owntone-server/src/httpd_streaming.c

/*
 * Copyright (C) 2023 Espen Jürgensen <espenjurgensen@gmail.com>
 *
 * This program 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 program 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 program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <uninorm.h>
#include <unistd.h>
#include <errno.h>

#include <event2/event.h>
#include <event2/buffer.h>

#include "httpd_internal.h"
#include "player.h"
#include "logger.h"
#include "conffile.h"

#define STREAMING_ICY_METALEN_MAX      4080  // 255*16 incl header/footer (16bytes)
#define STREAMING_ICY_METATITLELEN_MAX 4064  // STREAMING_ICY_METALEN_MAX -16 (not incl header/footer)

struct streaming_session {
  struct httpd_request *hreq;

  int id;
  struct event *audioev;
  struct event *metadataev;
  struct evbuffer *audiobuf;
  size_t bytes_sent;

  bool icy_is_requested;
  size_t icy_remaining;
  char icy_title[STREAMING_ICY_METATITLELEN_MAX];
};

static struct media_quality streaming_default_quality = {
  .sample_rate = 44100,
  .bits_per_sample = 16,
  .channels = 2,
  .bit_rate = 128000,
};

static void
session_free(struct streaming_session *session);

/* ------------------------------ ICY metadata -------------------------------*/

// To test mp3 and ICY tagm it is good to use:
//   mpv --display-tags=* http://localhost:3689/stream.mp3

// As streaming quality goes up, we send more data to the remote client.  With a
// smaller ICY_METAINT value we have to splice metadata more frequently - on
// some devices with small input buffers, a higher quality stream and low
// ICY_METAINT can lead to stuttering as observed on a Roku Soundbridge
static unsigned short streaming_icy_metaint = 16384;

// We know that the icymeta is limited to 1+255*16 (ie 4081) bytes so caller must
// provide a buf of this size to avoid needless mallocs
//
// The icy meta block is defined by a single byte indicating how many double byte
// words used for the actual meta.  Unused bytes are null padded
//
// https://stackoverflow.com/questions/4911062/pulling-track-info-from-an-audio-stream-using-php/4914538#4914538
// http://www.smackfu.com/stuff/programming/shoutcast.html
static uint8_t *
icy_meta_create(uint8_t buf[STREAMING_ICY_METALEN_MAX+1], unsigned *buflen, const char *title)
{
  unsigned titlelen;
  unsigned metalen;
  uint8_t no16s;

  *buflen = 0;

  if (title == NULL)
    {
      no16s = 0;
      memcpy(buf, &no16s, 1);

      *buflen = 1;
    }
  else
    {
      titlelen = strlen(title);
      if (titlelen > STREAMING_ICY_METATITLELEN_MAX)
	titlelen = STREAMING_ICY_METATITLELEN_MAX;  // dont worry about the null byte

      // [0]    1x byte N, indicate the total number of 16 bytes words required
      //        to represent the meta data
      // [1..N] meta data book ended by "StreamTitle='" and "';"
      //
      // The '15' is strlen of StreamTitle=' + ';
      no16s = (15 + titlelen)/16 +1;
      metalen = 1 + no16s*16;
      memset(buf, 0, metalen);

      memcpy(buf,             &no16s, 1);
      memcpy(buf+1,           (const uint8_t*)"StreamTitle='", 13);
      memcpy(buf+14,          title, titlelen);
      memcpy(buf+14+titlelen, (const uint8_t*)"';", 2);

      *buflen = metalen;
    }

  return buf;
}

static void
icy_meta_splice(struct evbuffer *out, struct evbuffer *in, size_t *icy_remaining, char *title)
{
  uint8_t meta[STREAMING_ICY_METALEN_MAX + 1];
  unsigned metalen;
  size_t buf_remaining;
  size_t consume;

  for (buf_remaining = evbuffer_get_length(in); buf_remaining > 0; buf_remaining -= consume)
    {
      consume = MIN(*icy_remaining, buf_remaining);
      evbuffer_remove_buffer(in, out, consume);
      *icy_remaining -= consume;
      if (*icy_remaining == 0)
	{
	  icy_meta_create(meta, &metalen, title);

	  evbuffer_add(out, meta, metalen);
	  *icy_remaining = streaming_icy_metaint;
	}
    }
}


/* ----------------------------- Event callbacks ---------------------------- */

static void
conn_close_cb(void *arg)
{
  struct streaming_session *session = arg;

  session_free(session);
}

static void
audio_cb(evutil_socket_t fd, short event, void *arg)
{
  struct streaming_session *session = arg;
  struct httpd_request *hreq;
  int len;

  CHECK_NULL(L_STREAMING, hreq = session->hreq);

  len = evbuffer_read(session->audiobuf, fd, -1);
  if (len < 0 && errno != EAGAIN)
    {
      DPRINTF(E_INFO, L_STREAMING, "Stopping mp3 streaming to %s:%d\n", session->hreq->peer_address, (int)session->hreq->peer_port);

      httpd_send_reply_end(session->hreq);
      session_free(session);
      return;
    }

  if (session->icy_is_requested)
    icy_meta_splice(hreq->out_body, session->audiobuf, &session->icy_remaining, session->icy_title);
  else
    evbuffer_add_buffer(hreq->out_body, session->audiobuf);

  httpd_send_reply_chunk(hreq, NULL, NULL);

  session->bytes_sent += len;
}

static void
metadata_cb(evutil_socket_t fd, short event, void *arg)
{
  struct streaming_session *session = arg;
  struct evbuffer *evbuf;
  int len;

  CHECK_NULL(L_STREAMING, evbuf = evbuffer_new());

  len = evbuffer_read(evbuf, fd, -1);
  if (len < 0)
    goto out;

  len = sizeof(session->icy_title);
  evbuffer_remove(evbuf, session->icy_title, len);
  session->icy_title[len - 1] = '\0';

 out:
  evbuffer_free(evbuf);
}


/* ----------------------------- Session helpers ---------------------------- */

static void
session_free(struct streaming_session *session)
{
  if (!session)
    return;

  player_streaming_deregister(session->id);

  if (session->audioev)
    event_free(session->audioev);
  if (session->metadataev)
    event_free(session->metadataev);

  evbuffer_free(session->audiobuf);
  free(session);
}

static struct streaming_session *
session_new(struct httpd_request *hreq, bool icy_is_requested, enum player_format format, struct media_quality quality)
{
  struct streaming_session *session;
  int audio_fd;
  int metadata_fd;

  CHECK_NULL(L_STREAMING, session = calloc(1, sizeof(struct streaming_session)));
  CHECK_NULL(L_STREAMING, session->audiobuf = evbuffer_new());

  session->hreq = hreq;
  session->icy_is_requested = icy_is_requested;
  session->icy_remaining = streaming_icy_metaint;

  // Ask streaming output module for a fd to read mp3 from
  session->id = player_streaming_register(&audio_fd, &metadata_fd, format, quality);
  if (session->id < 0)
    goto error;

  CHECK_NULL(L_STREAMING, session->audioev = event_new(hreq->evbase, audio_fd, EV_READ | EV_PERSIST, audio_cb, session));
  event_add(session->audioev, NULL);
  CHECK_NULL(L_STREAMING, session->metadataev = event_new(hreq->evbase, metadata_fd, EV_READ | EV_PERSIST, metadata_cb, session));
  event_add(session->metadataev, NULL);

  return session;

 error:
  session_free(session);
  return NULL;
}


/* -------------------------- Module implementation ------------------------- */

static int
streaming_mp3_handler(struct httpd_request *hreq)
{
  struct streaming_session *session = NULL;
  const char *name = cfg_getstr(cfg_getsec(cfg, "library"), "name");
  const char *param;
  bool icy_is_requested;
  char buf[9];

  param = httpd_header_find(hreq->in_headers, "Icy-MetaData");
  icy_is_requested = (param && strcmp(param, "1") == 0);
  if (icy_is_requested)
    {
      httpd_header_add(hreq->out_headers, "icy-name", name);
      snprintf(buf, sizeof(buf), "%d", streaming_icy_metaint);
      httpd_header_add(hreq->out_headers, "icy-metaint", buf);
    }

  session = session_new(hreq, icy_is_requested, PLAYER_FORMAT_MP3, streaming_default_quality);
  if (!session)
    return -1; // Error sent by caller

  httpd_request_close_cb_set(hreq, conn_close_cb, session);

  httpd_header_add(hreq->out_headers, "Content-Type", "audio/mpeg");
  httpd_header_add(hreq->out_headers, "Server", PACKAGE_NAME "/" VERSION);
  httpd_header_add(hreq->out_headers, "Cache-Control", "no-cache");
  httpd_header_add(hreq->out_headers, "Pragma", "no-cache");
  httpd_header_add(hreq->out_headers, "Expires", "Mon, 31 Aug 2015 06:00:00 GMT");

  httpd_send_reply_start(hreq, HTTP_OK, "OK");

  return 0;
}

static struct httpd_uri_map streaming_handlers[] =
  {
    {
      .regexp = "^/stream.mp3$",
      .handler = streaming_mp3_handler,
      .flags = HTTPD_HANDLER_REALTIME,
    },
    {
      .regexp = NULL,
      .handler = NULL
    }
  };

static void
streaming_request(struct httpd_request *hreq)
{
  int ret;

  if (!hreq->handler)
    {
      DPRINTF(E_LOG, L_STREAMING, "Unrecognized path in streaming request: '%s'\n", hreq->uri);

      httpd_send_error(hreq, HTTP_NOTFOUND, NULL);
      return;
    }

  ret = hreq->handler(hreq);
  if (ret < 0)
    httpd_send_error(hreq, HTTP_INTERNAL, NULL);
}

static int
streaming_init(void)
{
  int val;

  val = cfg_getint(cfg_getsec(cfg, "streaming"), "sample_rate");
  // Validate against the variations of libmp3lame's supported sample rates: 32000/44100/48000
  if (val % 11025 > 0 && val % 12000 > 0 && val % 8000 > 0)
    DPRINTF(E_LOG, L_STREAMING, "Unsupported streaming sample_rate=%d, defaulting\n", val);
  else
    streaming_default_quality.sample_rate = val;

  val = cfg_getint(cfg_getsec(cfg, "streaming"), "bit_rate");
  switch (val)
  {
    case  64:
    case  96:
    case 128:
    case 192:
    case 320:
      streaming_default_quality.bit_rate = val*1000;
      break;

    default:
      DPRINTF(E_LOG, L_STREAMING, "Unsuppported streaming bit_rate=%d, supports: 64/96/128/192/320, defaulting\n", val);
  }

  DPRINTF(E_INFO, L_STREAMING, "Streaming quality: %d/%d/%d @ %dkbps\n",
    streaming_default_quality.sample_rate, streaming_default_quality.bits_per_sample,
    streaming_default_quality.channels, streaming_default_quality.bit_rate/1000);

  val = cfg_getint(cfg_getsec(cfg, "streaming"), "icy_metaint");
  // Too low a value forces server to send more meta than data
  if (val >= 4096 && val <= 131072)
    streaming_icy_metaint = val;
  else
    DPRINTF(E_INFO, L_STREAMING, "Unsupported icy_metaint=%d, supported range: 4096..131072, defaulting to %d\n", val, streaming_icy_metaint);

  return 0;
}

struct httpd_module httpd_streaming =
{
  .name = "Streaming",
  .type = MODULE_STREAMING,
  .logdomain = L_STREAMING,
  .fullpaths = { "/stream.mp3", NULL },
  .handlers = streaming_handlers,
  .init = streaming_init,
  .request = streaming_request,
};