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pcm_utils: moved code from pcm_convertChannels() to separate functions

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Moved code from pcm_convertChannels() to pcm_convert_channels_1_to_2()
and pcm_convert_channels_2_to_1().  Improved the quality of
pcm_convert_channels_2_to_1() by calculating the arithmetic mean value
of both samples.
This commit is contained in:
Max Kellermann 2008-10-12 11:47:42 +02:00
parent 1a74d7be41
commit a7924d141d
1 changed files with 32 additions and 20 deletions
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52
src/pcm_utils.c
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@ -362,6 +362,29 @@ static size_t pcm_convertSampleRate(int8_t channels, uint32_t inSampleRate,
}
#endif /* !HAVE_LIBSAMPLERATE */
static void
pcm_convert_channels_1_to_2(int16_t *dest, const int16_t *src,
unsigned num_frames)
{
while (num_frames-- > 0) {
int16_t value = *src++;
*dest++ = value;
*dest++ = value;
}
}
static void
pcm_convert_channels_2_to_1(int16_t *dest, const int16_t *src,
unsigned num_frames)
{
while (num_frames-- > 0) {
int32_t a = *src++, b = *src++;
*dest++ = (a + b) / 2;
}
}
static const int16_t *
pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
size_t inSize, size_t *outSize)
@ -369,9 +392,6 @@ pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
static int16_t *buf;
static size_t len;
int16_t *outBuffer = NULL;
const int16_t *in;
int16_t *out;
int inSamples, i;
switch (channels) {
/* convert from 1 -> 2 channels */
@ -381,17 +401,13 @@ pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
len = *outSize;
buf = xrealloc(buf, len);
}
outBuffer = buf;
inSamples = inSize >> 1;
in = (const int16_t *)inBuffer;
out = (int16_t *)outBuffer;
for (i = 0; i < inSamples; i++) {
*out++ = *in;
*out++ = *in++;
}
pcm_convert_channels_1_to_2((int16_t *)buf,
(const int16_t *)inBuffer,
inSize >> 1);
break;
/* convert from 2 -> 1 channels */
case 2:
*outSize = inSize >> 1;
@ -401,15 +417,11 @@ pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
}
outBuffer = buf;
inSamples = inSize >> 2;
in = (const int16_t *)inBuffer;
out = (int16_t *)outBuffer;
for (i = 0; i < inSamples; i++) {
*out = (*in++) / 2;
*out++ += (*in++) / 2;
}
pcm_convert_channels_2_to_1((int16_t *)buf,
(const int16_t *)inBuffer,
inSize >> 2);
break;
default:
ERROR("only 1 or 2 channels are supported for conversion!\n");
}