kopia lustrzana https://github.com/F5OEO/tstools
173 wiersze
4.5 KiB
C
173 wiersze
4.5 KiB
C
/*
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* Support for ISO/IEC 14496-3:2001(E) AAC ADTS audio streams.
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*
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is the MPEG TS, PS and ES tools.
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*
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* The Initial Developer of the Original Code is Amino Communications Ltd.
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* Portions created by the Initial Developer are Copyright (C) 2008
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Amino Communications Ltd, Swavesey, Cambridge UK
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*
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* ***** END LICENSE BLOCK *****
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <string.h>
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#include "compat.h"
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#include "misc_fns.h"
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#include "adts_fns.h"
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#define DEBUG 0
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/*
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* Read the next ADTS frame.
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*
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* Assumes that the input stream is synchronised - i.e., it does not
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* try to cope if the next three bytes are not '1111 1111 1111'.
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*
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* - `file` is the file descriptor of the ADTS file to read from
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* - `frame` is the ADTS frame that is read
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* - `flags` indicates if we are forcing the recognition of "emphasis"
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* fields, etc.
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*
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* Returns 0 if all goes well, EOF if end-of-file is read, and 1 if something
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* goes wrong.
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*/
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extern int read_next_adts_frame(int file,
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audio_frame_p *frame,
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unsigned int flags)
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{
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#define JUST_ENOUGH 6 // just enough to hold the bits of the headers we want
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int err, ii;
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int id, layer;
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byte header[JUST_ENOUGH];
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byte *data = NULL;
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int frame_length;
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int has_emphasis = 0;
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offset_t posn = tell_file(file);
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#if DEBUG
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printf("Offset: " OFFSET_T_FORMAT "\n",posn);
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#endif
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err = read_bytes(file,JUST_ENOUGH,header);
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if (err == EOF)
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return EOF;
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else if (err)
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{
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fprintf(stderr,"### Error reading header bytes of ADTS frame\n");
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fprintf(stderr," (in frame starting at " OFFSET_T_FORMAT ")\n",posn);
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free(data);
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return 1;
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}
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#if DEBUG
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printf("ADTS frame\n");
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print_data(stdout,"Start",header,JUST_ENOUGH,JUST_ENOUGH);
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#endif
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if (header[0] != 0xFF || (header[1] & 0xF0) != 0xF0)
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{
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fprintf(stderr,"### ADTS frame does not start with '1111 1111 1111'"
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" syncword - lost synchronisation?\n"
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" Found 0x%X%X%X instead of 0xFFF\n",
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(unsigned)(header[0] & 0xF0) >> 4,
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(header[0] & 0x0F),
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(unsigned)(header[1] & 0xF0) >> 4);
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fprintf(stderr," (in frame starting at " OFFSET_T_FORMAT ")\n",posn);
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return 1;
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}
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id = (header[1] & 0x08) >> 3;
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#if DEBUG
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printf(" ID %d (%s)\n",id,(id==1?"MPEG-2 AAC":"MPEG-4"));
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#endif
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layer = (header[1] & 0x06) >> 1;
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if (layer != 0)
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printf(" layer is %d, not 0 (in frame at " OFFSET_T_FORMAT ")\n",
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layer,posn);
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// Experience appears to show that emphasis doesn't exist in MPEG-2 AVC.
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// But it does exist in (ID=1) MPEG-4 streams.
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//
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// .. or if forced.
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has_emphasis = (flags & ADTS_FLAG_NO_EMPHASIS) ? 0 :
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((flags & ADTS_FLAG_FORCE_EMPHASIS) || !id);
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if (!has_emphasis)
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{
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frame_length = ((header[3] & 0x03) << 11) | (header[4] << 3) |
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((unsigned)(header[5] & 0xE0) >> 5);
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}
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else
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{
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frame_length = (header[4] << 5) | ((unsigned)(header[5] & 0xF8) >> 3);
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}
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#if DEBUG
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printf(" length %d\n",frame_length);
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#endif
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data = malloc(frame_length);
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if (data == NULL)
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{
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fprintf(stderr,"### Unable to extend data buffer for ADTS frame\n");
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free(data);
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return 1;
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}
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for (ii=0; ii<JUST_ENOUGH; ii++)
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data[ii] = header[ii];
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err = read_bytes(file,frame_length - JUST_ENOUGH,&(data[JUST_ENOUGH]));
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if (err)
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{
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if (err == EOF)
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fprintf(stderr,"### Unexpected EOF reading rest of ADTS frame\n");
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else
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fprintf(stderr,"### Error reading rest of ADTS frame\n");
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free(data);
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return 1;
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}
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#if DEBUG
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print_data(stdout,"Again",data,frame_length,20);
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#endif
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err = build_audio_frame(frame);
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if (err)
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{
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free(data);
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return 1;
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}
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(*frame)->data = data;
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(*frame)->data_len = frame_length;
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return 0;
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}
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// Local Variables:
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// tab-width: 8
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// indent-tabs-mode: nil
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// c-basic-offset: 2
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// End:
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// vim: set tabstop=8 shiftwidth=2 expandtab:
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