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// RTP sink for 'ADUized' MP3 frames ("mpa-robust")
19// Implementation
20
21#include "MP3ADURTPSink.hh"
22
23MP3ADURTPSink::MP3ADURTPSink(UsageEnvironment& env, Groupsock* RTPgs,
24 unsigned char RTPPayloadType)
25 : AudioRTPSink(env, RTPgs, RTPPayloadType, 90000, "MPA-ROBUST") {
26}
27
28MP3ADURTPSink::~MP3ADURTPSink() {
29}
30
31MP3ADURTPSink*
32MP3ADURTPSink::createNew(UsageEnvironment& env, Groupsock* RTPgs,
33 unsigned char RTPPayloadType) {
34 return new MP3ADURTPSink(env, RTPgs, RTPPayloadType);
35}
36
37static void badDataSize(UsageEnvironment& env, unsigned numBytesInFrame) {
38 env << "MP3ADURTPSink::doSpecialFrameHandling(): invalid size ("
39 << numBytesInFrame << ") of non-fragmented input ADU!\n";
40}
41
42void MP3ADURTPSink::doSpecialFrameHandling(unsigned fragmentationOffset,
43 unsigned char* frameStart,
44 unsigned numBytesInFrame,
45 struct timeval framePresentationTime,
46 unsigned numRemainingBytes) {
47 // If this is the first (or only) fragment of an ADU, then
48 // check the "ADU descriptor" (that should be at the front) for validity:
49 if (fragmentationOffset == 0) {
50 unsigned aduDescriptorSize;
51
52 if (numBytesInFrame < 1) {
53 badDataSize(envir(), numBytesInFrame);
54 return;
55 }
56 if (frameStart[0]&0x40) {
57 // We have a 2-byte ADU descriptor
58 aduDescriptorSize = 2;
59 if (numBytesInFrame < 2) {
60 badDataSize(envir(), numBytesInFrame);
61 return;
62 }
63 fCurADUSize = ((frameStart[0]&~0xC0)<<8) | frameStart[1];
64 } else {
65 // We have a 1-byte ADU descriptor
66 aduDescriptorSize = 1;
67 fCurADUSize = frameStart[0]&~0x80;
68 }
69
70 if (frameStart[0]&0x80) {
71 envir() << "Unexpected \"C\" bit seen on non-fragment input ADU!\n";
72 return;
73 }
74
75 // Now, check whether the ADU size in the ADU descriptor is consistent
76 // with the total data size of (all fragments of) the input frame:
77 unsigned expectedADUSize =
78 fragmentationOffset + numBytesInFrame + numRemainingBytes
79 - aduDescriptorSize;
80 if (fCurADUSize != expectedADUSize) {
81 envir() << "MP3ADURTPSink::doSpecialFrameHandling(): Warning: Input ADU size "
82 << expectedADUSize << " (=" << fragmentationOffset
83 << "+" << numBytesInFrame << "+" << numRemainingBytes
84 << "-" << aduDescriptorSize
85 << ") did not match the value (" << fCurADUSize
86 << ") in the ADU descriptor!\n";
87 fCurADUSize = expectedADUSize;
88 }
89 } else {
90 // This is the second (or subsequent) fragment.
91 // Insert a new ADU descriptor:
92 unsigned char aduDescriptor[2];
93 aduDescriptor[0] = 0xC0|(fCurADUSize>>8);
94 aduDescriptor[1] = fCurADUSize&0xFF;
95 setSpecialHeaderBytes(aduDescriptor, 2);
96 }
97
98 // Important: Also call our base class's doSpecialFrameHandling(),
99 // to set the packet's timestamp:
100 MultiFramedRTPSink::doSpecialFrameHandling(fragmentationOffset,
101 frameStart, numBytesInFrame,
102 framePresentationTime,
103 numRemainingBytes);
104}
105
106unsigned MP3ADURTPSink::specialHeaderSize() const {
107 // Normally there's no special header.
108 // (The "ADU descriptor" is already present in the data.)
109 unsigned specialHeaderSize = 0;
110
111 // However, if we're about to output the second (or subsequent) fragment
112 // of a fragmented ADU, then we need to insert a new ADU descriptor at
113 // the front of the packet:
114 if (curFragmentationOffset() > 0) {
115 specialHeaderSize = 2;
116 }
117
118 return specialHeaderSize;
119}
120