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split out init of downmix coeffs into a separate function that can be called

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only when needed

Originally committed as revision 11441 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-01-07 00:18:02 +00:00
parent 4f632b065b
commit f0b3a7ba12
1 changed files with 30 additions and 10 deletions
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40
libavcodec/ac3dec.c
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@ -157,6 +157,8 @@ typedef struct {
int output_mode; ///< output channel configuration
int out_channels; ///< number of output channels
int center_mix_level; ///< Center mix level index
int surround_mix_level; ///< Surround mix level index
float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
float dynamic_range[2]; ///< dynamic range
float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
@ -331,7 +333,6 @@ static int ac3_parse_header(AC3DecodeContext *s)
{
AC3HeaderInfo hdr;
GetBitContext *gbc = &s->gbc;
float center_mix_level, surround_mix_level;
int err, i;
err = ff_ac3_parse_header(gbc->buffer, &hdr);
@ -359,6 +360,10 @@ static int ac3_parse_header(AC3DecodeContext *s)
if(s->lfe_on)
s->output_mode |= AC3_OUTPUT_LFEON;
/* set default mix levels */
s->center_mix_level = 3; // -4.5dB
s->surround_mix_level = 4; // -6.0dB
/* skip over portion of header which has already been read */
skip_bits(gbc, 16); // skip the sync_word
skip_bits(gbc, 16); // skip crc1
@ -368,9 +373,9 @@ static int ac3_parse_header(AC3DecodeContext *s)
skip_bits(gbc, 2); // skip dsurmod
} else {
if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
center_mix_level = gain_levels[center_levels[get_bits(gbc, 2)]];
s->center_mix_level = center_levels[get_bits(gbc, 2)];
if(s->channel_mode & 4)
surround_mix_level = gain_levels[surround_levels[get_bits(gbc, 2)]];
s->surround_mix_level = surround_levels[get_bits(gbc, 2)];
}
skip_bits1(gbc); // skip lfeon
@ -403,25 +408,34 @@ static int ac3_parse_header(AC3DecodeContext *s)
} while(i--);
}
/* set stereo downmixing coefficients
reference: Section 7.8.2 Downmixing Into Two Channels */
return 0;
}
/**
* Set stereo downmixing coefficients based on frame header info.
* reference: Section 7.8.2 Downmixing Into Two Channels
*/
static void set_downmix_coeffs(AC3DecodeContext *s)
{
int i;
float cmix = gain_levels[s->center_mix_level];
float smix = gain_levels[s->surround_mix_level];
for(i=0; i<s->fbw_channels; i++) {
s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
}
if(s->channel_mode > 1 && s->channel_mode & 1) {
s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = center_mix_level;
s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
}
if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
int nf = s->channel_mode - 2;
s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = surround_mix_level * LEVEL_MINUS_3DB;
s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
}
if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
int nf = s->channel_mode - 4;
s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = surround_mix_level;
s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
}
return 0;
}
/**
@ -1139,6 +1153,12 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
}
avctx->channels = s->out_channels;
/* set downmixing coefficients if needed */
if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
s->fbw_channels == s->out_channels)) {
set_downmix_coeffs(s);
}
/* parse the audio blocks */
for (blk = 0; blk < NB_BLOCKS; blk++) {
if (ac3_parse_audio_block(s, blk)) {