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added on-the-fly WAV resampling (disabled, causes echo)

This commit is contained in:
Thomas Jentzsch 2022-09-15 15:21:10 +02:00
parent 1263f28e49
commit 5e09f486af
2 changed files with 45 additions and 6 deletions
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35
src/common/SoundSDL2.cxx
View File

@ -175,6 +175,9 @@ void SoundSDL2::open(shared_ptr<AudioQueue> audioQueue,
openDevice();
myEmulationTiming = emulationTiming;
#ifdef RESAMPLE_WAV_CB
myWavSpeed = 262 * 60 * 2. / myEmulationTiming->audioSampleRate();
#endif
Logger::debug("SoundSDL2::open started ...");
mute(true);
@ -503,6 +506,34 @@ void SoundSDL2::wavCallback(void* udata, uInt8* stream, int len)
{
SDL_memset(stream, myWavSpec.silence, len);
if(myWavLen)
{
#ifdef RESAMPLE_WAV_CB
if(myWavSpeed != 1.0)
{
int newLen = std::round(len / myWavSpeed);
const int newFreq = std::round(static_cast<double>(myWavSpec.freq) * len / newLen);
if(static_cast<uInt32>(newLen) > myWavLen)
newLen = myWavLen;
SDL_AudioCVT cvt;
SDL_BuildAudioCVT(&cvt, myWavSpec.format, myWavSpec.channels, myWavSpec.freq,
myWavSpec.format, myWavSpec.channels, newFreq);
SDL_assert(cvt.needed); // Obviously, this one is always needed.
cvt.len = newLen * myWavSpec.channels; // Mono 8 bit sample frames
cvt.buf = static_cast<uInt8*>(SDL_malloc(cvt.len * cvt.len_mult * 2)); // Double buffer size to avoid memory access exception
// Read original data into conversion buffer
SDL_memcpy(cvt.buf, myWavPos, cvt.len);
SDL_ConvertAudio(&cvt);
// Mix volume adjusted WAV data into silent buffer
SDL_MixAudioFormat(stream, cvt.buf, myWavSpec.format, cvt.len_cvt,
SDL_MIX_MAXVOLUME * myWavVolumeFactor);
SDL_free(cvt.buf);
cerr << cvt.len_cvt << " ";
}
else
#endif
{
if(static_cast<uInt32>(len) > myWavLen)
len = myWavLen;
@ -510,6 +541,7 @@ void SoundSDL2::wavCallback(void* udata, uInt8* stream, int len)
// Mix volume adjusted WAV data into silent buffer
SDL_MixAudioFormat(stream, myWavPos, myWavSpec.format, len,
SDL_MIX_MAXVOLUME * myWavVolumeFactor);
}
myWavPos += len;
myWavLen -= len;
}
@ -520,5 +552,8 @@ float SoundSDL2::myWavVolumeFactor = 0xffff;
SDL_AudioSpec SoundSDL2::myWavSpec; // audio output format
uInt8* SoundSDL2::myWavPos = nullptr; // pointer to the audio buffer to be played
uInt32 SoundSDL2::myWavLen = 0; // remaining length of the sample we have to play
#ifdef RESAMPLE_WAV_CB
double SoundSDL2::myWavSpeed = 1.0;
#endif
#endif // SOUND_SUPPORT

6
src/common/SoundSDL2.hxx
View File

@ -20,7 +20,8 @@
#ifndef SOUND_SDL2_HXX
#define SOUND_SDL2_HXX
//#define RESAMPLE_WAV
//#define RESAMPLE_WAV // does not adjust to speed immediately
//#define RESAMPLE_WAV_CB // causes echo in in-the-fly resampling
class OSystem;
class AudioQueue;
@ -197,6 +198,9 @@ class SoundSDL2 : public Sound
#ifdef RESAMPLE_WAV
SDL_AudioCVT myCvt{0};
#endif
#ifdef RESAMPLE_WAV_CB
static double myWavSpeed;
#endif
static float myWavVolumeFactor;
static SDL_AudioSpec myWavSpec; // audio output format