pipewire/spa/plugins/audiomixer/audiomixer.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 <stdio.h>

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

#define MAX_BUFFERS     64
#define MAX_PORTS       128

typedef struct _SpaAudioMixer SpaAudioMixer;

typedef struct {
  SpaBuffer     *outbuf;
  bool           outstanding;
  SpaMetaHeader *h;
  SpaList        link;
} MixerBuffer;

typedef struct {
  SpaPortIO   *io;

  bool have_format;
  SpaPortInfo info;

  MixerBuffer  buffers[MAX_BUFFERS];
  uint32_t     n_buffers;

  SpaList      queue;
  size_t       queued_offset;
  size_t       queued_bytes;
} SpaAudioMixerPort;

typedef struct {
  uint32_t node;
  uint32_t format;
  SpaTypeMediaType media_type;
  SpaTypeMediaSubtype media_subtype;
  SpaTypeFormatAudio format_audio;
  SpaTypeAudioFormat audio_format;
  SpaTypeCommandNode command_node;
} Type;

static inline void
init_type (Type *type, SpaTypeMap *map)
{
  type->node = spa_type_map_get_id (map, SPA_TYPE__Node);
  type->format = spa_type_map_get_id (map, SPA_TYPE__Format);
  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_command_node_map (map, &type->command_node);
}

struct _SpaAudioMixer {
  SpaHandle  handle;
  SpaNode  node;

  Type type;
  SpaTypeMap *map;
  SpaLog *log;

  SpaEventNodeCallback event_cb;
  void *user_data;

  int port_count;
  int port_queued;
  SpaAudioMixerPort in_ports[MAX_PORTS];
  SpaAudioMixerPort out_ports[1];

  bool have_format;
  SpaAudioInfo format;
  uint8_t format_buffer[4096];

  bool started;
#define STATE_ERROR     0
#define STATE_IN        1
#define STATE_OUT       2
  int state;
};

#define CHECK_PORT_NUM(this,d,p)     (((d) == SPA_DIRECTION_INPUT && (p) < MAX_PORTS) || \
                                      ((d) == SPA_DIRECTION_OUTPUT && (p) == 0))
#define CHECK_FREE_IN_PORT(this,d,p) ((d) == SPA_DIRECTION_INPUT && (p) < MAX_PORTS && !this->in_ports[(p)].io)
#define CHECK_IN_PORT(this,d,p)      ((d) == SPA_DIRECTION_INPUT && (p) < MAX_PORTS && this->in_ports[(p)].io)
#define CHECK_OUT_PORT(this,d,p)     ((d) == SPA_DIRECTION_OUTPUT && (p) == 0)
#define CHECK_PORT(this,d,p)         (CHECK_OUT_PORT(this,d,p) || CHECK_IN_PORT (this,d,p))

#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_EN(f,key,type,n,...)                                               \
          SPA_POD_PROP (f,key,SPA_POD_PROP_RANGE_ENUM,type,n,__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 SpaResult
spa_audiomixer_node_get_props (SpaNode       *node,
                               SpaProps     **props)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static SpaResult
spa_audiomixer_node_set_props (SpaNode         *node,
                               const SpaProps  *props)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static SpaResult
spa_audiomixer_node_send_command (SpaNode    *node,
                                  SpaCommand *command)
{
  SpaAudioMixer *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, SpaAudioMixer, 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 SpaResult
spa_audiomixer_node_set_event_callback (SpaNode              *node,
                                        SpaEventNodeCallback  event,
                                        void                 *user_data)
{
  SpaAudioMixer *this;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

  this->event_cb = event;
  this->user_data = user_data;

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_get_n_ports (SpaNode       *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 = 0;
  if (max_input_ports)
    *max_input_ports = MAX_PORTS;
  if (n_output_ports)
    *n_output_ports = 1;
  if (max_output_ports)
    *max_output_ports = 1;

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_get_port_ids (SpaNode       *node,
                                  uint32_t       n_input_ports,
                                  uint32_t      *input_ids,
                                  uint32_t       n_output_ports,
                                  uint32_t      *output_ids)
{
  SpaAudioMixer *this;
  int i, idx;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

  if (input_ids) {
    for (i = 0, idx = 0; i < MAX_PORTS && idx < n_input_ports; i++) {
      if (this->in_ports[i].io)
        input_ids[idx++] = i;
    }
  }
  if (n_output_ports > 0 && output_ids)
    output_ids[0] = 0;

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_add_port (SpaNode        *node,
                              SpaDirection    direction,
                              uint32_t        port_id)
{
  SpaAudioMixer *this;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

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

  this->port_count++;
  spa_list_init (&this->in_ports[port_id].queue);

  this->in_ports[port_id].info.flags = SPA_PORT_INFO_FLAG_CAN_USE_BUFFERS |
                                    SPA_PORT_INFO_FLAG_REMOVABLE |
                                    SPA_PORT_INFO_FLAG_OPTIONAL |
                                    SPA_PORT_INFO_FLAG_IN_PLACE;
  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_remove_port (SpaNode        *node,
                                 SpaDirection    direction,
                                 uint32_t        port_id)
{
  SpaAudioMixer *this;
  SpaPortIO *io;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

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

  io = this->in_ports[port_id].io;
  if (io && io->buffer_id)
    this->port_queued--;

  this->in_ports[port_id].io = NULL;
  this->port_count--;

  return SPA_RESULT_OK;
}


static SpaResult
spa_audiomixer_node_port_enum_formats (SpaNode         *node,
                                       SpaDirection     direction,
                                       uint32_t         port_id,
                                       SpaFormat      **format,
                                       const SpaFormat *filter,
                                       uint32_t         index)
{
  SpaAudioMixer *this;
  SpaResult res;
  SpaFormat *fmt;
  uint8_t buffer[256];
  SpaPODBuilder b = { NULL, };
  SpaPODFrame 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, SpaAudioMixer, 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      (&f[1], this->type.format_audio.format,   SPA_POD_TYPE_ID,  this->type.audio_format.S16),
          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, SpaFormat);

  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, SpaFormat);

  return SPA_RESULT_OK;
}

static SpaResult
clear_buffers (SpaAudioMixer *this, SpaAudioMixerPort *port)
{
  if (port->n_buffers > 0) {
    spa_log_info (this->log, "audio-mixer %p: clear buffers %p", this, port);
    port->n_buffers = 0;
    spa_list_init (&port->queue);
  }
  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_port_set_format (SpaNode            *node,
                                     SpaDirection        direction,
                                     uint32_t            port_id,
                                     SpaPortFormatFlags  flags,
                                     const SpaFormat    *format)
{
  SpaAudioMixer *this;
  SpaAudioMixerPort *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, 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[0];

  if (format == NULL) {
    port->have_format = false;
    clear_buffers (this, port);
  } else {
    SpaAudioInfo 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->format = info;
    port->have_format = true;
  }

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_port_get_format (SpaNode          *node,
                                     SpaDirection      direction,
                                     uint32_t          port_id,
                                     const SpaFormat **format)
{
  SpaAudioMixer *this;
  SpaAudioMixerPort *port;
  SpaPODBuilder b = { NULL, };
  SpaPODFrame f[2];

  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, SpaAudioMixer, 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[0];

  if (!port->have_format)
    return SPA_RESULT_NO_FORMAT;

  spa_pod_builder_init (&b, this->format_buffer, sizeof (this->format_buffer));
  spa_pod_builder_format (&b, &f[0], this->type.format,
         this->type.media_type.audio, this->type.media_subtype.raw,
         PROP (&f[1], this->type.format_audio.format,   SPA_POD_TYPE_ID,  this->format.info.raw.format),
         PROP (&f[1], this->type.format_audio.rate,     SPA_POD_TYPE_INT, this->format.info.raw.rate),
         PROP (&f[1], this->type.format_audio.channels, SPA_POD_TYPE_INT, this->format.info.raw.channels));
  *format = SPA_POD_BUILDER_DEREF (&b, f[0].ref, SpaFormat);

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_port_get_info (SpaNode            *node,
                                   SpaDirection        direction,
                                   uint32_t            port_id,
                                   const SpaPortInfo **info)
{
  SpaAudioMixer *this;
  SpaAudioMixerPort *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, SpaAudioMixer, 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[0];
  *info = &port->info;

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_port_get_props (SpaNode       *node,
                                    SpaDirection   direction,
                                    uint32_t       port_id,
                                    SpaProps     **props)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static SpaResult
spa_audiomixer_node_port_set_props (SpaNode        *node,
                                    SpaDirection    direction,
                                    uint32_t        port_id,
                                    const SpaProps *props)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static SpaResult
spa_audiomixer_node_port_use_buffers (SpaNode         *node,
                                      SpaDirection     direction,
                                      uint32_t         port_id,
                                      SpaBuffer      **buffers,
                                      uint32_t         n_buffers)
{
  SpaAudioMixer *this;
  SpaAudioMixerPort *port;
  uint32_t i;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, 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_return_val_if_fail (port->have_format, SPA_RESULT_NO_FORMAT);

  clear_buffers (this, port);

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

    b = &port->buffers[i];
    b->outbuf = buffers[i];
    b->outstanding = direction == SPA_DIRECTION_INPUT ? true : false;
    b->h = spa_buffer_find_meta (buffers[i], SPA_META_TYPE_HEADER);

    switch (d[0].type) {
      case SPA_DATA_TYPE_MEMPTR:
      case SPA_DATA_TYPE_MEMFD:
      case SPA_DATA_TYPE_DMABUF:
        if (d[0].data == NULL) {
          spa_log_error (this->log, "volume %p: invalid memory on buffer %p", this, buffers[i]);
          continue;
        }
        break;
      default:
        break;
    }
    if (!b->outstanding)
      spa_list_insert (port->queue.prev, &b->link);
  }
  port->n_buffers = n_buffers;

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_node_port_alloc_buffers (SpaNode         *node,
                                        SpaDirection     direction,
                                        uint32_t         port_id,
                                        SpaAllocParam  **params,
                                        uint32_t         n_params,
                                        SpaBuffer      **buffers,
                                        uint32_t        *n_buffers)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static SpaResult
spa_audiomixer_node_port_set_io (SpaNode      *node,
                                 SpaDirection  direction,
                                 uint32_t      port_id,
                                 SpaPortIO    *io)
{
  SpaAudioMixer *this;
  SpaAudioMixerPort *port;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

  spa_return_val_if_fail (CHECK_PORT_NUM (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 (SpaAudioMixer *this, uint32_t id)
{
  SpaAudioMixerPort *port = &this->out_ports[0];

  MixerBuffer *b = &port->buffers[id];

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

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

static SpaResult
spa_audiomixer_node_port_reuse_buffer (SpaNode         *node,
                                       uint32_t         port_id,
                                       uint32_t         buffer_id)
{
  SpaAudioMixer *this;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

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

  recycle_buffer (this, buffer_id);

  return SPA_RESULT_NOT_IMPLEMENTED;
}

static SpaResult
spa_audiomixer_node_port_send_command (SpaNode        *node,
                                       SpaDirection    direction,
                                       uint32_t        port_id,
                                       SpaCommand     *command)
{
  return SPA_RESULT_NOT_IMPLEMENTED;
}

static void
clear_buffer (SpaAudioMixer *this, MixerBuffer *out)
{
  int16_t *op;
  size_t os;

  op = SPA_MEMBER (out->outbuf->datas[0].data, out->outbuf->datas[0].chunk->offset, void);
  os = out->outbuf->datas[0].chunk->size;
  memset (op, 0, os);
}

static void
add_port_data (SpaAudioMixer *this, MixerBuffer *out, SpaAudioMixerPort *port, int layer)
{
  int i;
  int16_t *op, *ip;
  size_t os, is, chunk;
  MixerBuffer *b;

  op = SPA_MEMBER (out->outbuf->datas[0].data, out->outbuf->datas[0].chunk->offset, void);
  os = out->outbuf->datas[0].chunk->size;

  b = spa_list_first (&port->queue, MixerBuffer, link);

  ip = SPA_MEMBER (b->outbuf->datas[0].data,
      port->queued_offset + b->outbuf->datas[0].chunk->offset, void);
  is = b->outbuf->datas[0].chunk->size - port->queued_offset;

  chunk = SPA_MIN (os, is);

  if (layer == 0) {
    for (i = 0; i < chunk / 2; i++)
      op[i] = ip[i];
  }
  else {
    for (i = 0; i < chunk / 2; i++)
      op[i] = SPA_CLAMP (op[i] + ip[i], INT16_MIN, INT16_MAX);
  }

  op += chunk / 2;
  os -= chunk;

  port->queued_offset += chunk;
  port->queued_bytes -= chunk;

  if (chunk == is) {
    spa_log_trace (this->log, "audiomixer %p: return buffer %d on port %p %zd",
              this, b->outbuf->id, port, chunk);
    port->io->buffer_id = b->outbuf->id;
    spa_list_remove (&b->link);
    b->outstanding = true;
    port->queued_offset = 0;
  } else {
    spa_log_trace (this->log, "audiomixer %p: keeping buffer %d on port %p %zd %zd",
        this, b->outbuf->id, port, port->queued_bytes, chunk);
  }
}

static SpaResult
mix_output (SpaAudioMixer *this, size_t n_bytes)
{
  MixerBuffer *outbuf;
  int i, layer;
  SpaAudioMixerPort *outport;
  SpaPortIO *output;

  outport = &this->out_ports[0];
  output = outport->io;

  if (spa_list_is_empty (&outport->queue))
    return SPA_RESULT_OUT_OF_BUFFERS;

  outbuf = spa_list_first (&outport->queue, MixerBuffer, link);
  spa_list_remove (&outbuf->link);

  n_bytes = SPA_MIN (n_bytes, outbuf->outbuf->datas[0].maxsize);

  spa_log_trace (this->log, "audiomixer %p: dequeue output buffer %d %zd", this, outbuf->outbuf->id, n_bytes);

  outbuf->outstanding = true;
  outbuf->outbuf->datas[0].chunk->offset = 0;
  outbuf->outbuf->datas[0].chunk->size = n_bytes;
  outbuf->outbuf->datas[0].chunk->stride = 0;

  for (layer = 0, i = 0; i < MAX_PORTS; i++) {
    SpaAudioMixerPort *port = &this->in_ports[i];

    if (port->io == NULL || port->n_buffers == 0)
      continue;

    if (spa_list_is_empty (&port->queue)) {
      spa_log_warn (this->log, "audiomixer %p: underrun stream %d", this, i);
      port->queued_bytes = 0;
      port->queued_offset = 0;
      continue;
    }
    add_port_data (this, outbuf, port, layer++);
  }
  if (layer == 0) {
    this->state = STATE_IN;
    return SPA_RESULT_NEED_INPUT;
  }

  output->buffer_id = outbuf->outbuf->id;
  output->status = SPA_RESULT_HAVE_OUTPUT;
  this->state = STATE_OUT;

  return SPA_RESULT_HAVE_OUTPUT;
}

static SpaResult
spa_audiomixer_node_process_input (SpaNode *node)
{
  SpaResult res;
  SpaAudioMixer *this;
  uint32_t i;
  SpaAudioMixerPort *outport;
  size_t min_queued = SIZE_MAX;
  SpaPortIO *output;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

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

  if (this->state == STATE_OUT)
    return SPA_RESULT_HAVE_OUTPUT;

  for (i = 0; i < MAX_PORTS; i++) {
    SpaAudioMixerPort *port = &this->in_ports[i];
    SpaPortIO *input;

    if ((input = port->io) == NULL || port->n_buffers == 0)
      continue;

    if (port->queued_bytes == 0 &&
        input->status == SPA_RESULT_HAVE_OUTPUT &&
        input->buffer_id != SPA_ID_INVALID) {
      MixerBuffer *b = &port->buffers[input->buffer_id];

      if (!b->outstanding) {
        spa_log_warn (this->log, "audiomixer %p: buffer was not outstanding %d", this, input->buffer_id);
        continue;
      }

      b->outstanding = false;
      input->buffer_id = SPA_ID_INVALID;

      spa_list_insert (port->queue.prev, &b->link);
      port->queued_bytes += b->outbuf->datas[0].chunk->size;

      spa_log_trace (this->log, "audiomixer %p: queue buffer %d on port %d %zd %zd",
          this, b->outbuf->id, i, port->queued_bytes, min_queued);
    }
    if (min_queued == SIZE_MAX || port->queued_bytes < min_queued)
      min_queued = port->queued_bytes;
  }

  if (min_queued != SIZE_MAX && min_queued > 0) {
    res = mix_output (this, min_queued);
  } else {
    res = SPA_RESULT_NEED_INPUT;
  }
  return res;
}

static SpaResult
spa_audiomixer_node_process_output (SpaNode *node)
{
  SpaResult res;
  SpaAudioMixer *this;
  SpaAudioMixerPort *port;
  SpaPortIO *output;
  int i;

  spa_return_val_if_fail (node != NULL, SPA_RESULT_INVALID_ARGUMENTS);

  this = SPA_CONTAINER_OF (node, SpaAudioMixer, node);

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

  spa_return_val_if_fail (port->n_buffers > 0, SPA_RESULT_NO_BUFFERS);

  /* recycle */
  if (output->buffer_id != SPA_ID_INVALID) {
    recycle_buffer (this, output->buffer_id);
    output->buffer_id = SPA_ID_INVALID;
  }
  res = SPA_RESULT_NEED_INPUT;
  /* produce more output if possible */
  if (this->state == STATE_OUT) {
    size_t min_queued = -1;

    for (i = 0; i < MAX_PORTS; i++) {
      SpaAudioMixerPort *port = &this->in_ports[i];

      if (port->io == NULL || port->n_buffers == 0)
        continue;

      if (min_queued == -1 || port->queued_bytes < min_queued)
        min_queued = port->queued_bytes;
    }
    if (min_queued != -1 && min_queued > 0) {
      res = mix_output (this, min_queued);
    } else {
      this->state = STATE_IN;
    }
  }
  /* take requested output range and apply to input */
  if (this->state == STATE_IN) {
    for (i = 0; i < MAX_PORTS; i++) {
      SpaAudioMixerPort *port = &this->in_ports[i];
      SpaPortIO *input;

      if ((input = port->io) == NULL || port->n_buffers == 0)
        continue;

      if (port->queued_bytes == 0) {
        input->range = output->range;
        input->status = SPA_RESULT_NEED_INPUT;
      }
      else {
        input->status = SPA_RESULT_OK;
      }
      spa_log_trace (this->log, "audiomixer %p: port %d %d queued %zd, res %d", this,
          i, output->range.min_size, port->queued_bytes, input->status);
    }
  }
  return res;
}

static const SpaNode audiomixer_node = {
  sizeof (SpaNode),
  NULL,
  spa_audiomixer_node_get_props,
  spa_audiomixer_node_set_props,
  spa_audiomixer_node_send_command,
  spa_audiomixer_node_set_event_callback,
  spa_audiomixer_node_get_n_ports,
  spa_audiomixer_node_get_port_ids,
  spa_audiomixer_node_add_port,
  spa_audiomixer_node_remove_port,
  spa_audiomixer_node_port_enum_formats,
  spa_audiomixer_node_port_set_format,
  spa_audiomixer_node_port_get_format,
  spa_audiomixer_node_port_get_info,
  spa_audiomixer_node_port_get_props,
  spa_audiomixer_node_port_set_props,
  spa_audiomixer_node_port_use_buffers,
  spa_audiomixer_node_port_alloc_buffers,
  spa_audiomixer_node_port_set_io,
  spa_audiomixer_node_port_reuse_buffer,
  spa_audiomixer_node_port_send_command,
  spa_audiomixer_node_process_input,
  spa_audiomixer_node_process_output,
};

static SpaResult
spa_audiomixer_get_interface (SpaHandle   *handle,
                              uint32_t     interface_id,
                              void       **interface)
{
  SpaAudioMixer *this;

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

  this = (SpaAudioMixer *) handle;

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

  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_clear (SpaHandle *handle)
{
  return SPA_RESULT_OK;
}

static SpaResult
spa_audiomixer_init (const SpaHandleFactory *factory,
                     SpaHandle              *handle,
                     const SpaDict          *info,
                     const SpaSupport       *support,
                     uint32_t                n_support)
{
  SpaAudioMixer *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 = spa_audiomixer_get_interface;
  handle->clear = spa_audiomixer_clear;

  this = (SpaAudioMixer *) 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, "an id-map is needed");
    return SPA_RESULT_ERROR;
  }
  init_type (&this->type, this->map);

  this->node = audiomixer_node;
  this->state = STATE_IN;

  this->out_ports[0].io = NULL;
  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].queue);

  return SPA_RESULT_OK;
}

static const SpaInterfaceInfo audiomixer_interfaces[] =
{
  { SPA_TYPE__Node, },
};

static SpaResult
audiomixer_enum_interface_info (const SpaHandleFactory  *factory,
                                const SpaInterfaceInfo **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 = &audiomixer_interfaces[index];
      break;
    default:
      return SPA_RESULT_ENUM_END;
  }
  return SPA_RESULT_OK;
}

const SpaHandleFactory spa_audiomixer_factory =
{ "audiomixer",
  NULL,
  sizeof (SpaAudioMixer),
  spa_audiomixer_init,
  audiomixer_enum_interface_info,
};