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/*
* Support for ISO/IEC 14496-3:2001(E) AAC ADTS 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):
* Amino Communications Ltd, Swavesey, 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 "adts_fns.h"
#define DEBUG 0
/*
* Read the next ADTS frame.
*
* Assumes that the input stream is synchronised - i.e., it does not
* try to cope if the next three bytes are not '1111 1111 1111'.
*
* - `file` is the file descriptor of the ADTS file to read from
* - `frame` is the ADTS frame that is read
* - `flags` indicates if we are forcing the recognition of "emphasis"
* fields, etc.
*
* Returns 0 if all goes well, EOF if end-of-file is read, and 1 if something
* goes wrong.
*/
extern int read_next_adts_frame(int file,
audio_frame_p *frame,
unsigned int flags)
{
#define JUST_ENOUGH 6 // just enough to hold the bits of the headers we want
int err, ii;
int id, layer;
byte header[JUST_ENOUGH];
byte *data = NULL;
int frame_length;
int has_emphasis = 0;
offset_t posn = tell_file(file);
#if DEBUG
fprint_msg("Offset: " OFFSET_T_FORMAT "\n",posn);
#endif
err = read_bytes(file,JUST_ENOUGH,header);
if (err == EOF)
return EOF;
else if (err)
{
fprint_err("### Error reading header bytes of ADTS frame\n"
" (in frame starting at " OFFSET_T_FORMAT ")\n",posn);
free(data);
return 1;
}
#if DEBUG
print_msg("ADTS frame\n");
print_data(TRUE,"Start",header,JUST_ENOUGH,JUST_ENOUGH);
#endif
if (header[0] != 0xFF || (header[1] & 0xF0) != 0xF0)
{
fprint_err("### ADTS frame does not start with '1111 1111 1111'"
" syncword - lost synchronisation?\n"
" Found 0x%X%X%X instead of 0xFFF\n",
(unsigned)(header[0] & 0xF0) >> 4,
(header[0] & 0x0F),
(unsigned)(header[1] & 0xF0) >> 4);
fprint_err(" (in frame starting at " OFFSET_T_FORMAT ")\n",posn);
return 1;
}
id = (header[1] & 0x08) >> 3;
#if DEBUG
fprint_msg(" ID %d (%s)\n",id,(id==1?"MPEG-2 AAC":"MPEG-4"));
#endif
layer = (header[1] & 0x06) >> 1;
if (layer != 0)
fprint_msg(" layer is %d, not 0 (in frame at " OFFSET_T_FORMAT ")\n",
layer,posn);
// Experience appears to show that emphasis doesn't exist in MPEG-2 AVC.
// But it does exist in (ID=1) MPEG-4 streams.
//
// .. or if forced.
has_emphasis = (flags & ADTS_FLAG_NO_EMPHASIS) ? 0 :
((flags & ADTS_FLAG_FORCE_EMPHASIS) || !id);
if (!has_emphasis)
{
frame_length = ((header[3] & 0x03) << 11) | (header[4] << 3) |
((unsigned)(header[5] & 0xE0) >> 5);
}
else
{
frame_length = (header[4] << 5) | ((unsigned)(header[5] & 0xF8) >> 3);
}
#if DEBUG
fprint_msg(" length %d\n",frame_length);
#endif
data = malloc(frame_length);
if (data == NULL)
{
print_err("### Unable to extend data buffer for ADTS frame\n");
free(data);
return 1;
}
for (ii=0; ii<JUST_ENOUGH; ii++)
data[ii] = header[ii];
err = read_bytes(file,frame_length - JUST_ENOUGH,&(data[JUST_ENOUGH]));
if (err)
{
if (err == EOF)
print_err("### Unexpected EOF reading rest of ADTS frame\n");
else
print_err("### Error reading rest of ADTS frame\n");
free(data);
return 1;
}
#if DEBUG
print_data(TRUE,"Again",data,frame_length,20);
#endif
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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