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mp3: moved code to dither_buffer()

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Preparing for simplifying and thus speeding up the dithering code:
moved dithering to a separate function which contains a trivial loop.
With this patch, only one sample is dithered at a time, but the
following patches will allow us to dither a whole block at a time,
without complicated buffer length checks.
This commit is contained in:
Max Kellermann 2008-08-26 08:27:12 +02:00
parent d9583aa95b
commit 09fbbdc366
1 changed files with 30 additions and 14 deletions
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44
src/inputPlugins/mp3_plugin.c
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@ -105,6 +105,30 @@ static signed long audio_linear_dither(unsigned int bits, mad_fixed_t sample,
return output >> scalebits; return output >> scalebits;
} }
static unsigned dither_buffer(mpd_sint16 *dest0, const struct mad_synth *synth,
struct audio_dither *dither,
unsigned int start, unsigned int end,
unsigned int num_channels)
{
mpd_sint16 *dest = dest0;
unsigned int i;
for (i = start; i < end; ++i) {
*dest++ = (mpd_sint16)
audio_linear_dither(16,
synth->pcm.samples[0][i],
dither);
if (num_channels == 2)
*dest++ = (mpd_sint16)
audio_linear_dither(16,
synth->pcm.samples[1][i],
dither);
}
return dest - dest0;
}
/* end of stolen stuff from mpg321 */ /* end of stolen stuff from mpg321 */
static int mp3_plugin_init(void) static int mp3_plugin_init(void)
@ -909,7 +933,7 @@ static int mp3Read(mp3DecodeData * data, struct decoder *decoder,
i = 0; i = 0;
for (; i < (data->synth).pcm.length; i++) { for (; i < (data->synth).pcm.length; i++) {
mpd_sint16 *sample; unsigned int num_samples;
samplesLeft--; samplesLeft--;
@ -921,19 +945,11 @@ static int mp3Read(mp3DecodeData * data, struct decoder *decoder,
return DECODE_BREAK; return DECODE_BREAK;
} }
sample = (mpd_sint16 *) data->outputPtr; num_samples = dither_buffer((mpd_sint16 *) data->outputPtr,
*sample = (mpd_sint16) audio_linear_dither(16, &data->synth, &data->dither,
(data->synth).pcm.samples[0][i], i, i + 1,
&(data->dither)); MAD_NCHANNELS(&(data->frame).header));
data->outputPtr += 2; data->outputPtr += 2 * num_samples;
if (MAD_NCHANNELS(&(data->frame).header) == 2) {
sample = (mpd_sint16 *) data->outputPtr;
*sample = (mpd_sint16) audio_linear_dither(16,
(data->synth).pcm.samples[1][i],
&(data->dither));
data->outputPtr += 2;
}
if (data->outputPtr >= data->outputBufferEnd) { if (data->outputPtr >= data->outputBufferEnd) {
enum decoder_command cmd; enum decoder_command cmd;