from http://www.cyberdogtech.com/firewalls/tutorial.php?page=fw

Copyright © 2006 Matt LaPlante. All rights reserved.

Firewall:~# apt-get remove ipchains 

Firewall:~# apt-get install shorewall

주의요망: 소개에서 언급한데로, 이 듀토리얼은 데비안 3.1"Sarge"시스템에 기반한다. 모든 리눅스 오퍼레이팅 시스템은 다른 패키지 셋과 릴리즈 주기를 사용한다. (패키지 이름이 비록 같을지라도) 이것은 데비안 기반의 우분투도에도 해당한다. 이건 다른 오퍼레이팅 시스템을 사용한다면 다른 소프트웨어 버전을 사용할지도 모른다는걸 의미한다. 이것때문에 튜토리얼 예제는 말한대로 작동하지 않을 수도 있다. 여기에 있는 예제들은 현재 데비안 stable 버전에서 shorewall 2.2의 작동을 가정한다. 만약 당신의 배포판이 다른 버전이라면, 당신은 제품 문서를 읽어서 예제들을 바꿀 수 있어야 한다.

추가적인 주의! - shorewall
iptables 설정의 문제는 새로운것이 없고 모든 작업을 수행하는 것과 마찬가지로 문제를 해결하는데 한가지 이상의 방법이 있다. 이 튜토리얼은 그 따분한 작업을 하는데 shorewall을 사용하지만 같은 작업을 하는 다른 프로그램등 여기저기에 있다. 대신 많이 사용하는 것이 FireHOL이다 (http://firehol.sourceforge.net). 만약 shorewall이 당신의 보트를 떠오르지 못하도록 한다면 대체물들은 항상 있다.

Firewall:~# nano -w /etc/default/shorewall

Firewall:~# cp /usr/share/doc/shorewall/default-config/* /etc/shorewall/

from http://www.inb.uni-luebeck.de/~boehme/libavcodec_update.html

Martin Bohme (boehme@inb.uni-luebeckREMOVETHIS.de)

#include <ffmpeg/avcodec.h>
#include <ffmpeg/avformat.h>

g++ -o avcodec_sample.0.4.9 avcodec_sample.0.4.9.cpp -lavformat -lavcodec -ldts -lz

while(GetNextFrame(pFormatCtx, pCodecCtx, videoStream, pFrame))
{
    img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24, (AVPicture*)pFrame, 
        pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

    // Process the video frame (save to disk etc.)
    DoSomethingWithTheImage(pFrameRGB);
}

while(av_read_frame(pFormatCtx, &packet)>=0)
{
    // Is this a packet from the video stream?
    if(packet.stream_index==videoStream)
    {
        // Decode video frame
        avcodec_decode_video(pCodecCtx, pFrame, &frameFinished, 
            packet.data, packet.size);

        // Did we get a video frame?
        if(frameFinished)
        {
            // Convert the image from its native format to RGB
            img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24, 
                (AVPicture*)pFrame, pCodecCtx->pix_fmt, pCodecCtx->width, 
                pCodecCtx->height);

            // Process the video frame (save to disk etc.)
            DoSomethingWithTheImage(pFrameRGB);
        }
    }

    // Free the packet that was allocated by av_read_frame
    av_free_packet(&packet);
}

AVFormatParameters formatParams;
AVInputFormat *iformat;

formatParams.device = "/dev/video0";
formatParams.channel = 0;
formatParams.standard = "ntsc";
formatParams.width = 640;
formatParams.height = 480;
formatParams.frame_rate = 29;
formatParams.frame_rate_base = 1;
filename = "";
iformat = av_find_input_format("video4linux");

av_open_input_file(&ffmpegFormatContext,
                 filename, iformat, 0, &formatParams);

AVFormatParameters formatParams;
AVInputFormat *iformat;

formatParams.device = "/dev/dv1394";
filename = "";
iformat = av_find_input_format("dv1394");

av_open_input_file(&ffmpegFormatContext,
                 filename, iformat, 0, &formatParams);

From http://www.inb.uni-luebeck.de/~boehme/using_libavcodec.html

av_register_all();

AVFormatContext *pFormatCtx;
const char      *filename="myvideo.mpg";

// Open video file
if(av_open_input_file(&pFormatCtx, filename, NULL, 0, NULL)!=0)
    handle_error(); // Couldn't open file

// Retrieve stream information
if(av_find_stream_info(pFormatCtx)<0)
    handle_error(); // Couldn't find stream information

dump_format(pFormatCtx, 0, filename, false);

int            i, videoStream;
AVCodecContext *pCodecCtx;

// Find the first video stream
videoStream=-1;
for(i=0; i<pFormatCtx->nb_streams; i++)
    if(pFormatCtx->streams[i]->codec.codec_type==CODEC_TYPE_VIDEO)
    {
        videoStream=i;
        break;
    }
if(videoStream==-1)
    handle_error(); // Didn't find a video stream

// Get a pointer to the codec context for the video stream
pCodecCtx=&pFormatCtx->streams[videoStream]->codec;

AVCodec *pCodec;

// Find the decoder for the video stream
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL)
    handle_error(); // Codec not found

// Inform the codec that we can handle truncated bitstreams -- i.e.,
// bitstreams where frame boundaries can fall in the middle of packets
if(pCodec->capabilities & CODEC_CAP_TRUNCATED)
    pCodecCtx->flags|=CODEC_FLAG_TRUNCATED;

// Open codec
if(avcodec_open(pCodecCtx, pCodec)<0)
    handle_error(); // Could not open codec

// Hack to correct wrong frame rates that seem to be generated by some 
// codecs
if(pCodecCtx->frame_rate>1000 && pCodecCtx->frame_rate_base==1)
    pCodecCtx->frame_rate_base=1000;

AVFrame *pFrame;

pFrame=avcodec_alloc_frame();

bool GetNextFrame(AVFormatContext *pFormatCtx, AVCodecContext *pCodecCtx, 
    int videoStream, AVFrame *pFrame)
{
    static AVPacket packet;
    static int      bytesRemaining=0;
    static uint8_t  *rawData;
    static bool     fFirstTime=true;
    int             bytesDecoded;
    int             frameFinished;

    // First time we're called, set packet.data to NULL to indicate it
    // doesn't have to be freed
    if(fFirstTime)
    {
        fFirstTime=false;
        packet.data=NULL;
    }

    // Decode packets until we have decoded a complete frame
    while(true)
    {
        // Work on the current packet until we have decoded all of it
        while(bytesRemaining > 0)
        {
            // Decode the next chunk of data
            bytesDecoded=avcodec_decode_video(pCodecCtx, pFrame,
                &frameFinished, rawData, bytesRemaining);

            // Was there an error?
            if(bytesDecoded < 0)
            {
                fprintf(stderr, "Error while decoding frame\n");
                return false;
            }

            bytesRemaining-=bytesDecoded;
            rawData+=bytesDecoded;

            // Did we finish the current frame? Then we can return
            if(frameFinished)
                return true;
        }

        // Read the next packet, skipping all packets that aren't for this
        // stream
        do
        {
            // Free old packet
            if(packet.data!=NULL)
                av_free_packet(&packet);

            // Read new packet
            if(av_read_packet(pFormatCtx, &packet)<0)
                goto loop_exit;
        } while(packet.stream_index!=videoStream);

        bytesRemaining=packet.size;
        rawData=packet.data;
    }

loop_exit:

    // Decode the rest of the last frame
    bytesDecoded=avcodec_decode_video(pCodecCtx, pFrame, &frameFinished, 
        rawData, bytesRemaining);

    // Free last packet
    if(packet.data!=NULL)
        av_free_packet(&packet);

    return frameFinished!=0;
}

while(GetNextFrame(pFormatCtx, pCodecCtx, videoStream, pFrame))
{
    img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24, (AVPicture*)pFrame, 
        pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

    // Process the video frame (save to disk etc.)
    DoSomethingWithTheImage(pFrameRGB);
}

AVFrame *pFrameRGB;
int     numBytes;
uint8_t *buffer;

// Allocate an AVFrame structure
pFrameRGB=avcodec_alloc_frame();
if(pFrameRGB==NULL)
    handle_error();

// Determine required buffer size and allocate buffer
numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,
    pCodecCtx->height);
buffer=new uint8_t[numBytes];

// Assign appropriate parts of buffer to image planes in pFrameRGB
avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
    pCodecCtx->width, pCodecCtx->height);

// Free the RGB image
delete [] buffer;
av_free(pFrameRGB);

// Free the YUV frame
av_free(pFrame);

// Close the codec
avcodec_close(pCodecCtx);

// Close the video file
av_close_input_file(pFormatCtx);

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