[PATCH] sbc: fix for overflow bug in quantization code

Siarhei Siamashka
2008-12-17T20:43:27Z

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Hello all,

This simple patch resolves one more SBC encoding quality issue. Now SBC
audio encoding quality should be fine in almost all cases after applying it
together with a new 8 subband filter.

The patch conflicts with the bitstream packing optimization, but I hope that
after all the encoding quality problems are fixed, we can get back to it.

Best regards,
Siarhei Siamashka

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>From 12088ac2053709bf89c3c84d47aef46b7f2da475 Mon Sep 17 00:00:00 2001
From: Siarhei Siamashka <siarhei.siamashka@nokia.com>
Date: Wed, 17 Dec 2008 22:32:11 +0200
Subject: [PATCH] sbc: fix for overflow bug in quantization code

The result of multiplication does not always fit into 32-bits. Using 64-bit
calculations helps to avoid overflows and sound quality problems in encoded
audio. Overflows are more likely to show up when using high values for
bitpool setting.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@nokia.com>
---
sbc/sbc.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/sbc/sbc.c b/sbc/sbc.c
index 7072673..6624921 100644
--- a/sbc/sbc.c
+++ b/sbc/sbc.c
@@ -1085,7 +1085,7 @@ static int sbc_pack_frame(uint8_t *data, struct sbc_frame *frame, size_t len)
for (sb = 0; sb < frame->subbands; sb++) {
if (levels[ch][sb] > 0) {
audio_sample =
- (uint16_t) ((((frame->sb_sample_f[blk][ch][sb]*levels[ch][sb]) >>
+ (uint16_t) (((((int64_t)frame->sb_sample_f[blk][ch][sb]*levels[ch][sb]) >>
(frame->scale_factor[ch][sb] + 1)) +
levels[ch][sb]) >> 1);
audio_sample <<= 16 - bits[ch][sb];
--
1.5.6.5