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ac3enc: clip coefficients after MDCT.

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This ensures that any processing between the MDCT and exponent extraction will
be using clipped coefficients.
This commit is contained in:
Justin Ruggles 2011-06-27 14:29:33 -04:00
parent 6054cd25b4
commit 523b7eba19
4 changed files with 35 additions and 3 deletions
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4
libavcodec/ac3enc.h
View File

@ -50,12 +50,16 @@
#if CONFIG_AC3ENC_FLOAT
#define AC3_NAME(x) ff_ac3_float_ ## x
#define MAC_COEF(d,a,b) ((d)+=(a)*(b))
#define COEF_MIN (-16777215.0/16777216.0)
#define COEF_MAX ( 16777215.0/16777216.0)
typedef float SampleType;
typedef float CoefType;
typedef float CoefSumType;
#else
#define AC3_NAME(x) ff_ac3_fixed_ ## x
#define MAC_COEF(d,a,b) MAC64(d,a,b)
#define COEF_MIN -16777215
#define COEF_MAX 16777215
typedef int16_t SampleType;
typedef int32_t CoefType;
typedef int64_t CoefSumType;

9
libavcodec/ac3enc_fixed.c
View File

@ -104,6 +104,15 @@ static void scale_coefficients(AC3EncodeContext *s)
}
/**
* Clip MDCT coefficients to allowable range.
*/
static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
{
dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
}
static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
{
AC3EncodeContext *s = avctx->priv_data;

9
libavcodec/ac3enc_float.c
View File

@ -111,6 +111,15 @@ static void scale_coefficients(AC3EncodeContext *s)
}
/**
* Clip MDCT coefficients to allowable range.
*/
static void clip_coefficients(DSPContext *dsp, float *coef, unsigned int len)
{
dsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
}
#if CONFIG_AC3_ENCODER
AVCodec ff_ac3_encoder = {
"ac3",

16
libavcodec/ac3enc_template.c
View File

@ -41,6 +41,8 @@ static void apply_window(DSPContext *dsp, SampleType *output,
static int normalize_samples(AC3EncodeContext *s);
static void clip_coefficients(DSPContext *dsp, CoefType *coef, unsigned int len);
int AC3_NAME(allocate_sample_buffers)(AC3EncodeContext *s)
{
@ -171,8 +173,8 @@ static void apply_channel_coupling(AC3EncodeContext *s)
cpl_coef[i] += ch_coef[i];
}
/* coefficients must be clipped to +/- 1.0 in order to be encoded */
s->dsp.vector_clipf(cpl_coef, cpl_coef, -1.0f, 1.0f, num_cpl_coefs);
/* coefficients must be clipped in order to be encoded */
clip_coefficients(&s->dsp, cpl_coef, num_cpl_coefs);
/* scale coupling coefficients from float to 24-bit fixed-point */
s->ac3dsp.float_to_fixed24(&block->fixed_coef[CPL_CH][cpl_start],
@ -300,6 +302,7 @@ static void apply_channel_coupling(AC3EncodeContext *s)
if (!block->cpl_in_use || !block->new_cpl_coords)
continue;
clip_coefficients(&s->dsp, cpl_coords[blk][1], s->fbw_channels * 16);
s->ac3dsp.float_to_fixed24(fixed_cpl_coords[blk][1],
cpl_coords[blk][1],
s->fbw_channels * 16);
@ -433,7 +436,11 @@ int AC3_NAME(encode_frame)(AVCodecContext *avctx, unsigned char *frame,
apply_mdct(s);
scale_coefficients(s);
if (s->fixed_point)
scale_coefficients(s);
clip_coefficients(&s->dsp, s->blocks[0].mdct_coef[1],
AC3_MAX_COEFS * AC3_MAX_BLOCKS * s->channels);
s->cpl_on = s->cpl_enabled;
ff_ac3_compute_coupling_strategy(s);
@ -443,6 +450,9 @@ int AC3_NAME(encode_frame)(AVCodecContext *avctx, unsigned char *frame,
compute_rematrixing_strategy(s);
if (!s->fixed_point)
scale_coefficients(s);
ff_ac3_apply_rematrixing(s);
ff_ac3_process_exponents(s);