oysteikt/mpd
0
0
Fork 0
Code Issues Pull Requests Releases Activity

pcm_utils: moved code from pcm_convertChannels() to separate functions

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
src/pcm_utils.c
View File

@ -362,6 +362,29 @@ static size_t pcm_convertSampleRate(int8_t channels, uint32_t inSampleRate,
} }
#endif /* !HAVE_LIBSAMPLERATE */ #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 * static const int16_t *
pcm_convertChannels(int8_t channels, const int16_t *inBuffer, pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
size_t inSize, size_t *outSize) size_t inSize, size_t *outSize)
@ -369,9 +392,6 @@ pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
static int16_t *buf; static int16_t *buf;
static size_t len; static size_t len;
int16_t *outBuffer = NULL; int16_t *outBuffer = NULL;
const int16_t *in;
int16_t *out;
int inSamples, i;
switch (channels) { switch (channels) {
/* convert from 1 -> 2 channels */ /* convert from 1 -> 2 channels */
@ -381,17 +401,13 @@ pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
len = *outSize; len = *outSize;
buf = xrealloc(buf, len); buf = xrealloc(buf, len);
} }
outBuffer = buf; outBuffer = buf;
pcm_convert_channels_1_to_2((int16_t *)buf,
inSamples = inSize >> 1; (const int16_t *)inBuffer,
in = (const int16_t *)inBuffer; inSize >> 1);
out = (int16_t *)outBuffer;
for (i = 0; i < inSamples; i++) {
*out++ = *in;
*out++ = *in++;
}
break; break;
/* convert from 2 -> 1 channels */ /* convert from 2 -> 1 channels */
case 2: case 2:
*outSize = inSize >> 1; *outSize = inSize >> 1;
@ -401,15 +417,11 @@ pcm_convertChannels(int8_t channels, const int16_t *inBuffer,
} }
outBuffer = buf; outBuffer = buf;
inSamples = inSize >> 2; pcm_convert_channels_2_to_1((int16_t *)buf,
in = (const int16_t *)inBuffer; (const int16_t *)inBuffer,
out = (int16_t *)outBuffer; inSize >> 2);
for (i = 0; i < inSamples; i++) {
*out = (*in++) / 2;
*out++ += (*in++) / 2;
}
break; break;
default: default:
ERROR("only 1 or 2 channels are supported for conversion!\n"); ERROR("only 1 or 2 channels are supported for conversion!\n");
} }