+            if (!(inputfmt->channelmask & inputbitmask)) {
+                trace ("pcm_convert: channelmask doesn't correspond inputfmt (channels=%d, channelmask=%X)!", inputfmt->channels, inputfmt->channelmask);
+                break;
+            }
+            if (outputfmt->channelmask & inputbitmask) {
+                int o = 0;
+                uint32_t outputbitmask = 1;
+                while (outputbitmask < 0x80000000 && (outputfmt->channelmask & outputbitmask) != inputbitmask) {
+                    outputbitmask <<= 1;
+                    o++;
+                }
+                if (!(inputfmt->channelmask & outputbitmask)) {
+                    // no corresponding output channel -- ignore
+                    continue;
+                }
+                outchannels |= outputbitmask;
+                channelmap[i] = o; // input channel i going to output channel o
+                trace ("channelmap[%d]=%d\n", i, o);
+            }
+            inputbitmask <<= 1;
+        }
+
+        if (outchannels != outputfmt->channelmask) {
+            // some of the channels are not used
+            memset (output, 0, nsamples * outputsamplesize);
+        }
+        for (int s = 0; s < nsamples; s++) {
+            for (int c = 0; c < inputfmt->channels; c++) {
+                if (channelmap[c] != -1) {
+                    pcm_write_sample (inputfmt, input, outputfmt, output + (outputfmt->bps >> 3) * channelmap[c]);
+                }
+                input += inputfmt->bps >> 3;
+            }
+            output += outputsamplesize;
+        }
+    }
+    return nsamples * outputsamplesize;
+}
+