This allows us to avoid an extra copy, allocate less memory and reduce cache
pressure. On the downside: we have to do a lot of tapdancing to resample the
buffer in reverse when the output is growing.
--HG--
extra : rebase_source : cab98b19216722eae3749cc1e1429d1c802e9782
It's expensive and (hopefully) unnecessary. If this becomes an overflow
problem, we could multiply both values by 0.5f before adding them, but let's
see if we can get by without the extra multiplication first.
--HG--
extra : rebase_source : b7b47e961eb974510e133882548ea36b40f6d7e3
We never seem to overflow the source buffer now; this might have been a
leftover from a bug that was covered by Vitaly's fixes?
Removing this conditional makes the resampler 10-20% faster. Left an
assert in there for debug builds, in case this still happens.
--HG--
extra : rebase_source : c05a536f5a80f065c0872b35d77d4f70a56b4e3e
Removed some needless things ("len / sizeof (Uint8)"), and made sure the
int32 -> float code uses doubles to avoid working with large integer values
in a 32-bit float.
--HG--
extra : rebase_source : c803b416ec487b8c0feba780ac06f8d11e90879b
Lukasz Biel
Tried to compile SDL2 using newest version of VS.
Got:
SDL_audiocvt.obj : error LNK2019: unresolved external symbol memcpy referenced in function SDL_ResampleCVT
1>E:\Users\dotPo\Lib\SDL\VisualC\x64\Release\SDL2.dll : fatal error LNK1120: 1 unresolved externals
whole compilation process: http://pastebin.com/eWDAvBce
Steps to reproduce:
clone http://hg.libsdl.org/SDL using tortoise hg,
open SDL\VisualC\SDL.sln,
when promted if should retarget solution click ok,
select release x64 build type,
Build/Build Solution
attempt 2, using Visual Studio cmake support:
open folder SDL\
select release x64 build type,
run CMake\Build CMakeLists.txt
build fails
When switched to debug build type, buils succeeds in both cases.
VS 2017 is still beta.
It causes audio pops if you're converting in chunks (and needs to
allocate/initialize/free on each convert). We'll either adjust this interface
when we break ABI for 2.1 to make this usable, or publish the SDL_AudioStream
API for those that want a streaming solution.
In the meantime, the "simple" resampler produces "good enough" audio without
pops and doesn't have to be initialized, so that'll do for now on the
SDL_AudioCVT interface.
--HG--
extra : rebase_source : 4c5656de3d1de9f88d6368e5ca363d834fc93af1
There was a draft of this where it did audio conversion into the final buffer,
if there was enough room available past what you asked for, but that interface
got removed, so the parameters didn't make sense (and we were using the
wrong one in any case, too!).
This no longer uses a script to generate code for every possible type
conversion or resampler. This caused a bloat in binary size and and compile
times. Now we use a handful of more generic functions and assume staying in
the CPU cache is the most important thing anyhow.
This shrinks the size of the final build (in this case: macOS X amd64, -Os to
optimize for size) by 15%. When compiling on a single core, build times drop
by about 15% too (although the previous cost was largely hidden by multicore
builds).
--HG--
extra : amend_source : ce9deadd24e237eb83d2ef900c493f25c7cf3a80
- Use the SDL_AUDIO_MASK_DATATYPE bit when selecting an implementation
where it matters. Previously two existing AUDIO_F32 cases had been
written, but were unreachable.
- Add AUDIO_F32 case for SDL_ConvertSurround_4.
- Fix incorrect pointer arithmetic causing the 2 to 6 channel
conversion for 4 byte audio formats to read and write beyond the end
of the buffer.
This lets us change things like this...
if (Failed) {
SDL_SetError("We failed");
return -1;
}
...into this...
if (Failed) {
return SDL_SetError("We failed");
}
Fixes Bugzilla #1778.
Markovtsev Vadim 2011-01-18 22:00:16 PST
SDL_audiocvt.c:
static void SDLCALL
SDL_ConvertStereo(SDL_AudioCVT * cvt, SDL_AudioFormat format):
#define dup_chans_1_to_2(type) \
{ \
const type *src = (const type *) (cvt->buf + cvt->len_cvt); \
type *dst = (type *) (cvt->buf + cvt->len_cvt * 2); \
for (i = cvt->len_cvt / 2; i; --i, --src) { \
const type val = *src; \
dst -= 2; \
dst[0] = dst[1] = val; \
} \
}
Pay attention to cvt->len_cvt / 2. 2 is the sizeof(Uint16), hovewer, below we
see that the conversion function supports Uint8 and Uint32:
switch (SDL_AUDIO_BITSIZE(format)) {
case 8:
dup_chans_1_to_2(Uint8);
break;
case 16:
dup_chans_1_to_2(Uint16);
break;
case 32:
dup_chans_1_to_2(Uint32);
break;
}
If type is Uint32, src will be decreased twice as it should be, memory being
written before the cvt->buf. If type is Uint8, the conversion will not be
complete. I suggest to change that define to
#define dup_chans_1_to_2(type) \
{ \
const type *src = (const type *) (cvt->buf + cvt->len_cvt); \
type *dst = (type *) (cvt->buf + cvt->len_cvt * 2); \
for (i = cvt->len_cvt / sizeof(type); i; --i, --src) { \
const type val = *src; \
dst -= 2; \
dst[0] = dst[1] = val; \
} \
}
I tested that and now it's working fine. I did not consider the similar defines
in functions nearby.
* Some math functions become intrinsic in release mode, so we need to
convert all the math functions into SDL math functions, like we did
with the stdlib functions.
* Constant initializers of 8-bit values become calls to memset() in
release mode, but memset() itself is an intrinsic when explicitly
called. So we'll just explicitly call memset() in those cases.
--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403474
