gstreamer/ext/alsa/gstalsa.c

/*
    Copyright (C) 2001 CodeFactory AB
    Copyright (C) 2001 Thomas Nyberg <thomas@codefactory.se>
    Copyright (C) 2001 Andy Wingo <apwingo@eos.ncsu.edu>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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 for more details.

    You should have received a copy of the GNU General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include <stdlib.h>
#include "gstalsa.h"

static GstElementDetails gst_alsa_sink_details = {  
    "Alsa Sink",
    "Sink/Audio",
    "Output to a sound card via ALSA: see plugins/alsa/README for more info",
    VERSION,
    "Thomas Nyberg <thomas@codefactory.se>, "
    "Andy Wingo <apwingo@eos.ncsu.edu>",
    "(C) 2001 "
};

static GstElementDetails gst_alsa_src_details = {  
    "Alsa Src",
    "Source/Audio",
    "Read from a sound card via ALSA: see plugins/alsa/README for more info",
    VERSION,
    "Thomas Nyberg <thomas@codefactory.se>, "
    "Andy Wingo <apwingo@eos.ncsu.edu>"
    "(C) 2001",
};

static GstElement *parent_class = NULL;

static void gst_alsa_init(GstAlsa *this);
static void gst_alsa_class_init(GstAlsaClass *klass);

static GstPadTemplate *gst_alsa_src_pad_factory();
static GstPadTemplate *gst_alsa_src_request_pad_factory();
static GstPadTemplate *gst_alsa_sink_pad_factory();
static GstPadTemplate *gst_alsa_sink_request_pad_factory();

static GstPad* gst_alsa_request_new_pad (GstElement *element, GstPadTemplate *templ, const
                                         gchar *name);

static void gst_alsa_set_property(GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
static void gst_alsa_get_property(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
static GstElementStateReturn gst_alsa_change_state(GstElement *element);
static GstPadNegotiateReturn gst_alsa_negotiate(GstPad *pad, GstCaps **caps, gpointer *user_data);

static GstCaps* gst_alsa_caps (GstAlsa *this);

static gboolean gst_alsa_open_audio(GstAlsa *this);
static gboolean gst_alsa_start_audio(GstAlsa *this);
static void gst_alsa_stop_audio(GstAlsa *this);
static void gst_alsa_close_audio(GstAlsa *this);

static gboolean gst_alsa_set_params(GstAlsa *this);
static void gst_alsa_loop (GstElement *element);
static gboolean gst_alsa_sink_process (GstAlsa *this, snd_pcm_uframes_t frames);
static gboolean gst_alsa_src_process (GstAlsa *this, snd_pcm_uframes_t frames);

static gboolean gst_alsa_get_channel_addresses (GstAlsa *this);
static void gst_alsa_release_channel_addresses (GstAlsa *this);

static void gst_alsa_sink_silence_on_channel (GstAlsa *this, guint32 chn, guint32 nframes);
static void memset_interleave (char *dst, char val, unsigned int bytes, 
                               unsigned int unit_bytes, 
                               unsigned int skip_bytes);


enum {
    ARG_0,
    ARG_DEVICE,
    ARG_FORMAT,
    ARG_CHANNELS,
    ARG_RATE,
    ARG_PERIODCOUNT,
    ARG_PERIODFRAMES
};

GType
gst_alsa_get_type (void) 
{
  static GType alsa_type = 0;

  if (!alsa_type) {
    static const GTypeInfo alsa_info = {
      sizeof(GstAlsaClass),
      NULL,
      NULL,
      NULL,
      NULL,
      NULL,
      sizeof(GstAlsa),
      0,
      NULL,
    };
    alsa_type = g_type_register_static (GST_TYPE_ELEMENT, "GstAlsa", &alsa_info, 0);
  }
  return alsa_type;
}

GType
gst_alsa_sink_get_type (void) 
{
  static GType alsa_type = 0;

  if (!alsa_type) {
    static const GTypeInfo alsa_info = {
      sizeof(GstAlsaClass),
      NULL,
      NULL,
      (GClassInitFunc)gst_alsa_class_init,
      NULL,
      NULL,
      sizeof(GstAlsa),
      0,
      (GInstanceInitFunc)gst_alsa_init,
    };
    alsa_type = g_type_register_static (GST_TYPE_ALSA, "GstAlsaSink", &alsa_info, 0);
  }
  return alsa_type;
}

GType
gst_alsa_src_get_type (void) 
{
  static GType alsa_type = 0;

  if (!alsa_type) {
    static const GTypeInfo alsa_info = {
      sizeof(GstAlsaClass),
      NULL,
      NULL,
      (GClassInitFunc)gst_alsa_class_init,
      NULL,
      NULL,
      sizeof(GstAlsa),
      0,
      (GInstanceInitFunc)gst_alsa_init,
    };
    alsa_type = g_type_register_static (GST_TYPE_ALSA, "GstAlsaSrc", &alsa_info, 0);
  }
  return alsa_type;
}

static GstPadTemplate*
gst_alsa_src_pad_factory(void)
{
    static GstPadTemplate *template = NULL;
    
    if (!template)
        template = gst_padtemplate_new("src", GST_PAD_SRC, GST_PAD_SOMETIMES, 
                                       gst_caps_new("src", "audio/raw", NULL),
                                       NULL);
    
    return template;
}

static GstPadTemplate*
gst_alsa_src_request_pad_factory(void)
{
    static GstPadTemplate *template = NULL;
    
    if (!template)
        template = gst_padtemplate_new("src%d", GST_PAD_SRC, GST_PAD_REQUEST, 
                                       gst_caps_new("src", "audio/raw",
                                                    gst_props_new("channels", GST_PROPS_INT(1), NULL)),
                                       NULL);
    
    return template;
}

static GstPadTemplate*
gst_alsa_sink_pad_factory(void)
{
    static GstPadTemplate *template = NULL;
    
    if (!template)
        template = gst_padtemplate_new("sink", GST_PAD_SINK, GST_PAD_SOMETIMES, 
                                       gst_caps_new("sink", "audio/raw", NULL),
                                       NULL);
    
    return template;
}

static GstPadTemplate*
gst_alsa_sink_request_pad_factory(void)
{
    static GstPadTemplate *template = NULL;
    
    if (!template)
        template = gst_padtemplate_new("sink%d", GST_PAD_SINK, GST_PAD_REQUEST, 
                                       gst_caps_new("sink-request", "audio/raw",
                                                    gst_props_new("channels", GST_PROPS_INT(1), NULL)),
                                       NULL);
    
    return template;
}

static void
gst_alsa_class_init(GstAlsaClass *klass)
{
    GObjectClass *object_class;
    GstElementClass *element_class;
    
    object_class = (GObjectClass *)klass;
    element_class = (GstElementClass *)klass;
    
    if (parent_class == NULL)
        parent_class = g_type_class_ref(GST_TYPE_ELEMENT);
    
    object_class->get_property = gst_alsa_get_property;
    object_class->set_property = gst_alsa_set_property;
    
    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_DEVICE,
                                    g_param_spec_string("device","device","alsa device: please see README for details",
                                                     "default",
                                                     G_PARAM_READWRITE));
    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_FORMAT,
                                    g_param_spec_int("format","format","format",
                                                     0, SND_PCM_FORMAT_LAST, SND_PCM_FORMAT_S16,
                                                     G_PARAM_READWRITE));
    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_CHANNELS,
                                    g_param_spec_int("channels","channels","channels",
                                                     1, 64, 1,
                                                     G_PARAM_READWRITE));
    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_RATE,
                                    g_param_spec_int("rate","rate","rate",
                                                     8000, 192000, 44100,
                                                     G_PARAM_READWRITE));
    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_PERIODCOUNT,
                                    g_param_spec_int("period_count","period count","period count",
                                                     2, 64, 2,
                                                     G_PARAM_READWRITE));
    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_PERIODFRAMES,
                                    g_param_spec_int("period_frames","period frames","period frames",
                                                     64, 4096, 256,
                                                     G_PARAM_READWRITE));
    
    element_class->change_state = gst_alsa_change_state;
    
    element_class->request_new_pad = gst_alsa_request_new_pad;
}

static void
gst_alsa_init(GstAlsa *this)
{
    /* init values */
    this->handle = NULL;
    
    /* i tried to trim this down to only the essentials needed for proper
     * functioning; we'll be setting this values 'in earnest' when caps come */
    
    this->rate = 44100;
    this->channels = 2;
    
    /* i wish i could leave these to defaults, but when caps come and typically
     * the number of channels doubles, you can't have the default count and size
     * that alsa gives you from the pre-caps setup apply to the post-caps setup
     * due to internal hw buffer size restrictions. these values seem to be
     * pretty common, though, although not pushing latency limits */
    this->period_count = 2;
    this->period_frames = 4096;
    
    this->device = g_strdup("default");
    
    /* is this right? */
    GST_FLAG_SET(this, GST_ELEMENT_THREAD_SUGGESTED);
    
    if (G_OBJECT_TYPE(this) == GST_TYPE_ALSA_SRC) {
        this->stream = SND_PCM_STREAM_CAPTURE;
        this->pads = g_list_append(NULL, g_new0(GstAlsaPad, 1));
        GST_ALSA_PAD(this->pads)->pad = gst_pad_new_from_template(gst_alsa_src_pad_factory(), "src");
        this->process = gst_alsa_src_process;
        this->format = SND_PCM_FORMAT_S16; /* native endian */
    } else if (G_OBJECT_TYPE(this) == GST_TYPE_ALSA_SINK) {
        this->stream = SND_PCM_STREAM_PLAYBACK;
        this->pads = g_list_append(NULL, g_new0(GstAlsaPad, 1));
        GST_ALSA_PAD(this->pads)->pad = gst_pad_new_from_template(gst_alsa_sink_pad_factory(), "sink");
        this->process = gst_alsa_sink_process;
        this->format = SND_PCM_FORMAT_UNKNOWN; /* we don't know until caps are
                                                * set */
    } else {
        g_print("you cannot instantiate an object of type gstalsa. use alsasink or alsasrc instead.\n");
        G_BREAKPOINT();
        return;
    }
    
    GST_ALSA_PAD(this->pads)->channel = -1;
    
    this->data_interleaved = TRUE;
    
    gst_element_add_pad(GST_ELEMENT(this), GST_ALSA_PAD(this->pads)->pad);
    
    gst_pad_set_negotiate_function(GST_ALSA_PAD(this->pads)->pad, gst_alsa_negotiate);
    gst_element_set_loop_function(GST_ELEMENT(this), gst_alsa_loop);
}

static GstPad*
gst_alsa_request_new_pad (GstElement *element, GstPadTemplate *templ, const gchar *name) 
{
    GstAlsa *this;
    gint channel;
    gchar *newname;
    GList *l;
    GstAlsaPad *pad;
    
    g_return_val_if_fail (this = GST_ALSA(element), NULL);
    
    /* you can't request a pad if the non-request pad is connected */
    g_return_val_if_fail (this->data_interleaved == FALSE ||
                          this->pads == NULL || 
                          GST_ALSA_PAD(this->pads) == NULL ||
                          GST_ALSA_PAD(this->pads)->pad == NULL ||
                          GST_PAD_PEER(GST_ALSA_PAD(this->pads)->pad) == NULL, 
                          NULL);
    
    if (name) {
        if (sscanf(name, templ->name_template, &channel) != 1) {
            g_warning("invalid pad name %s (trying to fit with %s)", name,
                      templ->name_template);
            return NULL;
        }
        l = this->pads;
        while (l) {
            if (GST_ALSA_PAD(l)->channel == channel) {
                g_warning("requested channel %d already in use.", channel);
                return NULL;
            }
            l = l->next;
        }
    } else {
        l = this->pads;
        channel = 0;
        while (l) {
            if (GST_ALSA_PAD(l)->channel > channel)
                channel = GST_ALSA_PAD(l)->channel;
            l = l->next;
        }
    }
    
    newname = g_strdup_printf (templ->name_template, channel);
    
    pad = g_new0(GstAlsaPad, 1);
    pad->channel = channel;
    pad->pad = gst_pad_new_from_template (templ, newname);
    gst_element_add_pad (GST_ELEMENT (this), pad->pad);
    gst_pad_set_negotiate_function(pad->pad, gst_alsa_negotiate);
    
    if (this->data_interleaved && this->pads) {
        gst_element_remove_pad (GST_ELEMENT (this), GST_ALSA_PAD(this->pads)->pad);
        g_free (GST_ALSA_PAD(this->pads));
        g_list_free (this->pads);
        this->pads = NULL;
    }
    
    this->pads = g_list_append(this->pads, pad);
    
    // FIXME: allow interleaved access (for hw:N,M access on consumer hardware)

    if (this->data_interleaved) {
        this->channels = pad->channel + 1;
        this->data_interleaved = FALSE;
    } else {
        this->channels = MAX(this->channels, pad->channel + 1);
    }
    
    return pad->pad;
}

static void
gst_alsa_set_property(GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
{
    GstAlsa *this;
    
    this = (GstAlsa *)object;
    switch (prop_id) {
    case ARG_DEVICE:
        if (this->device)
            g_free (this->device);
        this->device = g_strdup(g_value_get_string (value));
        break;
    case ARG_FORMAT:
        this->format = g_value_get_int (value);
        break;
    case ARG_CHANNELS:
        this->channels = g_value_get_int (value);
        break;
    case ARG_RATE:
        this->rate = g_value_get_int (value);
        break;
    case ARG_PERIODCOUNT:
        this->period_count = g_value_get_int (value);
        this->buffer_frames = this->period_count * this->period_frames;
        break;
    case ARG_PERIODFRAMES:
        this->period_frames = g_value_get_int (value);
        this->buffer_frames = this->period_count * this->period_frames;
        break;
    default:
        GST_DEBUG(0, "Unknown arg");
        return;
    }
    
    if (GST_STATE(this) == GST_STATE_NULL)
        return;
    
    if (GST_FLAG_IS_SET(this, GST_ALSA_RUNNING)) {
        gst_alsa_stop_audio(this);
        gst_alsa_set_params(this);
        gst_alsa_start_audio(this);
    } else {
        gst_alsa_set_params(this);
    }
}

static void
gst_alsa_get_property(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
{
    GstAlsa *this;

    this = (GstAlsa *)object;

    switch (prop_id) {
    case ARG_DEVICE:
        g_value_set_string (value, this->device);
        break;
    case ARG_FORMAT:
        g_value_set_int (value, this->format);
        break;
    case ARG_CHANNELS:
        g_value_set_int (value, this->channels);
        break;
    case ARG_RATE:
        g_value_set_int (value, this->rate);
        break;
    case ARG_PERIODCOUNT:
        g_value_set_int (value, this->period_count);
        break;
    case ARG_PERIODFRAMES:
        g_value_set_int (value, this->period_frames);
        break;
    default:
        GST_DEBUG(0, "Unknown arg");
        break;
    }
}

static GstElementStateReturn
gst_alsa_change_state(GstElement *element)
{
    GstAlsa *this;
    guint chn;
    
    g_return_val_if_fail(element != NULL, FALSE);
    this = GST_ALSA (element);
    
    switch (GST_STATE_PENDING(element)) {
    case GST_STATE_NULL:
        if (GST_FLAG_IS_SET(element, GST_ALSA_RUNNING))
            gst_alsa_stop_audio((GstAlsa *)element);
        if (GST_FLAG_IS_SET(element, GST_ALSA_OPEN))
            gst_alsa_close_audio((GstAlsa *)element);
        /* FIXME: clean up bytestreams, etc */
        break;
        
    case GST_STATE_READY:
        break;
        
    case GST_STATE_PAUSED:
        if (GST_FLAG_IS_SET(element, GST_ALSA_OPEN) == FALSE)
            if (gst_alsa_open_audio((GstAlsa *)element) == FALSE)
                return GST_STATE_FAILURE;
        if (GST_FLAG_IS_SET(element, GST_ALSA_RUNNING)) {
            if (this->stream == SND_PCM_STREAM_PLAYBACK) {
                for (chn = 0; chn < this->channels; chn++) {
                    gst_alsa_sink_silence_on_channel (this, chn, this->avail);
                }
            }
            gst_alsa_stop_audio((GstAlsa *)element);
        }
        break;
        
    case GST_STATE_PLAYING:
        if (GST_FLAG_IS_SET(element, GST_ALSA_RUNNING) == FALSE)
            if (gst_alsa_start_audio((GstAlsa *)element) == FALSE)
                return GST_STATE_FAILURE;
        break;
    }
    
    if (GST_ELEMENT_CLASS(parent_class)->change_state)
        return GST_ELEMENT_CLASS(parent_class)->change_state(element);

    return GST_STATE_SUCCESS;
}

static gboolean
gst_alsa_parse_caps (GstAlsa *this, GstCaps *caps)
{
    gint law, endianness, width, depth;
    gboolean sign;
    gint format = -1;
    const gchar* format_name;

    format_name = gst_caps_get_string(caps, "format");
    
    if (format_name == NULL) {
        return FALSE;
    } else if (strcmp(format_name, "int")==0) {
        width = gst_caps_get_int (caps, "width");
        depth = gst_caps_get_int (caps, "depth");
        
        law = gst_caps_get_int (caps, "law");
        endianness = gst_caps_get_int (caps, "endianness");
        sign = gst_caps_get_boolean (caps, "signed");
        
        if (law == 0) {
            if (width == 8) {
                if (sign == TRUE) {
                    format = SND_PCM_FORMAT_S8;
                } else {
                    format = SND_PCM_FORMAT_U8;
                }
            } else if (width == 16) {
                if (sign == TRUE) {
                    if (endianness == G_LITTLE_ENDIAN)
                        format = SND_PCM_FORMAT_S16_LE;
                    else if (endianness == G_BIG_ENDIAN)
                        format = SND_PCM_FORMAT_S16_BE;
                } else {
                    if (endianness == G_LITTLE_ENDIAN)
                        format = SND_PCM_FORMAT_U16_LE;
                    else if (endianness == G_BIG_ENDIAN)
                        format = SND_PCM_FORMAT_U16_BE;
                }
            } else if (width == 24) {
                if (sign == TRUE) {
                    if (endianness == G_LITTLE_ENDIAN)
                        format = SND_PCM_FORMAT_S24_LE;
                    else if (endianness == G_BIG_ENDIAN)
                        format = SND_PCM_FORMAT_S24_BE;
                } else {
                    if (endianness == G_LITTLE_ENDIAN)
                        format = SND_PCM_FORMAT_U24_LE;
                    else if (endianness == G_BIG_ENDIAN)
                        format = SND_PCM_FORMAT_U24_BE;
                }
            } else if (width == 32) {
                if (sign == TRUE) {
                    if (endianness == G_LITTLE_ENDIAN)
                        format = SND_PCM_FORMAT_S32_LE;
                    else if (endianness == G_BIG_ENDIAN)
                        format = SND_PCM_FORMAT_S32_BE;
                } else {
                    if (endianness == G_LITTLE_ENDIAN)
                        format = SND_PCM_FORMAT_U32_LE;
                    else if (endianness == G_BIG_ENDIAN)
                        format = SND_PCM_FORMAT_U32_BE;
                }
            }
        } else if (law == 1) { /* mu law */
            if (width == depth && width == 8 && sign == FALSE) {
                format = SND_PCM_FORMAT_MU_LAW;
            } else {
                return FALSE;
            }
        } else if (law == 2) { /* a law, ug. */
            if (width == depth && width == 8 && sign == FALSE) {
                format = SND_PCM_FORMAT_A_LAW;
            }
        } else {
            return FALSE;
        }
    } else if (strcmp(format_name, "float")==0) {
        if (strcmp(gst_caps_get_string(caps, "layout"), "gfloat")==0) {
            format = SND_PCM_FORMAT_FLOAT;
        } else {
            return FALSE;
            /* if you need float64, chat w/ me on irc.gstreamer.net and i'll tell you what needs to
             * be done. i'm 'wingo'. */
        }
    } else {
        return FALSE;
    }
    
    this->format = format;
    this->rate = gst_caps_get_int(caps, "rate");
    if (this->data_interleaved)
        this->channels = gst_caps_get_int(caps, "channels");
    else if (gst_caps_get_int(caps, "channels") != 1)
        return FALSE;
    
    return TRUE;
}

/* caps are so painful sometimes. */
static GstCaps*
gst_alsa_caps (GstAlsa *this)
{
    gint law, endianness, width, depth;
    gboolean sign;
    GstProps *props;
    
    g_return_val_if_fail (this != NULL && this->handle != NULL, NULL);
    
    if (this->format == SND_PCM_FORMAT_FLOAT) {
        props = gst_props_new ("format", GST_PROPS_STRING ("float"),
                               "layout", GST_PROPS_STRING ("gfloat"),
                               "rate",       GST_PROPS_INT (this->rate),
                               "channels",   GST_PROPS_INT ((this->data_interleaved ? this->channels : 1)),
                               NULL);
    } else {
        // we'll just have to assume int, i don't feel like checking
        if (this->format == SND_PCM_FORMAT_MU_LAW) {
            law = 1;
            width = 8;
            sign = FALSE;
            endianness = 0;
        } else if (this->format == SND_PCM_FORMAT_A_LAW) {
            law = 2;
            width = 8;
            sign = FALSE;
            endianness = 0;
        } else {
            law = 0;
            if (this->format == SND_PCM_FORMAT_S8) {
                width = 8;
                sign = TRUE;
                endianness = 0;
            } else if (this->format == SND_PCM_FORMAT_U8) {
                width = 8;
                sign = FALSE;
                endianness = 0;
            } else if (this->format == SND_PCM_FORMAT_S16_LE) {
                width = 16;
                sign = TRUE;
                endianness = G_LITTLE_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_S16_BE) {
                width = 16;
                sign = TRUE;
                endianness = G_BIG_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_U16_LE) {
                width = 16;
                sign = FALSE;
                endianness = G_LITTLE_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_U16_BE) {
                width = 16;
                sign = FALSE;
                endianness = G_BIG_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_S24_LE) {
                width = 24;
                sign = TRUE;
                endianness = G_LITTLE_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_S24_BE) {
                width = 24;
                sign = TRUE;
                endianness = G_BIG_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_U24_LE) {
                width = 24;
                sign = FALSE;
                endianness = G_LITTLE_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_U24_BE) {
                width = 24;
                sign = FALSE;
                endianness = G_BIG_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_S32_LE) {
                width = 32;
                sign = TRUE;
                endianness = G_LITTLE_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_S32_BE) {
                width = 32;
                sign = TRUE;
                endianness = G_BIG_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_U32_LE) {
                width = 32;
                sign = FALSE;
                endianness = G_LITTLE_ENDIAN;
            } else if (this->format == SND_PCM_FORMAT_U32_BE) {
                width = 32;
                sign = FALSE;
                endianness = G_BIG_ENDIAN;
            } else {
                g_error ("what is going on here?");
                return NULL;
            }
        }
        depth = width;
        props = gst_props_new ("format", GST_PROPS_STRING ("int"),
                               "rate",       GST_PROPS_INT (this->rate),
                               "channels",   GST_PROPS_INT ((this->data_interleaved ? this->channels : 1)),
                               "law",        GST_PROPS_INT (law),
                               "endianness", GST_PROPS_INT (endianness),
                               "signed",     GST_PROPS_BOOLEAN (sign),
                               "width",      GST_PROPS_INT (width),
                               "depth",      GST_PROPS_INT (depth),
                               NULL);
    }
    
    return gst_caps_new ("alsasrc", "audio/raw", props);
}

/*
 * Negotiates the caps, "borrowed" from gstosssink.c
 */
GstPadNegotiateReturn
gst_alsa_negotiate(GstPad *pad, GstCaps **caps, gpointer *user_data)
{
    GstAlsa *this;
    gboolean need_mmap;
    
    g_return_val_if_fail (pad != NULL, GST_PAD_NEGOTIATE_FAIL);
    g_return_val_if_fail (GST_IS_PAD (pad), GST_PAD_NEGOTIATE_FAIL);
    
    this = GST_ALSA(gst_pad_get_parent(pad));
    
    // we decide
    if (user_data == NULL) {
        *caps = NULL;
        return GST_PAD_NEGOTIATE_TRY;
    }
    // have we got caps?
    else if (*caps) {
        if (this->handle == NULL)
            return GST_PAD_NEGOTIATE_FAIL;
        
        if (gst_alsa_parse_caps(this, *caps)) {
            need_mmap = this->mmap_open;
            
            /* sync the params */
            if (GST_FLAG_IS_SET(this, GST_ALSA_RUNNING))
                gst_alsa_stop_audio(this);
            
            if (GST_FLAG_IS_SET(this, GST_ALSA_OPEN))
                gst_alsa_close_audio(this);
            
            // FIXME send out another caps if nego fails
            
            if (!gst_alsa_open_audio(this))
                return GST_PAD_NEGOTIATE_FAIL;
            
            if (!gst_alsa_start_audio(this))
                return GST_PAD_NEGOTIATE_FAIL;
            
            if (need_mmap && !gst_alsa_get_channel_addresses(this))
                return GST_PAD_NEGOTIATE_FAIL;
            
            return GST_PAD_NEGOTIATE_AGREE;
        }
        
        return GST_PAD_NEGOTIATE_FAIL;
    }
    
    return GST_PAD_NEGOTIATE_FAIL;
}

/* shamelessly stolen from pbd's audioengine. thanks, paul! */
static void
gst_alsa_loop (GstElement *element)
{
    struct pollfd pfd;
    gboolean xrun_detected;
    guint32 i;
    GstAlsa *this = GST_ALSA(element);
    
    g_return_if_fail(this != NULL);
    
    snd_pcm_poll_descriptors (this->handle, &pfd, 1);
    
    if (this->stream == SND_PCM_STREAM_PLAYBACK) {
        pfd.events = POLLOUT | POLLERR;
    } else {
        pfd.events = POLLIN | POLLERR;
    }
    
    do {
        if (poll (&pfd, 1, 1000) < 0) {
            if (errno == EINTR) {
                /* this happens mostly when run
                 * under gdb, or when exiting due to a signal */
                g_print ("EINTR\n");
                continue;
            }
            
            g_warning("poll call failed (%s)", strerror(errno));
            return;
        }
        
        if (pfd.revents & POLLERR) {
            g_warning("alsa: poll reports error.");
            return;
        }
        
        if (pfd.revents == 0) {
            g_print ("poll on alsa %s device \"%s\" timed out\n",
                     this->stream==SND_PCM_STREAM_CAPTURE ? "capture" : "playback",
                     this->device);
            /* timed out, such as when the device is paused */
            continue;
        }
        
        xrun_detected = FALSE;
        
        this->avail = snd_pcm_avail_update (this->handle);
//        g_print ("snd_pcm_avail_update() = %d\n", this->avail);
        
        if (this->avail < 0) {
            if (this->avail == -EPIPE) {
                xrun_detected = TRUE;
            } else {
                g_warning("unknown ALSA avail_update return value (%d)",
                          (int)this->avail);
                return;
            }
        }
        
        /* pretty sophisticated eh? */
        if (xrun_detected)
            g_warning ("xrun detected"); 
        
        /* we need to loop here because the available bytes might not be
         * contiguous */
        while (this->avail) {
            /* changes this->avail, as a side effect */
            if (!gst_alsa_get_channel_addresses (this) < 0) {
                g_error("could not get channels");
                return;
            }
            
            if (this->mute && this->stream == SND_PCM_STREAM_PLAYBACK) {
                for (i = 0; i < this->channels; i++) {
                    if (this->mute & (1<<i)) {
                        gst_alsa_sink_silence_on_channel (this, i, this->buffer_frames);
                    }
                }
            }
            
            if (!this->process(this, this->avail)) {
                g_warning("alsa: something happened while processing audio");
                return;
            }
            
            /* we could have released the mmap regions on a state change */
            if (this->mmap_open)
                gst_alsa_release_channel_addresses(this);
        }
	gst_element_yield (element);
    } while (TRUE);
}

static gboolean
gst_alsa_src_process (GstAlsa *this, snd_pcm_uframes_t frames)
{
    GstBuffer *buf;
    GList *l;
    GstAlsaPad *pad = NULL;
    GstCaps *caps;
    gint unit;
//    gint i=0;
    
    static gboolean caps_set = FALSE;
    
    if (!caps_set) {
        /* let's get on the caps-setting merry-go-round! */
        caps = gst_alsa_caps(this);
        l = this->pads;
        while (l) {
            if (!gst_pad_set_caps (GST_ALSA_PAD(l)->pad, caps)) {
                g_print ("DANGER WILL ROBINSON!\n");
                sleep(1);
                return FALSE;
            }
            
            l = l->next;
        }
        caps_set = TRUE;
    }
    
    unit = this->sample_bytes * (this->data_interleaved ? this->channels : 1);
    
    while (frames) {
//        g_print ("(%d) frames to process: %d\n", i++, frames);
        l = this->pads;
        while (l) {
            pad = GST_ALSA_PAD(l);
            
            if (!pad->buf) {
                pad->buf = g_malloc(this->period_frames * unit);
                //  g_print ("created buffer %p of size %d\n", pad->buf, this->period_frames * unit);
            }
            /*
            g_print ("pad->buf = %p, offset = %d\n", pad->buf, pad->offset);
            g_print ("about to memcpy(%p, %p, %d)\n", 
                     pad->buf + pad->offset * unit,
                     pad->access_addr,  
                     MIN(frames, this->period_frames - pad->offset) * unit);
            */
            memcpy(pad->buf + pad->offset * unit,
                   pad->access_addr, 
                   MIN(frames, this->period_frames - pad->offset) * unit);
            
            pad->offset += MIN(frames, this->period_frames - pad->offset);
            
            if (pad->offset >= this->period_frames) {
                if (pad->offset > this->period_frames)
                    G_BREAKPOINT();
                
                buf = gst_buffer_new();
                GST_BUFFER_DATA(buf)    = pad->buf;
                GST_BUFFER_SIZE(buf)    = this->period_frames * unit;
                GST_BUFFER_MAXSIZE(buf) = this->period_frames * unit;
                gst_pad_push(pad->pad, buf);
                pad->buf = NULL;
                pad->offset = 0;
            }
            l = l->next;
        }
        frames -= MIN(frames, this->period_frames - pad->offset); // shouldn't
        // matter which pad, in theory (tm)
    }
    
    return TRUE;
}

static gboolean
gst_alsa_sink_process (GstAlsa *this, snd_pcm_uframes_t frames)
{
    guint8 *peeked;
    guint32 len, avail;
    GstEvent *event = NULL;
    GList *l;
    
    /* this is necessary because the sample_bytes will change, probably, when
     * caps are set, which will occur after the first bytestream_peek. we
     * underestimate the amount of data we will need by peeking 'frames' only.
     * */
    
    if (!this->sample_bytes) {
        if (!GST_ALSA_PAD(this->pads)->bs)
            GST_ALSA_PAD(this->pads)->bs = gst_bytestream_new(GST_ALSA_PAD(this->pads)->pad);
        
        if (!(peeked = gst_bytestream_peek_bytes(GST_ALSA_PAD(this->pads)->bs, frames))) {
            g_warning("initial pull on pad %s returned NULL", GST_OBJECT_NAME(GST_ALSA_PAD(this->pads)->pad));
            gst_element_set_state(GST_ELEMENT(this), GST_STATE_PAUSED);
            return FALSE;
        }
        
        if (!this->sample_bytes) {
            g_critical ("alsa plugin requires a pipeline that can adequately set caps.");
            return FALSE;
        }
    }
    
    len = frames * this->channels * this->sample_bytes;
    
    l = this->pads;
    while (l) {
        if (!GST_ALSA_PAD(this->pads)->bs)
            GST_ALSA_PAD(this->pads)->bs = gst_bytestream_new(GST_ALSA_PAD(this->pads)->pad);
        
        if (!(peeked = gst_bytestream_peek_bytes(GST_ALSA_PAD(this->pads)->bs, len))) {
            gst_bytestream_get_status(GST_ALSA_PAD(this->pads)->bs, &avail, &event);
            if (event) {
                g_warning("got an event on alsasink");
                if (GST_EVENT_TYPE(event) == GST_EVENT_EOS) {
                    /* really, we should just cut this pad out of the graph. let
                     * me know when this is needed ;)
                     * also, for sample accuracy etc, we should play avail
                     * bytes, but hey. */
                    gst_element_set_eos(GST_ELEMENT(this));
                    gst_event_free(event);
                    return TRUE;
                }
            } else {
                /* the element at the top of the chain did not emit an eos
                 * event. this is a Bug(tm) */
                g_assert_not_reached();
            }
        }
        
        memcpy(GST_ALSA_PAD(this->pads)->access_addr, peeked, len);
        gst_bytestream_flush(GST_ALSA_PAD(this->pads)->bs, len);
        
        l=l->next;
    }
    
    return TRUE;
}

/* taken more or less from pbd's audioengine code */
static gboolean
gst_alsa_set_params (GstAlsa *this)
{
    snd_pcm_sw_params_t *sw_param;
    snd_pcm_hw_params_t *hw_param;
    snd_pcm_access_mask_t *mask;
    gint ret;
    
    g_return_val_if_fail(this != NULL, FALSE);
    g_return_val_if_fail(this->handle != NULL, FALSE);
    
    g_print("Preparing channel: %s %dHz, %d channels\n", 
            snd_pcm_format_name(this->format), 
            this->rate, this->channels);
        
    snd_pcm_hw_params_alloca(&hw_param);
    snd_pcm_sw_params_alloca(&sw_param);
        
    ret = snd_pcm_hw_params_any(this->handle, hw_param);
    if (ret < 0) {
        g_warning("Broken configuration for this PCM: no configurations available");
        return FALSE;
    }
    
    if ((ret = snd_pcm_hw_params_set_periods_integer (this->handle, hw_param)) < 0) {
        g_warning("cannot restrict period size to integral value.");
        return FALSE;
    }

    mask = alloca(snd_pcm_access_mask_sizeof());
    snd_pcm_access_mask_none(mask);
    
    if (this->data_interleaved)
        snd_pcm_access_mask_set(mask, SND_PCM_ACCESS_MMAP_INTERLEAVED);
    
    snd_pcm_access_mask_set(mask, SND_PCM_ACCESS_MMAP_NONINTERLEAVED);
    ret = snd_pcm_hw_params_set_access_mask(this->handle, hw_param, mask);
    if (ret < 0) {
        g_warning("the gstreamer alsa plugin does not support your hardware.");
        return FALSE;
    }
    
    if (this->format != SND_PCM_FORMAT_UNKNOWN) {
        ret = snd_pcm_hw_params_set_format(this->handle, hw_param, this->format);
        if (ret < 0) {
            g_warning("Sample format (%s) not available: %s", snd_pcm_format_name(this->format), snd_strerror(ret));
            return FALSE;
        }
        this->sample_bytes = snd_pcm_format_physical_width(this->format) / 8;
    }
    
    ret = snd_pcm_hw_params_set_channels(this->handle, hw_param, this->channels);
    if (ret < 0) {
        g_warning("Channels count (%d) not available: %s", this->channels, snd_strerror(ret));
        return FALSE;
    }
    this->channels = snd_pcm_hw_params_get_channels(hw_param);
    
    if (this->rate) {
        ret = snd_pcm_hw_params_set_rate(this->handle, hw_param, this->rate, 0);
        if (ret < 0) {
            g_warning("error setting rate (%d): %s", this->rate, snd_strerror(ret));
            return FALSE;
        }
    }
    
    if (this->period_count) {
        ret = snd_pcm_hw_params_set_periods (this->handle, hw_param, this->period_count, 0);
        if (ret < 0) {
            g_warning("error setting period count minimum (%d): %s", this->period_count, snd_strerror(ret));
            return FALSE;
        }
    }
    
    if (this->period_frames) {
        ret = snd_pcm_hw_params_set_period_size (this->handle, hw_param, this->period_frames, 0);
        if (ret < 0) {
            g_warning("error setting period in frames (%d): %s", this->period_frames, snd_strerror(ret));
            return FALSE;
        }
    }
    
    if (this->buffer_frames) {
        ret = snd_pcm_hw_params_set_buffer_size (this->handle, hw_param, this->buffer_frames);
        if (ret < 0) {
            g_warning("error setting buffer size (%d): %s", this->buffer_frames, snd_strerror(ret));
            return FALSE;
        }
    }
    
    ret = snd_pcm_hw_params(this->handle, hw_param);
    if (ret < 0) {
        g_warning("could not set hw params: %s", snd_strerror(ret));
        snd_pcm_hw_params_dump(hw_param, this->out);
        return FALSE;
    }
    
    if (!this->rate)
        this->rate = snd_pcm_hw_params_get_rate(hw_param, 0);
    if (!this->format)
        this->format = snd_pcm_hw_params_get_format(hw_param);
    if (!this->period_count)
        this->period_count = snd_pcm_hw_params_get_periods(hw_param, 0);
    if (!this->period_frames)
        this->period_frames = snd_pcm_hw_params_get_period_size(hw_param, 0);
    if (!this->buffer_frames)
        this->buffer_frames = snd_pcm_hw_params_get_buffer_size(hw_param);
    if (this->buffer_frames != this->period_count * this->period_frames)
        g_critical ("buffer size != period size * number of periods, unexpected things may happen!");
    
    snd_pcm_sw_params_current (this->handle, sw_param);

    ret = snd_pcm_sw_params_set_start_threshold (this->handle, sw_param, ~0U);
    if (ret < 0) {
        g_warning("could not set start mode: %s", snd_strerror(ret));
        return FALSE;
    }
    
    ret = snd_pcm_sw_params_set_stop_threshold (this->handle, sw_param, ~0U);
    if (ret < 0) {
        g_warning("could not set stop mode: %s", snd_strerror(ret));
        return FALSE;
    }
    
    ret = snd_pcm_sw_params_set_silence_threshold (this->handle, sw_param, 0);
    if (ret < 0) {
        g_warning("could not set silence threshold: %s", snd_strerror(ret));
        return FALSE;
    }
    
    ret = snd_pcm_sw_params_set_silence_size (this->handle, sw_param, this->buffer_frames);
    if (ret < 0) {
        g_warning("could not set silence size: %s", snd_strerror(ret));
        return FALSE;
    }
    
    ret = snd_pcm_sw_params_set_avail_min (this->handle, sw_param, this->period_frames);
    if (ret < 0) {
        g_warning("could not set avail min: %s", snd_strerror(ret));
        return FALSE;
    }
    
    ret = snd_pcm_sw_params (this->handle, sw_param);
    if (ret < 0) {
        g_warning("could not set sw_params: %s", snd_strerror(ret));
        return FALSE;
    }
    
    snd_pcm_dump(this->handle, this->out);
    
    this->access_interleaved = !(snd_pcm_hw_params_get_access (hw_param) ==
                                 SND_PCM_ACCESS_MMAP_NONINTERLEAVED);
    
    if (this->access_interleaved) {
        this->interleave_unit = this->sample_bytes;
        this->interleave_skip = this->interleave_unit * this->channels;
    } else {
        this->interleave_unit = 0; /* not used */
        this->interleave_skip = this->sample_bytes;
    }
    
    if (this->access_addr)
        g_free (this->access_addr);
    this->access_addr = g_new0 (char*, this->channels);
    
    return TRUE;
}

static gboolean
gst_alsa_open_audio(GstAlsa *this)
{
    gint ret;
    g_assert(this != NULL);

    if (this->handle)
        gst_alsa_close_audio(this);
    
    g_print("Opening alsa device \"%s\" for %s...\n", this->device,
            this->stream==SND_PCM_STREAM_PLAYBACK ? "playback" : "capture");
    
    ret = snd_output_stdio_attach(&this->out, stdout, 0);
    if (ret < 0) {
        g_print("error opening log output: %s", snd_strerror(ret));
        return FALSE;
    }
    
    /* blocking i/o */
    if ((ret = snd_pcm_open(&this->handle, this->device, this->stream, 0))) {
        g_print("error opening pcm device: %s", snd_strerror(ret));
        return FALSE;
    }
    
    if (gst_alsa_set_params(this) == FALSE) {
        gst_alsa_close_audio(this);
        return FALSE;
    }
    
    GST_FLAG_SET(this, GST_ALSA_OPEN);
    return TRUE;
}


static gboolean
gst_alsa_start_audio(GstAlsa *this)
{
    gint err;
    guint32 chn;
    
    g_return_val_if_fail(this != NULL, FALSE);
    g_return_val_if_fail(this->handle != NULL, FALSE);
    
    if ((err = snd_pcm_prepare (this->handle)) < 0) {
        g_warning("channel prepare failed: %s", snd_strerror (err));
        return FALSE;
    }
        
    this->avail = snd_pcm_avail_update (this->handle);
    
    if (this->stream == SND_PCM_STREAM_PLAYBACK &&
        this->avail != this->buffer_frames) {
        g_warning ("full buffer not available at start");
        return FALSE;
    }
    
    if (!gst_alsa_get_channel_addresses (this)) {
        return FALSE;
    }
    
    if (this->stream == SND_PCM_STREAM_PLAYBACK) {
        for (chn = 0; chn < this->channels; chn++) {
            gst_alsa_sink_silence_on_channel (this, chn, this->buffer_frames);
        }
    }
    
    gst_alsa_release_channel_addresses (this);
    
    if ((err = snd_pcm_start (this->handle)) < 0) {
        g_warning("could not start audio: %s", snd_strerror (err));
        return FALSE;
    }
    
    GST_FLAG_SET(this, GST_ALSA_RUNNING);
    return TRUE;
}

static void
gst_alsa_stop_audio(GstAlsa *this)
{
    gint err;
    g_assert(this != NULL);
    
    g_return_if_fail(this != NULL);
    g_return_if_fail(this->handle != NULL);

    if (this->mmap_open)
        gst_alsa_release_channel_addresses (this);
    
    if (this->stream == SND_PCM_STREAM_PLAYBACK && 
        (err = snd_pcm_drop (this->handle)) < 0) {
        g_warning("channel flush failed: %s", snd_strerror (err));
        return;
    }
    
    GST_FLAG_UNSET(this, GST_ALSA_RUNNING);
}

static void
gst_alsa_close_audio(GstAlsa *this)
{
//    gint err;
    g_return_if_fail(this != NULL);
    g_return_if_fail(this->handle != NULL);

/*    if ((err = snd_pcm_drop (this->handle)) < 0) {
        g_warning("channel flush for failed: %s", snd_strerror (err));
        return;
        } */
    
    snd_pcm_close(this->handle);
    
    this->handle = NULL;

    GST_FLAG_UNSET(this, GST_ALSA_OPEN);
}

static gboolean
gst_alsa_get_channel_addresses (GstAlsa *this)
{
    guint32 err, i;
    const snd_pcm_channel_area_t *a;
    GList *l;
    
    g_return_val_if_fail (this->mmap_open == FALSE, FALSE);
    
    if ((err = snd_pcm_mmap_begin (this->handle, &this->mmap_areas, &this->offset, &this->avail)) < 0) {
        g_warning("gstalsa: mmap failed: %s", snd_strerror(err));
        return FALSE;
    }
    
    GST_DEBUG(0, "got %d mmap'd frames\n", (int)this->avail);
    
//    g_print ("snd_pcm_mmap_begin() sets avail = %d\n", this->avail);
    
    l = this->pads;
    while (l) {
        a = &this->mmap_areas[GST_ALSA_PAD(l)->channel > 0 ?
                             GST_ALSA_PAD(l)->channel-1 : 0];
        GST_ALSA_PAD(l)->access_addr = (char *) a->addr + ((a->first + a->step *
                                                            this->offset) / 8);
        l = l->next;
    }
    
    for (i=0; i<this->channels; i++) {
        a = &this->mmap_areas[i];
        this->access_addr[i] = (char *) a->addr + ((a->first + a->step * this->offset) / 8);
    }
    
    this->mmap_open = TRUE;
    
    return TRUE;
}

static void
gst_alsa_release_channel_addresses (GstAlsa *this)
{
    guint32 err, i;
    GList *l;
    
    g_return_if_fail (this->mmap_open == TRUE);
    
    GST_DEBUG(0, "releasing mmap'd data region: %d frames\n", (int)this->avail);
    
    if ((err = snd_pcm_mmap_commit (this->handle, this->offset, this->avail)) < 0) {
        g_warning("gstalsa: mmap commit failed: %s", snd_strerror(err));
        return;
    }
    
    l = this->pads;
    while (l) {
        GST_ALSA_PAD(l)->access_addr = NULL;
        l = l->next;
    }
    
    for (i=0; i<this->channels; i++) {
        this->access_addr[i] = NULL;
    }
    
    this->mmap_open = FALSE;
    this->avail=0;
}

static void 
gst_alsa_sink_silence_on_channel (GstAlsa *this, guint32 chn, guint32 nframes) 
{
    if (this->access_interleaved) {
        memset_interleave 
            (this->access_addr[chn],
             0, nframes * this->sample_bytes,
             this->interleave_unit,
             this->interleave_skip);
    } else {
        memset (this->access_addr[chn], 0, nframes * this->sample_bytes);
    }
//    mark_channel_done (chn);
}

/* taken directly from paul davis' memops.cc */
static void
memset_interleave (char *dst, char val, unsigned int bytes, 
                   unsigned int unit_bytes, 
                   unsigned int skip_bytes) 
{
    switch (unit_bytes) {
    case 1:
        while (bytes--) {
            *dst = val;
            dst += skip_bytes;
        }
        break;
    case 2:
        while (bytes) {
            *((short *) dst) = (short) val;
            dst += skip_bytes;
            bytes -= 2;
        }
        break;
    case 4:		    
        while (bytes) {
            *((int *) dst) = (int) val;
            dst += skip_bytes;
            bytes -= 4;
        }
        break;
    }
}

static gboolean
plugin_init (GModule *module, GstPlugin *plugin)
{
    GstElementFactory *factory;
    
    if (!gst_library_load ("gstbytestream")) {
        gst_info("alsa: could not load support library: 'gstbytestream'\n");
        return FALSE;
    }
    
    factory = gst_elementfactory_new ("alsasrc", GST_TYPE_ALSA_SRC, &gst_alsa_src_details);
    g_return_val_if_fail (factory != NULL, FALSE);
    gst_elementfactory_add_padtemplate (factory, gst_alsa_src_pad_factory());
    gst_elementfactory_add_padtemplate (factory, gst_alsa_src_request_pad_factory());
    gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));
    
    factory = gst_elementfactory_new ("alsasink", GST_TYPE_ALSA_SINK, &gst_alsa_sink_details);
    g_return_val_if_fail (factory != NULL, FALSE);
    gst_elementfactory_add_padtemplate (factory, gst_alsa_sink_pad_factory());
    gst_elementfactory_add_padtemplate (factory, gst_alsa_sink_request_pad_factory());
    gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));
    
    gst_plugin_set_longname(plugin, "ALSA plugin library");
    
    return TRUE;
}

GstPluginDesc plugin_desc = {
    GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "alsa",
    plugin_init
};