ref: dd388d7b9611a79af627c010a3e6173e199019a3
parent: f946c5325bca769ee6b2b0f69bd62843a551f9fb
author: cbagwell <cbagwell>
date: Fri Apr 2 20:32:59 EST 1999
Adding swap effect
--- /dev/null
+++ b/src/swap.c
@@ -1,0 +1,143 @@
+/*
+ * swap - effect to swap ordering of channels in multi-channel audio.
+ *
+ * Written by Chris Bagwell (cbagwell@sprynet.com) - March 16, 1999
+ *
+ * Copyright 1999 Chris Bagwell And Sundry Contributors
+ * This source code is freely redistributable and may be used for
+ * any purpose. This copyright notice must be maintained.
+ * Chris Bagwell And Sundry Contributors are not responsible for
+ * the consequences of using this software.
+ */
+
+
+#include "st.h"
+
+/* Private data for SKEL file */
+typedef struct swapstuff {+ int order[4];
+} *swap_t;
+
+/*
+ * Process options
+ *
+ * Don't do initialization now.
+ * The 'info' fields are not yet filled in.
+ */
+void swap_getopts(effp, n, argv)
+eff_t effp;
+int n;
+char **argv;
+{+ swap_t swap = (swap_t) effp->priv;
+
+ swap->order[0] = swap->order[1] = swap->order[2] = swap->order[3] = 0;
+ if (n)
+ {+ if (n != 4)
+ {+ fail("Usage: swap [1 2 3 4]");+ }
+ else
+ {+ sscanf(argv[0],"%d",&swap->order[0]);
+ sscanf(argv[1],"%d",&swap->order[1]);
+ sscanf(argv[2],"%d",&swap->order[2]);
+ sscanf(argv[3],"%d",&swap->order[3]);
+ }
+ }
+}
+
+/*
+ * Prepare processing.
+ * Do all initializations.
+ */
+swap_start(effp)
+eff_t effp;
+{+ if (effp->outinfo.channels == 1)
+ fail("Can't swap channels on mono data.");+}
+
+/*
+ * Processed signed long samples from ibuf to obuf.
+ * Return number of samples processed.
+ */
+
+void swap_flow(effp, ibuf, obuf, isamp, osamp)
+eff_t effp;
+LONG *ibuf, *obuf;
+int *isamp, *osamp;
+{+ swap_t swap = (swap_t) effp->priv;
+ int len, done;
+
+ switch (effp->outinfo.channels)
+ {+ case 2:
+ /* Length to process will be buffer length / 2 since we
+ * work with two samples at a time.
+ */
+ len = ((*isamp > *osamp) ? *osamp : *isamp) / 2;
+ for(done = 0; done < len; done++)
+ {+ obuf[0] = ibuf[1];
+ obuf[1] = ibuf[0];
+ /* Advance buffer by 2 samples */
+ obuf += 2;
+ }
+
+ *isamp = len * 2;
+ *osamp = len * 2;
+
+ break;
+
+ case 4:
+ /* If nothing set then default to the following order */
+ if (!swap->order[0] && !swap->order[1] &&
+ !swap->order[2] && !swap->order[3])
+ {+ swap->order[0] = 1;
+ swap->order[1] = 0;
+ swap->order[2] = 3;
+ swap->order[3] = 2;
+ }
+ /* Length to process will be buffer length / 4 since we
+ * work with four samples at a time.
+ */
+ len = ((*isamp > *osamp) ? *osamp : *isamp) / 4;
+ for(done = 0; done < len; done++)
+ {+ obuf[0] = ibuf[swap->order[0]];
+ obuf[1] = ibuf[swap->order[1]];
+ obuf[2] = ibuf[swap->order[2]];
+ obuf[3] = ibuf[swap->order[3]];
+ /* Advance buffer by 2 samples */
+ obuf += 4;
+ }
+ *isamp = len * 4;
+ *osamp = len * 4;
+
+ break;
+}
+
+/*
+ * Drain out remaining samples if the effect generates any.
+ */
+
+void swap_drain(effp, obuf, osamp)
+LONG *obuf;
+int *osamp;
+{+ *osamp = 0;
+}
+
+/*
+ * Do anything required when you stop reading samples.
+ * (free allocated memory, etc.)
+ */
+void swap_stop(effp)
+eff_t effp;
+{+ /* nothing to do */
+}