gsttypefindfunctions.c

/* GStreamer
 * Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
 * Copyright (C) 2005-2009 Tim-Philipp Müller <tim centricular net>
 * Copyright (C) 2009 Sebastian Dröge <sebastian.droege@collabora.co.uk>
 *
 * gsttypefindfunctions.c: collection of various typefind functions
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <glib.h>
#include <glib/gprintf.h>

/* don't want to add gio xdgmime typefinder if gio was disabled via configure */
#ifdef HAVE_GIO
#include <gio/gio.h>
#define USE_GIO
#endif

#include <gst/gst.h>

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#include <gst/pbutils/pbutils.h>

GST_DEBUG_CATEGORY_STATIC (type_find_debug);
#define GST_CAT_DEFAULT type_find_debug

/* DataScanCtx: helper for typefind functions that scan through data
 * step-by-step, to avoid doing a peek at each and every offset */

#define DATA_SCAN_CTX_CHUNK_SIZE 4096

typedef struct
{
  guint64 offset;
  const guint8 *data;
  gint size;
} DataScanCtx;

static inline void
data_scan_ctx_advance (GstTypeFind * tf, DataScanCtx * c, guint bytes_to_skip)
{
  c->offset += bytes_to_skip;
  if (G_LIKELY (c->size > bytes_to_skip)) {
    c->size -= bytes_to_skip;
    c->data += bytes_to_skip;
  } else {
    c->data += c->size;
    c->size = 0;
  }
}

static inline gboolean
data_scan_ctx_ensure_data (GstTypeFind * tf, DataScanCtx * c, gint min_len)
{
  const guint8 *data;
  guint64 len;
  guint chunk_len = MAX (DATA_SCAN_CTX_CHUNK_SIZE, min_len);

  if (G_LIKELY (c->size >= min_len))
    return TRUE;

  data = gst_type_find_peek (tf, c->offset, chunk_len);
  if (G_LIKELY (data != NULL)) {
    c->data = data;
    c->size = chunk_len;
    return TRUE;
  }

  /* if there's less than our chunk size, try to get as much as we can, but
   * always at least min_len bytes (we might be typefinding the first buffer
   * of the stream and not have as much data available as we'd like) */
  len = gst_type_find_get_length (tf);
  if (len > 0) {
    len = CLAMP (len - c->offset, min_len, chunk_len);
  } else {
    len = min_len;
  }

  data = gst_type_find_peek (tf, c->offset, len);
  if (data != NULL) {
    c->data = data;
    c->size = len;
    return TRUE;
  }

  return FALSE;
}

static inline gboolean
data_scan_ctx_memcmp (GstTypeFind * tf, DataScanCtx * c, guint offset,
    const gchar * data, guint len)
{
  if (!data_scan_ctx_ensure_data (tf, c, offset + len))
    return FALSE;

  return (memcmp (c->data + offset, data, len) == 0);
}

/*** text/plain ***/
static gboolean xml_check_first_element (GstTypeFind * tf,
    const gchar * element, guint elen, gboolean strict);
static gboolean sdp_check_header (GstTypeFind * tf);

static GstStaticCaps utf8_caps = GST_STATIC_CAPS ("text/plain");

#define UTF8_CAPS gst_static_caps_get(&utf8_caps)

static gboolean
utf8_type_find_have_valid_utf8_at_offset (GstTypeFind * tf, guint64 offset,
    GstTypeFindProbability * prob)
{
  guint8 *data;

  /* randomly decided values */
  guint min_size = 16;          /* minimum size  */
  guint size = 32 * 1024;       /* starting size */
  guint probability = 95;       /* starting probability */
  guint step = 10;              /* how much we reduce probability in each
                                 * iteration */

  while (probability > step && size > min_size) {
    data = gst_type_find_peek (tf, offset, size);
    if (data) {
      gchar *end;
      gchar *start = (gchar *) data;

      if (g_utf8_validate (start, size, (const gchar **) &end) || (end - start + 4 > size)) {   /* allow last char to be cut off */
        *prob = probability;
        return TRUE;
      }
      *prob = 0;
      return FALSE;
    }
    size /= 2;
    probability -= step;
  }
  *prob = 0;
  return FALSE;
}

static void
utf8_type_find (GstTypeFind * tf, gpointer unused)
{
  GstTypeFindProbability start_prob, mid_prob;
  guint64 length;

  /* leave xml to the xml typefinders */
  if (xml_check_first_element (tf, "", 0, TRUE))
    return;

  /* leave sdp to the sdp typefinders */
  if (sdp_check_header (tf))
    return;

  /* check beginning of stream */
  if (!utf8_type_find_have_valid_utf8_at_offset (tf, 0, &start_prob))
    return;

  GST_LOG ("start is plain text with probability of %u", start_prob);

  /* POSSIBLE is the highest probability we ever return if we can't
   * probe into the middle of the file and don't know its length */

  length = gst_type_find_get_length (tf);
  if (length == 0 || length == (guint64) - 1) {
    gst_type_find_suggest (tf, MIN (start_prob, GST_TYPE_FIND_POSSIBLE),
        UTF8_CAPS);
    return;
  }

  if (length < 64 * 1024) {
    gst_type_find_suggest (tf, start_prob, UTF8_CAPS);
    return;
  }

  /* check middle of stream */
  if (!utf8_type_find_have_valid_utf8_at_offset (tf, length / 2, &mid_prob))
    return;

  GST_LOG ("middle is plain text with probability of %u", mid_prob);
  gst_type_find_suggest (tf, (start_prob + mid_prob) / 2, UTF8_CAPS);
}

/*** text/uri-list ***/

static GstStaticCaps uri_caps = GST_STATIC_CAPS ("text/uri-list");

#define URI_CAPS (gst_static_caps_get(&uri_caps))
#define BUFFER_SIZE 16          /* If the string is < 16 bytes we're screwed */
#define INC_BUFFER {                                                    \
  pos++;                                                                \
  if (pos == BUFFER_SIZE) {                                             \
    pos = 0;                                                            \
    offset += BUFFER_SIZE;                                              \
    data = gst_type_find_peek (tf, offset, BUFFER_SIZE);                \
    if (data == NULL) return;                                           \
  } else {                                                              \
    data++;                                                             \
  }                                                                     \
}
static void
uri_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = gst_type_find_peek (tf, 0, BUFFER_SIZE);
  guint pos = 0;
  guint offset = 0;

  if (data) {
    /* Search for # comment lines */
    while (*data == '#') {
      /* Goto end of line */
      while (*data != '\n') {
        INC_BUFFER;
      }

      INC_BUFFER;
    }

    if (!g_ascii_isalpha (*data)) {
      /* Had a non alpha char - can't be uri-list */
      return;
    }

    INC_BUFFER;

    while (g_ascii_isalnum (*data)) {
      INC_BUFFER;
    }

    if (*data != ':') {
      /* First non alpha char is not a : */
      return;
    }

    /* Get the next 2 bytes as well */
    data = gst_type_find_peek (tf, offset + pos, 3);
    if (data == NULL)
      return;

    if (data[1] != '/' && data[2] != '/') {
      return;
    }

    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, URI_CAPS);
  }
}


/*** application/xml **********************************************************/

#define XML_BUFFER_SIZE 16
#define XML_INC_BUFFER {                                                \
  pos++;                                                                \
  if (pos == XML_BUFFER_SIZE) {                                         \
    pos = 0;                                                            \
    offset += XML_BUFFER_SIZE;                                          \
    data = gst_type_find_peek (tf, offset, XML_BUFFER_SIZE);            \
    if (data == NULL) return FALSE;                                     \
  } else {                                                              \
    data++;                                                             \
  }                                                                     \
}

static gboolean
xml_check_first_element (GstTypeFind * tf, const gchar * element, guint elen,
    gboolean strict)
{
  gboolean got_xmldec;
  guint8 *data;
  guint offset = 0;
  guint pos = 0;

  data = gst_type_find_peek (tf, 0, XML_BUFFER_SIZE);
  if (!data)
    return FALSE;

  /* look for the XMLDec
   * see XML spec 2.8, Prolog and Document Type Declaration
   * http://www.w3.org/TR/2004/REC-xml-20040204/#sec-prolog-dtd */
  got_xmldec = (memcmp (data, "<?xml", 5) == 0);

  if (strict && !got_xmldec)
    return FALSE;

  /* skip XMLDec in any case if we've got one */
  if (got_xmldec) {
    pos += 5;
    data += 5;
  }

  /* look for the first element, it has to be the requested element. Bail
   * out if it is not within the first 4kB. */
  while (data && (offset + pos) < 4096) {
    while (*data != '<' && (offset + pos) < 4096) {
      XML_INC_BUFFER;
    }

    XML_INC_BUFFER;
    if (!g_ascii_isalpha (*data)) {
      /* if not alphabetic, it's a PI or an element / attribute declaration
       * like <?xxx or <!xxx */
      XML_INC_BUFFER;
      continue;
    }

    /* the first normal element, check if it's the one asked for */
    data = gst_type_find_peek (tf, offset + pos, elen + 1);
    return (data && element && strncmp ((char *) data, element, elen) == 0);
  }

  return FALSE;
}

static GstStaticCaps generic_xml_caps = GST_STATIC_CAPS ("application/xml");

#define GENERIC_XML_CAPS (gst_static_caps_get(&generic_xml_caps))
static void
xml_type_find (GstTypeFind * tf, gpointer unused)
{
  if (xml_check_first_element (tf, "", 0, TRUE)) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MINIMUM, GENERIC_XML_CAPS);
  }
}

/*** application/sdp *********************************************************/

static GstStaticCaps sdp_caps = GST_STATIC_CAPS ("application/sdp");

#define SDP_CAPS (gst_static_caps_get(&sdp_caps))
static gboolean
sdp_check_header (GstTypeFind * tf)
{
  guint8 *data;

  data = gst_type_find_peek (tf, 0, 5);
  if (!data)
    return FALSE;

  /* sdp must start with v=0[\r]\n */
  if (memcmp (data, "v=0", 3))
    return FALSE;

  if (data[3] == '\r' && data[4] == '\n')
    return TRUE;
  if (data[3] == '\n')
    return TRUE;

  return FALSE;
}

static void
sdp_type_find (GstTypeFind * tf, gpointer unused)
{
  if (sdp_check_header (tf))
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, SDP_CAPS);
}

/*** application/smil *********************************************************/

static GstStaticCaps smil_caps = GST_STATIC_CAPS ("application/smil");

#define SMIL_CAPS (gst_static_caps_get(&smil_caps))
static void
smil_type_find (GstTypeFind * tf, gpointer unused)
{
  if (xml_check_first_element (tf, "smil", 4, FALSE)) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, SMIL_CAPS);
  }
}

/*** text/html ***/

static GstStaticCaps html_caps = GST_STATIC_CAPS ("text/html");

#define HTML_CAPS gst_static_caps_get (&html_caps)

static void
html_type_find (GstTypeFind * tf, gpointer unused)
{
  gchar *d, *data;

  data = (gchar *) gst_type_find_peek (tf, 0, 16);
  if (!data)
    return;

  if (!g_ascii_strncasecmp (data, "<!DOCTYPE HTML", 14)) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, HTML_CAPS);
  } else if (xml_check_first_element (tf, "html", 4, FALSE)) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, HTML_CAPS);
  } else if ((d = memchr (data, '<', 16))) {
    data = (gchar *) gst_type_find_peek (tf, d - data, 6);
    if (data && g_ascii_strncasecmp (data, "<html>", 6) == 0) {
      gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, HTML_CAPS);
    }
  }
}

/*** audio/midi ***/

static GstStaticCaps mid_caps = GST_STATIC_CAPS ("audio/midi");

#define MID_CAPS gst_static_caps_get(&mid_caps)
static void
mid_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = gst_type_find_peek (tf, 0, 4);

  /* http://jedi.ks.uiuc.edu/~johns/links/music/midifile.html */
  if (data && data[0] == 'M' && data[1] == 'T' && data[2] == 'h'
      && data[3] == 'd')
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, MID_CAPS);
}

/*** audio/mobile-xmf ***/

static GstStaticCaps mxmf_caps = GST_STATIC_CAPS ("audio/mobile-xmf");

#define MXMF_CAPS gst_static_caps_get(&mxmf_caps)
static void
mxmf_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = NULL;

  /* Search FileId "XMF_" 4 bytes */
  data = gst_type_find_peek (tf, 0, 4);
  if (data && data[0] == 'X' && data[1] == 'M' && data[2] == 'F'
      && data[3] == '_') {
    /* Search Format version "2.00" 4 bytes */
    data = gst_type_find_peek (tf, 4, 4);
    if (data && data[0] == '2' && data[1] == '.' && data[2] == '0'
        && data[3] == '0') {
      /* Search TypeId 2     1 byte */
      data = gst_type_find_peek (tf, 11, 1);
      if (data && data[0] == 2) {
        gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, MXMF_CAPS);
      }
    }
  }
}


/*** video/x-fli ***/

static GstStaticCaps flx_caps = GST_STATIC_CAPS ("video/x-fli");

#define FLX_CAPS gst_static_caps_get(&flx_caps)
static void
flx_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = gst_type_find_peek (tf, 0, 134);

  if (data) {
    /* check magic and the frame type of the first frame */
    if ((data[4] == 0x11 || data[4] == 0x12 ||
            data[4] == 0x30 || data[4] == 0x44) &&
        data[5] == 0xaf &&
        ((data[132] == 0x00 || data[132] == 0xfa) && data[133] == 0xf1)) {
      gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, FLX_CAPS);
    }
    return;
  }
  data = gst_type_find_peek (tf, 0, 6);
  if (data) {
    /* check magic only */
    if ((data[4] == 0x11 || data[4] == 0x12 ||
            data[4] == 0x30 || data[4] == 0x44) && data[5] == 0xaf) {
      gst_type_find_suggest (tf, GST_TYPE_FIND_LIKELY, FLX_CAPS);
    }
    return;
  }
}

/*** application/x-id3 ***/

static GstStaticCaps id3_caps = GST_STATIC_CAPS ("application/x-id3");

#define ID3_CAPS gst_static_caps_get(&id3_caps)
static void
id3v2_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = gst_type_find_peek (tf, 0, 10);

  if (data && memcmp (data, "ID3", 3) == 0 &&
      data[3] != 0xFF && data[4] != 0xFF &&
      (data[6] & 0x80) == 0 && (data[7] & 0x80) == 0 &&
      (data[8] & 0x80) == 0 && (data[9] & 0x80) == 0) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, ID3_CAPS);
  }
}

static void
id3v1_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = gst_type_find_peek (tf, -128, 3);

  if (data && memcmp (data, "TAG", 3) == 0) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, ID3_CAPS);
  }
}

/*** application/x-ape ***/

static GstStaticCaps apetag_caps = GST_STATIC_CAPS ("application/x-apetag");

#define APETAG_CAPS gst_static_caps_get(&apetag_caps)
static void
apetag_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data;

  /* APEv1/2 at start of file */
  data = gst_type_find_peek (tf, 0, 8);
  if (data && !memcmp (data, "APETAGEX", 8)) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, APETAG_CAPS);
    return;
  }

  /* APEv1/2 at end of file */
  data = gst_type_find_peek (tf, -32, 8);
  if (data && !memcmp (data, "APETAGEX", 8)) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, APETAG_CAPS);
    return;
  }
}

/*** audio/x-ttafile ***/

static GstStaticCaps tta_caps = GST_STATIC_CAPS ("audio/x-ttafile");

#define TTA_CAPS gst_static_caps_get(&tta_caps)
static void
tta_type_find (GstTypeFind * tf, gpointer unused)
{
  guint8 *data = gst_type_find_peek (tf, 0, 3);

  if (data) {
    if (memcmp (data, "TTA", 3) == 0) {
      gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, TTA_CAPS);
      return;
    }
  }
}

/*** audio/x-flac ***/
static GstStaticCaps flac_caps = GST_STATIC_CAPS ("audio/x-flac");

#define FLAC_CAPS (gst_static_caps_get(&flac_caps))

static void
flac_type_find (GstTypeFind * tf, gpointer unused)
{
  DataScanCtx c = { 0, NULL, 0 };

  if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 4)))
    return;

  /* standard flac (also old/broken flac-in-ogg with an initial 4-byte marker
   * packet and without the usual packet framing) */
  if (memcmp (c.data, "fLaC", 4) == 0) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, FLAC_CAPS);
    return;
  }

  if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 6)))
    return;

  /* flac-in-ogg, see http://flac.sourceforge.net/ogg_mapping.html */
  if (memcmp (c.data, "\177FLAC\001", 6) == 0) {
    gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, FLAC_CAPS);
    return;
  }

/* disabled because it happily typefinds /dev/urandom as audio/x-flac, and
 * because I yet have to see header-less flac in the wild */
#if 0
  /* flac without headers (subset format) */
  /* 64K should be enough */
  while (c.offset < (64 * 1024)) {
    if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 4)))
      break;

    /* look for frame header,
     * http://flac.sourceforge.net/format.html#frame_header
     */
    if (c.data[0] == 0xff && (c.data[1] >> 2) == 0x3e) {
      /* bit 15 in the header must be 0 */
      if (((c.data[1] >> 1) & 0x01) == 0x01)
        goto advance;

      /* blocksize must be != 0x00 */
      if ((c.data[2] >> 4) == 0x00)
        goto advance;

      /* samplerate must be != 0x0f */
      if ((c.data[2] & 0x0f) == 0x0f)
        goto advance;
      /* also 0 is invalid, as it means get the info from the header and we
       * don't have headers if we are here */
      if ((c.data[2] & 0x0f) == 0x00)
        goto advance;

      /* channel assignment must be < 11 */
      if ((c.data[3] >> 4) >= 11)
        goto advance;

      /* sample size must be != 0x07 and != 0x05 */
      if (((c.data[3] >> 1) & 0x07) == 0x07)
        goto advance;
      if (((c.data[3] >> 1) & 0x07) == 0x05)
        goto advance;
      /* also 0 is invalid, as it means get the info from the header and we
       * don't have headers if we are here */
      if (((c.data[3] >> 1) & 0x07) == 0x00)
        goto advance;

      /* next bit must be 0 */
      if ((c.data[3] & 0x01) == 0x01)
        goto advance;

      /* FIXME: shouldn't we include the crc check ? */

      GST_DEBUG ("Found flac without headers at %d", (gint) c.offset);
      gst_type_find_suggest (tf, GST_TYPE_FIND_POSSIBLE, FLAC_CAPS);
      return;
    }
  advance:
    data_scan_ctx_advance (tf, &c, 1);
  }
#endif
}

/*** audio/mpeg version 2, 4 ***/

static GstStaticCaps aac_caps = GST_STATIC_CAPS ("audio/mpeg, "
    "mpegversion = (int) { 2, 4 }, framed = (bool) false");
#define AAC_CAPS (gst_static_caps_get(&aac_caps))
#define AAC_AMOUNT (4096)
static void
aac_type_find (GstTypeFind * tf, gpointer unused)
{
  /* LUT to convert the AudioObjectType from the ADTS header to a string */
  DataScanCtx c = { 0, NULL, 0 };

  while (c.offset < AAC_AMOUNT) {
    guint snc, len;

    /* detect adts header or adif header.
     * The ADIF header is 4 bytes, that should be OK. The ADTS header, on
     * the other hand, is 14 bits only, so we require one valid frame with
     * again a valid syncpoint on the next one (28 bits) for certainty. We
     * require 4 kB, which is quite a lot, since frames are generally 200-400
     * bytes.
     * LOAS has 2 possible syncwords, which are 11 bits and 16 bits long.
     * The following stream syntax depends on which one is found.
     */
    if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 6)))
      break;

    snc = GST_READ_UINT16_BE (c.data);
    if (G_UNLIKELY ((snc & 0xfff6) == 0xfff0)) {
      /* ADTS header - find frame length */
      GST_DEBUG ("Found one ADTS syncpoint at offset 0x%" G_GINT64_MODIFIER
          "x, tracing next...", c.offset);
      len = ((c.data[3] & 0x03) << 11) |
          (c.data[4] << 3) | ((c.data[5] & 0xe0) >> 5);

      if (len == 0 || !data_scan_ctx_ensure_data (tf, &c, len + 2)) {
        GST_DEBUG ("Wrong sync or next frame not within reach, len=%u", len);
        goto next;
      }

      /* check if there's a second ADTS frame */
      snc = GST_READ_UINT16_BE (c.data + len);
      if ((snc & 0xfff6) == 0xfff0) {
        GstCaps *caps;
        guint mpegversion, sample_freq_idx, channel_config, profile_idx, rate;
        guint8 audio_config[2];

        mpegversion = (c.data[1] & 0x08) ? 2 : 4;
        profile_idx = c.data[2] >> 6;
        sample_freq_idx = ((c.data[2] & 0x3c) >> 2);
        channel_config = ((c.data[2] & 0x01) << 2) + (c.data[3] >> 6);

        GST_DEBUG ("Found second ADTS-%d syncpoint at offset 0x%"
            G_GINT64_MODIFIER "x, framelen %u", mpegversion, c.offset, len);

        /* 0xd and 0xe are reserved. 0xf means the sample frequency is directly
         * specified in the header, but that's not allowed for ADTS */
        if (sample_freq_idx > 0xc) {
          GST_DEBUG ("Unexpected sample frequency index %d or wrong sync",
              sample_freq_idx);
          goto next;
        }

        rate = gst_codec_utils_aac_get_sample_rate_from_index (sample_freq_idx);
        GST_LOG ("ADTS: profile=%u, rate=%u", profile_idx, rate);

        /* The ADTS frame header is slightly different from the
         * AudioSpecificConfig defined for the MPEG-4 container, so we just
         * construct enough of it for getting the level here. */
        /* ADTS counts profiles from 0 instead of 1 to save bits */
        audio_config[0] = (profile_idx + 1) << 3;
        audio_config[0] |= (sample_freq_idx >> 1) & 0x7;
        audio_config[1] = (sample_freq_idx & 0x1) << 7;
        audio_config[1] |= (channel_config & 0xf) << 3;

        caps = gst_caps_new_simple ("audio/mpeg",
            "framed", G_TYPE_BOOLEAN, FALSE,
            "mpegversion", G_TYPE_INT, mpegversion,
            "stream-format", G_TYPE_STRING, "adts", NULL);

        gst_codec_utils_aac_caps_set_level_and_profile (caps, audio_config, 2);

        /* add rate and number of channels if we can */
        if (channel_config != 0 && channel_config <= 7) {
          const guint channels_map[] = { 0, 1, 2, 3, 4, 5, 6, 8 };

          gst_caps_set_simple (caps, "channels", G_TYPE_INT,
              channels_map[channel_config], "rate", G_TYPE_INT, rate, NULL);
        }

        gst_type_find_suggest (tf, GST_TYPE_FIND_LIKELY, caps);
        gst_caps_unref (caps);
        break;
      }

      GST_DEBUG ("No next frame found... (should have been at 0x%x)", len);
    } else if (G_UNLIKELY (((snc & 0xffe0) == 0x56e0) || (snc == 0x4de1))) {
      /* LOAS frame */

      GST_DEBUG ("Found one LOAS syncword at offset 0x%" G_GINT64_MODIFIER
          "x, tracing next...", c.offset);

      /* check length of frame for each type of detectable LOAS streams */
      if (snc == 0x4de1) {
        /* EPAudioSyncStream */
        len = ((c.data[2] & 0x0f) << 9) | (c.data[3] << 1) |
            ((c.data[4] & 0x80) >> 7);
        /* add size of EP sync stream header */
        len += 7;
      } else {
        /* AudioSyncStream */
        len = ((c.data[1] & 0x1f) << 8) | c.data[2];
        /* add size of sync stream header */
        len += 3;
      }

      if (len == 0 || !data_scan_ctx_ensure_data (tf, &c, len + 2)) {
        GST_DEBUG ("Wrong sync or next frame not within reach, len=%u", len);
        goto next;
      }

      /* check if there's a second LOAS frame */
      snc = GST_READ_UINT16_BE (c.data + len);
      if (((snc & 0xffe0) == 0x56e0) || (snc == 0x4de1)) {
        GST_DEBUG ("Found second LOAS syncword at offset 0x%"
            G_GINT64_MODIFIER "x, framelen %u", c.offset, len);

        gst_type_find_suggest_simple (tf, GST_TYPE_FIND_LIKELY, "audio/mpeg",
            "framed", G_TYPE_BOOLEAN, FALSE,
            "mpegversion", G_TYPE_INT, 4,
            "stream-format", G_TYPE_STRING, "loas", NULL);
        break;
      }

      GST_DEBUG ("No next frame found... (should have been at 0x%x)", len);
    } else if (!memcmp (c.data, "ADIF", 4)) {
      /* ADIF header */
      gst_type_find_suggest_simple (tf, GST_TYPE_FIND_LIKELY, "audio/mpeg",
          "framed", G_TYPE_BOOLEAN, FALSE, "mpegversion", G_TYPE_INT, 4,
          "stream-format", G_TYPE_STRING, "adif", NULL);
      break;
    }

  next:

    data_scan_ctx_advance (tf, &c, 1);
  }
}

/*** audio/mpeg version 1 ***/

/*
 * The chance that random data is identified as a valid mp3 header is 63 / 2^18
 * (0.024%) per try. This makes the function for calculating false positives
 *   1 - (1 - ((63 / 2 ^18) ^ GST_MP3_TYPEFIND_MIN_HEADERS)) ^ buffersize)
 * This has the following probabilities of false positives:
 * datasize               MIN_HEADERS
 * (bytes)      1       2       3       4
 * 4096         62.6%    0.02%   0%      0%
 * 16384        98%      0.09%   0%      0%
 * 1 MiB       100%      5.88%   0%      0%
 * 1 GiB       100%    100%      1.44%   0%
 * 1 TiB       100%    100%    100%      0.35%
 * This means that the current choice (3 headers by most of the time 4096 byte
 * buffers is pretty safe for now.
 *
 * The max. size of each frame is 1440 bytes, which means that for N frames to
 * be detected, we need 1440 * GST_MP3_TYPEFIND_MIN_HEADERS + 3 bytes of data.
 * Assuming we step into the stream right after the frame header, this
 * means we need 1440 * (GST_MP3_TYPEFIND_MIN_HEADERS + 1) - 1 + 3 bytes
 * of data (5762) to always detect any mp3.
 */

static const guint mp3types_bitrates[2][3][16] =
    { {{0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448,},
    {0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384,},
    {0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320,}},
{{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256,},
    {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160,},
    {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160,}},
};

static const guint mp3types_freqs[3][3] = { {11025, 12000, 8000},
{22050, 24000, 16000},
{44100, 48000, 32000}
};

static inline guint
mp3_type_frame_length_from_header (guint32 header, guint * put_layer,
    guint * put_channels, guint * put_bitrate, guint * put_samplerate,
    gboolean * may_be_free_format, gint possible_free_framelen)
{
  guint bitrate, layer, length, mode, samplerate, version, channels;

  if ((header & 0xffe00000) != 0xffe00000)
    return 0;

  /* we don't need extension, copyright, original or
   * emphasis for the frame length */
  header >>= 6;

  /* mode */
  mode = header & 0x3;
  header >>= 3;

  /* padding */
  length = header & 0x1;
  header >>= 1;

  /* sampling frequency */
  samplerate = header & 0x3;
  if (samplerate == 3)
    return 0;
  header >>= 2;

  /* bitrate index */
  bitrate = header & 0xF;
  if (bitrate == 0 && possible_free_framelen == -1) {
    GST_LOG ("Possibly a free format mp3 - signalling");
    *may_be_free_format = TRUE;
  }
  if (bitrate == 15 || (bitrate == 0 && possible_free_framelen == -1))
    return 0;

  /* ignore error correction, too */
  header >>= 5;

  /* layer */
  layer = 4 - (header & 0x3);
  if (layer == 4)
    return 0;
  header >>= 2;

  /* version 0=MPEG2.5; 2=MPEG2; 3=MPEG1 */
  version = header & 0x3;
  if (version == 1)
    return 0;

  /* lookup */
  channels = (mode == 3) ? 1 : 2;
  samplerate = mp3types_freqs[version > 0 ? version - 1 : 0][samplerate];
  if (bitrate == 0) {
    if (layer == 1) {
      length *= 4;
      length += possible_free_framelen;
      bitrate = length * samplerate / 48000;
    } else {
      length += possible_free_framelen;
      bitrate = length * samplerate /
          ((layer == 3 && version != 3) ? 72000 : 144000);
    }
  } else {
    /* calculating */
    bitrate = mp3types_bitrates[version == 3 ? 0 : 1][layer - 1][bitrate];
    if (layer == 1) {
      length = ((12000 * bitrate / samplerate) + length) * 4;
    } else {
      length += ((layer == 3
              && version != 3) ? 72000 : 144000) * bitrate / samplerate;
    }
  }

  GST_LOG ("mp3typefind: calculated mp3 frame length of %u bytes", length);
  GST_LOG
      ("mp3typefind: samplerate = %u - bitrate = %u - layer = %u - version = %u"
      " - channels = %u", samplerate, bitrate, layer, version, channels);

  if (put_layer)
    *put_layer = layer;
  if (put_channels)
    *put_channels = channels;
  if (put_bitrate)
    *put_bitrate = bitrate;
  if (put_samplerate)
    *put_samplerate = samplerate;

  return length;
}


static GstStaticCaps mp3_caps = GST_STATIC_CAPS ("audio/mpeg, "
    "mpegversion = (int) 1, layer = (int) [ 1, 3 ]");
#define MP3_CAPS (gst_static_caps_get(&mp3_caps))
/*
 * random values for typefinding
 * if no more data is available, we will return a probability of
 * (found_headers/TRY_HEADERS) * (MAXIMUM * (TRY_SYNC - bytes_skipped)
 *        / TRY_SYNC)
 * if found_headers >= MIN_HEADERS
 */
#define GST_MP3_TYPEFIND_MIN_HEADERS (2)
#define GST_MP3_TYPEFIND_TRY_HEADERS (5)
#define GST_MP3_TYPEFIND_TRY_SYNC (GST_TYPE_FIND_MAXIMUM * 100) /* 10kB */
#define GST_MP3_TYPEFIND_SYNC_SIZE (2048)
#define GST_MP3_WRONG_HEADER (10)

static void
mp3_type_find_at_offset (GstTypeFind * tf, guint64 start_off,
    guint * found_layer, GstTypeFindProbability * found_prob)
{
  guint8 *data = NULL;
  guint8 *data_end = NULL;
  guint size;
  guint64 skipped;
  gint last_free_offset = -1;
  gint last_free_framelen = -1;
  gboolean headerstart = TRUE;

  *found_layer = 0;
  *found_prob = 0;

  size = 0;
  skipped = 0;
  while (skipped < GST_MP3_TYPEFIND_TRY_SYNC) {
    if (size <= 0) {
      size = GST_MP3_TYPEFIND_SYNC_SIZE * 2;
      do {
        size /= 2;
        data = gst_type_find_peek (tf, skipped + start_off, size);
      } while (size > 10 && !data);
      if (!data)
        break;
      data_end = data + size;
    }
    if (*data == 0xFF) {
      guint8 *head_data = NULL;
      guint layer = 0, bitrate, samplerate, channels;
      guint found = 0;          /* number of valid headers found */
      guint64 offset = skipped;

      while (found < GST_MP3_TYPEFIND_TRY_HEADERS) {
        guint32 head;
        guint length;
        guint prev_layer = 0, prev_bitrate = 0;
        guint prev_channels = 0, prev_samplerate = 0;
        gboolean free = FALSE;

        if ((gint64) (offset - skipped + 4) >= 0 &&
            data + offset - skipped + 4 < data_end) {
          head_data = data + offset - skipped;
        } else {
          head_data = gst_type_find_peek (tf, offset + start_off, 4);
        }
        if (!head_data)
          break;
        head = GST_READ_UINT32_BE (head_data);
        if (!(length = mp3_type_frame_length_from_header (head, &layer,
                    &channels, &bitrate, &samplerate, &free,