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/*
This file is part of libextractor.
Copyright (C) 2004, 2009, 2012 Vidyut Samanta and Christian Grothoff
libextractor 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 3, or (at your
option) any later version.
libextractor 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 libextractor; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
This code was based on bitcollider 0.6.0
(PD) 2004 The Bitzi Corporation
http://bitzi.com/
(PD) 2001 The Bitzi Corporation
Please see file COPYING or http://bitzi.com/publicdomain
for more info.
*/
/**
* @file plugins/wav_extractor.c
* @brief plugin to support WAV files
* @author Christian Grothoff
*/
#include "platform.h"
#include "extractor.h"
#if BIG_ENDIAN_HOST
static uint16_t
little_endian_to_host16 (uint16_t in)
{
unsigned char *ptr = (unsigned char *) ∈
return ((ptr[1] & 0xFF) << 8) | (ptr[0] & 0xFF);
}
static uint32_t
little_endian_to_host32 (uint32_t in)
{
unsigned char *ptr = (unsigned char *) ∈
return ((ptr[3] & 0xFF) << 24) | ((ptr[2] & 0xFF) << 16) |
((ptr[1] & 0xFF) << 8) | (ptr[0] & 0xFF);
}
#endif
/**
* Extract information from WAV files.
*
* @param ec extraction context
*
* @detail
* A WAV header looks as follows:
*
* Offset Value meaning
* 16 4 bytes 0x00000010 // Length of the fmt data (16 bytes)
* 20 2 bytes 0x0001 // Format tag: 1 = PCM
* 22 2 bytes <channels> // Channels: 1 = mono, 2 = stereo
* 24 4 bytes <sample rate> // Samples per second: e.g., 44100
*/
void
EXTRACTOR_wav_extract_method (struct EXTRACTOR_ExtractContext *ec)
{
void *data;
const unsigned char *buf;
uint16_t channels;
uint16_t sample_size;
uint32_t sample_rate;
uint32_t data_len;
uint32_t samples;
char scratch[256];
if (44 >
ec->read (ec->cls, &data, 44))
return;
buf = data;
if ((buf[0] != 'R' || buf[1] != 'I' ||
buf[2] != 'F' || buf[3] != 'F' ||
buf[8] != 'W' || buf[9] != 'A' ||
buf[10] != 'V' || buf[11] != 'E' ||
buf[12] != 'f' || buf[13] != 'm' || buf[14] != 't' || buf[15] != ' '))
return; /* not a WAV file */
channels = *((uint16_t *) &buf[22]);
sample_rate = *((uint32_t *) &buf[24]);
sample_size = *((uint16_t *) &buf[34]);
data_len = *((uint32_t *) &buf[40]);
#if BIG_ENDIAN_HOST
channels = little_endian_to_host16 (channels);
sample_size = little_endian_to_host16 (sample_size);
sample_rate = little_endian_to_host32 (sample_rate);
data_len = little_endian_to_host32 (data_len);
#endif
if ( (8 != sample_size) &&
(16 != sample_size) )
return; /* invalid sample size found in wav file */
if (0 == channels)
return; /* invalid channels value -- avoid division by 0! */
if (0 == sample_rate)
return; /* invalid sample_rate */
samples = data_len / (channels * (sample_size >> 3));
snprintf (scratch,
sizeof (scratch),
"%u ms, %d Hz, %s",
(samples < sample_rate)
? (samples * 1000 / sample_rate)
: (samples / sample_rate) * 1000,
sample_rate, (1 == channels) ? _("mono") : _("stereo"));
if (0 != ec->proc (ec->cls,
"wav",
EXTRACTOR_METATYPE_RESOURCE_TYPE,
EXTRACTOR_METAFORMAT_UTF8,
"text/plain",
scratch,
strlen (scratch) + 1))
return;
if (0 != ec->proc (ec->cls,
"wav",
EXTRACTOR_METATYPE_MIMETYPE,
EXTRACTOR_METAFORMAT_UTF8,
"text/plain",
"audio/x-wav",
strlen ("audio/x-wav") +1 ))
return;
}
/* end of wav_extractor.c */
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