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Split out setting of bit allocation parameters to a separate function. 

Th new function only needs to be called at initialization because bit
allocation parameters currently do not change during encoding.

Originally committed as revision 26003 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2010-12-14 14:53:43 +00:00
parent 8999944ecb
commit 793bbf9544
1 changed files with 32 additions and 18 deletions
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50
libavcodec/ac3enc.c
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@ -744,6 +744,37 @@ static int process_exponents(AC3EncodeContext *s,
}
/**
* Initialize bit allocation.
* Set default parameter codes and calculate parameter values.
*/
static void bit_alloc_init(AC3EncodeContext *s)
{
int ch;
/* init default parameters */
s->slow_decay_code = 2;
s->fast_decay_code = 1;
s->slow_gain_code = 1;
s->db_per_bit_code = 2;
s->floor_code = 4;
for (ch = 0; ch < s->channels; ch++)
s->fast_gain_code[ch] = 4;
/* initial snr offset */
s->coarse_snr_offset = 40;
/* compute real values */
/* currently none of these values change during encoding, so we can just
set them once at initialization */
s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
}
/**
* Count the bits used to encode the frame, minus exponents and mantissas.
* @return bit count
@ -936,22 +967,6 @@ static int compute_bit_allocation(AC3EncodeContext *s,
int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS];
/* init default parameters */
s->slow_decay_code = 2;
s->fast_decay_code = 1;
s->slow_gain_code = 1;
s->db_per_bit_code = 2;
s->floor_code = 4;
for (ch = 0; ch < s->channels; ch++)
s->fast_gain_code[ch] = 4;
/* compute real values */
s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
/* count frame bits other than exponents and mantissas */
frame_bits += count_frame_bits(s, exp_strategy);
@ -1615,8 +1630,7 @@ static av_cold int ac3_encode_init(AVCodecContext *avctx)
set_bandwidth(s, avctx->cutoff);
/* initial snr offset */
s->coarse_snr_offset = 40;
bit_alloc_init(s);
mdct_init(9);