source: trunk/src/3rdparty/phonon/gstreamer/alsasink2.c

/* GStreamer
 * Copyright (C) 2001 CodeFactory AB
 * Copyright (C) 2001 Thomas Nyberg <[email protected]>
 * Copyright (C) 2001-2002 Andy Wingo <[email protected]>
 * Copyright (C) 2003 Benjamin Otte <[email protected]>
 * Copyright (C) 2005 Wim Taymans <[email protected]>
 * Copyright (C) 2005, 2006 Tim-Philipp MÃŒller <tim centricular net>
 * Copyright (C) 2008 Matthias Kretz <[email protected]>
 *
 * gstalsasink2.c:
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library 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
 * Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public 
 *  License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * SECTION:element-alsasink2
 * @short_description: play audio to an ALSA device
 * @see_also: alsasrc, alsamixer
 *
 * <refsect2>
 * <para>
 * This element renders raw audio samples using the ALSA api.
 * </para>
 * <title>Example pipelines</title>
 * <para>
 * Play an Ogg/Vorbis file.
 * </para>
 * <programlisting>
 * gst-launch -v filesrc location=sine.ogg ! oggdemux ! vorbisdec ! audioconvert ! audioresample ! alsasink2
 * </programlisting>
 * </refsect2>
 *
 * Last reviewed on 2006-03-01 (0.10.4)
 */

#define _XOPEN_SOURCE 600

#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <getopt.h>
#include <alsa/asoundlib.h>

#include "alsasink2.h"

#include <gst/interfaces/propertyprobe.h>
#include <gst/audio/multichannel.h>

#define _(text) (text)

#define GST_CHECK_ALSA_VERSION(major,minor,micro) \
    (SND_LIB_MAJOR > (major) || \
     (SND_LIB_MAJOR == (major) && SND_LIB_MINOR > (minor)) || \
     (SND_LIB_MAJOR == (major) && SND_LIB_MINOR == (minor) && \
      SND_LIB_SUBMINOR >= (micro)))

static const GList *
gst_alsa_device_property_probe_get_properties (GstPropertyProbe * probe)
{
  GObjectClass *klass = G_OBJECT_GET_CLASS (probe);
  static GList *list = NULL;

  /* well, not perfect, but better than no locking at all.
   * In the worst case we leak a list node, so who cares? */
  GST_CLASS_LOCK (GST_OBJECT_CLASS (klass));

  if (!list) {
    GParamSpec *pspec;

    pspec = g_object_class_find_property (klass, "device");
    list = g_list_append (NULL, pspec);
  }

  GST_CLASS_UNLOCK (GST_OBJECT_CLASS (klass));

  return list;
}

static GList *
gst_alsa_get_device_list (snd_pcm_stream_t stream)
{
  snd_ctl_t *handle;
  int card, err, dev;
  snd_ctl_card_info_t *info;
  snd_pcm_info_t *pcminfo;
  gboolean mixer = (stream == ~0u);
  GList *list = NULL;

  if (stream == ~0u)
    stream = 0;

  snd_ctl_card_info_malloc (&info);
  snd_pcm_info_malloc (&pcminfo);
  card = -1;

  if (snd_card_next (&card) < 0 || card < 0) {
    /* no soundcard found */
    return NULL;
  }

  while (card >= 0) {
    gchar name[32];

    g_snprintf (name, sizeof (name), "hw:%d", card);
    if ((err = snd_ctl_open (&handle, name, 0)) < 0) {
      goto next_card;
    }
    if ((err = snd_ctl_card_info (handle, info)) < 0) {
      snd_ctl_close (handle);
      goto next_card;
    }

    if (mixer) {
      list = g_list_append (list, g_strdup (name));
    } else {
      g_snprintf (name, sizeof (name), "default:CARD=%d", card);
      list = g_list_append (list, g_strdup (name));
      dev = -1;
      while (1) {
        gchar *gst_device;

        snd_ctl_pcm_next_device (handle, &dev);

        if (dev < 0)
          break;
        snd_pcm_info_set_device (pcminfo, dev);
        snd_pcm_info_set_subdevice (pcminfo, 0);
        snd_pcm_info_set_stream (pcminfo, stream);
        if ((err = snd_ctl_pcm_info (handle, pcminfo)) < 0) {
          continue;
        }

        gst_device = g_strdup_printf ("hw:%d,%d", card, dev);
        list = g_list_append (list, gst_device);
      }
    }
    snd_ctl_close (handle);
  next_card:
    if (snd_card_next (&card) < 0) {
      break;
    }
  }

  snd_ctl_card_info_free (info);
  snd_pcm_info_free (pcminfo);

  return list;
}

static void
gst_alsa_device_property_probe_probe_property (GstPropertyProbe * probe,
    guint prop_id, const GParamSpec * pspec)
{
  if (!g_str_equal (pspec->name, "device")) {
    G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
  }
}

static gboolean
gst_alsa_device_property_probe_needs_probe (GstPropertyProbe * probe,
    guint prop_id, const GParamSpec * pspec)
{
  /* don't cache probed data */
  return TRUE;
}

static GValueArray *
gst_alsa_device_property_probe_get_values (GstPropertyProbe * probe,
    guint prop_id, const GParamSpec * pspec)
{
  GstElementClass *klass;
  const GList *templates;
  snd_pcm_stream_t mode = -1;
  GValueArray *array;
  GValue value = { 0, };
  GList *l, *list;

  if (!g_str_equal (pspec->name, "device")) {
    G_OBJECT_WARN_INVALID_PROPERTY_ID (probe, prop_id, pspec);
    return NULL;
  }

  klass = GST_ELEMENT_GET_CLASS (GST_ELEMENT (probe));

  /* I'm pretty sure ALSA has a good way to do this. However, their cool
   * auto-generated documentation is pretty much useless if you try to
   * do function-wise look-ups. */
  /* we assume one pad template at max [zero=mixer] */
  templates = gst_element_class_get_pad_template_list (klass);
  if (templates) {
    if (GST_PAD_TEMPLATE_DIRECTION (templates->data) == GST_PAD_SRC)
      mode = SND_PCM_STREAM_CAPTURE;
    else
      mode = SND_PCM_STREAM_PLAYBACK;
  }

  list = gst_alsa_get_device_list (mode);

  if (list == NULL) {
    GST_LOG_OBJECT (probe, "No devices found");
    return NULL;
  }

  array = g_value_array_new (g_list_length (list));
  g_value_init (&value, G_TYPE_STRING);
  for (l = list; l != NULL; l = l->next) {
    GST_LOG_OBJECT (probe, "Found device: %s", (gchar *) l->data);
    g_value_take_string (&value, (gchar *) l->data);
    l->data = NULL;
    g_value_array_append (array, &value);
  }
  g_value_unset (&value);
  g_list_free (list);

  return array;
}

static void
gst_alsa_property_probe_interface_init (GstPropertyProbeInterface * iface)
{
  iface->get_properties = gst_alsa_device_property_probe_get_properties;
  iface->probe_property = gst_alsa_device_property_probe_probe_property;
  iface->needs_probe = gst_alsa_device_property_probe_needs_probe;
  iface->get_values = gst_alsa_device_property_probe_get_values;
}

static void
gst_alsa_type_add_device_property_probe_interface (GType type)
{
  static const GInterfaceInfo probe_iface_info = {
    (GInterfaceInitFunc) gst_alsa_property_probe_interface_init,
    NULL,
    NULL,
  };

  g_type_add_interface_static (type, GST_TYPE_PROPERTY_PROBE,
      &probe_iface_info);
}

static GstCaps *
gst_alsa_detect_rates (GstObject * obj, snd_pcm_hw_params_t * hw_params,
    GstCaps * in_caps)
{
  GstCaps *caps;
  guint min, max;
  gint err, dir, min_rate, max_rate;
  guint i;

  GST_LOG_OBJECT (obj, "probing sample rates ...");

  if ((err = snd_pcm_hw_params_get_rate_min (hw_params, &min, &dir)) < 0)
    goto min_rate_err;

  if ((err = snd_pcm_hw_params_get_rate_max (hw_params, &max, &dir)) < 0)
    goto max_rate_err;

  min_rate = min;
  max_rate = max;

  if (min_rate < 4000)
    min_rate = 4000;            /* random 'sensible minimum' */

  if (max_rate <= 0)
    max_rate = G_MAXINT;        /* or maybe just use 192400 or so? */
  else if (max_rate > 0 && max_rate < 4000)
    max_rate = MAX (4000, min_rate);

  GST_DEBUG_OBJECT (obj, "Min. rate = %u (%d)", min_rate, min);
  GST_DEBUG_OBJECT (obj, "Max. rate = %u (%d)", max_rate, max);

  caps = gst_caps_make_writable (in_caps);

  for (i = 0; i < gst_caps_get_size (caps); ++i) {
    GstStructure *s;

    s = gst_caps_get_structure (caps, i);
    if (min_rate == max_rate) {
      gst_structure_set (s, "rate", G_TYPE_INT, min_rate, NULL);
    } else {
      gst_structure_set (s, "rate", GST_TYPE_INT_RANGE,
          min_rate, max_rate, NULL);
    }
  }

  return caps;

  /* ERRORS */
min_rate_err:
  {
    GST_ERROR_OBJECT (obj, "failed to query minimum sample rate: %s",
        snd_strerror (err));
    gst_caps_unref (in_caps);
    return NULL;
  }
max_rate_err:
  {
    GST_ERROR_OBJECT (obj, "failed to query maximum sample rate: %s",
        snd_strerror (err));
    gst_caps_unref (in_caps);
    return NULL;
  }
}

static const struct
{
  const int width;
  const int depth;
  const int sformat;
  const int uformat;
} pcmformats[] = {
  {
  8, 8, SND_PCM_FORMAT_S8, SND_PCM_FORMAT_U8}, {
  16, 16, SND_PCM_FORMAT_S16, SND_PCM_FORMAT_U16}, {
  32, 24, SND_PCM_FORMAT_S24, SND_PCM_FORMAT_U24}, {
#if (G_BYTE_ORDER == G_LITTLE_ENDIAN)   /* no endian-unspecific enum available */
  24, 24, SND_PCM_FORMAT_S24_3LE, SND_PCM_FORMAT_U24_3LE}, {
#else
  24, 24, SND_PCM_FORMAT_S24_3BE, SND_PCM_FORMAT_U24_3BE}, {
#endif
  32, 32, SND_PCM_FORMAT_S32, SND_PCM_FORMAT_U32}
};

static GstCaps *
gst_alsa_detect_formats (GstObject * obj, snd_pcm_hw_params_t * hw_params,
    GstCaps * in_caps)
{
  snd_pcm_format_mask_t *mask;
  GstStructure *s;
  GstCaps *caps;
  guint i;

  snd_pcm_format_mask_malloc (&mask);
  snd_pcm_hw_params_get_format_mask (hw_params, mask);

  caps = gst_caps_new_empty ();

  for (i = 0; i < gst_caps_get_size (in_caps); ++i) {
    GstStructure *scopy;
    guint w;
    gint width = 0, depth = 0;

    s = gst_caps_get_structure (in_caps, i);
    if (!gst_structure_has_name (s, "audio/x-raw-int")) {
      GST_WARNING_OBJECT (obj, "skipping non-int format");
      continue;
    }
    if (!gst_structure_get_int (s, "width", &width) ||
        !gst_structure_get_int (s, "depth", &depth))
      continue;
    if (width == 0 || (width % 8) != 0)
      continue;                 /* Only full byte widths are valid */
    for (w = 0; w < G_N_ELEMENTS (pcmformats); w++)
      if (pcmformats[w].width == width && pcmformats[w].depth == depth)
        break;
    if (w == G_N_ELEMENTS (pcmformats))
      continue;                 /* Unknown format */

    if (snd_pcm_format_mask_test (mask, pcmformats[w].sformat) &&
        snd_pcm_format_mask_test (mask, pcmformats[w].uformat)) {
      /* template contains { true, false } or just one, leave it as it is */
      scopy = gst_structure_copy (s);
    } else if (snd_pcm_format_mask_test (mask, pcmformats[w].sformat)) {
      scopy = gst_structure_copy (s);
      gst_structure_set (scopy, "signed", G_TYPE_BOOLEAN, TRUE, NULL);
    } else if (snd_pcm_format_mask_test (mask, pcmformats[w].uformat)) {
      scopy = gst_structure_copy (s);
      gst_structure_set (scopy, "signed", G_TYPE_BOOLEAN, FALSE, NULL);
    } else {
      scopy = NULL;
    }
    if (scopy) {
      if (width > 8) {
        /* TODO: proper endianness detection, for now it's CPU endianness only */
        gst_structure_set (scopy, "endianness", G_TYPE_INT, G_BYTE_ORDER, NULL);
      }
      gst_caps_append_structure (caps, scopy);
    }
  }

  snd_pcm_format_mask_free (mask);
  gst_caps_unref (in_caps);
  return caps;
}

/* we don't have channel mappings for more than this many channels */
#define GST_ALSA_MAX_CHANNELS 8

static GstStructure *
get_channel_free_structure (const GstStructure * in_structure)
{
  GstStructure *s = gst_structure_copy (in_structure);

  gst_structure_remove_field (s, "channels");
  return s;
}

static void
caps_add_channel_configuration (GstCaps * caps,
    const GstStructure * in_structure, gint min_chans, gint max_chans)
{
  GstAudioChannelPosition pos[8] = {
    GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
    GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
    GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
    GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT,
    GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER,
    GST_AUDIO_CHANNEL_POSITION_LFE,
    GST_AUDIO_CHANNEL_POSITION_SIDE_LEFT,
    GST_AUDIO_CHANNEL_POSITION_SIDE_RIGHT
  };
  GstStructure *s = NULL;
  gint c;

  if (min_chans == max_chans && max_chans <= 2) {
    s = get_channel_free_structure (in_structure);
    gst_structure_set (s, "channels", G_TYPE_INT, max_chans, NULL);
    gst_caps_append_structure (caps, s);
    return;
  }

  g_assert (min_chans >= 1);

  /* mono and stereo don't need channel configurations */
  if (min_chans == 2) {
    s = get_channel_free_structure (in_structure);
    gst_structure_set (s, "channels", G_TYPE_INT, 2, NULL);
    gst_caps_append_structure (caps, s);
  } else if (min_chans == 1 && max_chans >= 2) {
    s = get_channel_free_structure (in_structure);
    gst_structure_set (s, "channels", GST_TYPE_INT_RANGE, 1, 2, NULL);
    gst_caps_append_structure (caps, s);
  }

  /* don't know whether to use 2.1 or 3.0 here - but I suspect
   * alsa might work around that/fix it somehow. Can we tell alsa
   * what our channel layout is like? */
  if (max_chans >= 3 && min_chans <= 3) {
    GstAudioChannelPosition pos_21[3] = {
      GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
      GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
      GST_AUDIO_CHANNEL_POSITION_LFE
    };

    s = get_channel_free_structure (in_structure);
    gst_structure_set (s, "channels", G_TYPE_INT, 3, NULL);
    gst_audio_set_channel_positions (s, pos_21);
    gst_caps_append_structure (caps, s);
  }

  /* everything else (4, 6, 8 channels) needs a channel layout */
  for (c = MAX (4, min_chans); c <= 8; c += 2) {
    if (max_chans >= c) {
      s = get_channel_free_structure (in_structure);
      gst_structure_set (s, "channels", G_TYPE_INT, c, NULL);
      gst_audio_set_channel_positions (s, pos);
      gst_caps_append_structure (caps, s);
    }
  }

  for (c = MAX (9, min_chans); c <= max_chans; ++c) {
    GstAudioChannelPosition *ch_layout;
    gint i;

    ch_layout = g_new (GstAudioChannelPosition, c);
    for (i = 0; i < c; ++i) {
      ch_layout[i] = GST_AUDIO_CHANNEL_POSITION_NONE;
    }
    s = get_channel_free_structure (in_structure);
    gst_structure_set (s, "channels", G_TYPE_INT, c, NULL);
    gst_audio_set_channel_positions (s, ch_layout);
    gst_caps_append_structure (caps, s);
    g_free (ch_layout);
  }
}

static GstCaps *
gst_alsa_detect_channels (GstObject * obj, snd_pcm_hw_params_t * hw_params,
    GstCaps * in_caps)
{
  GstCaps *caps;
  guint min, max;
  gint min_chans, max_chans;
  gint err;
  guint i;

  GST_LOG_OBJECT (obj, "probing channels ...");

  if ((err = snd_pcm_hw_params_get_channels_min (hw_params, &min)) < 0)
    goto min_chan_error;

  if ((err = snd_pcm_hw_params_get_channels_max (hw_params, &max)) < 0)
    goto max_chan_error;

  /* note: the above functions may return (guint) -1 */
  min_chans = min;
  max_chans = max;

  if (min_chans < 0) {
    min_chans = 1;
    max_chans = GST_ALSA_MAX_CHANNELS;
  } else if (max_chans < 0) {
    max_chans = GST_ALSA_MAX_CHANNELS;
  }

  if (min_chans > max_chans) {
    gint temp;

    GST_WARNING_OBJECT (obj, "minimum channels > maximum channels (%d > %d), "
        "please fix your soundcard drivers", min, max);
    temp = min_chans;
    min_chans = max_chans;
    max_chans = temp;
  }

  /* pro cards seem to return large numbers for min_channels */
  if (min_chans > GST_ALSA_MAX_CHANNELS) {
    GST_DEBUG_OBJECT (obj, "min_chans = %u, looks like a pro card", min_chans);
    if (max_chans < min_chans) {
      max_chans = min_chans;
    } else {
      /* only support [max_chans; max_chans] for these cards for now
       * to avoid inflating the source caps with loads of structures ... */
      min_chans = max_chans;
    }
  } else {
    min_chans = MAX (min_chans, 1);
    max_chans = MIN (GST_ALSA_MAX_CHANNELS, max_chans);
  }

  GST_DEBUG_OBJECT (obj, "Min. channels = %d (%d)", min_chans, min);
  GST_DEBUG_OBJECT (obj, "Max. channels = %d (%d)", max_chans, max);

  caps = gst_caps_new_empty ();

  for (i = 0; i < gst_caps_get_size (in_caps); ++i) {
    GstStructure *s;
    GType field_type;
    gint c_min = min_chans;
    gint c_max = max_chans;

    s = gst_caps_get_structure (in_caps, i);
    /* the template caps might limit the number of channels (like alsasrc),
     * in which case we don't want to return a superset, so hack around this
     * for the two common cases where the channels are either a fixed number
     * or a min/max range). Example: alsasrc template has channels = [1,2] and 
     * the detection will claim to support 8 channels for device 'plughw:0' */
    field_type = gst_structure_get_field_type (s, "channels");
    if (field_type == G_TYPE_INT) {
      gst_structure_get_int (s, "channels", &c_min);
      gst_structure_get_int (s, "channels", &c_max);
    } else if (field_type == GST_TYPE_INT_RANGE) {
      const GValue *val;

      val = gst_structure_get_value (s, "channels");
      c_min = CLAMP (gst_value_get_int_range_min (val), min_chans, max_chans);
      c_max = CLAMP (gst_value_get_int_range_max (val), min_chans, max_chans);
    } else {
      c_min = min_chans;
      c_max = max_chans;
    }

    caps_add_channel_configuration (caps, s, c_min, c_max);
  }

  gst_caps_unref (in_caps);

  return caps;

  /* ERRORS */
min_chan_error:
  {
    GST_ERROR_OBJECT (obj, "failed to query minimum channel count: %s",
        snd_strerror (err));
    return NULL;
  }
max_chan_error:
  {
    GST_ERROR_OBJECT (obj, "failed to query maximum channel count: %s",
        snd_strerror (err));
    return NULL;
  }
}

#ifndef GST_CHECK_VERSION
#define GST_CHECK_VERSION(major,minor,micro) \
    (GST_VERSION_MAJOR > (major) || \
     (GST_VERSION_MAJOR == (major) && GST_VERSION_MINOR > (minor)) || \
     (GST_VERSION_MAJOR == (major) && GST_VERSION_MINOR == (minor) && GST_VERSION_MICRO >= (micro)))
#endif

#if GST_CHECK_VERSION(0, 10, 18)
snd_pcm_t *
gst_alsa_open_iec958_pcm (GstObject * obj)
{
  char *iec958_pcm_name = NULL;
  snd_pcm_t *pcm = NULL;
  int res;
  char devstr[256];             /* Storage for local 'default' device string */

  /*
   * Try and open our default iec958 device. Fall back to searching on card x
   * if this fails, which should only happen on older alsa setups
   */

  /* The string will be one of these:
   * SPDIF_CON: Non-audio flag not set:
   *    spdif:{AES0 0x0 AES1 0x82 AES2 0x0 AES3 0x2}
   * SPDIF_CON: Non-audio flag set:
   *    spdif:{AES0 0x2 AES1 0x82 AES2 0x0 AES3 0x2}
   */
  sprintf (devstr,
      "iec958:{AES0 0x%02x AES1 0x%02x AES2 0x%02x AES3 0x%02x}",
      IEC958_AES0_CON_EMPHASIS_NONE | IEC958_AES0_NONAUDIO,
      IEC958_AES1_CON_ORIGINAL | IEC958_AES1_CON_PCM_CODER,
      0, IEC958_AES3_CON_FS_48000);

  GST_DEBUG_OBJECT (obj, "Generated device string \"%s\"", devstr);
  iec958_pcm_name = devstr;

  res = snd_pcm_open (&pcm, iec958_pcm_name, SND_PCM_STREAM_PLAYBACK, 0);
  if (G_UNLIKELY (res < 0)) {
    GST_DEBUG_OBJECT (obj, "failed opening IEC958 device: %s",
        snd_strerror (res));
    pcm = NULL;
  }

  return pcm;
}
#endif


/*
 * gst_alsa_probe_supported_formats:
 *
 * Takes the template caps and returns the subset which is actually
 * supported by this device.
 *
 */

GstCaps *
gst_alsa_probe_supported_formats (GstObject * obj, snd_pcm_t * handle,
    const GstCaps * template_caps)
{
  snd_pcm_hw_params_t *hw_params;
  snd_pcm_stream_t stream_type;
  GstCaps *caps;
  gint err;

  snd_pcm_hw_params_malloc (&hw_params);
  if ((err = snd_pcm_hw_params_any (handle, hw_params)) < 0)
    goto error;

  stream_type = snd_pcm_stream (handle);

  caps = gst_caps_copy (template_caps);

  if (!(caps = gst_alsa_detect_formats (obj, hw_params, caps)))
    goto subroutine_error;

  if (!(caps = gst_alsa_detect_rates (obj, hw_params, caps)))
    goto subroutine_error;

  if (!(caps = gst_alsa_detect_channels (obj, hw_params, caps)))
    goto subroutine_error;

#if GST_CHECK_VERSION(0, 10, 18)
  /* Try opening IEC958 device to see if we can support that format (playback
   * only for now but we could add SPDIF capture later) */
  if (stream_type == SND_PCM_STREAM_PLAYBACK) {
    snd_pcm_t *pcm = gst_alsa_open_iec958_pcm (obj);

    if (G_LIKELY (pcm)) {
      gst_caps_append (caps, gst_caps_new_simple ("audio/x-iec958", NULL));
      snd_pcm_close (pcm);
    }
  }
#endif

  snd_pcm_hw_params_free (hw_params);
  return caps;

  /* ERRORS */
error:
  {
    GST_ERROR_OBJECT (obj, "failed to query formats: %s", snd_strerror (err));
    snd_pcm_hw_params_free (hw_params);
    return NULL;
  }
subroutine_error:
  {
    GST_ERROR_OBJECT (obj, "failed to query formats");
    snd_pcm_hw_params_free (hw_params);
    return NULL;
  }
}

static gchar *
gst_alsa_find_device_name_no_handle (GstObject * obj, const gchar * devcard,
    gint device_num, snd_pcm_stream_t stream)
{
  snd_ctl_card_info_t *info = NULL;
  snd_ctl_t *ctl = NULL;
  gchar *ret = NULL;
  gint dev = -1;

  GST_LOG_OBJECT (obj, "[%s] device=%d", devcard, device_num);

  if (snd_ctl_open (&ctl, devcard, 0) < 0)
    return NULL;

  snd_ctl_card_info_malloc (&info);
  if (snd_ctl_card_info (ctl, info) < 0)
    goto done;

  while (snd_ctl_pcm_next_device (ctl, &dev) == 0 && dev >= 0) {
    if (dev == device_num) {
      snd_pcm_info_t *pcminfo;

      snd_pcm_info_malloc (&pcminfo);
      snd_pcm_info_set_device (pcminfo, dev);
      snd_pcm_info_set_subdevice (pcminfo, 0);
      snd_pcm_info_set_stream (pcminfo, stream);
      if (snd_ctl_pcm_info (ctl, pcminfo) < 0) {
        snd_pcm_info_free (pcminfo);
        break;
      }

      ret = g_strdup (snd_pcm_info_get_name (pcminfo));
      snd_pcm_info_free (pcminfo);
      GST_LOG_OBJECT (obj, "name from pcminfo: %s", GST_STR_NULL (ret));
    }
  }

  if (ret == NULL) {
    char *name = NULL;
    gint card;

    GST_LOG_OBJECT (obj, "no luck so far, trying backup");
    card = snd_ctl_card_info_get_card (info);
    snd_card_get_name (card, &name);
    ret = g_strdup (name);
    free (name);
  }

done:
  snd_ctl_card_info_free (info);
  snd_ctl_close (ctl);

  return ret;
}

gchar *
gst_alsa_find_device_name (GstObject * obj, const gchar * device,
    snd_pcm_t * handle, snd_pcm_stream_t stream)
{
  gchar *ret = NULL;

  if (device != NULL) {
    gchar *dev, *comma;
    gint devnum;

    GST_LOG_OBJECT (obj, "Trying to get device name from string '%s'", device);

    /* only want name:card bit, but not devices and subdevices */
    dev = g_strdup (device);
    if ((comma = strchr (dev, ','))) {
      *comma = '\0';
      devnum = atoi (comma + 1);
      ret = gst_alsa_find_device_name_no_handle (obj, dev, devnum, stream);
    }
    g_free (dev);
  }

  if (ret == NULL && handle != NULL) {
    snd_pcm_info_t *info;

    GST_LOG_OBJECT (obj, "Trying to get device name from open handle");
    snd_pcm_info_malloc (&info);
    snd_pcm_info (handle, info);
    ret = g_strdup (snd_pcm_info_get_name (info));