src/java.desktop/linux/native/libjsound/PLATFORM_API_LinuxOS_ALSA_PCM.c
changeset 49289 148e29df1644
parent 47216 71c04702a3d5
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.desktop/linux/native/libjsound/PLATFORM_API_LinuxOS_ALSA_PCM.c	Fri Mar 23 09:51:02 2018 +0100
@@ -0,0 +1,941 @@
+/*
+ * Copyright (c) 2002, 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#define USE_ERROR
+#define USE_TRACE
+
+#include "PLATFORM_API_LinuxOS_ALSA_PCMUtils.h"
+#include "PLATFORM_API_LinuxOS_ALSA_CommonUtils.h"
+#include "DirectAudio.h"
+
+#if USE_DAUDIO == TRUE
+
+// GetPosition method 1: based on how many bytes are passed to the kernel driver
+//                       + does not need much processor resources
+//                       - not very exact, "jumps"
+// GetPosition method 2: ask kernel about actual position of playback.
+//                       - very exact
+//                       - switch to kernel layer for each call
+// GetPosition method 3: use snd_pcm_avail() call - not yet in official ALSA
+// quick tests on a Pentium 200MMX showed max. 1.5% processor usage
+// for playing back a CD-quality file and printing 20x per second a line
+// on the console with the current time. So I guess performance is not such a
+// factor here.
+//#define GET_POSITION_METHOD1
+#define GET_POSITION_METHOD2
+
+
+// The default time for a period in microseconds.
+// For very small buffers, only 2 periods are used.
+#define DEFAULT_PERIOD_TIME 20000 /* 20ms */
+
+///// implemented functions of DirectAudio.h
+
+INT32 DAUDIO_GetDirectAudioDeviceCount() {
+    return (INT32) getAudioDeviceCount();
+}
+
+
+INT32 DAUDIO_GetDirectAudioDeviceDescription(INT32 mixerIndex, DirectAudioDeviceDescription* description) {
+    ALSA_AudioDeviceDescription adesc;
+
+    adesc.index = (int) mixerIndex;
+    adesc.strLen = DAUDIO_STRING_LENGTH;
+
+    adesc.maxSimultaneousLines = (int*) (&(description->maxSimulLines));
+    adesc.deviceID = &(description->deviceID);
+    adesc.name = description->name;
+    adesc.vendor = description->vendor;
+    adesc.description = description->description;
+    adesc.version = description->version;
+
+    return getAudioDeviceDescriptionByIndex(&adesc);
+}
+
+#define MAX_BIT_INDEX 6
+// returns
+// 6: for anything above 24-bit
+// 5: for 4 bytes sample size, 24-bit
+// 4: for 3 bytes sample size, 24-bit
+// 3: for 3 bytes sample size, 20-bit
+// 2: for 2 bytes sample size, 16-bit
+// 1: for 1 byte sample size, 8-bit
+// 0: for anything else
+int getBitIndex(int sampleSizeInBytes, int significantBits) {
+    if (significantBits > 24) return 6;
+    if (sampleSizeInBytes == 4 && significantBits == 24) return 5;
+    if (sampleSizeInBytes == 3) {
+        if (significantBits == 24) return 4;
+        if (significantBits == 20) return 3;
+    }
+    if (sampleSizeInBytes == 2 && significantBits == 16) return 2;
+    if (sampleSizeInBytes == 1 && significantBits == 8) return 1;
+    return 0;
+}
+
+int getSampleSizeInBytes(int bitIndex, int sampleSizeInBytes) {
+    switch(bitIndex) {
+    case 1: return 1;
+    case 2: return 2;
+    case 3: /* fall through */
+    case 4: return 3;
+    case 5: return 4;
+    }
+    return sampleSizeInBytes;
+}
+
+int getSignificantBits(int bitIndex, int significantBits) {
+    switch(bitIndex) {
+    case 1: return 8;
+    case 2: return 16;
+    case 3: return 20;
+    case 4: /* fall through */
+    case 5: return 24;
+    }
+    return significantBits;
+}
+
+void DAUDIO_GetFormats(INT32 mixerIndex, INT32 deviceID, int isSource, void* creator) {
+    snd_pcm_t* handle;
+    snd_pcm_format_mask_t* formatMask;
+    snd_pcm_format_t format;
+    snd_pcm_hw_params_t* hwParams;
+    int handledBits[MAX_BIT_INDEX+1];
+
+    int ret;
+    int sampleSizeInBytes, significantBits, isSigned, isBigEndian, enc;
+    int origSampleSizeInBytes, origSignificantBits;
+    unsigned int channels, minChannels, maxChannels;
+    int rate, bitIndex;
+
+    for (bitIndex = 0; bitIndex <= MAX_BIT_INDEX; bitIndex++) handledBits[bitIndex] = FALSE;
+    if (openPCMfromDeviceID(deviceID, &handle, isSource, TRUE /*query hardware*/) < 0) {
+        return;
+    }
+    ret = snd_pcm_format_mask_malloc(&formatMask);
+    if (ret != 0) {
+        ERROR1("snd_pcm_format_mask_malloc returned error %d\n", ret);
+    } else {
+        ret = snd_pcm_hw_params_malloc(&hwParams);
+        if (ret != 0) {
+            ERROR1("snd_pcm_hw_params_malloc returned error %d\n", ret);
+        } else {
+            ret = snd_pcm_hw_params_any(handle, hwParams);
+            /* snd_pcm_hw_params_any can return a positive value on success too */
+            if (ret < 0) {
+                 ERROR1("snd_pcm_hw_params_any returned error %d\n", ret);
+            } else {
+                /* for the logic following this code, set ret to 0 to indicate success */
+                ret = 0;
+            }
+        }
+        snd_pcm_hw_params_get_format_mask(hwParams, formatMask);
+        if (ret == 0) {
+            ret = snd_pcm_hw_params_get_channels_min(hwParams, &minChannels);
+            if (ret != 0) {
+                ERROR1("snd_pcm_hw_params_get_channels_min returned error %d\n", ret);
+            }
+        }
+        if (ret == 0) {
+            ret = snd_pcm_hw_params_get_channels_max(hwParams, &maxChannels);
+            if (ret != 0) {
+                ERROR1("snd_pcm_hw_params_get_channels_max returned error %d\n", ret);
+            }
+        }
+
+        // since we queried the hw: device, for many soundcards, it will only
+        // report the maximum number of channels (which is the only way to talk
+        // to the hw: device). Since we will, however, open the plughw: device
+        // when opening the Source/TargetDataLine, we can safely assume that
+        // also the channels 1..maxChannels are available.
+#ifdef ALSA_PCM_USE_PLUGHW
+        minChannels = 1;
+#endif
+        if (ret == 0) {
+            // plughw: supports any sample rate
+            rate = -1;
+            for (format = 0; format <= SND_PCM_FORMAT_LAST; format++) {
+                if (snd_pcm_format_mask_test(formatMask, format)) {
+                    // format exists
+                    if (getFormatFromAlsaFormat(format, &origSampleSizeInBytes,
+                                                &origSignificantBits,
+                                                &isSigned, &isBigEndian, &enc)) {
+                        // now if we use plughw:, we can use any bit size below the
+                        // natively supported ones. Some ALSA drivers only support the maximum
+                        // bit size, so we add any sample rates below the reported one.
+                        // E.g. this iteration reports support for 16-bit.
+                        // getBitIndex will return 2, so it will add entries for
+                        // 16-bit (bitIndex=2) and in the next do-while loop iteration,
+                        // it will decrease bitIndex and will therefore add 8-bit support.
+                        bitIndex = getBitIndex(origSampleSizeInBytes, origSignificantBits);
+                        do {
+                            if (bitIndex == 0
+                                || bitIndex == MAX_BIT_INDEX
+                                || !handledBits[bitIndex]) {
+                                handledBits[bitIndex] = TRUE;
+                                sampleSizeInBytes = getSampleSizeInBytes(bitIndex, origSampleSizeInBytes);
+                                significantBits = getSignificantBits(bitIndex, origSignificantBits);
+                                if (maxChannels - minChannels > MAXIMUM_LISTED_CHANNELS) {
+                                    // avoid too many channels explicitly listed
+                                    // just add -1, min, and max
+                                    DAUDIO_AddAudioFormat(creator, significantBits,
+                                                          -1, -1, rate,
+                                                          enc, isSigned, isBigEndian);
+                                    DAUDIO_AddAudioFormat(creator, significantBits,
+                                                          sampleSizeInBytes * minChannels,
+                                                          minChannels, rate,
+                                                          enc, isSigned, isBigEndian);
+                                    DAUDIO_AddAudioFormat(creator, significantBits,
+                                                          sampleSizeInBytes * maxChannels,
+                                                          maxChannels, rate,
+                                                          enc, isSigned, isBigEndian);
+                                } else {
+                                    for (channels = minChannels; channels <= maxChannels; channels++) {
+                                        DAUDIO_AddAudioFormat(creator, significantBits,
+                                                              sampleSizeInBytes * channels,
+                                                              channels, rate,
+                                                              enc, isSigned, isBigEndian);
+                                    }
+                                }
+                            }
+#ifndef ALSA_PCM_USE_PLUGHW
+                            // without plugin, do not add fake formats
+                            break;
+#endif
+                        } while (--bitIndex > 0);
+                    } else {
+                        TRACE1("could not get format from alsa for format %d\n", format);
+                    }
+                } else {
+                    //TRACE1("Format %d not supported\n", format);
+                }
+            } // for loop
+            snd_pcm_hw_params_free(hwParams);
+        }
+        snd_pcm_format_mask_free(formatMask);
+    }
+    snd_pcm_close(handle);
+}
+
+/** Workaround for cr 7033899, 7030629:
+ * dmix plugin doesn't like flush (snd_pcm_drop) when the buffer is empty
+ * (just opened, underruned or already flushed).
+ * Sometimes it causes PCM falls to -EBADFD error,
+ * sometimes causes bufferSize change.
+ * To prevent unnecessary flushes AlsaPcmInfo::isRunning & isFlushed are used.
+ */
+/* ******* ALSA PCM INFO ******************** */
+typedef struct tag_AlsaPcmInfo {
+    snd_pcm_t* handle;
+    snd_pcm_hw_params_t* hwParams;
+    snd_pcm_sw_params_t* swParams;
+    int bufferSizeInBytes;
+    int frameSize; // storage size in Bytes
+    unsigned int periods;
+    snd_pcm_uframes_t periodSize;
+    short int isRunning;    // see comment above
+    short int isFlushed;    // see comment above
+#ifdef GET_POSITION_METHOD2
+    // to be used exclusively by getBytePosition!
+    snd_pcm_status_t* positionStatus;
+#endif
+} AlsaPcmInfo;
+
+
+int setStartThresholdNoCommit(AlsaPcmInfo* info, int useThreshold) {
+    int ret;
+    int threshold;
+
+    if (useThreshold) {
+        // start device whenever anything is written to the buffer
+        threshold = 1;
+    } else {
+        // never start the device automatically
+        threshold = 2000000000; /* near UINT_MAX */
+    }
+    ret = snd_pcm_sw_params_set_start_threshold(info->handle, info->swParams, threshold);
+    if (ret < 0) {
+        ERROR1("Unable to set start threshold mode: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    return TRUE;
+}
+
+int setStartThreshold(AlsaPcmInfo* info, int useThreshold) {
+    int ret = 0;
+
+    if (!setStartThresholdNoCommit(info, useThreshold)) {
+        ret = -1;
+    }
+    if (ret == 0) {
+        // commit it
+        ret = snd_pcm_sw_params(info->handle, info->swParams);
+        if (ret < 0) {
+            ERROR1("Unable to set sw params: %s\n", snd_strerror(ret));
+        }
+    }
+    return (ret == 0)?TRUE:FALSE;
+}
+
+
+// returns TRUE if successful
+int setHWParams(AlsaPcmInfo* info,
+                float sampleRate,
+                int channels,
+                int bufferSizeInFrames,
+                snd_pcm_format_t format) {
+    unsigned int rrate, periodTime, periods;
+    int ret, dir;
+    snd_pcm_uframes_t alsaBufferSizeInFrames = (snd_pcm_uframes_t) bufferSizeInFrames;
+
+    /* choose all parameters */
+    ret = snd_pcm_hw_params_any(info->handle, info->hwParams);
+    if (ret < 0) {
+        ERROR1("Broken configuration: no configurations available: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    /* set the interleaved read/write format */
+    ret = snd_pcm_hw_params_set_access(info->handle, info->hwParams, SND_PCM_ACCESS_RW_INTERLEAVED);
+    if (ret < 0) {
+        ERROR1("SND_PCM_ACCESS_RW_INTERLEAVED access type not available: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    /* set the sample format */
+    ret = snd_pcm_hw_params_set_format(info->handle, info->hwParams, format);
+    if (ret < 0) {
+        ERROR1("Sample format not available: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    /* set the count of channels */
+    ret = snd_pcm_hw_params_set_channels(info->handle, info->hwParams, channels);
+    if (ret < 0) {
+        ERROR2("Channels count (%d) not available: %s\n", channels, snd_strerror(ret));
+        return FALSE;
+    }
+    /* set the stream rate */
+    rrate = (int) (sampleRate + 0.5f);
+    dir = 0;
+    ret = snd_pcm_hw_params_set_rate_near(info->handle, info->hwParams, &rrate, &dir);
+    if (ret < 0) {
+        ERROR2("Rate %dHz not available for playback: %s\n", (int) (sampleRate+0.5f), snd_strerror(ret));
+        return FALSE;
+    }
+    if ((rrate-sampleRate > 2) || (rrate-sampleRate < - 2)) {
+        ERROR2("Rate doesn't match (requested %2.2fHz, got %dHz)\n", sampleRate, rrate);
+        return FALSE;
+    }
+    /* set the buffer time */
+    ret = snd_pcm_hw_params_set_buffer_size_near(info->handle, info->hwParams, &alsaBufferSizeInFrames);
+    if (ret < 0) {
+        ERROR2("Unable to set buffer size to %d frames: %s\n",
+               (int) alsaBufferSizeInFrames, snd_strerror(ret));
+        return FALSE;
+    }
+    bufferSizeInFrames = (int) alsaBufferSizeInFrames;
+    /* set the period time */
+    if (bufferSizeInFrames > 1024) {
+        dir = 0;
+        periodTime = DEFAULT_PERIOD_TIME;
+        ret = snd_pcm_hw_params_set_period_time_near(info->handle, info->hwParams, &periodTime, &dir);
+        if (ret < 0) {
+            ERROR2("Unable to set period time to %d: %s\n", DEFAULT_PERIOD_TIME, snd_strerror(ret));
+            return FALSE;
+        }
+    } else {
+        /* set the period count for very small buffer sizes to 2 */
+        dir = 0;
+        periods = 2;
+        ret = snd_pcm_hw_params_set_periods_near(info->handle, info->hwParams, &periods, &dir);
+        if (ret < 0) {
+            ERROR2("Unable to set period count to %d: %s\n", /*periods*/ 2, snd_strerror(ret));
+            return FALSE;
+        }
+    }
+    /* write the parameters to device */
+    ret = snd_pcm_hw_params(info->handle, info->hwParams);
+    if (ret < 0) {
+        ERROR1("Unable to set hw params: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    return TRUE;
+}
+
+// returns 1 if successful
+int setSWParams(AlsaPcmInfo* info) {
+    int ret;
+
+    /* get the current swparams */
+    ret = snd_pcm_sw_params_current(info->handle, info->swParams);
+    if (ret < 0) {
+        ERROR1("Unable to determine current swparams: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    /* never start the transfer automatically */
+    if (!setStartThresholdNoCommit(info, FALSE /* don't use threshold */)) {
+        return FALSE;
+    }
+
+    /* allow the transfer when at least period_size samples can be processed */
+    ret = snd_pcm_sw_params_set_avail_min(info->handle, info->swParams, info->periodSize);
+    if (ret < 0) {
+        ERROR1("Unable to set avail min for playback: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    /* write the parameters to the playback device */
+    ret = snd_pcm_sw_params(info->handle, info->swParams);
+    if (ret < 0) {
+        ERROR1("Unable to set sw params: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    return TRUE;
+}
+
+static snd_output_t* ALSA_OUTPUT = NULL;
+
+void* DAUDIO_Open(INT32 mixerIndex, INT32 deviceID, int isSource,
+                  int encoding, float sampleRate, int sampleSizeInBits,
+                  int frameSize, int channels,
+                  int isSigned, int isBigEndian, int bufferSizeInBytes) {
+    snd_pcm_format_mask_t* formatMask;
+    snd_pcm_format_t format;
+    int dir;
+    int ret = 0;
+    AlsaPcmInfo* info = NULL;
+    /* snd_pcm_uframes_t is 64 bit on 64-bit systems */
+    snd_pcm_uframes_t alsaBufferSizeInFrames = 0;
+
+
+    TRACE0("> DAUDIO_Open\n");
+#ifdef USE_TRACE
+    // for using ALSA debug dump methods
+    if (ALSA_OUTPUT == NULL) {
+        snd_output_stdio_attach(&ALSA_OUTPUT, stdout, 0);
+    }
+#endif
+    if (channels <= 0) {
+        ERROR1("ERROR: Invalid number of channels=%d!\n", channels);
+        return NULL;
+    }
+    info = (AlsaPcmInfo*) malloc(sizeof(AlsaPcmInfo));
+    if (!info) {
+        ERROR0("Out of memory\n");
+        return NULL;
+    }
+    memset(info, 0, sizeof(AlsaPcmInfo));
+    // initial values are: stopped, flushed
+    info->isRunning = 0;
+    info->isFlushed = 1;
+
+    ret = openPCMfromDeviceID(deviceID, &(info->handle), isSource, FALSE /* do open device*/);
+    if (ret == 0) {
+        // set to blocking mode
+        snd_pcm_nonblock(info->handle, 0);
+        ret = snd_pcm_hw_params_malloc(&(info->hwParams));
+        if (ret != 0) {
+            ERROR1("  snd_pcm_hw_params_malloc returned error %d\n", ret);
+        } else {
+            ret = -1;
+            if (getAlsaFormatFromFormat(&format, frameSize / channels, sampleSizeInBits,
+                                        isSigned, isBigEndian, encoding)) {
+                if (setHWParams(info,
+                                sampleRate,
+                                channels,
+                                bufferSizeInBytes / frameSize,
+                                format)) {
+                    info->frameSize = frameSize;
+                    ret = snd_pcm_hw_params_get_period_size(info->hwParams, &info->periodSize, &dir);
+                    if (ret < 0) {
+                        ERROR1("ERROR: snd_pcm_hw_params_get_period: %s\n", snd_strerror(ret));
+                    }
+                    snd_pcm_hw_params_get_periods(info->hwParams, &(info->periods), &dir);
+                    snd_pcm_hw_params_get_buffer_size(info->hwParams, &alsaBufferSizeInFrames);
+                    info->bufferSizeInBytes = (int) alsaBufferSizeInFrames * frameSize;
+                    TRACE3("  DAUDIO_Open: period size = %d frames, periods = %d. Buffer size: %d bytes.\n",
+                           (int) info->periodSize, info->periods, info->bufferSizeInBytes);
+                }
+            }
+        }
+        if (ret == 0) {
+            // set software parameters
+            ret = snd_pcm_sw_params_malloc(&(info->swParams));
+            if (ret != 0) {
+                ERROR1("snd_pcm_hw_params_malloc returned error %d\n", ret);
+            } else {
+                if (!setSWParams(info)) {
+                    ret = -1;
+                }
+            }
+        }
+        if (ret == 0) {
+            // prepare device
+            ret = snd_pcm_prepare(info->handle);
+            if (ret < 0) {
+                ERROR1("ERROR: snd_pcm_prepare: %s\n", snd_strerror(ret));
+            }
+        }
+
+#ifdef GET_POSITION_METHOD2
+        if (ret == 0) {
+            ret = snd_pcm_status_malloc(&(info->positionStatus));
+            if (ret != 0) {
+                ERROR1("ERROR in snd_pcm_status_malloc: %s\n", snd_strerror(ret));
+            }
+        }
+#endif
+    }
+    if (ret != 0) {
+        DAUDIO_Close((void*) info, isSource);
+        info = NULL;
+    } else {
+        // set to non-blocking mode
+        snd_pcm_nonblock(info->handle, 1);
+        TRACE1("< DAUDIO_Open: Opened device successfully. Handle=%p\n",
+               (void*) info->handle);
+    }
+    return (void*) info;
+}
+
+#ifdef USE_TRACE
+void printState(snd_pcm_state_t state) {
+    if (state == SND_PCM_STATE_OPEN) {
+        TRACE0("State: SND_PCM_STATE_OPEN\n");
+    }
+    else if (state == SND_PCM_STATE_SETUP) {
+        TRACE0("State: SND_PCM_STATE_SETUP\n");
+    }
+    else if (state == SND_PCM_STATE_PREPARED) {
+        TRACE0("State: SND_PCM_STATE_PREPARED\n");
+    }
+    else if (state == SND_PCM_STATE_RUNNING) {
+        TRACE0("State: SND_PCM_STATE_RUNNING\n");
+    }
+    else if (state == SND_PCM_STATE_XRUN) {
+        TRACE0("State: SND_PCM_STATE_XRUN\n");
+    }
+    else if (state == SND_PCM_STATE_DRAINING) {
+        TRACE0("State: SND_PCM_STATE_DRAINING\n");
+    }
+    else if (state == SND_PCM_STATE_PAUSED) {
+        TRACE0("State: SND_PCM_STATE_PAUSED\n");
+    }
+    else if (state == SND_PCM_STATE_SUSPENDED) {
+        TRACE0("State: SND_PCM_STATE_SUSPENDED\n");
+    }
+}
+#endif
+
+int DAUDIO_Start(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    int ret;
+    snd_pcm_state_t state;
+
+    TRACE0("> DAUDIO_Start\n");
+    // set to blocking mode
+    snd_pcm_nonblock(info->handle, 0);
+    // set start mode so that it always starts as soon as data is there
+    setStartThreshold(info, TRUE /* use threshold */);
+    state = snd_pcm_state(info->handle);
+    if (state == SND_PCM_STATE_PAUSED) {
+        // in case it was stopped previously
+        TRACE0("  Un-pausing...\n");
+        ret = snd_pcm_pause(info->handle, FALSE);
+        if (ret != 0) {
+            ERROR2("  NOTE: error in snd_pcm_pause:%d: %s\n", ret, snd_strerror(ret));
+        }
+    }
+    if (state == SND_PCM_STATE_SUSPENDED) {
+        TRACE0("  Resuming...\n");
+        ret = snd_pcm_resume(info->handle);
+        if (ret < 0) {
+            if ((ret != -EAGAIN) && (ret != -ENOSYS)) {
+                ERROR2("  ERROR: error in snd_pcm_resume:%d: %s\n", ret, snd_strerror(ret));
+            }
+        }
+    }
+    if (state == SND_PCM_STATE_SETUP) {
+        TRACE0("need to call prepare again...\n");
+        // prepare device
+        ret = snd_pcm_prepare(info->handle);
+        if (ret < 0) {
+            ERROR1("ERROR: snd_pcm_prepare: %s\n", snd_strerror(ret));
+        }
+    }
+    // in case there is still data in the buffers
+    ret = snd_pcm_start(info->handle);
+    if (ret != 0) {
+        if (ret != -EPIPE) {
+            ERROR2("  NOTE: error in snd_pcm_start: %d: %s\n", ret, snd_strerror(ret));
+        }
+    }
+    // set to non-blocking mode
+    ret = snd_pcm_nonblock(info->handle, 1);
+    if (ret != 0) {
+        ERROR1("  ERROR in snd_pcm_nonblock: %s\n", snd_strerror(ret));
+    }
+    state = snd_pcm_state(info->handle);
+#ifdef USE_TRACE
+    printState(state);
+#endif
+    ret = (state == SND_PCM_STATE_PREPARED)
+        || (state == SND_PCM_STATE_RUNNING)
+        || (state == SND_PCM_STATE_XRUN)
+        || (state == SND_PCM_STATE_SUSPENDED);
+    if (ret) {
+        info->isRunning = 1;
+        // source line should keep isFlushed value until Write() is called;
+        // for target data line reset it right now.
+        if (!isSource) {
+            info->isFlushed = 0;
+        }
+    }
+    TRACE1("< DAUDIO_Start %s\n", ret?"success":"error");
+    return ret?TRUE:FALSE;
+}
+
+int DAUDIO_Stop(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    int ret;
+
+    TRACE0("> DAUDIO_Stop\n");
+    // set to blocking mode
+    snd_pcm_nonblock(info->handle, 0);
+    setStartThreshold(info, FALSE /* don't use threshold */); // device will not start after buffer xrun
+    ret = snd_pcm_pause(info->handle, 1);
+    // set to non-blocking mode
+    snd_pcm_nonblock(info->handle, 1);
+    if (ret != 0) {
+        ERROR1("ERROR in snd_pcm_pause: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+    info->isRunning = 0;
+    TRACE0("< DAUDIO_Stop success\n");
+    return TRUE;
+}
+
+void DAUDIO_Close(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+
+    TRACE0("DAUDIO_Close\n");
+    if (info != NULL) {
+        if (info->handle != NULL) {
+            snd_pcm_close(info->handle);
+        }
+        if (info->hwParams) {
+            snd_pcm_hw_params_free(info->hwParams);
+        }
+        if (info->swParams) {
+            snd_pcm_sw_params_free(info->swParams);
+        }
+#ifdef GET_POSITION_METHOD2
+        if (info->positionStatus) {
+            snd_pcm_status_free(info->positionStatus);
+        }
+#endif
+        free(info);
+    }
+}
+
+/*
+ * Underrun and suspend recovery
+ * returns
+ * 0:  exit native and return 0
+ * 1:  try again to write/read
+ * -1: error - exit native with return value -1
+ */
+int xrun_recovery(AlsaPcmInfo* info, int err) {
+    int ret;
+
+    if (err == -EPIPE) {    /* underrun / overflow */
+        TRACE0("xrun_recovery: underrun/overflow.\n");
+        ret = snd_pcm_prepare(info->handle);
+        if (ret < 0) {
+            ERROR1("Can't recover from underrun/overflow, prepare failed: %s\n", snd_strerror(ret));
+            return -1;
+        }
+        return 1;
+    } else if (err == -ESTRPIPE) {
+        TRACE0("xrun_recovery: suspended.\n");
+        ret = snd_pcm_resume(info->handle);
+        if (ret < 0) {
+            if (ret == -EAGAIN) {
+                return 0; /* wait until the suspend flag is released */
+            }
+            return -1;
+        }
+        ret = snd_pcm_prepare(info->handle);
+        if (ret < 0) {
+            ERROR1("Can't recover from underrun/overflow, prepare failed: %s\n", snd_strerror(ret));
+            return -1;
+        }
+        return 1;
+    } else if (err == -EAGAIN) {
+        TRACE0("xrun_recovery: EAGAIN try again flag.\n");
+        return 0;
+    }
+
+    TRACE2("xrun_recovery: unexpected error %d: %s\n", err, snd_strerror(err));
+    return -1;
+}
+
+// returns -1 on error
+int DAUDIO_Write(void* id, char* data, int byteSize) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    int ret, count;
+    snd_pcm_sframes_t frameSize, writtenFrames;
+
+    TRACE1("> DAUDIO_Write %d bytes\n", byteSize);
+
+    /* sanity */
+    if (byteSize <= 0 || info->frameSize <= 0) {
+        ERROR2(" DAUDIO_Write: byteSize=%d, frameSize=%d!\n",
+               (int) byteSize, (int) info->frameSize);
+        TRACE0("< DAUDIO_Write returning -1\n");
+        return -1;
+    }
+
+    count = 2; // maximum number of trials to recover from underrun
+    //frameSize = snd_pcm_bytes_to_frames(info->handle, byteSize);
+    frameSize = (snd_pcm_sframes_t) (byteSize / info->frameSize);
+    do {
+        writtenFrames = snd_pcm_writei(info->handle, (const void*) data, (snd_pcm_uframes_t) frameSize);
+
+        if (writtenFrames < 0) {
+            ret = xrun_recovery(info, (int) writtenFrames);
+            if (ret <= 0) {
+                TRACE1("DAUDIO_Write: xrun recovery returned %d -> return.\n", ret);
+                return ret;
+            }
+            if (count-- <= 0) {
+                ERROR0("DAUDIO_Write: too many attempts to recover from xrun/suspend\n");
+                return -1;
+            }
+        } else {
+            break;
+        }
+    } while (TRUE);
+    //ret =  snd_pcm_frames_to_bytes(info->handle, writtenFrames);
+
+    if (writtenFrames > 0) {
+        // reset "flushed" flag
+        info->isFlushed = 0;
+    }
+
+    ret =  (int) (writtenFrames * info->frameSize);
+    TRACE1("< DAUDIO_Write: returning %d bytes.\n", ret);
+    return ret;
+}
+
+// returns -1 on error
+int DAUDIO_Read(void* id, char* data, int byteSize) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    int ret, count;
+    snd_pcm_sframes_t frameSize, readFrames;
+
+    TRACE1("> DAUDIO_Read %d bytes\n", byteSize);
+    /*TRACE3("  info=%p, data=%p, byteSize=%d\n",
+      (void*) info, (void*) data, (int) byteSize);
+      TRACE2("  info->frameSize=%d, info->handle=%p\n",
+      (int) info->frameSize, (void*) info->handle);
+    */
+    /* sanity */
+    if (byteSize <= 0 || info->frameSize <= 0) {
+        ERROR2(" DAUDIO_Read: byteSize=%d, frameSize=%d!\n",
+               (int) byteSize, (int) info->frameSize);
+        TRACE0("< DAUDIO_Read returning -1\n");
+        return -1;
+    }
+    if (!info->isRunning && info->isFlushed) {
+        // PCM has nothing to read
+        return 0;
+    }
+
+    count = 2; // maximum number of trials to recover from error
+    //frameSize = snd_pcm_bytes_to_frames(info->handle, byteSize);
+    frameSize = (snd_pcm_sframes_t) (byteSize / info->frameSize);
+    do {
+        readFrames = snd_pcm_readi(info->handle, (void*) data, (snd_pcm_uframes_t) frameSize);
+        if (readFrames < 0) {
+            ret = xrun_recovery(info, (int) readFrames);
+            if (ret <= 0) {
+                TRACE1("DAUDIO_Read: xrun recovery returned %d -> return.\n", ret);
+                return ret;
+            }
+            if (count-- <= 0) {
+                ERROR0("DAUDIO_Read: too many attempts to recover from xrun/suspend\n");
+                return -1;
+            }
+        } else {
+            break;
+        }
+    } while (TRUE);
+    //ret =  snd_pcm_frames_to_bytes(info->handle, readFrames);
+    ret =  (int) (readFrames * info->frameSize);
+    TRACE1("< DAUDIO_Read: returning %d bytes.\n", ret);
+    return ret;
+}
+
+
+int DAUDIO_GetBufferSize(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+
+    return info->bufferSizeInBytes;
+}
+
+int DAUDIO_StillDraining(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    snd_pcm_state_t state;
+
+    state = snd_pcm_state(info->handle);
+    //printState(state);
+    //TRACE1("Still draining: %s\n", (state != SND_PCM_STATE_XRUN)?"TRUE":"FALSE");
+    return (state == SND_PCM_STATE_RUNNING)?TRUE:FALSE;
+}
+
+
+int DAUDIO_Flush(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    int ret;
+
+    TRACE0("DAUDIO_Flush\n");
+
+    if (info->isFlushed) {
+        // nothing to drop
+        return 1;
+    }
+
+    ret = snd_pcm_drop(info->handle);
+    if (ret != 0) {
+        ERROR1("ERROR in snd_pcm_drop: %s\n", snd_strerror(ret));
+        return FALSE;
+    }
+
+    info->isFlushed = 1;
+    if (info->isRunning) {
+        ret = DAUDIO_Start(id, isSource);
+    }
+    return ret;
+}
+
+int DAUDIO_GetAvailable(void* id, int isSource) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    snd_pcm_sframes_t availableInFrames;
+    snd_pcm_state_t state;
+    int ret;
+
+    state = snd_pcm_state(info->handle);
+    if (info->isFlushed || state == SND_PCM_STATE_XRUN) {
+        // if in xrun state then we have the entire buffer available,
+        // not 0 as alsa reports
+        ret = info->bufferSizeInBytes;
+    } else {
+        availableInFrames = snd_pcm_avail_update(info->handle);
+        if (availableInFrames < 0) {
+            ret = 0;
+        } else {
+            //ret = snd_pcm_frames_to_bytes(info->handle, availableInFrames);
+            ret = (int) (availableInFrames * info->frameSize);
+        }
+    }
+    TRACE1("DAUDIO_GetAvailable returns %d bytes\n", ret);
+    return ret;
+}
+
+INT64 estimatePositionFromAvail(AlsaPcmInfo* info, int isSource, INT64 javaBytePos, int availInBytes) {
+    // estimate the current position with the buffer size and
+    // the available bytes to read or write in the buffer.
+    // not an elegant solution - bytePos will stop on xruns,
+    // and in race conditions it may jump backwards
+    // Advantage is that it is indeed based on the samples that go through
+    // the system (rather than time-based methods)
+    if (isSource) {
+        // javaBytePos is the position that is reached when the current
+        // buffer is played completely
+        return (INT64) (javaBytePos - info->bufferSizeInBytes + availInBytes);
+    } else {
+        // javaBytePos is the position that was when the current buffer was empty
+        return (INT64) (javaBytePos + availInBytes);
+    }
+}
+
+INT64 DAUDIO_GetBytePosition(void* id, int isSource, INT64 javaBytePos) {
+    AlsaPcmInfo* info = (AlsaPcmInfo*) id;
+    int ret;
+    INT64 result = javaBytePos;
+    snd_pcm_state_t state;
+    state = snd_pcm_state(info->handle);
+
+    if (!info->isFlushed && state != SND_PCM_STATE_XRUN) {
+#ifdef GET_POSITION_METHOD2
+        snd_timestamp_t* ts;
+        snd_pcm_uframes_t framesAvail;
+
+        // note: slight race condition if this is called simultaneously from 2 threads
+        ret = snd_pcm_status(info->handle, info->positionStatus);
+        if (ret != 0) {
+            ERROR1("ERROR in snd_pcm_status: %s\n", snd_strerror(ret));
+            result = javaBytePos;
+        } else {
+            // calculate from time value, or from available bytes
+            framesAvail = snd_pcm_status_get_avail(info->positionStatus);
+            result = estimatePositionFromAvail(info, isSource, javaBytePos, framesAvail * info->frameSize);
+        }
+#endif
+#ifdef GET_POSITION_METHOD3
+        snd_pcm_uframes_t framesAvail;
+        ret = snd_pcm_avail(info->handle, &framesAvail);
+        if (ret != 0) {
+            ERROR1("ERROR in snd_pcm_avail: %s\n", snd_strerror(ret));
+            result = javaBytePos;
+        } else {
+            result = estimatePositionFromAvail(info, isSource, javaBytePos, framesAvail * info->frameSize);
+        }
+#endif
+#ifdef GET_POSITION_METHOD1
+        result = estimatePositionFromAvail(info, isSource, javaBytePos, DAUDIO_GetAvailable(id, isSource));
+#endif
+    }
+    //printf("getbyteposition: javaBytePos=%d , return=%d\n", (int) javaBytePos, (int) result);
+    return result;
+}
+
+
+
+void DAUDIO_SetBytePosition(void* id, int isSource, INT64 javaBytePos) {
+    /* save to ignore, since GetBytePosition
+     * takes the javaBytePos param into account
+     */
+}
+
+int DAUDIO_RequiresServicing(void* id, int isSource) {
+    // never need servicing on Linux
+    return FALSE;
+}
+
+void DAUDIO_Service(void* id, int isSource) {
+    // never need servicing on Linux
+}
+
+
+#endif // USE_DAUDIO