commit 821e4c101be89279ecdc5216b12da2da8e54152d
from: Omar Polo <op@omarpolo.com>
date: Mon Feb 21 17:25:27 2022 UTC

mp3: don't scale back to 16bps

libmad gives us sample at 32bps, but we scaled back to 16 because
minimad.c does so.  However, the scale producedure from minimad.c
kinds of corrupts some audio files, they don't play well.  We can
leave the problem to sndio which solves it better than us.

commit - e24324f1e5f50d7f1ceb3f8ae4c5513fa27d89f5
commit + 821e4c101be89279ecdc5216b12da2da8e54152d
blob - 23565c675b73ec5687d981392dfc887517e8a07e
blob + ec306437e1e982b5390524f70a201a30a2957cf5
--- player_mad.c
+++ player_mad.c
@@ -30,6 +30,8 @@
 #include <imsg.h>
 #include <unistd.h>
 
+#include <string.h>
+
 #include <mad.h>
 
 #include "amused.h"
@@ -61,31 +63,14 @@ input(void *d, struct mad_stream *stream)
 	return MAD_FLOW_CONTINUE;
 }
 
-/* scale a mad sample to 16 bits */
-static inline int
-scale(mad_fixed_t sample)
-{
-	/* round */
-	sample += (1L << (MAD_F_FRACBITS - 16));
-
-	/* clip */
-	if (sample >= MAD_F_ONE)
-		sample = MAD_F_ONE - 1;
-	else if (sample < -MAD_F_ONE)
-		sample -= MAD_F_ONE;
-
-	/* quantize */
-	return sample >> (MAD_F_FRACBITS + 1 - 16);
-}
-
 static enum mad_flow
 output(void *data, const struct mad_header *header, struct mad_pcm *pcm)
 {
-	static uint8_t buf[BUFSIZ];
+	static uint32_t buf[BUFSIZ];
 	size_t len;
 	struct buffer *buffer = data;
 	int nsamples, i;
-	uint16_t sample;
+	uint32_t sample;
 	const mad_fixed_t *leftch, *rightch;
 
 	if (player_shouldstop())
@@ -99,29 +84,27 @@ output(void *data, const struct mad_header *header, st
 	    buffer->channels != pcm->channels) {
 		buffer->sample_rate = pcm->samplerate;
 		buffer->channels = pcm->channels;
-		if (player_setup(16, pcm->samplerate, pcm->channels) == -1)
+		if (player_setup(32, pcm->samplerate, pcm->channels) == -1)
 			err(1, "player_setrate");
 	}
 
 	for (i = 0, len = 0; i < nsamples; ++i) {
-		if (len+4 >= sizeof(buf)) {
-			sio_write(hdl, buf, len);
+		if (len+2 >= sizeof(buf)) {
+			sio_write(hdl, buf, len * sizeof(sample));
 			len = 0;
 		}
 
-		sample = scale(*leftch++);
-		buf[len++] = sample & 0xff;
-		buf[len++] = (sample >> 8) & 0xff;
+		sample = *leftch++;
+		buf[len++] = sample;
 
 		if (pcm->channels == 2) {
-			sample = scale(*rightch++);
-			buf[len++] = sample & 0xff;
-			buf[len++] = (sample >> 8) & 0xff;
+			sample = *rightch++;
+			buf[len++] = sample;
 		}
 	}
 
 	if (len != 0)
-		sio_write(hdl, buf, len);
+		sio_write(hdl, buf, len * sizeof(sample));
 
 	return MAD_FLOW_CONTINUE;
 }