1/**********
2This library is free software; you can redistribute it and/or modify it under
3the terms of the GNU Lesser General Public License as published by the
4Free Software Foundation; either version 3 of the License, or (at your
5option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)
6
7This library is distributed in the hope that it will be useful, but WITHOUT
8ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
9FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
10more details.
11
12You should have received a copy of the GNU Lesser General Public License
13along with this library; if not, write to the Free Software Foundation, Inc.,
1451 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
15**********/
16// "liveMedia"
17// Copyright (c) 1996-2020 Live Networks, Inc. All rights reserved.
18// Descriptor preceding frames of 'ADU' MP3 streams (for improved loss-tolerance)
19// Implementation
20
21#include "MP3ADUdescriptor.hh"
22
23////////// ADUdescriptor //////////
24
25//##### NOTE: For now, ignore fragmentation. Fix this later! #####
26
27#define TWO_BYTE_DESCR_FLAG 0x40
28
29unsigned ADUdescriptor::generateDescriptor(unsigned char*& toPtr,
30 unsigned remainingFrameSize) {
31 unsigned descriptorSize = ADUdescriptor::computeSize(remainingFrameSize);
32 switch (descriptorSize) {
33 case 1: {
34 *toPtr++ = (unsigned char)remainingFrameSize;
35 break;
36 }
37 case 2: {
38 generateTwoByteDescriptor(toPtr, remainingFrameSize);
39 break;
40 }
41 }
42
43 return descriptorSize;
44}
45
46void ADUdescriptor::generateTwoByteDescriptor(unsigned char*& toPtr,
47 unsigned remainingFrameSize) {
48 *toPtr++ = (TWO_BYTE_DESCR_FLAG|(unsigned char)(remainingFrameSize>>8));
49 *toPtr++ = (unsigned char)(remainingFrameSize&0xFF);
50}
51
52unsigned ADUdescriptor::getRemainingFrameSize(unsigned char*& fromPtr) {
53 unsigned char firstByte = *fromPtr++;
54
55 if (firstByte&TWO_BYTE_DESCR_FLAG) {
56 // This is a 2-byte descriptor
57 unsigned char secondByte = *fromPtr++;
58
59 return ((firstByte&0x3F)<<8) | secondByte;
60 } else {
61 // This is a 1-byte descriptor
62 return (firstByte&0x3F);
63 }
64}
65
66