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
FIXME: this is a memory leak. We don't have an SDL_FreeAudioCVT() yet.
--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403342
Bring SDL to iPhone and iPod Touch
by Holmes Futrell, mentored by Sam Lantinga
--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403222
Audio Ideas - Resampling and Pitch Shifting
by Aaron Wishnick, mentored by Ryan C. Gordon
--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403165
