Recherche avancée

Sur d’autres sites (7423)

• How To Write An Oscilloscope

  29 avril 2012, par Multimedia Mike — General, gme, oscilloscope, visualization

  I’m trying to figure out how to write a software oscilloscope audio visualization. It’s made more frustrating by the knowledge that I am certain that I have accomplished this task before.

  In this context, the oscilloscope is used to draw the time-domain samples of an audio wave form. I have written such a plugin as part of the xine project. However, for that project, I didn’t have to write the full playback pipeline— my plugin was just handed some PCM data and drew some graphical data in response. Now I’m trying to write the entire engine in a standalone program and I’m wondering how to get it just right.

  
  
  

  This is an SDL-based oscilloscope visualizer and audio player for Game Music Emu library. My approach is to have an audio buffer that holds a second of audio (44100 stereo 16-bit samples). The player updates the visualization at 30 frames per second. The o-scope is 512 pixels wide. So, at every 1/30th second interval, the player dips into the audio buffer at position ((frame_number % 30) * 44100 / 30) and takes the first 512 stereo frames for plotting on the graph.

  It seems to be working okay, I guess. The only problem is that the A/V sync seems to be slightly misaligned. I am just wondering if this is the correct approach. Perhaps the player should be performing some slightly more complicated calculation over those (44100/30) audio frames during each update in order to obtain a more accurate graph ? I described my process to an electrical engineer friend of mine and he insisted that I needed to apply something called hysteresis to the output or I would never get accurate A/V sync in this scenario.

  Further, I know that some schools of thought on these matters require that the dots in those graphs be connected, that the scattered points simply won’t do. I guess it’s a stylistic choice.

  Still, I think I have a reasonable, workable approach here. I might just be starting the visualization 1/30th of a second too late.

• Anomalie #3872 : urls et

  20 janvier 2017, par denis -

  Titre de la rubrique -> #128 - 15 ans !

  Urls obtenue :

  /nl/prog/2012/128-15-ans/
  /fr/prog/2012/128-15-ans/
  /en/prog/2012/128-15-ans/

  Urls selon pourrait donner :

  /nl/prog/2012/128-15-jaar/
  /fr/prog/2012/128-15-ans/
  /en/prog/2012/128-15-year/

• ffmpeg installation undefined reference to

  8 février 2017, par user1683302

  I used this official link to download ffmpeg and compile it. I know it creates a static library and I have to reference the library folder. When i try to compile this tutorial . i get this errors

  tutorial01.c: In function ‘main’:
  
  tutorial01.c:96:5: warning: ‘codec’ is deprecated [-Wdeprecated- declarations]
  
   if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
  
   ^
  
  In file included from tutorial01.c:27:0:
  
   /home/osboxes/ffmpeg_build/include/libavformat/avformat.h:893:21: note:  declared here
  
   AVCodecContext *codec;
  
                   ^
  
  tutorial01.c:104:3: warning: ‘codec’ is deprecated [-Wdeprecated-declarations]
  
  pCodecCtxOrig=pFormatCtx->streams[videoStream]->codec;
  
  ^
  
  In file included from tutorial01.c:27:0:
  
  /home/osboxes/ffmpeg_build/include/libavformat/avformat.h:893:21: note: declared here
  
   AVCodecContext *codec;
  
                   ^
  
  tutorial01.c:113:3: warning: ‘avcodec_copy_context’ is deprecated  [-Wdeprecated-declarations]
  
   if(avcodec_copy_context(pCodecCtx, pCodecCtxOrig) != 0) {
  
   ^
  
  In file included from tutorial01.c:26:0:
  
  /home/osboxes/ffmpeg_build/include/libavcodec/avcodec.h:4240:5: note: declared here
  
  int avcodec_copy_context(AVCodecContext *dest, const AVCodecContext *src);
  
   ^
  
  tutorial01.c:131:3: warning: ‘avpicture_get_size’ is deprecated   [-Wdeprecated-declarations]
  
   numBytes=avpicture_get_size(AV_PIX_FMT_RGB24, pCodecCtx->width,
  
   ^
  
   In file included from tutorial01.c:26:0:
  
   /home/osboxes/ffmpeg_build/include/libavcodec/avcodec.h:5467:5: note: declared here
  
   int avpicture_get_size(enum AVPixelFormat pix_fmt, int width, int height);
  
   ^
  
    tutorial01.c:138:3: warning: ‘avpicture_fill’ is deprecated [-Wdeprecated-declarations]
  
     avpicture_fill((AVPicture *)pFrameRGB, buffer, AV_PIX_FMT_RGB24,
  
     ^
  
    In file included from tutorial01.c:26:0:
  
    /home/osboxes/ffmpeg_build/include/libavcodec/avcodec.h:5452:5: note: declared here
  
    int avpicture_fill(AVPicture *picture, const uint8_t *ptr,
  
   ^
  
     tutorial01.c:160:7: warning: ‘avcodec_decode_video2’ is deprecated [-Wdeprecated-declarations]
  
         avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
         ^
  
   In file included from tutorial01.c:26:0:
  
    /home/osboxes/ffmpeg_build/include/libavcodec/avcodec.h:4811:5: note: declared here
  
    int avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture,
  
   ^
  
    tutorial01.c:177:5: warning: ‘av_free_packet’ is deprecated [-Wdeprecated-declarations]
  
    av_free_packet(&packet);
  
    ^
  
   In file included from tutorial01.c:26:0:
  
   /home/osboxes/ffmpeg_build/include/libavcodec/avcodec.h:4472:6: note: declared here
  
   void av_free_packet(AVPacket *pkt);
  
    ^
  
  /tmp/ccHYDd9j.o: In function `main':
  
  tutorial01.c:(.text+0x178): undefined reference to `av_register_all'
  
  tutorial01.c:(.text+0x19f): undefined reference to `avformat_open_input'
  
  tutorial01.c:(.text+0x1c1): undefined reference to `avformat_find_stream_info'
  
  tutorial01.c:(.text+0x1f6): undefined reference to `av_dump_format'
  
  tutorial01.c:(.text+0x2ab): undefined reference to `avcodec_find_decoder'
  
  tutorial01.c:(.text+0x2ea): undefined reference to `avcodec_alloc_context3'
  
  tutorial01.c:(.text+0x304): undefined reference to `avcodec_copy_context'
  
  tutorial01.c:(.text+0x348): undefined reference to `avcodec_open2'
  
  tutorial01.c:(.text+0x35b): undefined reference to `av_frame_alloc'
  
  tutorial01.c:(.text+0x367): undefined reference to `av_frame_alloc'
  
  tutorial01.c:(.text+0x3a4): undefined reference to `avpicture_get_size'
  
  tutorial01.c:(.text+0x3ba): undefined reference to `av_malloc'
  
  tutorial01.c:(.text+0x3ef): undefined reference to `avpicture_fill'
  
  tutorial01.c:(.text+0x439): undefined reference to `sws_getContext'
  
  tutorial01.c:(.text+0x47d): undefined reference to `avcodec_decode_video2'
  
  tutorial01.c:(.text+0x4de): undefined reference to `sws_scale'
  
  tutorial01.c:(.text+0x527): undefined reference to `av_free_packet'
  
  tutorial01.c:(.text+0x53d): undefined reference to `av_read_frame'
  
  tutorial01.c:(.text+0x551): undefined reference to `av_free'
  
  tutorial01.c:(.text+0x560): undefined reference to `av_frame_free'
  
  tutorial01.c:(.text+0x56f): undefined reference to `av_frame_free'
  
  tutorial01.c:(.text+0x57b): undefined reference to `avcodec_close'
  
  tutorial01.c:(.text+0x58a): undefined reference to `avcodec_close'
  
  tutorial01.c:(.text+0x599): undefined reference to `avformat_close_input'
  
  collect2: error: ld returned 1 exit status

  i used this sudo gcc -I /home/osboxes/ffmpeg_build/include -L /home/osboxes/ffmpeg_build/lib -lavcode -lavformat -lavutil -lswscale -lz -lm tutorial01.c

  my ffmpeg is

   ffmpeg version N-82113-g490c6bd Copyright (c) 2000-2016 the FFmpeg developers
  
     built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.2) 20160609
  
     configuration: --prefix=/home/osboxes/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/osboxes/ffmpeg_build/include --extra-ldflags=- L/home/osboxes/ffmpeg_build/lib --bindir=/home/osboxes/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libopus --enable-libx264 --enable-nonfree
  
    libavutil      55. 33.100 / 55. 33.100
  
    libavcodec     57. 63.103 / 57. 63.103
  
    libavformat    57. 55.100 / 57. 55.100
  
    libavdevice    57.  0.103 / 57.  0.103
  
    libavfilter     6. 64.100 /  6. 64.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  2.100 /  2.  2.100
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Hyper fast Audio and Video encoder
  
  usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

  the tutorial code was update to work on new ffmpeg versions.I’m using VM Ubuntu 16.0.4 64 bit fresh install on windows 10 host.

  so why I’m having all of these errors ?

  Update :
  I moved to Ubuntu 12.04 VM and ffmpeg 0.11, I instilled it with opencv 2.4.2 here is the link . This should work yet i don’t why I’m having hard time compiling such small program.

  ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
  
   built on Oct 25 2016 13:39:37 with gcc 4.6.3
  
    configuration: --enable-gpl --enable-libfaac --enable-libmp3lame    --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab --enable-shared --enable-pic
  
   libavutil      51. 54.100 / 51. 54.100
  
   libavcodec     54. 23.100 / 54. 23.100
  
   libavformat    54.  6.100 / 54.  6.100
  
   libavdevice    54.  0.100 / 54.  0.100
  
   libavfilter     2. 77.100 /  2. 77.100
  
   libswscale      2.  1.100 /  2.  1.100
  
   libswresample   0. 15.100 /  0. 15.100
  
   libpostproc    52.  0.100 / 52.  0.100
  
  Hyper fast Audio and Video encoder
  
  usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

  yet i still have the problem but it is less sever

   gcc -o tutorial01 tutorial01.c -Wl,--start-group -lavcodec -lavformat  -lswscale -lavutil -lz -lm -Wl,--end-group     
  
    /tmp/ccnFfu84.o: In function `main':
  
    tutorial01.c:(.text+0x500): undefined reference to `avcodec_free_frame'
  
    tutorial01.c:(.text+0x511): undefined reference to `avcodec_free_frame'
  
    collect2: ld returned 1 exit status

  i tried this ldconfig -p | grep av

    libxklavier.so.16 (libc6,x86-64) => /usr/lib/libxklavier.so.16
  
    libwavpack.so.1 (libc6,x86-64) => /usr/lib/x86_64-linux gnu/libwavpack.so.1
  
  libjavascriptcoregtk-3.0.so.0 (libc6,x86-64) => /usr/lib/libjavascriptcoregtk-3.0.so.0
  
  libdvdnavmini.so.4 (libc6,x86-64) => /usr/lib/libdvdnavmini.so.4
  
  libdvdnav.so.4 (libc6,x86-64) => /usr/lib/libdvdnav.so.4
  
  libavutil.so.51 (libc6,x86-64) => /usr/local/lib/libavutil.so.51
  
  libavutil.so.51 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavutil.so.51
  
  libavutil.so (libc6,x86-64) => /usr/local/lib/libavutil.so
  
  libavformat.so.54 (libc6,x86-64) => /usr/local/lib/libavformat.so.54
  
  libavformat.so.53 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavformat.so.53
  
  libavformat.so (libc6,x86-64) => /usr/local/lib/libavformat.so
  
  libavfilter.so.2 (libc6,x86-64) => /usr/local/lib/libavfilter.so.2
  
  libavfilter.so (libc6,x86-64) => /usr/local/lib/libavfilter.so
  
  libavdevice.so.54 (libc6,x86-64) => /usr/local/lib/libavdevice.so.54
  
  libavdevice.so (libc6,x86-64) => /usr/local/lib/libavdevice.so
  
  libavc1394.so.0 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavc1394.so.0
  
  libavcodec.so.54 (libc6,x86-64) => /usr/local/lib/libavcodec.so.54
  
  libavcodec.so.53 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavcodec.so.53
  
  libavcodec.so (libc6,x86-64) => /usr/local/lib/libavcodec.so
  
  libavahi-ui-gtk3.so.0 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-ui-gtk3.so.0
  
  libavahi-gobject.so.0 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-gobject.so.0
  
  libavahi-glib.so.1 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-glib.so.1
  
  libavahi-core.so.7 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-core.so.7
  
  libavahi-common.so.3 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-common.so.3
  
  libavahi-common.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-common.so
  
  libavahi-client.so.3 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-client.so.3
  
  libavahi-client.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libavahi-client.so

  Update2

  I changged avcodec_free_frame to av_free and the file complied

  Dranger code is old

  Update 3
  i downloaded ffmpeg 1.0.10 which has the same library version that is the tutorial tested on. Everything complied without any problem now.