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Fix the dither calculation -- it was 12 dB too high, really noticable on the U8 setting.

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This commit is contained in:
Mike Brady
2019-06-02 17:56:47 +01:00
parent 25f0fbc24d
commit 85cc1bdd97
2 changed files with 14 additions and 10 deletions
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common.c
+7 -5
View File
@@ -1376,12 +1376,14 @@ int64_t generate_zero_frames(char *outp, size_t number_of_frames, enum sps_forma
int64_t hyper_sample = 0;
// add a TPDF dither -- see
// http://www.users.qwest.net/%7Evolt42/cadenzarecording/DitherExplained.pdf
// http://educypedia.karadimov.info/library/DitherExplained.pdf
// and the discussion around https://www.hydrogenaud.io/forums/index.php?showtopic=16963&st=25
// I think, for a 32 --> 16 bits, the range of
// random numbers needs to be from -2^16 to 2^16, i.e. from -65536 to 65536 inclusive, not from
// -32768 to +32767
// Actually, what would be generated here is from -65535 to 65535, i.e. one less on the limits.
// See the original paper at
// http://www.ece.rochester.edu/courses/ECE472/resources/Papers/Lipshitz_1992.pdf
@@ -1392,23 +1394,23 @@ int64_t generate_zero_frames(char *outp, size_t number_of_frames, enum sps_forma
case SPS_FORMAT_S32:
case SPS_FORMAT_S32_LE:
case SPS_FORMAT_S32_BE:
dither_mask = (int64_t)1 << (64 + 1 - 32);
dither_mask = (int64_t)1 << (64 - 32);
break;
case SPS_FORMAT_S24:
case SPS_FORMAT_S24_LE:
case SPS_FORMAT_S24_BE:
case SPS_FORMAT_S24_3LE:
case SPS_FORMAT_S24_3BE:
dither_mask = (int64_t)1 << (64 + 1 - 24);
dither_mask = (int64_t)1 << (64 - 24);
break;
case SPS_FORMAT_S16:
case SPS_FORMAT_S16_LE:
case SPS_FORMAT_S16_BE:
dither_mask = (int64_t)1 << (64 + 1 - 16);
dither_mask = (int64_t)1 << (64 - 16);
break;
case SPS_FORMAT_S8:
case SPS_FORMAT_U8:
dither_mask = (int64_t)1 << (64 + 1 - 8);
dither_mask = (int64_t)1 << (64 - 8);
break;
case SPS_FORMAT_UNKNOWN:
die("Unexpected SPS_FORMAT_UNKNOWN while calculating dither mask.");
player.c
+7 -5
View File
@@ -650,12 +650,14 @@ static inline void process_sample(int32_t sample, char **outp, enum sps_format_t
if (dither) {
// add a TPDF dither -- see
// http://www.users.qwest.net/%7Evolt42/cadenzarecording/DitherExplained.pdf
// http://educypedia.karadimov.info/library/DitherExplained.pdf
// and the discussion around https://www.hydrogenaud.io/forums/index.php?showtopic=16963&st=25
// I think, for a 32 --> 16 bits, the range of
// random numbers needs to be from -2^16 to 2^16, i.e. from -65536 to 65536 inclusive, not from
// -32768 to +32767
// Actually, what would be generated here is from -65535 to 65535, i.e. one less on the limits.
// See the original paper at
// http://www.ece.rochester.edu/courses/ECE472/resources/Papers/Lipshitz_1992.pdf
@@ -666,23 +668,23 @@ static inline void process_sample(int32_t sample, char **outp, enum sps_format_t
case SPS_FORMAT_S32:
case SPS_FORMAT_S32_LE:
case SPS_FORMAT_S32_BE:
dither_mask = (int64_t)1 << (64 + 1 - 32);
dither_mask = (int64_t)1 << (64 - 32);
break;
case SPS_FORMAT_S24:
case SPS_FORMAT_S24_LE:
case SPS_FORMAT_S24_BE:
case SPS_FORMAT_S24_3LE:
case SPS_FORMAT_S24_3BE:
dither_mask = (int64_t)1 << (64 + 1 - 24);
dither_mask = (int64_t)1 << (64 - 24);
break;
case SPS_FORMAT_S16:
case SPS_FORMAT_S16_LE:
case SPS_FORMAT_S16_BE:
dither_mask = (int64_t)1 << (64 + 1 - 16);
dither_mask = (int64_t)1 << (64 - 16);
break;
case SPS_FORMAT_S8:
case SPS_FORMAT_U8:
dither_mask = (int64_t)1 << (64 + 1 - 8);
dither_mask = (int64_t)1 << (64 - 8);
break;
case SPS_FORMAT_UNKNOWN:
die("Unexpected SPS_FORMAT_UNKNOWN while calculating dither mask.");