[PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

[PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

[Siarhei Siamashka]

[-- Attachment #1: Type: text/plain, Size: 630 bytes --]

Hello all,

With bluez-4.25 release I hope that the SBC encoder sound quality issues are
now solved (though this is yet to be confirmed).

Nevertheless, I think it is time to focus on performance :) The attached patch
contains code preparations which are needed for SIMD optimizations for
the analysis filter. Also theoretically it should be possible to tweak code to
have both 32-bit and 16-bit fixed point analysis filter compiled in and switch
between them at runtime (at user's request or semi-intelligently depending
on audio bitrate).

This patch should be stable and ready to be committed.

Best regards,
Siarhei Siamashka

[-- Attachment #2: 0001-Added-possibility-to-analyze-4-blocks-at-once-in-SBC.patch --]
[-- Type: text/x-diff, Size: 6308 bytes --]

>From e7e029ee7acb75e0a846c61f19a4244810242cdb Mon Sep 17 00:00:00 2001
From: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Date: Wed, 31 Dec 2008 09:14:25 +0200
Subject: [PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

This change is needed for SIMD optimizations which will follow
shortly. And even for non-SIMD capable platforms it still may
be useful to have possibility to merge several analyzing functions
together into one for better code scheduling or reusing loaded
constants. Also analysis filter functions are now called using
function pointers, which allows the default implementation to be
overrided at runtime (with high precision variant or MMX/SSE2/NEON
optimized code).
---
 sbc/sbc.c |  131 ++++++++++++++++++++++++++++++++++++++-----------------------
 1 files changed, 82 insertions(+), 49 deletions(-)

diff --git a/sbc/sbc.c b/sbc/sbc.c
index ce52e1e..01b4011 100644
--- a/sbc/sbc.c
+++ b/sbc/sbc.c
@@ -94,7 +94,11 @@ struct sbc_decoder_state {
 struct sbc_encoder_state {
 	int subbands;
 	int position[2];
-	int16_t X[2][160];
+	int16_t X[2][256];
+	void (*sbc_analyze_4b_4s)(int16_t *pcm, int16_t *x,
+				  int32_t *out, int out_stride);
+	void (*sbc_analyze_4b_8s)(int16_t *pcm, int16_t *x,
+				  int32_t *out, int out_stride);
 };
 
 /*
@@ -649,14 +653,6 @@ static int sbc_synthesize_audio(struct sbc_decoder_state *state,
 	}
 }
 
-static void sbc_encoder_init(struct sbc_encoder_state *state,
-				const struct sbc_frame *frame)
-{
-	memset(&state->X, 0, sizeof(state->X));
-	state->subbands = frame->subbands;
-	state->position[0] = state->position[1] = 9 * frame->subbands;
-}
-
 static inline void _sbc_analyze_four(const int16_t *in, int32_t *out)
 {
 	FIXED_A t1[4];
@@ -694,23 +690,27 @@ static inline void _sbc_analyze_four(const int16_t *in, int32_t *out)
 	}
 }
 
-static inline void sbc_analyze_four(struct sbc_encoder_state *state,
-				struct sbc_frame *frame, int ch, int blk)
+static void sbc_analyze_4b_4s(int16_t *pcm, int16_t *x,
+			      int32_t *out, int out_stride)
 {
-	int16_t *x = &state->X[ch][state->position[ch]];
-	int16_t *pcm = &frame->pcm_sample[ch][blk * 4];
-
-	/* Input 4 Audio Samples */
-	x[40] = x[0] = pcm[3];
-	x[41] = x[1] = pcm[2];
-	x[42] = x[2] = pcm[1];
-	x[43] = x[3] = pcm[0];
-
-	_sbc_analyze_four(x, frame->sb_sample_f[blk][ch]);
+	int i;
+
+	/* Input 4 x 4 Audio Samples */
+	for (i = 0; i < 16; i += 4) {
+		x[64 + i] = x[0 + i] = pcm[15 - i];
+		x[65 + i] = x[1 + i] = pcm[14 - i];
+		x[66 + i] = x[2 + i] = pcm[13 - i];
+		x[67 + i] = x[3 + i] = pcm[12 - i];
+	}
 
-	state->position[ch] -= 4;
-	if (state->position[ch] < 0)
-		state->position[ch] = 36;
+	/* Analyze four blocks */
+	_sbc_analyze_four(x + 12, out);
+	out += out_stride;
+	_sbc_analyze_four(x + 8, out);
+	out += out_stride;
+	_sbc_analyze_four(x + 4, out);
+	out += out_stride;
+	_sbc_analyze_four(x, out);
 }
 
 static inline void _sbc_analyze_eight(const int16_t *in, int32_t *out)
@@ -766,28 +766,31 @@ static inline void _sbc_analyze_eight(const int16_t *in, int32_t *out)
 	}
 }
 
-static inline void sbc_analyze_eight(struct sbc_encoder_state *state,
-					struct sbc_frame *frame, int ch,
-					int blk)
+static void sbc_analyze_4b_8s(int16_t *pcm, int16_t *x,
+			      int32_t *out, int out_stride)
 {
-	int16_t *x = &state->X[ch][state->position[ch]];
-	int16_t *pcm = &frame->pcm_sample[ch][blk * 8];
-
-	/* Input 8 Audio Samples */
-	x[80] = x[0] = pcm[7];
-	x[81] = x[1] = pcm[6];
-	x[82] = x[2] = pcm[5];
-	x[83] = x[3] = pcm[4];
-	x[84] = x[4] = pcm[3];
-	x[85] = x[5] = pcm[2];
-	x[86] = x[6] = pcm[1];
-	x[87] = x[7] = pcm[0];
-
-	_sbc_analyze_eight(x, frame->sb_sample_f[blk][ch]);
-
-	state->position[ch] -= 8;
-	if (state->position[ch] < 0)
-		state->position[ch] = 72;
+	int i;
+
+	/* Input 4 x 8 Audio Samples */
+	for (i = 0; i < 32; i += 8) {
+		x[128 + i] = x[0 + i] = pcm[31 - i];
+		x[129 + i] = x[1 + i] = pcm[30 - i];
+		x[130 + i] = x[2 + i] = pcm[29 - i];
+		x[131 + i] = x[3 + i] = pcm[28 - i];
+		x[132 + i] = x[4 + i] = pcm[27 - i];
+		x[133 + i] = x[5 + i] = pcm[26 - i];
+		x[134 + i] = x[6 + i] = pcm[25 - i];
+		x[135 + i] = x[7 + i] = pcm[24 - i];
+	}
+
+	/* Analyze four blocks */
+	_sbc_analyze_eight(x + 24, out);
+	out += out_stride;
+	_sbc_analyze_eight(x + 16, out);
+	out += out_stride;
+	_sbc_analyze_eight(x + 8, out);
+	out += out_stride;
+	_sbc_analyze_eight(x, out);
 }
 
 static int sbc_analyze_audio(struct sbc_encoder_state *state,
@@ -798,14 +801,32 @@ static int sbc_analyze_audio(struct sbc_encoder_state *state,
 	switch (frame->subbands) {
 	case 4:
 		for (ch = 0; ch < frame->channels; ch++)
-			for (blk = 0; blk < frame->blocks; blk++)
-				sbc_analyze_four(state, frame, ch, blk);
+			for (blk = 0; blk < frame->blocks; blk += 4) {
+				state->sbc_analyze_4b_4s(
+					&frame->pcm_sample[ch][blk * 4],
+					&state->X[ch][state->position[ch]],
+					frame->sb_sample_f[blk][ch],
+					frame->sb_sample_f[blk + 1][ch] -
+					frame->sb_sample_f[blk][ch]);
+				state->position[ch] -= 16;
+				if (state->position[ch] < 0)
+					state->position[ch] = 64 - 16;
+			}
 		return frame->blocks * 4;
 
 	case 8:
 		for (ch = 0; ch < frame->channels; ch++)
-			for (blk = 0; blk < frame->blocks; blk++)
-				sbc_analyze_eight(state, frame, ch, blk);
+			for (blk = 0; blk < frame->blocks; blk += 4) {
+				state->sbc_analyze_4b_8s(
+					&frame->pcm_sample[ch][blk * 8],
+					&state->X[ch][state->position[ch]],
+					frame->sb_sample_f[blk][ch],
+					frame->sb_sample_f[blk + 1][ch] -
+					frame->sb_sample_f[blk][ch]);
+				state->position[ch] -= 32;
+				if (state->position[ch] < 0)
+					state->position[ch] = 128 - 32;
+			}
 		return frame->blocks * 8;
 
 	default:
@@ -1025,6 +1046,18 @@ static int sbc_pack_frame(uint8_t *data, struct sbc_frame *frame, size_t len)
 	return data_ptr - data;
 }
 
+static void sbc_encoder_init(struct sbc_encoder_state *state,
+				const struct sbc_frame *frame)
+{
+	memset(&state->X, 0, sizeof(state->X));
+	state->subbands = frame->subbands;
+	state->position[0] = state->position[1] = 12 * frame->subbands;
+
+	/* Default implementation for analyze function */
+	state->sbc_analyze_4b_4s = sbc_analyze_4b_4s;
+	state->sbc_analyze_4b_8s = sbc_analyze_4b_8s;
+}
+
 struct sbc_priv {
 	int init;
 	struct sbc_frame frame;
-- 
1.5.6.5

Re: [PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

[Luiz Augusto von Dentz]

Hi Siarhei,


> Nevertheless, I think it is time to focus on performance :) The attached patch
> contains code preparations which are needed for SIMD optimizations for
> the analysis filter. Also theoretically it should be possible to tweak code to
> have both 32-bit and 16-bit fixed point analysis filter compiled in and switch
> between them at runtime (at user's request or semi-intelligently depending
> on audio bitrate).

Picking a implementation at runtime would be really great, that is why
I suggested using liboil in the other thread.


-- 
Luiz Augusto von Dentz
Engenheiro de Computação

Re: [PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

[Siarhei Siamashka]

On Wednesday 31 December 2008 23:04:20 ext Luiz Augusto von Dentz wrote:
> Hi Siarhei,
>
> > Nevertheless, I think it is time to focus on performance :) The attached
> > patch contains code preparations which are needed for SIMD optimizations
> > for the analysis filter. Also theoretically it should be possible to
> > tweak code to have both 32-bit and 16-bit fixed point analysis filter
> > compiled in and switch between them at runtime (at user's request or
> > semi-intelligently depending on audio bitrate).
>
> Picking a implementation at runtime would be really great,

What I had in mind was that we can have two source files which
include 'sbc_tables.h'. Then compile one of them with
SBC_HIGH_PRECISION macro defined, and the other one
without it. This way we will have two sets of functions, which
can be called via function pointers transparently from the rest
of code, as long as they have the same interface.

Having high precision analysis filter variant may be beneficial for
extremely high bitrates, when we might want to keep as much of
precision as possible. For the normal cases the extra precision is
just excessive.

I also have an idea about improving precision for the case of 16-bit
multiplications only. This would involve only tweaking coefficients in
the tables with no code changes at all. I hope to reduce rounding
errors to the very minimum. Will post about the progress a bit later.

If the precision difference between 16-bit and 32-bit implementations
can be reduced, there will be a bit less reasons to use a slow high
precision version anymore :)

> that is why I suggested using liboil in the other thread.

I don't see much relation with liboil here.

I'm not against liboil in general, but its usefullness for sbc codec just
needs to be proved.

-- 
Best regards,
Siarhei Siamashka

Re: [PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

[Marcel Holtmann]

Hi Siarhei,

> With bluez-4.25 release I hope that the SBC encoder sound quality issues are
> now solved (though this is yet to be confirmed).
> 
> Nevertheless, I think it is time to focus on performance :) The attached patch
> contains code preparations which are needed for SIMD optimizations for
> the analysis filter. Also theoretically it should be possible to tweak code to
> have both 32-bit and 16-bit fixed point analysis filter compiled in and switch
> between them at runtime (at user's request or semi-intelligently depending
> on audio bitrate).
> 
> This patch should be stable and ready to be committed.

your patch has been applied. Thanks.

Regards

Marcel

Re: [PATCH] Added possibility to analyze 4 blocks at once in SBC encoder

[Siarhei Siamashka]

On Thursday 01 January 2009 10:54:02 ext Marcel Holtmann wrote:
> Hi Siarhei,
>
> > With bluez-4.25 release I hope that the SBC encoder sound quality issues
> > are now solved (though this is yet to be confirmed).
> >
> > Nevertheless, I think it is time to focus on performance :) The attached
> > patch contains code preparations which are needed for SIMD optimizations
> > for the analysis filter. Also theoretically it should be possible to
> > tweak code to have both 32-bit and 16-bit fixed point analysis filter
> > compiled in and switch between them at runtime (at user's request or
> > semi-intelligently depending on audio bitrate).
> >
> > This patch should be stable and ready to be committed.
>
> your patch has been applied. Thanks.

Thank you very much for taking a good care of my patches :)


Best regards,
Siarhei Siamashka