| Subject: | Fix broken dithering |
Hi,
I'm forwarding Debian bug https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501250, "libaudio-flac-decoder-perl: Does not produce same output as flac -d: data interleaved in weird way". The Debian package of Audio-FLAC-Decoder has, since late 2009, carried the patch below, which I'd like to suggest for inclusion upstream.
Florian
Author: Daniel Barlow <dan@telent.net>
Origin: http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=10;filename=Decoder.patch;att=1;bug=501250
Description: Fix broken dithering.
Bug-Debian: http://bugs.debian.org/501250
Index: libaudio-flac-decoder-perl/Decoder.xs
===================================================================
--- libaudio-flac-decoder-perl.orig/Decoder.xs 2009-11-01 19:31:59.000000000 +0000
+++ libaudio-flac-decoder-perl/Decoder.xs 2009-11-02 22:33:15.000000000 +0000
@@ -489,11 +489,32 @@
const unsigned n = min(datasource->wide_samples_in_reservoir, SAMPLES_PER_WRITE);
const unsigned delta = n * channels;
unsigned i;
-
+ FLAC__byte *out=datasource->sample_buffer;
+ /*
int bytes = (int)pack_pcm_signed_little_endian(
datasource->sample_buffer, datasource->reservoir, n, channels, bps, bps
);
-
+ bps==bps (trivially) so all the fancy dithering stuff
+ that pack_pcm_signed_little_endian might do will
+ never get called. Let's just do it inline
+ */
+ int bytes;
+ for(i=0; i<channels*n; i++) {
+ FLAC__int32 sample=(datasource->reservoir)[i];
+ switch(bps) {
+ case 8:
+ out[0] = sample ^ 0x80;
+ break;
+ case 24:
+ out[2] = (FLAC__byte)(sample >> 16);
+ /* fall through */
+ case 16:
+ out[1] = (FLAC__byte)(sample >> 8);
+ out[0] = (FLAC__byte)sample;
+ }
+ out+=bps/8;
+ }
+ bytes=(out-datasource->sample_buffer);
for (i = delta; i < datasource->wide_samples_in_reservoir * channels; i++) {
datasource->reservoir[i-delta] = datasource->reservoir[i];
}