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Sur d’autres sites (11920)

  • Cracking Aztec Game Audio

    7 juin 2011, par Multimedia Mike — Game Hacking

    Here’s a mild multimedia-related reverse engineering challenge for you. It’s pretty straightforward for those skilled in the art.

    The Setup
    One side effect of running this ridiculously niche interest blog at the intersection of multimedia, reverse engineering, and game hacking is that people occasionally contact me for assistance on those very matters. So it was when one of my MobyGames peers asked if I can help to extract some music from a game called Aztec Wars. The game consists of 2 discs, each with a music.xbe file that contains multiple tunes and is hundreds of megabytes large.



    That’s all the data I received from the first email. At first I’m wondering what makes people think I have some magical insight into cracking these formats with such little information. Ordinarily, I would need to have the entire data file to work with and possibly the game binaries. But I didn’t want to ask him to upload hundreds of megabytes of data and I didn’t feel like downloading it ; commitment issues and all.

    But then I gathered a little confidence and remembered that the .xbe files are probably just Game Resource Archive Formats (GRAF) which are, traditionally, absurdly simple. I asked my colleague to send me a hexdump of the first kilobyte of one of the .xbe GRAFs ('hexdump -C -n 1024 music.xbe > file') as well as the total file size of the GRAF.

    The Hexdump
    The first music.xbe file is 192817376 bytes large. These are the first 1024 144 bytes (more than enough) :

    00000000  01 00 00 00 60 04 00 00  14 00 00 00 01 00 00 00  |....`...........|
    00000010  0d 00 00 00 48 00 00 00  94 39 63 01 1c a4 21 03  |....H....9c..¤ !.|
    00000020  7a d2 54 04 04 28 ad 05  d8 88 fd 06 d8 88 fd 06  |zÒT..(­.Ø.ý.Ø.ý.|
    00000030  2a 6e 46 08 2a 6e 46 08  2a 6e 46 08 2a 6e 46 08  |*nF.*nF.*nF.*nF.|
    00000040  50 13 2f 0a e0 28 7e 0b  52 49 46 46 44 39 63 01  |P./.à( .RIFFD9c.|
    00000050  57 41 56 45 66 6d 74 20  10 00 00 00 01 00 02 00  |WAVEfmt ........|
    00000060  44 ac 00 00 10 b1 02 00  04 00 10 00 64 61 74 61  |D¬...±......data|
    00000070  fc 13 63 01 00 00 00 00  00 00 00 00 00 00 00 00  |ü.c.............|
    00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
    

    The Challenge
    Armed with only the information in the foregoing section, figure out a method for extracting all the audio files in that file and advise on their playback/conversion. Ideally, this method should require minimal effort from both you and the person on the other end of the conversation.

    The Resolution
    The reason I ask is because I came up with a solution but knew, deep down, that there must be a slightly easier way. How would you solve this ?

    The music files in question are now preserved on YouTube (until they see fit to remove them for one reason or another).

  • Convert raw image using open-source library with permissive license

    30 août 2011, par Brian

    I need to convert a raw, rgb32-formatted image to a PNG with a library (written in, in order of preference, Java, C, C++) having a permissive (e.g. BSD or Apache) license.

    I'm able to convert the image using FFmpeg with this call :

    ffmpeg.exe -vframes 1 -vcodec rawvideo -f rawvideo -pix_fmt rgb32 -s 20x40 -i infile -f image2 -vcodec png out.png

    where 20x40 is the width by the height.

    But, sadly, I need to avoid FFmpeg due to its license.

    I've seen people speculate that libpng could do the job, but I'm skeptical given the documentation I've seen at the libpng site. Perhaps you'll give an example.

    I don't know what the rawvideo and rgb32 values mean to FFmpeg, so I asked this question.

    EDIT 1 : edited the ffmpeg call to show width x height.

  • How to publish selfmade stream with ffmpeg and c++ to rtmp server ?

    25 octobre 2013, par Alexandr R

    Have a nice day to you, people !

    I am writing an application for Windows that will capture the screen and send the stream to Wowza server by rtmp (for broadcasting). My application use ffmpeg and Qt.
    I capture the screen with WinApi, convert a buffer to YUV444(because it's simplest) and encode frame as described at the file decoding_encoding.c (from FFmpeg examples) :

    ///////////////////////////
    //Encoder initialization
    ///////////////////////////
    avcodec_register_all();
    codec=avcodec_find_encoder(AV_CODEC_ID_H264);
    c = avcodec_alloc_context3(codec);
    c->width=scr_width;
    c->height=scr_height;
    c->bit_rate = 400000;
    int base_num=1;
    int base_den=1;//for one frame per second
    c->time_base= (AVRational){base_num,base_den};
    c->gop_size = 10;
    c->max_b_frames=1;
    c->pix_fmt = AV_PIX_FMT_YUV444P;
    av_opt_set(c->priv_data, "preset", "slow", 0);

    frame = avcodec_alloc_frame();
    frame->format = c->pix_fmt;
    frame->width  = c->width;
    frame->height = c->height;

    for(int counter=0;counter<10;counter++)
    {
    ///////////////////////////
    //Capturing Screen
    ///////////////////////////
       GetCapScr(shotbuf,scr_width,scr_height);//result: shotbuf is filled by screendata from HBITMAP
    ///////////////////////////
    //Convert buffer to YUV444 (standard formula)
    //It's handmade function because of problems with prepare buffer to swscale from HBITMAP
    ///////////////////////////
       RGBtoYUV(shotbuf,frame->linesize,frame->data,scr_width,scr_height);//result in frame->data
    ///////////////////////////
    //Encode Screenshot
    ///////////////////////////
       av_init_packet(&pkt);
       pkt.data = NULL;    // packet data will be allocated by the encoder
       pkt.size = 0;
       frame->pts = counter;
       avcodec_encode_video2(c, &pkt, frame, &got_output);
       if (got_output)
       {
           //I think that  sending packet by rtmp  must be here!
           av_free_packet(&pkt);            

       }

    }
    // Get the delayed frames
    for (int got_output = 1,i=0; got_output; i++)
    {
       ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
       if (ret < 0)
           {
               fprintf(stderr, "Error encoding frame\n");
               exit(1);
           }
           if (got_output)
           {
           //I think that  sending packet by rtmp  must be here!
           av_free_packet(&pkt);      
           }
    }

    ///////////////////////////
    //Deinitialize encoder
    ///////////////////////////
    avcodec_close(c);
    av_free(c);
    av_freep(&frame->data[0]);
    avcodec_free_frame(&frame);

    I need to send video stream generated by this code to RTMP server.
    In other words, I need c++/c analog for this command :

    ffmpeg -re -i "sample.h264" -f flv rtmp://sample.url.com/screen/test_stream

    It's useful, but I don't want to save stream to file, I want to use ffmpeg libraries for realtime encoding screen capture and sending encoded frames to RTMP server inside my own application.
    Please give me a little example how to initialize AVFormatContext properly and to send my encoded video AVPackets to server.

    Thanks.