Make audio buffer size configurable

doc/en/sidplayfp.ini.pod

@@ -162,6 +162,12 @@ Number of bits ber sample, used only for wav/au output. Using
 values other than the ones specified will produce invalid
 output.
 
+=item B<BufferLength>=I<< <number> >>
+
+Length of the buffer in milliseconds, default is 250.
+Increase if you experience audio problems or reduce to
+improve latency.
+
 =back
 
 

src/IniConfig.cpp

@@ -106,6 +106,7 @@ void IniConfig::clear()
     audio_s.frequency = SidConfig::DEFAULT_SAMPLING_FREQ;
     audio_s.channels  = 0;
     audio_s.precision = 16;
+    audio_s.bufLength = 250;
 
     emulation_s.modelDefault  = SidConfig::PAL;
     emulation_s.modelForced   = false;
@@ -376,6 +377,8 @@ void IniConfig::readAudio(iniHandler &ini)
     readInt(ini, TEXT("Channels"),  audio_s.channels);
 
     readInt(ini, TEXT("BitsPerSample"), audio_s.precision);
+
+    readInt(ini, TEXT("BufferLength"), audio_s.bufLength);
 }
 
 

src/IniConfig.h

@@ -63,9 +63,11 @@ class IniConfig
 
     struct audio_section
     {   // INI Section - [Audio]
-        int frequency;
-        int channels;
-        int precision;
+        int frequency; // sample rate
+        int channels;  // number of channels
+        int precision; // sample precision in bits
+        int bufLength; // buffer length in milliseconds
+        int getBufSize() const { return (bufLength * frequency) / 1000; }
     };
 
     struct emulation_section

src/audio/AudioConfig.h

@@ -29,15 +29,13 @@ class AudioConfig
     uint_least32_t frequency;
     int            precision;
     int            channels;
-    uint_least32_t bufSize;       // sample buffer size
+    uint_least32_t bufSize;       // sample buffer size measured in frames
 
     AudioConfig() :
         frequency(48000),
         precision(16),
         channels(1),
         bufSize(0) {}
-
-    uint_least32_t bytesPerMillis() const { return (precision/8 * channels * frequency) / 1000; }
 };
 
 #endif  // AUDIOCONFIG_H

src/audio/AudioDrv.cpp

@@ -47,6 +47,8 @@
 #  define HAVE_NULL
 #endif
 
+#include <iostream>
+
 bool audioDrv::open(AudioConfig &cfg)
 {
     bool res = false;
@@ -69,6 +71,7 @@ bool audioDrv::open(AudioConfig &cfg)
     {
         audio.reset(new Audio_ALSA());
         res = audio->open(cfg);
+        if (res) std::cerr << "ALSA" << std::endl;
     }
 #endif
 #ifdef HAVE_OSS

src/audio/AudioDrv.h

@@ -37,7 +37,7 @@ class audioDrv : public IAudio
 
     bool open(AudioConfig &cfg) override;
     void reset() override { audio->reset(); }
-    bool write(uint_least32_t size) override { return audio->write(size); }
+    bool write(uint_least32_t frames) override { return audio->write(frames); }
     void close() override { audio->close(); }
     void pause() override { audio->pause(); }
     short *buffer() const override { return audio->buffer(); }

src/audio/IAudio.h

@@ -33,7 +33,7 @@ class IAudio
 
     virtual bool open(AudioConfig &cfg) = 0;
     virtual void reset() = 0;
-    virtual bool write(uint_least32_t size) = 0;
+    virtual bool write(uint_least32_t frames) = 0;
     virtual void close() = 0;
     virtual void pause() = 0;
     virtual short *buffer() const = 0;

src/audio/alsa/audiodrv.cpp

@@ -84,7 +84,7 @@ bool Audio_ALSA::open(AudioConfig &cfg)
             tmpCfg.frequency = rate;
         }
 
-        snd_pcm_uframes_t buffer_size = tmpCfg.frequency / 5;
+        snd_pcm_uframes_t buffer_size = tmpCfg.bufSize;
         checkResult(snd_pcm_hw_params_set_buffer_size_near(_audioHandle, hw_params, &buffer_size));
         tmpCfg.bufSize = buffer_size;
 
@@ -136,15 +136,15 @@ void Audio_ALSA::close()
     }
 }
 
-bool Audio_ALSA::write(uint_least32_t size)
+bool Audio_ALSA::write(uint_least32_t frames)
 {
     if (_audioHandle == nullptr)
     {
         setError("Device not open.");
         return false;
     }
 
-    int err = snd_pcm_writei(_audioHandle, _sampleBuffer, size);
+    int err = snd_pcm_writei(_audioHandle, _sampleBuffer, frames);
     if (err < 0)
     {
         err = snd_pcm_recover(_audioHandle, err, 0);

src/audio/alsa/audiodrv.h

@@ -54,7 +54,7 @@ class Audio_ALSA: public AudioBase
     bool open  (AudioConfig &cfg) override;
     void close () override;
     void reset () override {}
-    bool write (uint_least32_t size) override;
+    bool write (uint_least32_t frames) override;
     void pause () override {}
 };
 

src/audio/au/auFile.cpp

@@ -186,20 +186,21 @@ auFile::auFile(const std::string &name) :
     auHdr(defaultAuHdr),
     file(nullptr),
     headerWritten(false),
-    precision(32)
+    m_precision(32)
 {}
 
 bool auFile::open(AudioConfig &cfg)
 {
-    precision = cfg.precision;
+    m_precision = cfg.precision;
+    m_channels = cfg.channels;
 
-    unsigned short bits       = precision;
-    unsigned long  format     = (precision == 16) ? 3 : 6;
-    unsigned long  channels   = cfg.channels;
+    unsigned short bits       = m_precision;
+    unsigned long  format     = (m_precision == 16) ? 3 : 6;
+    unsigned long  channels   = m_channels;
     unsigned long  freq       = cfg.frequency;
     unsigned short blockAlign = (bits>>3)*channels;
     unsigned long  bufSize    = freq * blockAlign;
-    cfg.bufSize = bufSize;
+    cfg.bufSize = freq;
 
     if (name.empty())
         return false;
@@ -238,18 +239,19 @@ bool auFile::open(AudioConfig &cfg)
     return true;
 }
 
-bool auFile::write(uint_least32_t size)
+bool auFile::write(uint_least32_t frames)
 {
     if (file && !file->fail())
     {
+        uint_least32_t size = frames * m_channels;
         unsigned long int bytes = size;
         if (!headerWritten)
         {
             file->write((char*)&auHdr, sizeof(auHeader));
             headerWritten = true;
         }
 
-        if (precision == 16)
+        if (m_precision == 16)
         {
             std::vector<uint_least16_t> buffer(size);
             bytes *= 2;

src/audio/au/auFile.h

@@ -57,7 +57,8 @@ class auFile: public AudioBase
 
     std::ostream *file;
     bool headerWritten;
-    int precision;
+    int m_precision;
+    int m_channels;
 
 public:
     auFile(const std::string &name);

src/audio/directx/audiodrv.cpp

@@ -131,8 +131,7 @@ bool Audio_DirectX::open (AudioConfig &cfg, HWND hwnd)
         }
         lpDsbPrimary->Release ();
 
-        // Buffer size reduced to 2 blocks of 500ms
-        bufSize = wfm.nSamplesPerSec / 2 * wfm.nBlockAlign;
+        bufSize = cfg.bufSize * wfm.nBlockAlign;
 
         // Allocate secondary buffers
         memset (&dsbdesc, 0, sizeof(DSBUFFERDESC));
@@ -182,7 +181,7 @@ bool Audio_DirectX::open (AudioConfig &cfg, HWND hwnd)
         }
 
         // Update the users settings
-        cfg.bufSize   = bufSize / 2;
+        m_frameSize   = wfm.nBlockAlign;
         _settings     = cfg;
         isPlaying     = false;
         _sampleBuffer = (short*)lpvData;
@@ -198,15 +197,16 @@ bool Audio_DirectX::open (AudioConfig &cfg, HWND hwnd)
     }
 }
 
-bool Audio_DirectX::write (uint_least32_t size)
+bool Audio_DirectX::write (uint_least32_t frames)
 {
     if (!isOpen)
     {
         setError("Device not open.");
         return false;
     }
-
-    size *= 2;
+
+    // get the number of bytes
+    DWORD size = frames * m_frameSize;
 
     // Unlock the current buffer for playing
     lpDsb->Unlock (lpvData, size, NULL, 0);

src/audio/directx/audiodrv.h

@@ -59,6 +59,8 @@ class Audio_DirectX: public AudioBase
     HANDLE rghEvent[AUDIO_DIRECTX_BUFFERS];
     DWORD  bufSize;
 
+    int m_frameSize;
+
     bool isOpen;
     bool isPlaying;
 
@@ -75,7 +77,7 @@ class Audio_DirectX: public AudioBase
     bool open  (AudioConfig &cfg, HWND hwnd);
     void close () override;
     void reset () override;
-    bool write (uint_least32_t size) override;
+    bool write (uint_least32_t frames) override;
     void pause () override;
 };
 

src/audio/mmsystem/audiodrv.cpp

@@ -113,11 +113,10 @@ bool Audio_MMSystem::open(AudioConfig &cfg)
     wfm.cbSize          = 0;
 
     // Rev 1.3 (saw) - Calculate buffer to hold 250ms of data
-    bufSize = wfm.nSamplesPerSec / 4 * wfm.nBlockAlign;
+    bufSize = cfg.bufSize * wfm.nBlockAlign;
 
     try
     {
-        cfg.bufSize = bufSize / 2;
         checkResult(waveOutOpen(&waveHandle, WAVE_MAPPER, &wfm, 0, 0, 0));
 
         _settings = cfg;
@@ -160,6 +159,7 @@ bool Audio_MMSystem::open(AudioConfig &cfg)
             header->dwFlags        = WHDR_DONE; /* mark the block is done */
         }
 
+        m_frameSize = wfm.nBlockAlign;
         blockNum = 0;
         _sampleBuffer = blocks[blockNum];
         return true;
@@ -173,17 +173,20 @@ bool Audio_MMSystem::open(AudioConfig &cfg)
     }
 }
 
-bool Audio_MMSystem::write(uint_least32_t size)
+bool Audio_MMSystem::write(uint_least32_t frames)
 {
     if (!isOpen)
     {
         setError("Device not open.");
         return false;
     }
 
+    // get the number of bytes
+    DWORD size = frames * m_frameSize;
+
     /* Reset wave header fields: */
     blockHeaders[blockNum]->dwFlags = 0;
-    blockHeaders[blockNum]->dwBufferLength = size * 2;
+    blockHeaders[blockNum]->dwBufferLength = size;
 
     /* Prepare block header: */
     checkResult(waveOutPrepareHeader(waveHandle, blockHeaders[blockNum], sizeof(WAVEHDR)));

src/audio/mmsystem/audiodrv.h

@@ -53,6 +53,8 @@ class Audio_MMSystem: public AudioBase
     HGLOBAL  blockHeaderHandles[MAXBUFBLOCKS];
     int      blockNum;
     int      bufSize;
+    int      m_frameSize;
+
     bool     isOpen;
 
 private:
@@ -66,7 +68,7 @@ class Audio_MMSystem: public AudioBase
     bool open  (AudioConfig &cfg) override;
     void close () override;
     void reset () override;
-    bool write (uint_least32_t size) override;
+    bool write (uint_least32_t frames) override;
     void pause () override {}
 };
 

src/audio/null/null.h

@@ -50,7 +50,7 @@ class Audio_Null: public AudioBase
     bool open  (AudioConfig &cfg) override;
     void close () override;
     void reset () override {}
-    bool write (uint_least32_t size) override;
+    bool write (uint_least32_t frames) override;
     void pause () override {}
 };
 

src/audio/oss/audiodrv.cpp

@@ -117,6 +117,7 @@ bool Audio_OSS::open (AudioConfig &cfg)
         }
 
         // Setup internal Config
+        m_frameSize = 2 * cfg.channels;
         _settings = cfg;
         return true;
     }
@@ -155,15 +156,16 @@ void Audio_OSS::reset ()
     }
 }
 
-bool Audio_OSS::write (uint_least32_t size)
+bool Audio_OSS::write (uint_least32_t frames)
 {
     if (_audiofd == -1)
     {
         setError("Device not open.");
         return false;
     }
 
-    ::write (_audiofd, _sampleBuffer, 2 * size);
+    size_t const bytes = static_cast<size_t>(frames) * m_frameSize;
+    ::write (_audiofd, _sampleBuffer, bytes);
     return true;
 }
 

src/audio/oss/audiodrv.h

@@ -59,6 +59,9 @@ class Audio_OSS: public AudioBase
     static   const char AUDIODEVICE[];
     volatile int   _audiofd;
 
+    int m_frameSize;
+
+private:
     void outOfOrder ();
 
 public:  // --------------------------------------------------------- public
@@ -68,7 +71,7 @@ class Audio_OSS: public AudioBase
     bool open  (AudioConfig &cfg) override;
     void close () override;
     void reset () override;
-    bool write (uint_least32_t size) override;
+    bool write (uint_least32_t frames) override;
     void pause () override {}
 };