/*****************************************************************************
* adpcm.c : adpcm variant audio decoder
*****************************************************************************
- * Copyright (C) 2001, 2002 VideoLAN
- * $Id: adpcm.c,v 1.15 2003/11/05 01:47:40 fenrir Exp $
+ * Copyright (C) 2001, 2002 the VideoLAN team
+ * $Id$
*
* Authors: Laurent Aimar <fenrir@via.ecp.fr>
+ * Rémi Denis-Courmont <rem # videolan.org>
*
* 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
*
* 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, USA.
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
*****************************************************************************/
/*****************************************************************************
*
* Documentation: http://www.pcisys.net/~melanson/codecs/adpcm.txt
*****************************************************************************/
-#include <stdlib.h> /* malloc(), free() */
-
#include <vlc/vlc.h>
-#include <vlc/aout.h>
-#include <vlc/decoder.h>
-#include <vlc/input.h>
-
-#include "codecs.h"
+#include <vlc_aout.h>
+#include <vlc_codec.h>
/*****************************************************************************
* Module descriptor
*****************************************************************************/
-static int Open ( vlc_object_t * );
+static int OpenDecoder( vlc_object_t * );
+static void CloseDecoder( vlc_object_t * );
+
+static aout_buffer_t *DecodeBlock( decoder_t *, block_t ** );
vlc_module_begin();
set_description( _("ADPCM audio decoder") );
set_capability( "decoder", 50 );
- set_callbacks( Open, NULL );
+ set_category( CAT_INPUT );
+ set_subcategory( SUBCAT_INPUT_ACODEC );
+ set_callbacks( OpenDecoder, CloseDecoder );
vlc_module_end();
-
/*****************************************************************************
* Local prototypes
*****************************************************************************/
ADPCM_IMA_WAV,
ADPCM_MS,
ADPCM_DK3,
- ADPCM_DK4
+ ADPCM_DK4,
+ ADPCM_EA
};
struct decoder_sys_t
{
- WAVEFORMATEX *p_wf;
enum adpcm_codec_e codec;
int i_block;
int i_samplesperblock;
- /* audio output */
- aout_instance_t * p_aout; /* opaque */
- aout_input_t * p_aout_input; /* opaque */
- audio_sample_format_t output_format;
-
- audio_date_t date;
+ audio_date_t end_date;
};
-static int Init ( decoder_t * );
-static int Decode( decoder_t *, block_t * );
-static int End ( decoder_t * );
-
-
-
-static void DecodeAdpcmMs ( decoder_sys_t *, int16_t *, uint8_t * );
-static void DecodeAdpcmImaWav ( decoder_sys_t *, int16_t *, uint8_t * );
-static void DecodeAdpcmImaQT ( decoder_sys_t *, int16_t *, uint8_t * );
-static void DecodeAdpcmDk4 ( decoder_sys_t *, int16_t *, uint8_t * );
-static void DecodeAdpcmDk3 ( decoder_sys_t *, int16_t *, uint8_t * );
+static void DecodeAdpcmMs ( decoder_t *, int16_t *, uint8_t * );
+static void DecodeAdpcmImaWav( decoder_t *, int16_t *, uint8_t * );
+static void DecodeAdpcmImaQT ( decoder_t *, int16_t *, uint8_t * );
+static void DecodeAdpcmDk4 ( decoder_t *, int16_t *, uint8_t * );
+static void DecodeAdpcmDk3 ( decoder_t *, int16_t *, uint8_t * );
+static void DecodeAdpcmEA ( decoder_t *, int16_t *, uint8_t * );
static int pi_channels_maps[6] =
{
0, -256, 0, 64, 0, -208, -232
};
-
/*****************************************************************************
* OpenDecoder: probe the decoder and return score
- *****************************************************************************
- * Tries to launch a decoder and return score so that the interface is able
- * to choose.
*****************************************************************************/
-static int Open( vlc_object_t *p_this )
+static int OpenDecoder( vlc_object_t *p_this )
{
decoder_t *p_dec = (decoder_t*)p_this;
+ decoder_sys_t *p_sys;
- switch( p_dec->p_fifo->i_fourcc )
+ switch( p_dec->fmt_in.i_codec )
{
case VLC_FOURCC('i','m','a', '4'): /* IMA ADPCM */
case VLC_FOURCC('m','s',0x00,0x02): /* MS ADPCM */
case VLC_FOURCC('m','s',0x00,0x11): /* IMA ADPCM */
case VLC_FOURCC('m','s',0x00,0x61): /* Duck DK4 ADPCM */
case VLC_FOURCC('m','s',0x00,0x62): /* Duck DK3 ADPCM */
-
- p_dec->pf_init = Init;
- p_dec->pf_decode = Decode;
- p_dec->pf_end = End;
-
- p_dec->p_sys = malloc( sizeof( decoder_sys_t ) );
- return VLC_SUCCESS;
-
+ case VLC_FOURCC('X','A','J', 0): /* EA ADPCM */
+ break;
default:
return VLC_EGENERIC;
}
-}
-/*****************************************************************************
- * Init:
- *****************************************************************************/
-static int Init ( decoder_t *p_dec )
-{
- decoder_sys_t *p_sys = p_dec->p_sys;
-
- WAVEFORMATEX *p_wf;
- if( ( p_wf = (WAVEFORMATEX*)p_dec->p_fifo->p_waveformatex ) == NULL )
+ if( p_dec->fmt_in.audio.i_channels <= 0 ||
+ p_dec->fmt_in.audio.i_channels > 5 )
{
- msg_Err( p_dec, "unknown raw format" );
+ msg_Err( p_dec, "invalid number of channel (not between 1 and 5): %i",
+ p_dec->fmt_in.audio.i_channels );
return VLC_EGENERIC;
}
- if( p_wf->nChannels < 1 || p_wf->nChannels > 2 )
+ if( p_dec->fmt_in.audio.i_rate <= 0 )
{
- msg_Err( p_dec, "bad channels count(1-2)" );
+ msg_Err( p_dec, "bad samplerate" );
return VLC_EGENERIC;
}
- if( p_wf->nSamplesPerSec <= 0 )
+
+ /* Allocate the memory needed to store the decoder's structure */
+ if( ( p_dec->p_sys = p_sys =
+ (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
{
- msg_Err( p_dec, "bad samplerate" );
- return VLC_EGENERIC;
+ msg_Err( p_dec, "out of memory" );
+ return VLC_ENOMEM;
}
- p_sys->p_wf = p_wf;
- switch( p_dec->p_fifo->i_fourcc )
+ switch( p_dec->fmt_in.i_codec )
{
case VLC_FOURCC('i','m','a', '4'): /* IMA ADPCM */
p_sys->codec = ADPCM_IMA_QT;
case VLC_FOURCC('m','s',0x00,0x62): /* Duck DK3 ADPCM */
p_sys->codec = ADPCM_DK3;
break;
+ case VLC_FOURCC('X','A','J', 0): /* EA ADPCM */
+ p_sys->codec = ADPCM_EA;
+ p_dec->fmt_in.p_extra = calloc( 2 * p_dec->fmt_in.audio.i_channels,
+ sizeof( int16_t ) );
+ if( p_dec->fmt_in.p_extra == NULL )
+ {
+ free( p_sys );
+ return VLC_ENOMEM;
+ }
+ break;
}
- if( ( p_sys->i_block = p_wf->nBlockAlign ) <= 0 )
+ if( p_dec->fmt_in.audio.i_blockalign <= 0 )
{
- p_sys->i_block = p_sys->codec==ADPCM_IMA_QT ? 34*p_wf->nChannels:1024;
- msg_Warn( p_dec, "block size undefined, -> using %d", p_sys->i_block );
+ p_sys->i_block = (p_sys->codec == ADPCM_IMA_QT) ?
+ 34 * p_dec->fmt_in.audio.i_channels : 1024;
+ msg_Warn( p_dec, "block size undefined, using %d", p_sys->i_block );
+ }
+ else
+ {
+ p_sys->i_block = p_dec->fmt_in.audio.i_blockalign;
}
/* calculate samples per block */
switch( p_sys->codec )
{
- case ADPCM_IMA_QT:
- p_sys->i_samplesperblock = 64;
- break;
- case ADPCM_IMA_WAV:
- p_sys->i_samplesperblock =
- 2 * ( p_sys->i_block - 4 * p_wf->nChannels )/ p_wf->nChannels;
- break;
- case ADPCM_MS:
- p_sys->i_samplesperblock =
- 2 * (p_sys->i_block - 7 * p_wf->nChannels)/p_wf->nChannels + 2;
- break;
- case ADPCM_DK4:
- p_sys->i_samplesperblock =
- 2 * (p_sys->i_block - 4 * p_wf->nChannels)/p_wf->nChannels + 1;
- break;
- case ADPCM_DK3:
- p_wf->nChannels = 2;
- p_sys->i_samplesperblock = ( 4 * ( p_sys->i_block - 16 ) + 2 )/ 3;
- break;
+ case ADPCM_IMA_QT:
+ p_sys->i_samplesperblock = 64;
+ break;
+ case ADPCM_IMA_WAV:
+ p_sys->i_samplesperblock =
+ 2 * ( p_sys->i_block - 4 * p_dec->fmt_in.audio.i_channels ) /
+ p_dec->fmt_in.audio.i_channels;
+ break;
+ case ADPCM_MS:
+ p_sys->i_samplesperblock =
+ 2 * (p_sys->i_block - 7 * p_dec->fmt_in.audio.i_channels) /
+ p_dec->fmt_in.audio.i_channels + 2;
+ break;
+ case ADPCM_DK4:
+ p_sys->i_samplesperblock =
+ 2 * (p_sys->i_block - 4 * p_dec->fmt_in.audio.i_channels) /
+ p_dec->fmt_in.audio.i_channels + 1;
+ break;
+ case ADPCM_DK3:
+ p_dec->fmt_in.audio.i_channels = 2;
+ p_sys->i_samplesperblock = ( 4 * ( p_sys->i_block - 16 ) + 2 )/ 3;
+ break;
+ case ADPCM_EA:
+ p_sys->i_samplesperblock =
+ 2 * (p_sys->i_block - p_dec->fmt_in.audio.i_channels) /
+ p_dec->fmt_in.audio.i_channels;
}
- msg_Dbg( p_dec,
- "format: samplerate:%dHz channels:%d bits/sample:%d blockalign:%d samplesperblock %d",
- p_wf->nSamplesPerSec, p_wf->nChannels,
- p_wf->wBitsPerSample, p_wf->nBlockAlign,
+
+ msg_Dbg( p_dec, "format: samplerate:%d Hz channels:%d bits/sample:%d "
+ "blockalign:%d samplesperblock:%d",
+ p_dec->fmt_in.audio.i_rate, p_dec->fmt_in.audio.i_channels,
+ p_dec->fmt_in.audio.i_bitspersample, p_sys->i_block,
p_sys->i_samplesperblock );
- p_sys->output_format.i_format = AOUT_FMT_S16_NE;
- p_sys->output_format.i_rate = p_wf->nSamplesPerSec;
- p_sys->output_format.i_physical_channels =
- p_sys->output_format.i_original_channels =
- pi_channels_maps[p_wf->nChannels];
+ p_dec->fmt_out.i_codec = AOUT_FMT_S16_NE;
+ p_dec->fmt_out.audio.i_rate = p_dec->fmt_in.audio.i_rate;
+ p_dec->fmt_out.audio.i_channels = p_dec->fmt_in.audio.i_channels;
+ p_dec->fmt_out.audio.i_physical_channels =
+ p_dec->fmt_out.audio.i_original_channels =
+ pi_channels_maps[p_dec->fmt_in.audio.i_channels];
- p_sys->p_aout = NULL;
- p_sys->p_aout_input = aout_DecNew( p_dec,
- &p_sys->p_aout, &p_sys->output_format);
- if( p_sys->p_aout_input == NULL )
- {
- msg_Err( p_dec, "cannot create aout" );
- return VLC_EGENERIC;
- }
+ aout_DateInit( &p_sys->end_date, p_dec->fmt_out.audio.i_rate );
+ aout_DateSet( &p_sys->end_date, 0 );
- aout_DateInit( &p_sys->date, p_sys->output_format.i_rate );
- aout_DateSet( &p_sys->date, 0 );
+ p_dec->pf_decode_audio = DecodeBlock;
return VLC_SUCCESS;
}
/*****************************************************************************
- * Decode:
+ * DecodeBlock:
*****************************************************************************/
-static int Decode( decoder_t *p_dec, block_t *p_block )
+static aout_buffer_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
{
decoder_sys_t *p_sys = p_dec->p_sys;
- mtime_t i_pts = p_block->i_pts;
- uint8_t *p_data = p_block->p_buffer;
- int i_data = p_block->i_buffer;
+ block_t *p_block;
+
+ if( !pp_block || !*pp_block ) return NULL;
- while( i_data >= p_sys->i_block )
+ p_block = *pp_block;
+
+ if( p_block->i_pts != 0 &&
+ p_block->i_pts != aout_DateGet( &p_sys->end_date ) )
+ {
+ aout_DateSet( &p_sys->end_date, p_block->i_pts );
+ }
+ else if( !aout_DateGet( &p_sys->end_date ) )
{
- aout_buffer_t *out;
+ /* We've just started the stream, wait for the first PTS. */
+ block_Release( p_block );
+ return NULL;
+ }
- if( i_pts != 0 && i_pts != aout_DateGet( &p_sys->date ) )
- {
- aout_DateSet( &p_sys->date, i_pts );
- }
- else if( !aout_DateGet( &p_sys->date ) )
- {
- block_Release( p_block );
- return VLC_SUCCESS;
- }
- i_pts = 0;
+ /* Don't re-use the same pts twice */
+ p_block->i_pts = 0;
- out = aout_DecNewBuffer( p_sys->p_aout,
- p_sys->p_aout_input,
- p_sys->i_samplesperblock );
- if( out == NULL )
+ if( p_block->i_buffer >= p_sys->i_block )
+ {
+ aout_buffer_t *p_out;
+
+ p_out = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_samplesperblock );
+ if( p_out == NULL )
{
- msg_Err( p_dec, "cannot get aout buffer" );
block_Release( p_block );
- return VLC_EGENERIC;
+ return NULL;
}
- out->start_date = aout_DateGet( &p_sys->date );
- out->end_date = aout_DateIncrement( &p_sys->date,
- p_sys->i_samplesperblock );
+
+ p_out->start_date = aout_DateGet( &p_sys->end_date );
+ p_out->end_date =
+ aout_DateIncrement( &p_sys->end_date, p_sys->i_samplesperblock );
switch( p_sys->codec )
{
- case ADPCM_IMA_QT:
- DecodeAdpcmImaQT( p_sys, (int16_t*)out->p_buffer, p_data );
- break;
- case ADPCM_IMA_WAV:
- DecodeAdpcmImaWav( p_sys, (int16_t*)out->p_buffer, p_data );
- break;
- case ADPCM_MS:
- DecodeAdpcmMs( p_sys, (int16_t*)out->p_buffer, p_data );
- break;
- case ADPCM_DK4:
- DecodeAdpcmDk4( p_sys, (int16_t*)out->p_buffer, p_data );
- break;
- case ADPCM_DK3:
- DecodeAdpcmDk3( p_sys, (int16_t*)out->p_buffer, p_data );
- break;
- default:
- break;
+ case ADPCM_IMA_QT:
+ DecodeAdpcmImaQT( p_dec, (int16_t*)p_out->p_buffer,
+ p_block->p_buffer );
+ break;
+ case ADPCM_IMA_WAV:
+ DecodeAdpcmImaWav( p_dec, (int16_t*)p_out->p_buffer,
+ p_block->p_buffer );
+ break;
+ case ADPCM_MS:
+ DecodeAdpcmMs( p_dec, (int16_t*)p_out->p_buffer,
+ p_block->p_buffer );
+ break;
+ case ADPCM_DK4:
+ DecodeAdpcmDk4( p_dec, (int16_t*)p_out->p_buffer,
+ p_block->p_buffer );
+ break;
+ case ADPCM_DK3:
+ DecodeAdpcmDk3( p_dec, (int16_t*)p_out->p_buffer,
+ p_block->p_buffer );
+ break;
+ case ADPCM_EA:
+ DecodeAdpcmEA( p_dec, (int16_t*)p_out->p_buffer,
+ p_block->p_buffer );
+ default:
+ break;
}
- aout_DecPlay( p_sys->p_aout, p_sys->p_aout_input, out );
- p_data += p_sys->i_block;
- i_data -= p_sys->i_block;
+ p_block->p_buffer += p_sys->i_block;
+ p_block->i_buffer -= p_sys->i_block;
+ return p_out;
}
block_Release( p_block );
- return VLC_SUCCESS;
+ return NULL;
}
/*****************************************************************************
- * End:
+ * CloseDecoder:
*****************************************************************************/
-static int End ( decoder_t *p_dec )
+static void CloseDecoder( vlc_object_t *p_this )
{
+ decoder_t *p_dec = (decoder_t *)p_this;
decoder_sys_t *p_sys = p_dec->p_sys;
- if( p_sys->p_aout_input )
- {
- aout_DecDelete( p_sys->p_aout, p_sys->p_aout_input );
- }
+ if( p_sys->codec == ADPCM_EA )
+ free( p_dec->fmt_in.p_extra );
free( p_sys );
-
- return VLC_SUCCESS;
}
+/*****************************************************************************
+ * Local functions
+ *****************************************************************************/
#define CLAMP( v, min, max ) \
if( (v) < (min) ) (v) = (min); \
if( (v) > (max) ) (v) = (max)
return( i_predictor );
}
-static void DecodeAdpcmMs( decoder_sys_t *p_sys, int16_t *p_sample, uint8_t *p_buffer )
+static void DecodeAdpcmMs( decoder_t *p_dec, int16_t *p_sample,
+ uint8_t *p_buffer )
{
+ decoder_sys_t *p_sys = p_dec->p_sys;
adpcm_ms_channel_t channel[2];
int i_nibbles;
int b_stereo;
int i_block_predictor;
- b_stereo = p_sys->p_wf->nChannels == 2 ? 1 : 0;
+ b_stereo = p_dec->fmt_in.audio.i_channels == 2 ? 1 : 0;
GetByte( i_block_predictor );
CLAMP( i_block_predictor, 0, 6 );
*p_sample++ = channel[0].i_sample1;
}
- for( i_nibbles = 2 *( p_sys->i_block - 7 * p_sys->p_wf->nChannels );
- i_nibbles > 0; i_nibbles -= 2,p_buffer++ )
+ for( i_nibbles = 2 * (p_sys->i_block - 7 * p_dec->fmt_in.audio.i_channels);
+ i_nibbles > 0; i_nibbles -= 2, p_buffer++ )
{
*p_sample++ = AdpcmMsExpandNibble( &channel[0], (*p_buffer) >> 4);
*p_sample++ = AdpcmMsExpandNibble( &channel[b_stereo ? 1 : 0],
return( p_channel->i_predictor );
}
-static void DecodeAdpcmImaWav( decoder_sys_t *p_sys, int16_t *p_sample, uint8_t *p_buffer )
+static void DecodeAdpcmImaWav( decoder_t *p_dec, int16_t *p_sample,
+ uint8_t *p_buffer )
{
+ decoder_sys_t *p_sys = p_dec->p_sys;
adpcm_ima_wav_channel_t channel[2];
int i_nibbles;
int b_stereo;
- b_stereo = p_sys->p_wf->nChannels == 2 ? 1 : 0;
+ b_stereo = p_dec->fmt_in.audio.i_channels == 2 ? 1 : 0;
GetWord( channel[0].i_predictor );
GetByte( channel[0].i_step_index );
/*
* Ima4 in QT file
*/
-static void DecodeAdpcmImaQT( decoder_sys_t *p_sys, int16_t *p_sample, uint8_t *p_buffer )
+static void DecodeAdpcmImaQT( decoder_t *p_dec, int16_t *p_sample,
+ uint8_t *p_buffer )
{
adpcm_ima_wav_channel_t channel[2];
int i_nibbles;
int i_ch;
int i_step;
- i_step = p_sys->p_wf->nChannels;
+ i_step = p_dec->fmt_in.audio.i_channels;
- for( i_ch = 0; i_ch < p_sys->p_wf->nChannels; i_ch++ )
+ for( i_ch = 0; i_ch < p_dec->fmt_in.audio.i_channels; i_ch++ )
{
/* load preambule */
channel[i_ch].i_predictor = (int16_t)((( ( p_buffer[0] << 1 )|( p_buffer[1] >> 7 ) ))<<7);
/*
* Dk4
*/
-
-static void DecodeAdpcmDk4( decoder_sys_t *p_sys, int16_t *p_sample, uint8_t *p_buffer )
+static void DecodeAdpcmDk4( decoder_t *p_dec, int16_t *p_sample,
+ uint8_t *p_buffer )
{
+ decoder_sys_t *p_sys = p_dec->p_sys;
adpcm_ima_wav_channel_t channel[2];
int i_nibbles;
int b_stereo;
- b_stereo = p_sys->p_wf->nChannels == 2 ? 1 : 0;
+ b_stereo = p_dec->fmt_in.audio.i_channels == 2 ? 1 : 0;
GetWord( channel[0].i_predictor );
GetByte( channel[0].i_step_index );
/*
* Dk3
*/
-static void DecodeAdpcmDk3( decoder_sys_t *p_sys, int16_t *p_sample, uint8_t *p_buffer )
+static void DecodeAdpcmDk3( decoder_t *p_dec, int16_t *p_sample,
+ uint8_t *p_buffer )
{
+ decoder_sys_t *p_sys = p_dec->p_sys;
uint8_t *p_end = &p_buffer[p_sys->i_block];
adpcm_ima_wav_channel_t sum;
adpcm_ima_wav_channel_t diff;
}
}
+
+/*
+ * EA ADPCM
+ */
+#define MAX_CHAN 5
+static void DecodeAdpcmEA( decoder_t *p_dec, int16_t *p_sample,
+ uint8_t *p_buffer )
+{
+ static const uint32_t EATable[]=
+ {
+ 0x00000000, 0x000000F0, 0x000001CC, 0x00000188,
+ 0x00000000, 0x00000000, 0xFFFFFF30, 0xFFFFFF24,
+ 0x00000000, 0x00000001, 0x00000003, 0x00000004,
+ 0x00000007, 0x00000008, 0x0000000A, 0x0000000B,
+ 0x00000000, 0xFFFFFFFF, 0xFFFFFFFD, 0xFFFFFFFC
+ };
+ decoder_sys_t *p_sys = p_dec->p_sys;
+ uint8_t *p_end;
+ unsigned i_channels, c;
+ int16_t *prev, *cur;
+ int32_t c1[MAX_CHAN], c2[MAX_CHAN];
+ int8_t d[MAX_CHAN];
+
+ i_channels = p_dec->fmt_in.audio.i_channels;
+ p_end = &p_buffer[p_sys->i_block];
+
+ prev = (int16_t *)p_dec->fmt_in.p_extra;
+ cur = prev + i_channels;
+
+ for (c = 0; c < i_channels; c++)
+ {
+ uint8_t input;
+
+ input = p_buffer[c];
+ c1[c] = EATable[input >> 4];
+ c2[c] = EATable[(input >> 4) + 4];
+ d[c] = (input & 0xf) + 8;
+ }
+
+ for( p_buffer += i_channels; p_buffer < p_end ; p_buffer += i_channels)
+ {
+ for (c = 0; c < i_channels; c++)
+ {
+ int32_t spl;
+
+ spl = (p_buffer[c] >> 4) & 0xf;
+ spl = (spl << 0x1c) >> d[c];
+ spl = (spl + cur[c] * c1[c] + prev[c] * c2[c] + 0x80) >> 8;
+ CLAMP( spl, -32768, 32767 );
+ prev[c] = cur[c];
+ cur[c] = spl;
+
+ *(p_sample++) = spl;
+ }
+
+ for (c = 0; c < i_channels; c++)
+ {
+ int32_t spl;
+
+ spl = p_buffer[c] & 0xf;
+ spl = (spl << 0x1c) >> d[c];
+ spl = (spl + cur[c] * c1[c] + prev[c] * c2[c] + 0x80) >> 8;
+ CLAMP( spl, -32768, 32767 );
+ prev[c] = cur[c];
+ cur[c] = spl;
+
+ *(p_sample++) = spl;
+ }
+ }
+}
projects / vlc / blobdiff