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/* $Id: declpcm.c,v 1.8 2005/11/04 14:44:01 titer Exp $
This file is part of the HandBrake source code.
Homepage: <http://handbrake.m0k.org/>.
It may be used under the terms of the GNU General Public License. */
#include "hb.h"
struct hb_work_private_s
{
hb_job_t *job;
uint32_t size; /* frame size in bytes */
uint32_t count; /* frame size in samples */
uint32_t pos; /* buffer offset for next input data */
int64_t next_pts; /* pts for next output frame */
int64_t sequence;
/* the following is frame info for the frame we're currently accumulating */
uint64_t duration; /* frame duratin (in 90KHz ticks) */
uint32_t offset; /* where in buf frame starts */
uint32_t samplerate; /* sample rate in bits/sec */
uint8_t nchannels;
uint8_t sample_size; /* bits per sample */
uint8_t frame[HB_DVD_READ_BUFFER_SIZE*2];
};
static hb_buffer_t * Decode( hb_work_object_t * w );
int declpcmInit( hb_work_object_t *, hb_job_t * );
int declpcmWork( hb_work_object_t *, hb_buffer_t **, hb_buffer_t ** );
void declpcmClose( hb_work_object_t * );
hb_work_object_t hb_declpcm =
{
WORK_DECLPCM,
"LPCM decoder",
declpcmInit,
declpcmWork,
declpcmClose
};
static const int hdr2samplerate[] = { 48000, 96000, 44100, 32000 };
static const int hdr2samplesize[] = { 16, 20, 24, 16 };
static void lpcmInfo( hb_work_object_t *w, hb_buffer_t *in )
{
hb_work_private_t * pv = w->private_data;
/*
* LPCM packets have a 7 byte header (the substream id is stripped off
* before we get here so it's numbered -1 below)::
* byte -1 Substream id
* byte 0 Number of frames that begin in this packet
* (last frame may finish in next packet)
* byte 1,2 offset to first frame that begins in this packet (not including hdr)
* byte 3:
* bits 0-4 continuity counter (increments modulo 20)
* bit 5 reserved
* bit 6 audio mute on/off
* bit 7 audio emphasis on/off
* byte 4:
* bits 0-2 #channels - 1 (e.g., stereo = 1)
* bit 3 reserved
* bits 4-5 sample rate (0=48K,1=96K,2=44.1K,3=32K)
* bits 6-7 bits per sample (0=16 bit, 1=20 bit, 2=24 bit)
* byte 5 Dynamic range control (0x80 = off)
*
* The audio is viewed as "frames" of 150 90KHz ticks each (80 samples @ 48KHz).
* The frames are laid down continuously without regard to MPEG packet
* boundaries. E.g., for 48KHz stereo, the first packet will contain 6
* frames plus the start of the 7th, the second packet will contain the
* end of the 7th, 8-13 & the start of 14, etc. The frame structure is
* important because the PTS on the packet gives the time of the first
* frame that starts in the packet *NOT* the time of the first sample
* in the packet. Also samples get split across packet boundaries
* so we can't assume that we can consume all the data in one packet
* on every call to the work routine.
*/
pv->offset = ( ( in->data[1] << 8 ) | in->data[2] ) + 2;
if ( pv->offset >= HB_DVD_READ_BUFFER_SIZE )
{
hb_log( "declpcm: illegal frame offset %d", pv->offset );
pv->offset = 2; /*XXX*/
}
pv->samplerate = hdr2samplerate[ ( in->data[4] >> 4 ) & 0x3 ];
pv->nchannels = ( in->data[4] & 7 ) + 1;
pv->sample_size = hdr2samplesize[in->data[4] >> 6];
/*
* PCM frames have a constant duration (150 90KHz ticks).
* We need to convert that to the amount of data expected. It's the
* duration divided by the sample rate (to get #samples) times the number
* of channels times the bits per sample divided by 8 to get bytes.
* (we have to compute in bits because 20 bit samples are not an integral
* number of bytes). We do all the multiplies first then the divides to
* avoid truncation errors.
*/
pv->duration = in->data[0] * 150;
pv->count = ( pv->duration * pv->nchannels * pv->samplerate ) / 90000;
pv->size = ( pv->count * pv->sample_size ) / 8;
pv->next_pts = in->start;
}
int declpcmInit( hb_work_object_t * w, hb_job_t * job )
{
hb_work_private_t * pv = calloc( 1, sizeof( hb_work_private_t ) );
w->private_data = pv;
pv->job = job;
return 0;
}
/*
* Convert DVD encapsulated LPCM to floating point PCM audio buffers.
* The amount of audio in a PCM frame is always <= the amount that will fit
* in a DVD block (2048 bytes) but the standard doesn't require that the audio
* frames line up with the DVD frames. Since audio frame boundaries are unrelated
* to DVD PES boundaries, this routine has to reconstruct then extract the audio
* frames. Because of the arbitrary alignment, it can output zero, one or two buf's.
*/
int declpcmWork( hb_work_object_t * w, hb_buffer_t ** buf_in,
hb_buffer_t ** buf_out )
{
hb_work_private_t * pv = w->private_data;
hb_buffer_t *in;
hb_buffer_t *buf = NULL;
/* need an input buffer to do anything */
if( ! buf_in || ! ( in = *buf_in ) )
{
*buf_out = buf;
return HB_WORK_OK;
}
pv->sequence = in->sequence;
/* if we have a frame to finish, add enough data from this buf to finish it */
if ( pv->size )
{
memcpy( pv->frame + pv->pos, in->data + 6, pv->size - pv->pos );
buf = Decode( w );
}
*buf_out = buf;
/* save the (rest of) data from this buf in our frame buffer */
lpcmInfo( w, in );
int off = pv->offset;
int amt = in->size - off;
pv->pos = amt;
memcpy( pv->frame, in->data + off, amt );
if ( amt >= pv->size )
{
if ( buf )
{
buf->next = Decode( w );
}
else
{
*buf_out = Decode( w );
}
pv->size = 0;
}
return HB_WORK_OK;
}
static hb_buffer_t *Decode( hb_work_object_t *w )
{
hb_work_private_t *pv = w->private_data;
hb_buffer_t *out = hb_buffer_init( pv->count * sizeof( float ) );
out->start = pv->next_pts;
pv->next_pts += pv->duration;
out->stop = pv->next_pts;
uint8_t *frm = pv->frame;
float *odat = (float *)out->data;
int count = pv->count;
switch( pv->sample_size )
{
case 16: // 2 byte, big endian, signed (the right shift sign extends)
while ( --count >= 0 )
{
*odat++ = ( (int)( frm[0] << 24 ) >> 16 ) | frm[1];
frm += 2;
}
break;
case 20:
// 20 bit big endian signed (5 bytes for 2 samples = 2.5 bytes/sample
// so we do two samples per iteration).
count /= 2;
while ( --count >= 0 )
{
*odat++ = (float)( ( (int)( frm[0] << 24 ) >> 12 ) |
( frm[1] << 4 ) | ( frm[2] >> 4 ) ) / 16.;
*odat++ = (float)( ( (int)( frm[2] << 28 ) >> 16 ) |
( frm[3] << 8 ) | frm[4] ) / 16.;
frm += 5;
}
break;
case 24:
// This format is bizarre. It's 24 bit samples but some confused
// individual apparently thought they would be easier to interpret
// as 16 bits if they were scrambled in the following way:
// Things are stored in 4 sample (12 byte) chunks. Each chunk has
// 4 samples containing the two top bytes of the actual samples in
// 16 bit big-endian order followed by the four least significant bytes
// of each sample.
count /= 4; // the loop has to work in 4 sample chunks
while ( --count >= 0 )
{
*odat++ = (float)( ( (int)( frm[0] << 24 ) >> 8 ) |
( frm[1] << 8 ) | frm[8] ) / 256.;
*odat++ = (float)( ( (int)( frm[2] << 24 ) >> 8 ) |
( frm[3] << 8 ) | frm[9] ) / 256.;
*odat++ = (float)( ( (int)( frm[4] << 24 ) >> 8 ) |
( frm[5] << 8 ) | frm[10] ) / 256.;
*odat++ = (float)( ( (int)( frm[6] << 24 ) >> 8 ) |
( frm[7] << 8 ) | frm[11] ) / 256.;
frm += 12;
}
break;
}
return out;
}
void declpcmClose( hb_work_object_t * w )
{
if ( w->private_data )
{
free( w->private_data );
w->private_data = 0;
}
}
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