diff options
| author | Michael Niedermayer <michaelni@gmx.at> | 2012-08-02 04:21:53 +0200 |
|---|---|---|
| committer | Michael Niedermayer <michaelni@gmx.at> | 2012-08-02 04:21:53 +0200 |
| commit | 571572fcddc16ebe3d60054ae5a2db05800c1d6d (patch) | |
| tree | 77b2fadc220bc7df13653d49446b9f981bfb98a8 | |
| parent | 98a2f4e87b5c9439cf66a36b1089c7168206f9b2 (diff) | |
mp3dec: adjust IMDCT scaling to avoid overflows
Fixes ticket268
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
| -rw-r--r-- | libavcodec/mpegaudio.h | 2 | ||||
| -rw-r--r-- | libavcodec/mpegaudio_tablegen.h | 4 | ||||
| -rw-r--r-- | libavcodec/mpegaudiodsp_template.c | 2 |
3 files changed, 5 insertions, 3 deletions
diff --git a/libavcodec/mpegaudio.h b/libavcodec/mpegaudio.h index b829cd3f8a..b880b7a832 100644 --- a/libavcodec/mpegaudio.h +++ b/libavcodec/mpegaudio.h @@ -52,6 +52,8 @@ #define WFRAC_BITS 16 /* fractional bits for window */ #endif +#define IMDCT_SCALAR 1.759 + #define FRAC_ONE (1 << FRAC_BITS) #define FIX(a) ((int)((a) * FRAC_ONE)) diff --git a/libavcodec/mpegaudio_tablegen.h b/libavcodec/mpegaudio_tablegen.h index 291e40b9aa..a8756fa5c2 100644 --- a/libavcodec/mpegaudio_tablegen.h +++ b/libavcodec/mpegaudio_tablegen.h @@ -47,7 +47,7 @@ static void mpegaudio_tableinit(void) double value = i / 4; double f, fm; int e, m; - f = value * cbrtf(value) * pow(2, (i & 3) * 0.25); + f = value / IMDCT_SCALAR * cbrtf(value) * pow(2, (i & 3) * 0.25); fm = frexp(f, &e); m = (uint32_t)(fm * (1LL << 31) + 0.5); e += FRAC_BITS - 31 + 5 - 100; @@ -58,7 +58,7 @@ static void mpegaudio_tableinit(void) } for (exponent = 0; exponent < 512; exponent++) { for (value = 0; value < 16; value++) { - double f = (double)value * cbrtf(value) * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5); + double f = (double)value * cbrtf(value) * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5) / IMDCT_SCALAR; expval_table_fixed[exponent][value] = llrint(f); expval_table_float[exponent][value] = f; } diff --git a/libavcodec/mpegaudiodsp_template.c b/libavcodec/mpegaudiodsp_template.c index 8df2ff3079..5d004674ca 100644 --- a/libavcodec/mpegaudiodsp_template.c +++ b/libavcodec/mpegaudiodsp_template.c @@ -243,7 +243,7 @@ void RENAME(ff_init_mpadsp_tabs)(void) else if (i < 18) d = 1; } //merge last stage of imdct into the window coefficients - d *= 0.5 / cos(M_PI * (2 * i + 19) / 72); + d *= 0.5 * IMDCT_SCALAR / cos(M_PI * (2 * i + 19) / 72); if (j == 2) RENAME(ff_mdct_win)[j][i/3] = FIXHR((d / (1<<5))); |