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Add support for 16 bit 'half float' format PCM. 

I'm not 100% sure that the rounding of denormals is correct. As compared to foobar2000,
some samples are off by +1 LSB.  However, since I can't output 24 bit PCM easily with
rockbox, I'm not sure if this is due to a bug or just how rockbox rounds.  In practice
I don't think it matters so I'm just going to commit this for now.

Change-Id: Ic0792fcb172e4369a5512d202121c2b918b36079
This commit is contained in:
Michael Giacomelli 2012-11-22 05:05:35 +01:00
parent 3a39f77ed6
commit d594b36133
1 changed files with 28 additions and 1 deletions
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29
lib/rbcodec/codecs/libpcm/ieee_float.c
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@ -38,7 +38,7 @@ static bool set_format(struct pcm_format *format)
return false;
}
if (fmt->bitspersample != 32 && fmt->bitspersample != 64)
if (fmt->bitspersample != 16 && fmt->bitspersample != 32 && fmt->bitspersample != 64)
{
DEBUGF("CODEC_ERROR: ieee float must be 32 or 64 bitspersample: %d\n",
fmt->bitspersample);
@ -114,6 +114,33 @@ static int decode(const uint8_t *inbuf, size_t inbufsize,
}
*outbufsize = inbufsize >> 2;
}
else if (fmt->bitspersample == 16)
{
for (i = 0; i < inbufsize; i += 2)
{
pcm = inbuf[0]|((inbuf[1]&0x03)<<8);
exp = ((inbuf[1]&0x7c)>>2)-15;
sgn = (inbuf[1] & 0x80)>>7;
if(exp == -15)
pcm =0;
else
{
pcm+=1<<10;
exp+=2; /*shift by 2 for rockbox fixed format*/
if(exp>=0)
pcm <<= (exp);
else
pcm >>= (-exp);
if (sgn)
pcm = -pcm;
}
outbuf[i/2] = pcm;
inbuf += 2;
}
*outbufsize = inbufsize >> 1;
}
else
{
for (i = 0; i < inbufsize; i += 8)