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/*
* Support for ATSC Digital Audio Compression Standard, Revision B
* (AC3) audio streams.
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is the MPEG TS, PS and ES tools.
*
* The Initial Developer of the Original Code is Amino Communications Ltd.
* Portions created by the Initial Developer are Copyright (C) 2008
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Kynesim, Cambridge UK
*
* ***** END LICENSE BLOCK *****
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include "compat.h"
#include "printing_fns.h"
#include "misc_fns.h"
#include "ac3_fns.h"
static const unsigned int // Table 5.18, frame sizes
l_frmsizecod[19][3] = {
{ 64, 69, 96 },
{ 80, 87, 120 },
{ 96, 104, 144 },
{ 112, 121, 168 },
{ 128, 139, 192 },
{ 160, 174, 240 },
{ 192, 208, 288 },
{ 224, 243, 336 },
{ 256, 278, 384 },
{ 320, 348, 480 },
{ 384, 417, 576 },
{ 448, 487, 672 },
{ 512, 557, 768 },
{ 640, 696, 960 },
{ 768, 835, 1152 },
{ 896, 975, 1344 },
{ 1024, 1114, 1536 },
{ 1152, 1253, 1728 },
{ 1280, 1393, 1920 }
};
/*
* Read the next AC3 frame.
*
* Assumes that the input stream is synchronised - i.e., it does not
* try to cope if the next two bytes are not '0000 1011 0111 0111'
*
* - `file` is the file descriptor of the AC3 file to read from
* - `frame` is the AC3 frame that is read
*
* Returns 0 if all goes well, EOF if end-of-file is read, and 1 if something
* goes wrong.
*/
#define SYNCINFO_SIZE 5
int read_next_ac3_frame(int file,
audio_frame_p *frame)
{
int i, err;
byte sync_info[SYNCINFO_SIZE];
byte *data = NULL;
int fscod;
int frmsizecod;
int frame_length;
offset_t posn = tell_file(file);
err = read_bytes(file, SYNCINFO_SIZE, sync_info);
if (err == EOF)
return EOF;
else if (err)
{
fprint_err("### Error reading syncinfo from AC3 file\n"
" (in frame starting at " OFFSET_T_FORMAT ")\n", posn);
return 1;
}
if (sync_info[0] != 0x0b || sync_info[1] != 0x77)
{
fprint_err("### AC3 frame does not start with 0x0b77"
" syncword - lost synchronisation?\n"
" Found 0x%02x%02x instead of 0x0b77\n",
(unsigned)sync_info[0], (unsigned)sync_info[1]);
fprint_err(" (in frame starting at " OFFSET_T_FORMAT ")\n", posn);
return 1;
}
fscod = sync_info[4] >> 6;
if (fscod == 3)
{
// Bad sample rate code
fprint_err("### Bad sample rate code in AC3 syncinfo\n"
" (in frame starting at " OFFSET_T_FORMAT ")\n", posn);
return 1;
}
frmsizecod = sync_info[4] & 0x3f;
if (frmsizecod > 37)
{
fprint_err("### Bad frame size code %d in AC3 syncinfo\n",
frmsizecod);
fprint_err(" (in frame starting at " OFFSET_T_FORMAT ")\n", posn);
return 1;
}
frame_length = l_frmsizecod[frmsizecod >> 1][fscod];
if (fscod == 1)
frame_length += frmsizecod & 1;
frame_length <<= 1; // Convert from 16-bit words to bytes
data = malloc(frame_length);
if (data == NULL)
{
print_err("### Unable to extend data buffer for AC3 frame\n");
return 1;
}
for (i = 0; i < SYNCINFO_SIZE; i++)
data[i] = sync_info[i];
err = read_bytes(file, frame_length - SYNCINFO_SIZE,
&data[SYNCINFO_SIZE]);
if (err)
{
if (err == EOF)
print_err("### Unexpected EOF reading rest of AC3 frame\n");
else
print_err("### Error reading rest of AC3 frame\n");
free(data);
return 1;
}
err = build_audio_frame(frame);
if (err)
{
free(data);
return 1;
}
(*frame)->data = data;
(*frame)->data_len = frame_length;
return 0;
}
// Local Variables:
// tab-width: 8
// indent-tabs-mode: nil
// c-basic-offset: 2
// End:
// vim: set tabstop=8 shiftwidth=2 expandtab:
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