98 lines
3.5 KiB
C++
Executable File
98 lines
3.5 KiB
C++
Executable File
/**********
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This library is free software; you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License as published by the
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Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)
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This library is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
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more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this library; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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**********/
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// "liveMedia"
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// Copyright (c) 1996-2016 Live Networks, Inc. All rights reserved.
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// RTP sink for AC3 audio
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// Implementation
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#include "AC3AudioRTPSink.hh"
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AC3AudioRTPSink::AC3AudioRTPSink(UsageEnvironment& env, Groupsock* RTPgs,
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u_int8_t rtpPayloadFormat,
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u_int32_t rtpTimestampFrequency)
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: AudioRTPSink(env, RTPgs, rtpPayloadFormat,
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rtpTimestampFrequency, "AC3"),
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fTotNumFragmentsUsed(0) {
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}
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AC3AudioRTPSink::~AC3AudioRTPSink() {
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}
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AC3AudioRTPSink*
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AC3AudioRTPSink::createNew(UsageEnvironment& env, Groupsock* RTPgs,
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u_int8_t rtpPayloadFormat,
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u_int32_t rtpTimestampFrequency) {
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return new AC3AudioRTPSink(env, RTPgs,
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rtpPayloadFormat, rtpTimestampFrequency);
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}
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Boolean AC3AudioRTPSink
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::frameCanAppearAfterPacketStart(unsigned char const* /*frameStart*/,
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unsigned /*numBytesInFrame*/) const {
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// (For now) allow at most 1 frame in a single packet:
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return False;
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}
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void AC3AudioRTPSink
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::doSpecialFrameHandling(unsigned fragmentationOffset,
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unsigned char* frameStart,
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unsigned numBytesInFrame,
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struct timeval framePresentationTime,
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unsigned numRemainingBytes) {
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// Set the 2-byte "payload header", as defined in RFC 4184.
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unsigned char headers[2];
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Boolean isFragment = numRemainingBytes > 0 || fragmentationOffset > 0;
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if (!isFragment) {
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headers[0] = 0; // One or more complete frames
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headers[1] = 1; // because we (for now) allow at most 1 frame per packet
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} else {
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if (fragmentationOffset > 0) {
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headers[0] = 3; // Fragment of frame other than initial fragment
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} else {
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// An initial fragment of the frame
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unsigned const totalFrameSize = fragmentationOffset + numBytesInFrame + numRemainingBytes;
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unsigned const fiveEighthsPoint = totalFrameSize/2 + totalFrameSize/8;
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headers[0] = numBytesInFrame >= fiveEighthsPoint ? 1 : 2;
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// Because this outgoing packet will be full (because it's an initial fragment), we can compute how many total
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// fragments (and thus packets) will make up the complete AC-3 frame:
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fTotNumFragmentsUsed = (totalFrameSize + (numBytesInFrame-1))/numBytesInFrame;
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}
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headers[1] = fTotNumFragmentsUsed;
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}
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setSpecialHeaderBytes(headers, sizeof headers);
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if (numRemainingBytes == 0) {
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// This packet contains the last (or only) fragment of the frame.
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// Set the RTP 'M' ('marker') bit:
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setMarkerBit();
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}
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// Important: Also call our base class's doSpecialFrameHandling(),
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// to set the packet's timestamp:
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MultiFramedRTPSink::doSpecialFrameHandling(fragmentationOffset,
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frameStart, numBytesInFrame,
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framePresentationTime,
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numRemainingBytes);
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}
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unsigned AC3AudioRTPSink::specialHeaderSize() const {
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return 2;
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}
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