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avcodec/ac3dec: add consistent noise generation option.

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use av_lfg_init_from_data() to seed AC-3 dithering from the AC-3 frame
data to make it consistent given the same AC-3 frame, if option is set.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Jonathan Campbell 2016-09-03 03:34:01 -07:00 committed by Michael Niedermayer
parent 76c5a69e26
commit d5d474aea5
4 changed files with 13 additions and 0 deletions
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7
libavcodec/ac3dec.c
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@ -1426,6 +1426,13 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data,
(const uint16_t *) buf, cnt);
} else
memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE));
/* if consistent noise generation is enabled, seed the linear feedback generator
* with the contents of the AC-3 frame so that the noise is identical across
* decodes given the same AC-3 frame data, for use with non-linear edititing software. */
if (s->consistent_noise_generation)
av_lfg_init_from_data(&s->dith_state, s->input_buffer, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE));
buf = s->input_buffer;
/* initialize the GetBitContext with the start of valid AC-3 Frame */
if ((ret = init_get_bits8(&s->gbc, buf, buf_size)) < 0)

4
libavcodec/ac3dec.h
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@ -177,6 +177,10 @@ typedef struct AC3DecodeContext {
int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin (endmant)
///@}
///@name Consistent noise generation
int consistent_noise_generation; ///< seed noise generation with AC-3 frame on decode
///@}
///@name Rematrixing
int num_rematrixing_bands; ///< number of rematrixing bands (nrematbnd)
int rematrixing_flags[4]; ///< rematrixing flags (rematflg)

1
libavcodec/ac3dec_fixed.c
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@ -168,6 +168,7 @@ static void ac3_downmix_c_fixed16(int16_t **samples, int16_t (*matrix)[2],
#include "ac3dec.c"
static const AVOption options[] = {
{ "cons_noisegen", "enable consistent noise generation", OFFSET(consistent_noise_generation), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, PAR },
{ "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 6.0, PAR },
{ "heavy_compr", "enable heavy dynamic range compression", OFFSET(heavy_compression), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, PAR },
{ NULL},

1
libavcodec/ac3dec_float.c
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@ -32,6 +32,7 @@
#include "ac3dec.c"
static const AVOption options[] = {
{ "cons_noisegen", "enable consistent noise generation", OFFSET(consistent_noise_generation), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, PAR },
{ "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 6.0, PAR },
{ "heavy_compr", "enable heavy dynamic range compression", OFFSET(heavy_compression), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, PAR },
{ "target_level", "target level in -dBFS (0 not applied)", OFFSET(target_level), AV_OPT_TYPE_INT, {.i64 = 0 }, -31, 0, PAR },