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sbc: added saturated clipping of decoder output to 16-bit

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This prevents overflows and audible artefacts for the audio files which
originally had loudness maximized. Music from audio CD disks is an
example of such files, see http://en.wikipedia.org/wiki/Loudness_war
This commit is contained in:
Siarhei Siamashka 2011-03-14 15:07:38 -03:00 • committed by Luiz Augusto von Dentz
parent 4d2f0daba1
commit 84d91fb708
1 changed files with 15 additions and 5 deletions
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20
src/modules/bluetooth/sbc/sbc.c
View file

@ -534,6 +534,16 @@ static void sbc_decoder_init(struct sbc_decoder_state *state,
state->offset[ch][i] = (10 * i + 10);
}
static SBC_ALWAYS_INLINE int16_t sbc_clip16(int32_t s)
{
if (s > 0x7FFF)
return 0x7FFF;
else if (s < -0x8000)
return -0x8000;
else
return s;
}
static inline void sbc_synthesize_four(struct sbc_decoder_state *state,
struct sbc_frame *frame, int ch, int blk)
{
@ -562,7 +572,7 @@ static inline void sbc_synthesize_four(struct sbc_decoder_state *state,
k = (i + 4) & 0xf;
/* Store in output, Q0 */
frame->pcm_sample[ch][blk * 4 + i] = SCALE4_STAGED1(
frame->pcm_sample[ch][blk * 4 + i] = sbc_clip16(SCALE4_STAGED1(
MULA(v[offset[i] + 0], sbc_proto_4_40m0[idx + 0],
MULA(v[offset[k] + 1], sbc_proto_4_40m1[idx + 0],
MULA(v[offset[i] + 2], sbc_proto_4_40m0[idx + 1],
@ -572,7 +582,7 @@ static inline void sbc_synthesize_four(struct sbc_decoder_state *state,
MULA(v[offset[i] + 6], sbc_proto_4_40m0[idx + 3],
MULA(v[offset[k] + 7], sbc_proto_4_40m1[idx + 3],
MULA(v[offset[i] + 8], sbc_proto_4_40m0[idx + 4],
MUL( v[offset[k] + 9], sbc_proto_4_40m1[idx + 4])))))))))));
MUL( v[offset[k] + 9], sbc_proto_4_40m1[idx + 4]))))))))))));
}
}
@ -607,8 +617,8 @@ static inline void sbc_synthesize_eight(struct sbc_decoder_state *state,
for (idx = 0, i = 0; i < 8; i++, idx += 5) {
k = (i + 8) & 0xf;
/* Store in output */
frame->pcm_sample[ch][blk * 8 + i] = SCALE8_STAGED1( // Q0
/* Store in output, Q0 */
frame->pcm_sample[ch][blk * 8 + i] = sbc_clip16(SCALE8_STAGED1(
MULA(state->V[ch][offset[i] + 0], sbc_proto_8_80m0[idx + 0],
MULA(state->V[ch][offset[k] + 1], sbc_proto_8_80m1[idx + 0],
MULA(state->V[ch][offset[i] + 2], sbc_proto_8_80m0[idx + 1],
@ -618,7 +628,7 @@ static inline void sbc_synthesize_eight(struct sbc_decoder_state *state,
MULA(state->V[ch][offset[i] + 6], sbc_proto_8_80m0[idx + 3],
MULA(state->V[ch][offset[k] + 7], sbc_proto_8_80m1[idx + 3],
MULA(state->V[ch][offset[i] + 8], sbc_proto_8_80m0[idx + 4],
MUL( state->V[ch][offset[k] + 9], sbc_proto_8_80m1[idx + 4])))))))))));
MUL( state->V[ch][offset[k] + 9], sbc_proto_8_80m1[idx + 4]))))))))))));
}
}