pipewire/spa/plugins/volume/volume.c

/* Spa
 * Copyright (C) 2016 Wim Taymans <wim.taymans@gmail.com>
 *
 * 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 Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include <string.h>
#include <stddef.h>

#include <spa/log.h>
#include <spa/type-map.h>
#include <spa/node.h>
#include <spa/list.h>
#include <spa/audio/format-utils.h>
#include <spa/format-builder.h>
#include <spa/param-alloc.h>
#include <lib/props.h>

#define NAME "volume"

#define MAX_BUFFERS     16

struct props {
  double volume;
  bool mute;
};

struct buffer {
  struct spa_buffer *outbuf;
  bool               outstanding;
  struct spa_meta_header     *h;
  void              *ptr;
  size_t             size;
  struct spa_list    link;
};

struct port {
  bool            have_format;

  struct spa_port_info     info;
  uint8_t         params_buffer[1024];

  struct buffer buffers[MAX_BUFFERS];
  uint32_t        n_buffers;
  struct spa_port_io      *io;

  struct spa_list empty;
};

struct type {
  uint32_t node;
  uint32_t format;
  uint32_t props;
  uint32_t prop_volume;
  uint32_t prop_mute;
  struct spa_type_meta meta;
  struct spa_type_data data;
  struct spa_type_media_type media_type;
  struct spa_type_media_subtype media_subtype;
  struct spa_type_format_audio format_audio;
  struct spa_type_audio_format audio_format;
  struct spa_type_event_node event_node;
  struct spa_type_command_node command_node;
  struct spa_type_param_alloc_buffers param_alloc_buffers;
  struct spa_type_param_alloc_meta_enable param_alloc_meta_enable;
};

static inline void
init_type (struct type *type, struct spa_type_map *map)
{
  type->node = spa_type_map_get_id (map, SPA_TYPE__Node);
  type->format = spa_type_map_get_id (map, SPA_TYPE__Format);
  type->props = spa_type_map_get_id (map, SPA_TYPE__Props);
  type->prop_volume = spa_type_map_get_id (map, SPA_TYPE_PROPS__volume);
  type->prop_mute = spa_type_map_get_id (map, SPA_TYPE_PROPS__mute);
  spa_type_meta_map (map, &type->meta);
  spa_type_data_map (map, &type->data);
  spa_type_media_type_map (map, &type->media_type);
  spa_type_media_subtype_map (map, &type->media_subtype);
  spa_type_format_audio_map (map, &type->format_audio);
  spa_type_audio_format_map (map, &type->audio_format);
  spa_type_event_node_map (map, &type->event_node);
  spa_type_command_node_map (map, &type->command_node);
  spa_type_param_alloc_buffers_map (map, &type->param_alloc_buffers);
  spa_type_param_alloc_meta_enable_map (map, &type->param_alloc_meta_enable);
}

struct impl {
  struct spa_handle  handle;
  struct spa_node  node;

  struct type type;
  struct spa_type_map *map;
  struct spa_log *log;

  uint8_t props_buffer[512];
  struct props props;

  struct spa_node_callbacks callbacks;
  void *user_data;

  uint8_t format_buffer[1024];
  struct spa_audio_info current_format;

  struct port in_ports[1];
  struct port out_ports[1];

  bool started;
};

#define CHECK_IN_PORT(this,d,p)  ((d) == SPA_DIRECTION_INPUT && (p) == 0)
#define CHECK_OUT_PORT(this,d,p) ((d) == SPA_DIRECTION_OUTPUT && (p) == 0)
#define CHECK_PORT(this,d,p)     ((p) == 0)

#define DEFAULT_VOLUME 1.0
#define DEFAULT_MUTE false

static void
reset_props (struct props *props)
{
  props->volume = DEFAULT_VOLUME;
  props->mute = DEFAULT_MUTE;
}

#define PROP(f,key,type,...)                                                    \
          SPA_POD_PROP (f,key,0,type,1,__VA_ARGS__)
#define PROP_MM(f,key,type,...)                                                 \
          SPA_POD_PROP (f,key,SPA_POD_PROP_RANGE_MIN_MAX,type,3,__VA_ARGS__)
#define PROP_U_MM(f,key,type,...)                                               \
          SPA_POD_PROP (f,key,SPA_POD_PROP_FLAG_UNSET |                         \
                              SPA_POD_PROP_RANGE_MIN_MAX,type,3,__VA_ARGS__)
#define PROP_U_EN(f,key,type,n,...)                                             \
          SPA_POD_PROP (f,key,SPA_POD_PROP_FLAG_UNSET |                         \
                              SPA_POD_PROP_RANGE_ENUM,type,n,__VA_ARGS__)


static int
impl_node_get_props (struct spa_node        *node,
                           struct spa_props     **props)
{
  struct impl *this;
  struct spa_pod_builder b = { NULL,  };
  struct spa_pod_frame f[2];

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (props != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_pod_builder_init (&b, this->props_buffer, sizeof (this->props_buffer));
  spa_pod_builder_props (&b, &f[0], this->type.props,
      PROP_MM (&f[1], this->type.prop_volume, SPA_POD_TYPE_DOUBLE, this->props.volume, 0.0, 10.0),
      PROP    (&f[1], this->type.prop_mute,   SPA_POD_TYPE_BOOL,   this->props.mute));

  *props = SPA_POD_BUILDER_DEREF (&b, f[0].ref, struct spa_props);

  return SPA_RESULT_OK;
}

static int
impl_node_set_props (struct spa_node        *node,
                           const struct spa_props *props)
{
  struct impl *this;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  if (props == NULL) {
    reset_props (&this->props);
  } else {
    spa_props_query (props,
        this->type.prop_volume, SPA_POD_TYPE_DOUBLE, &this->props.volume,
        this->type.prop_mute,   SPA_POD_TYPE_BOOL,   &this->props.mute,
        0);
  }
  return SPA_RESULT_OK;
}

static int
impl_node_send_command (struct spa_node    *node,
                              struct spa_command *command)
{
  struct impl *this;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (command != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  if (SPA_COMMAND_TYPE (command) == this->type.command_node.Start) {
    this->started = true;
  }
  else if (SPA_COMMAND_TYPE (command) == this->type.command_node.Pause) {
    this->started = false;
  }
  else
    return SPA_RESULT_NOT_IMPLEMENTED;

  return SPA_RESULT_OK;
}

static int
impl_node_set_callbacks (struct spa_node                *node,
                               const struct spa_node_callbacks *callbacks,
                               size_t                  callbacks_size,
                               void                   *user_data)
{
  struct impl *this;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  this->callbacks = *callbacks;
  this->user_data = user_data;

  return SPA_RESULT_OK;
}

static int
impl_node_get_n_ports (struct spa_node       *node,
                             uint32_t      *n_input_ports,
                             uint32_t      *max_input_ports,
                             uint32_t      *n_output_ports,
                             uint32_t      *max_output_ports)
{
  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  if (n_input_ports)
    *n_input_ports = 1;
  if (max_input_ports)
    *max_input_ports = 1;
  if (n_output_ports)
    *n_output_ports = 1;
  if (max_output_ports)
    *max_output_ports = 1;

  return SPA_RESULT_OK;
}

static int
impl_node_get_port_ids (struct spa_node       *node,
                              uint32_t       n_input_ports,
                              uint32_t      *input_ids,
                              uint32_t       n_output_ports,
                              uint32_t      *output_ids)
{
  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  if (n_input_ports > 0 && input_ids)
    input_ids[0] = 0;
  if (n_output_ports > 0 && output_ids)
    output_ids[0] = 0;

  return SPA_RESULT_OK;
}


static int
impl_node_add_port (struct spa_node        *node,
                          enum spa_direction    direction,
                          uint32_t        port_id)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static int
impl_node_remove_port (struct spa_node        *node,
                             enum spa_direction    direction,
                             uint32_t        port_id)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static int
impl_node_port_enum_formats (struct spa_node          *node,
                                   enum spa_direction      direction,
                                   uint32_t          port_id,
                                   struct spa_format       **format,
                                   const struct spa_format  *filter,
                                   uint32_t          index)
{
  struct impl *this;
  int res;
  struct spa_format *fmt;
  uint8_t buffer[1024];
  struct spa_pod_builder b = { NULL, };
  struct spa_pod_frame f[2];
  uint32_t count, match;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (format != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  count = match = filter ? 0 : index;

next:
  spa_pod_builder_init (&b, buffer, sizeof (buffer));

  switch (count++) {
    case 0:
      spa_pod_builder_format (&b, &f[0], this->type.format,
          this->type.media_type.audio, this->type.media_subtype.raw,
          PROP_U_EN    (&f[1], this->type.format_audio.format,   SPA_POD_TYPE_ID, 3,
                                                                this->type.audio_format.S16,
                                                                this->type.audio_format.S16,
                                                                this->type.audio_format.S32),
          PROP_U_MM    (&f[1], this->type.format_audio.rate,     SPA_POD_TYPE_INT, 44100, 1, INT32_MAX),
          PROP_U_MM    (&f[1], this->type.format_audio.channels, SPA_POD_TYPE_INT, 2, 1, INT32_MAX));

      break;
    default:
      return SPA_RESULT_ENUM_END;
  }
  fmt = SPA_POD_BUILDER_DEREF (&b, f[0].ref, struct spa_format);
  spa_pod_builder_init (&b, this->format_buffer, sizeof (this->format_buffer));

  if ((res = spa_format_filter (fmt, filter, &b)) != SPA_RESULT_OK || match++ != index)
    goto next;

  *format = SPA_POD_BUILDER_DEREF (&b, 0, struct spa_format);

  return SPA_RESULT_OK;
}

static int
clear_buffers (struct impl *this, struct port *port)
{
  if (port->n_buffers > 0) {
    spa_log_info (this->log, NAME " %p: clear buffers", this);
    port->n_buffers = 0;
    spa_list_init (&port->empty);
  }
  return SPA_RESULT_OK;
}

static int
impl_node_port_set_format (struct spa_node         *node,
                                 enum spa_direction     direction,
                                 uint32_t         port_id,
                                 uint32_t         flags,
                                 const struct spa_format *format)
{
  struct impl *this;
  struct port *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  port = direction == SPA_DIRECTION_INPUT ? &this->in_ports[port_id] : &this->out_ports[port_id];

  if (format == NULL) {
    port->have_format = false;
    clear_buffers (this, port);
  } else {
    struct spa_audio_info info = { SPA_FORMAT_MEDIA_TYPE (format),
                                   SPA_FORMAT_MEDIA_SUBTYPE (format), };

    if (info.media_type != this->type.media_type.audio ||
        info.media_subtype != this->type.media_subtype.raw)
      return SPA_RESULT_INVALID_MEDIA_TYPE;

    if (!spa_format_audio_raw_parse (format, &info.info.raw, &this->type.format_audio))
      return SPA_RESULT_INVALID_MEDIA_TYPE;

    this->current_format = info;
    port->have_format = true;
  }

  return SPA_RESULT_OK;
}

static int
impl_node_port_get_format (struct spa_node          *node,
                                 enum spa_direction      direction,
                                 uint32_t          port_id,
                                 const struct spa_format **format)
{
  struct impl *this;
  struct port *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (format != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  port = direction == SPA_DIRECTION_INPUT ? &this->in_ports[port_id] : &this->out_ports[port_id];

  if (!port->have_format)
    return SPA_RESULT_NO_FORMAT;

  *format = NULL;

  return SPA_RESULT_OK;
}

static int
impl_node_port_get_info (struct spa_node            *node,
                               enum spa_direction        direction,
                               uint32_t            port_id,
                               const struct spa_port_info **info)
{
  struct impl *this;
  struct port *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (info != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  port = direction == SPA_DIRECTION_INPUT ? &this->in_ports[port_id] : &this->out_ports[port_id];
  *info = &port->info;

  return SPA_RESULT_OK;
}

static int
impl_node_port_enum_params (struct spa_node       *node,
                                  enum spa_direction   direction,
                                  uint32_t       port_id,
                                  uint32_t       index,
                                  struct spa_param     **param)
{
  struct spa_pod_builder b = { NULL };
  struct spa_pod_frame f[2];
  struct impl *this;
  struct port *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (param != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  port = direction == SPA_DIRECTION_INPUT ? &this->in_ports[port_id] : &this->out_ports[port_id];

  spa_pod_builder_init (&b, port->params_buffer, sizeof (port->params_buffer));

  switch (index) {
  case 0:
    spa_pod_builder_object (&b, &f[0], 0, this->type.param_alloc_buffers.Buffers,
      PROP      (&f[1], this->type.param_alloc_buffers.size,    SPA_POD_TYPE_INT, 16),
      PROP      (&f[1], this->type.param_alloc_buffers.stride,  SPA_POD_TYPE_INT, 16),
      PROP_U_MM (&f[1], this->type.param_alloc_buffers.buffers, SPA_POD_TYPE_INT, MAX_BUFFERS, 2, MAX_BUFFERS),
      PROP      (&f[1], this->type.param_alloc_buffers.align,   SPA_POD_TYPE_INT, 16));
    break;

  case 1:
    spa_pod_builder_object (&b, &f[0], 0, this->type.param_alloc_meta_enable.MetaEnable,
      PROP      (&f[1], this->type.param_alloc_meta_enable.type, SPA_POD_TYPE_ID, this->type.meta.Header),
      PROP      (&f[1], this->type.param_alloc_meta_enable.size, SPA_POD_TYPE_INT, sizeof (struct spa_meta_header)));
    break;

  default:
    return SPA_RESULT_NOT_IMPLEMENTED;
  }

  *param = SPA_POD_BUILDER_DEREF (&b, f[0].ref, struct spa_param);

  return SPA_RESULT_OK;
}

static int
impl_node_port_set_param (struct spa_node        *node,
                                enum spa_direction    direction,
                                uint32_t        port_id,
                                const struct spa_param *param)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static int
impl_node_port_use_buffers (struct spa_node            *node,
                                  enum spa_direction        direction,
                                  uint32_t            port_id,
                                  struct spa_buffer **buffers,
                                  uint32_t            n_buffers)
{
  struct impl *this;
  struct port *port;
  uint32_t i;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  port = direction == SPA_DIRECTION_INPUT ? &this->in_ports[port_id] : &this->out_ports[port_id];

  if (!port->have_format)
    return SPA_RESULT_NO_FORMAT;

  clear_buffers (this, port);

  for (i = 0; i < n_buffers; i++) {
    struct buffer *b;
    struct spa_data *d = buffers[i]->datas;

    b = &port->buffers[i];
    b->outbuf = buffers[i];
    b->outstanding = true;
    b->h = spa_buffer_find_meta (buffers[i], this->type.meta.Header);

    if ((d[0].type == this->type.data.MemPtr ||
         d[0].type == this->type.data.MemFd ||
         d[0].type == this->type.data.DmaBuf) &&
        d[0].data != NULL) {
      b->ptr = d[0].data;
      b->size = d[0].maxsize;
    }
    else {
      spa_log_error (this->log, NAME " %p: invalid memory on buffer %p", this, buffers[i]);
      return SPA_RESULT_ERROR;
    }
    spa_list_insert (port->empty.prev, &b->link);
  }
  port->n_buffers = n_buffers;

  return SPA_RESULT_OK;
}

static int
impl_node_port_alloc_buffers (struct spa_node            *node,
                                    enum spa_direction        direction,
                                    uint32_t            port_id,
                                    struct spa_param          **params,
                                    uint32_t            n_params,
                                    struct spa_buffer **buffers,
                                    uint32_t           *n_buffers)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static int
impl_node_port_set_io (struct spa_node      *node,
                             enum spa_direction  direction,
                             uint32_t      port_id,
                             struct spa_port_io    *io)
{
  struct impl *this;
  struct port *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, direction, port_id), SPA_RESULT_INVALID_PORT);

  port = direction == SPA_DIRECTION_INPUT ? &this->in_ports[port_id] : &this->out_ports[port_id];
  port->io = io;

  return SPA_RESULT_OK;
}

static void
recycle_buffer (struct impl *this, uint32_t id)
{
  struct port *port = &this->out_ports[0];
  struct buffer *b = &port->buffers[id];

  if (!b->outstanding) {
    spa_log_warn (this->log, NAME " %p: buffer %d not outstanding", this, id);
    return;
  }

  spa_list_insert (port->empty.prev, &b->link);
  b->outstanding = false;
  spa_log_trace (this->log, NAME " %p: recycle buffer %d", this, id);
}

static int
impl_node_port_reuse_buffer (struct spa_node         *node,
                                   uint32_t         port_id,
                                   uint32_t         buffer_id)
{
  struct impl *this;
  struct port *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  spa_return_val_if_fail (CHECK_PORT (this, SPA_DIRECTION_OUTPUT, port_id), SPA_RESULT_INVALID_PORT);

  port = &this->out_ports[port_id];

  if (port->n_buffers == 0)
    return SPA_RESULT_NO_BUFFERS;

  if (buffer_id >= port->n_buffers)
    return SPA_RESULT_INVALID_BUFFER_ID;

  recycle_buffer (this, buffer_id);

  return SPA_RESULT_OK;
}

static int
impl_node_port_send_command (struct spa_node            *node,
                                   enum spa_direction        direction,
                                   uint32_t            port_id,
                                   struct spa_command *command)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static struct spa_buffer *
find_free_buffer (struct impl *this, struct port *port)
{
  struct buffer *b;

  if (spa_list_is_empty (&port->empty))
    return NULL;

  b = spa_list_first (&port->empty, struct buffer, link);
  spa_list_remove (&b->link);
  b->outstanding = true;

  return b->outbuf;
}

static inline void
release_buffer (struct impl *this, struct spa_buffer *buffer)
{
  if (this->callbacks.reuse_buffer)
    this->callbacks.reuse_buffer (&this->node, 0, buffer->id, this->user_data);
}

static void
do_volume (struct impl *this, struct spa_buffer *dbuf, struct spa_buffer *sbuf)
{
  uint32_t si, di, i, n_samples, n_bytes, soff, doff ;
  struct spa_data *sd, *dd;
  uint16_t *src, *dst;
  double volume;

  volume = this->props.volume;

  si = di = 0;
  soff = doff = 0;

  while (true) {
    if (si == sbuf->n_datas || di == dbuf->n_datas)
      break;

    sd = &sbuf->datas[si];
    dd = &dbuf->datas[di];

    src = (uint16_t*) ((uint8_t*)sd->data + sd->chunk->offset + soff);
    dst = (uint16_t*) ((uint8_t*)dd->data + dd->chunk->offset + doff);

    n_bytes = SPA_MIN (sd->chunk->size - soff, dd->chunk->size - doff);
    n_samples = n_bytes / sizeof (uint16_t);

    for (i = 0; i < n_samples; i++)
      *src++ = *dst++ * volume;

    soff += n_bytes;
    doff += n_bytes;

    if (soff >= sd->chunk->size) {
      si++;
      soff = 0;
    }
    if (doff >= dd->chunk->size) {
      di++;
      doff = 0;
    }
  }
}

static int
impl_node_process_input (struct spa_node *node)
{
  struct impl *this;
  struct spa_port_io *input;
  struct spa_port_io *output;
  struct port *in_port, *out_port;
  struct spa_buffer *dbuf, *sbuf;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  out_port = &this->out_ports[0];
  output = out_port->io;
  spa_return_val_if_fail (output != NULL, SPA_RESULT_ERROR);

  if (output->status == SPA_RESULT_HAVE_BUFFER)
    return SPA_RESULT_HAVE_BUFFER;

  in_port = &this->in_ports[0];
  input = in_port->io;
  spa_return_val_if_fail (input != NULL, SPA_RESULT_ERROR);

  if ((dbuf = find_free_buffer (this, out_port)) == NULL)
    return SPA_RESULT_OUT_OF_BUFFERS;

  sbuf = in_port->buffers[input->buffer_id].outbuf;

  input->status = SPA_RESULT_NEED_BUFFER;

  do_volume (this, sbuf, dbuf);

  output->buffer_id = dbuf->id;
  output->status = SPA_RESULT_HAVE_BUFFER;

  return SPA_RESULT_HAVE_BUFFER;
}

static int
impl_node_process_output (struct spa_node *node)
{
  struct impl *this;
  struct port *in_port, *out_port;
  struct spa_port_io *input, *output;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, struct impl, node);

  out_port = &this->out_ports[0];
  output = out_port->io;
  spa_return_val_if_fail (output != NULL, SPA_RESULT_ERROR);

  if (output->status == SPA_RESULT_HAVE_BUFFER)
    return SPA_RESULT_HAVE_BUFFER;

  /* recycle */
  if (output->buffer_id != SPA_ID_INVALID) {
    recycle_buffer (this, output->buffer_id);
    output->buffer_id = SPA_ID_INVALID;
  }

  in_port = &this->in_ports[0];
  input = in_port->io;
  spa_return_val_if_fail (input != NULL, SPA_RESULT_ERROR);

  input->range = output->range;
  input->status = SPA_RESULT_NEED_BUFFER;

  return SPA_RESULT_NEED_BUFFER;
}

static const struct spa_node impl_node = {
  sizeof (struct spa_node),
  NULL,
  impl_node_get_props,
  impl_node_set_props,
  impl_node_send_command,
  impl_node_set_callbacks,
  impl_node_get_n_ports,
  impl_node_get_port_ids,
  impl_node_add_port,
  impl_node_remove_port,
  impl_node_port_enum_formats,
  impl_node_port_set_format,
  impl_node_port_get_format,
  impl_node_port_get_info,
  impl_node_port_enum_params,
  impl_node_port_set_param,
  impl_node_port_use_buffers,
  impl_node_port_alloc_buffers,
  impl_node_port_set_io,
  impl_node_port_reuse_buffer,
  impl_node_port_send_command,
  impl_node_process_input,
  impl_node_process_output,
};

static int
impl_get_interface (struct spa_handle               *handle,
                          uint32_t                 interface_id,
                          void                   **interface)
{
  struct impl *this;

  spa_return_val_if_fail (handle != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (interface != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = (struct impl *) handle;

  if (interface_id == this->type.node)
    *interface = &this->node;
  else
    return SPA_RESULT_UNKNOWN_INTERFACE;

  return SPA_RESULT_OK;
}

static int
impl_clear (struct spa_handle *handle)
{
  return SPA_RESULT_OK;
}

static int
impl_init (const struct spa_handle_factory  *factory,
             struct spa_handle               *handle,
             const struct spa_dict           *info,
             const struct spa_support        *support,
             uint32_t                 n_support)
{
  struct impl *this;
  uint32_t i;

  spa_return_val_if_fail (factory != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (handle != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  handle->get_interface = impl_get_interface;
  handle->clear = impl_clear;

  this = (struct impl *) handle;

  for (i = 0; i < n_support; i++) {
    if (strcmp (support[i].type, SPA_TYPE__TypeMap) == 0)
      this->map = support[i].data;
    else if (strcmp (support[i].type, SPA_TYPE__Log) == 0)
      this->log = support[i].data;
  }
  if (this->map == NULL) {
    spa_log_error (this->log, "a type-map is needed");
    return SPA_RESULT_ERROR;
  }
  init_type (&this->type, this->map);

  this->node = impl_node;
  reset_props (&this->props);

  this->in_ports[0].info.flags = SPA_PORT_INFO_FLAG_CAN_USE_BUFFERS |
                                 SPA_PORT_INFO_FLAG_IN_PLACE;
  spa_list_init (&this->in_ports[0].empty);

  this->out_ports[0].info.flags = SPA_PORT_INFO_FLAG_CAN_USE_BUFFERS |
                                  SPA_PORT_INFO_FLAG_NO_REF;
  spa_list_init (&this->out_ports[0].empty);

  return SPA_RESULT_OK;
}

static const struct spa_interface_info impl_interfaces[] =
{
  { SPA_TYPE__Node, },
};

static int
impl_enum_interface_info (const struct spa_handle_factory  *factory,
                            const struct spa_interface_info **info,
                            uint32_t                 index)
{
  spa_return_val_if_fail (factory != NULL, SPA_RESULT_INVALID_ARGUMENTS);
  spa_return_val_if_fail (info != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  switch (index) {
    case 0:
      *info = &impl_interfaces[index];
      break;
    default:
      return SPA_RESULT_ENUM_END;
  }
  return SPA_RESULT_OK;
}

const struct spa_handle_factory spa_volume_factory =
{ NAME,
  NULL,
  sizeof (struct impl),
  impl_init,
  impl_enum_interface_info,
};