diff options
Diffstat (limited to 'mpeglib/lib/splay/mpegAudioFrame.cpp')
| -rw-r--r-- | mpeglib/lib/splay/mpegAudioFrame.cpp | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/mpeglib/lib/splay/mpegAudioFrame.cpp b/mpeglib/lib/splay/mpegAudioFrame.cpp new file mode 100644 index 00000000..807a23a6 --- /dev/null +++ b/mpeglib/lib/splay/mpegAudioFrame.cpp @@ -0,0 +1,200 @@ +/* + converts raw mpeg audio stream data into mpeg I encoded audio frames/packets + Copyright (C) 2001 Martin Vogt + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU Library General Public License as published by + the Free Software Foundation. + + For more information look at the file COPYRIGHT in this package + + */ + + +#include "mpegAudioFrame.h" + +#define MPEGAUDIOFRAMESIZE 4096 + +#define FRAME_SYNC 0 +#define FRAME_CHECK_HEADER_1 1 +#define FRAME_CHECK_HEADER_2 2 + +#include <iostream> + +using namespace std; + +MpegAudioFrame::MpegAudioFrame():Framer(MPEGAUDIOFRAMESIZE) { + mpegAudioHeader=new MpegAudioHeader(); +} + + +MpegAudioFrame::~MpegAudioFrame() { + delete mpegAudioHeader; +} + + +void MpegAudioFrame::unsync(RawDataBuffer* store,int ) { + // invalidate header in buffer + unsigned char* start=store->ptr(); + start[0]=0x0; + start[1]=0x0; + store->setpos(0); + find_frame_state=FRAME_SYNC; + framesize=0; +} + + +/** + here we parse byte by byte the raw input, first + we search for the magic bytes: 0xfffx, then + we read the remaining 2 bytes for the header, + check if they are "wrong" in a mpeg I audio special way. + If everything is fine, we continue with the next state. + + Note: we can be sure here, that the "store" can at least + store 4 bytes. +*/ +int MpegAudioFrame::find_frame(RawDataBuffer* input_buffer, + RawDataBuffer* store_buffer) { + unsigned char* store=store_buffer->current(); + int back=false; + + if (find_frame_state == FRAME_SYNC) { + if (store_buffer->pos() != 0) { + cout << "store buffer not at beginning MpegAudioFrame::find_frame"<<endl; + cout << "current state requires this"<<endl; + exit(0); + } + } + + while(input_buffer->eof()==false) { + // search for sync bytes + unsigned char* input=input_buffer->current(); + if (find_frame_state == FRAME_SYNC) { + while(input_buffer->eof() == false) { + input=input_buffer->current(); + // shift + store[0]=store[1]; + store[1]=input[0]; + input_buffer->inc(); + + if (store[0] != 0xff) { + continue; + } + // upper 4 bit are syncword, except bit one + // which is layer 2.5 indicator. + if ( (store[1] & 0xe0) != 0xe0) { + continue; + } + + // found header, now check if other info is ok, too. + store_buffer->setpos(2); + find_frame_state=FRAME_CHECK_HEADER_1; + break; + } + // back to "main loop" + continue; + } + // ok, try to read two other bytes and then validate the header + if (find_frame_state == FRAME_CHECK_HEADER_1) { + store[2]=input[0]; + input_buffer->inc(); + find_frame_state=FRAME_CHECK_HEADER_2; + // back to main loop + continue; + } + if (find_frame_state == FRAME_CHECK_HEADER_2) { + store[3]=input[0]; + input_buffer->inc(); + } + + // ok, read 4 header bytes. Now check the validity of the + // header. + int lHeaderOk; + lHeaderOk=mpegAudioHeader->parseHeader(store); + if (lHeaderOk == false) { + find_frame_state=FRAME_SYNC; + store_buffer->setpos(0); + // go back to "sync for frame" + continue; + } + framesize=mpegAudioHeader->getFramesize(); + // if framesize > max mepg framsize its an error + if (framesize+4 >= store_buffer->size()) { + find_frame_state=FRAME_SYNC; + store_buffer->setpos(0); + // go back to "sync for frame" + continue; + } + // don't allow stupid framesizes: + if (framesize <= 4) { + find_frame_state=FRAME_SYNC; + store_buffer->setpos(0); + continue; + } + // yup! found valid header. forward states + store_buffer->setpos(4); + back=true; + break; + } + return back; +} + + +/** + here we read data until len=framesize. + Then we go to the HAS_FRAME state. +*/ +int MpegAudioFrame::read_frame(RawDataBuffer* input_buffer, + RawDataBuffer* store_buffer) { + unsigned char* store=store_buffer->current(); + + while(input_buffer->eof()==false) { + int has=store_buffer->pos(); + int need=framesize-has; + if(need == 0) { + // yup! frame fully read. forward states. + // go to end state for main_state. + return true; + } + // try to do a memcpy for speed. + int can=input_buffer->untilend(); + if(can > need) { + can=need; + } + unsigned char* input=input_buffer->current(); + memcpy(store,input,can); + store_buffer->inc(can); + input_buffer->inc(can); + } + int need=framesize-store_buffer->pos(); + + if(need == 0) { + // yup! frame fully read. forward states. + // go to end state for main_state. + return true; + } + return false; +} + + + +void MpegAudioFrame::printPrivateStates() { + cout << "MpegAudioFrame::printPrivateStates"<<endl; + switch(find_frame_state) { + case FRAME_SYNC: + cout << "frame_state: FRAME_SYNC"<<endl; + break; + case FRAME_CHECK_HEADER_1: + cout << "frame_state: FRAME_CHECK_HEADER_1"<<endl; + break; + case FRAME_CHECK_HEADER_2: + cout << "frame_state: FRAME_CHECK_HEADER_2"<<endl; + break; + default: + cout << "unknown illegal frame_state:"<<find_frame_state<<endl; + } + + +} + |