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pcm/PcmChannels: implement fake N-to-M mapping

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This is really just a mono mapper, but the important part is that this
library cannot fail anymore.
This commit is contained in:
Max Kellermann 2013-12-02 11:42:19 +01:00
parent 71b47ae3ef
commit cee1ac150e
1 changed files with 27 additions and 1 deletions
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28
src/pcm/PcmChannels.cxx
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@ -90,6 +90,31 @@ NToStereo(typename Traits::pointer_type dest,
return dest;
}
template<SampleFormat F, class Traits=SampleTraits<F>>
static typename Traits::pointer_type
NToM(typename Traits::pointer_type dest,
unsigned dest_channels,
unsigned src_channels,
typename Traits::const_pointer_type src,
typename Traits::const_pointer_type end)
{
assert((end - src) % src_channels == 0);
while (src != end) {
typename Traits::long_type sum = *src++;
for (unsigned c = 1; c < src_channels; ++c)
sum += *src++;
typename Traits::value_type value(sum / int(src_channels));
/* TODO: this is actually only mono ... */
for (unsigned c = 0; c < dest_channels; ++c)
*dest++ = value;
}
return dest;
}
template<SampleFormat F, class Traits=SampleTraits<F>>
static ConstBuffer<typename Traits::value_type>
ConvertChannels(PcmBuffer &buffer,
@ -109,7 +134,8 @@ ConvertChannels(PcmBuffer &buffer,
else if (dest_channels == 2)
NToStereo<F>(dest, src_channels, src.begin(), src.end());
else
return nullptr;
NToM<F>(dest, dest_channels,
src_channels, src.begin(), src.end());
return { dest, dest_size };
}