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• Sequencing MIDI From A Chiptune

  28 avril 2013, par Multimedia Mike — Outlandish Brainstorms

  The feature requests for my game music appreciation website project continue to pour in. Many of them take the form of “please add player support for system XYZ and the chiptune library to go with it.” Most of these requests are A) plausible, and B) in process. I have also received recommendations for UI improvements which I take under consideration. Then there are the numerous requests to port everything from Native Client to JavaScript so that it will work everywhere, even on mobile, a notion which might take a separate post to debunk entirely.

  But here’s an interesting request about which I would like to speculate : Automatically convert a chiptune into a MIDI file. I immediately wanted to dismiss it as impossible or highly implausible. But, as is my habit, I started pondering the concept a little more carefully and decided that there’s an outside chance of getting some part of the idea to work.

  Intro to MIDI
  MIDI stands for Musical Instrument Digital Interface. It’s a standard musical interchange format and allows music instruments and computers to exchange musical information. The file interchange format bears the extension .mid and contains a sequence of numbers that translate into commands separated by time deltas. E.g. : turn key on (this note, this velocity) ; wait x ticks ; turn key off ; wait y ticks ; etc. I’m vastly oversimplifying, as usual.

  MIDI fascinated me back in the days of dialup internet and discrete sound cards (see also my write-up on the Gravis Ultrasound). Typical song-length MIDI files often ranged from a few kilobytes to a few 10s of kilobytes. They were significantly smaller than the MOD et al. family of tracker music formats mostly by virtue of the fact that MIDI files aren’t burdened by transporting digital audio samples.
  
  I know I’m missing a lot of details. I haven’t dealt much with MIDI in the past… 15 years or so (ever since computer audio became a blur of MP3 and AAC audio). But I’m led to believe it’s still relevant. The individual who requested this feature expressed an interest in being able to import the sequenced data into any of the many music programs that can interpret .mid files.

  The Pitch
  To limit the scope, let’s focus on music that comes from the 8-bit Nintendo Entertainment System or the original Game Boy. The former features 2 square wave channels, a triangle wave, a noise channel, and a limited digital channel. The latter creates music via 2 square waves, a wave channel, and a noise channel. The roles that these various channels usually play typically break down as : square waves represent the primary melody, triangle wave is used to simulate a bass line, noise channel approximates a variety of percussive sounds, and the DPCM/wave channels are fairly free-form. They can have random game sound effects or, if they are to assist in the music, are often used for more authentic percussive sounds.

  The various channels are controlled via an assortment of memory-mapped hardware registers. These registers are fed values such as frequency, volume, and duty cycle. My idea is to modify the music playback engine to track when various events occur. Whenever a channel is turned on or off, that corresponds to a MIDI key on or off event. If a channel is already playing but a new frequency is written, that would likely count as a note change, so log a key off event followed by a new key on event.

  There is the major obstacle of what specific note is represented by a channel in a particular state. The MIDI standard defines 128 different notes spanning 11 octaves. Empirically, I wonder if I could create a table which maps the assorted frequencies to different MIDI notes ?

  I think this strategy would only work with the square and triangle waves. Noise and digital channels ? I’m not prepared to tackle that challenge.

  Prior Work ?
  I have to wonder if there is any existing work in this area. I’m certain that people have wanted to do this before ; I wonder if anyone has succeeded ?

  Just like reverse engineering a binary program entails trying to obtain a higher level abstraction of a program from a very low level representation, this challenge feels like reverse engineering a piece of music as it is being performed and automatically expressing it in a higher level form.

• Streaming Webcam using VLC +FFmpeg over lan - Error : cannot pre fill buffer

  23 juin 2016, par user1804015

  I’ve been trying to stream my webcam over lan using VLC and FFmpeg

  but I end up with the error "Main stream error : cannot pre fill buffer"

  Here is the code I’ve tried

  ffmpeg -f x11grab -s 1680x1050 -r 30 -i :0.0+0,0 -vf "movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie]; [in] setpts=PTS-STARTPTS, [movie] overlay=main_w-overlay_w-10:main_h-overlay_h-10 [out]" -f alsa -ac 2 -i pulse -vcodec libx264 -preset ultrafast -s 1280x768 -acodec libfaac -threads 0 -f mpegts - | vlc -I dummy - --sout '#std{access=http,mux=ts,dst=thalha:3030}'

  And this is the output

  VLC media player 1.1.9 The Luggage (revision exported)
  
  FFmpeg version 0.6.6-4:0.6.6-0ubuntu0.11.04.1, Copyright (c) 2000-2010 the Libav developers
  
    built on Jun 12 2012 16:28:21 with gcc 4.5.2
  
    configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  
    WARNING: library configuration mismatch
  
    libavutil   configuration: --extra-version=4:0.6.6-1ubuntu1+medibuntu1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libdirac --enable-libgsm --enable-libopenjpeg --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-version3 --enable-vaapi --enable-libopenjpeg --enable-libfaac --enable-nonfree --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libfaad --enable-libdirac --enable-libfaad --enable-libmp3lame --enable-librtmp --enable-libx264 --enable-libxvid --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavcodec  configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavformat configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavdevice configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavfilter configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libswscale  configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libpostproc configuration: --extra-version=4:0.6.6-0ubuntu0.11.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
  
    libavutil     50.15. 1 / 50.15. 1
  
    libavcodec    52.72. 2 / 52.72. 2
  
    libavformat   52.64. 2 / 52.64. 2
  
    libavdevice   52. 2. 0 / 52. 2. 0
  
    libavfilter    1.19. 0 /  1.19. 0
  
    libswscale     0.11. 0 /  0.11. 0
  
    libpostproc   51. 2. 0 / 51. 2. 0
  
  [x11grab @ 0x98e8420]device: :0.0+0,0 -> display: :0.0 x: 0 y: 0 width: 1680 height: 1050
  
  [x11grab @ 0x98e8420]shared memory extension  found
  
  X Error of failed request:  BadMatch (invalid parameter attributes)
  
    Major opcode of failed request:  140 (MIT-SHM)
  
    Minor opcode of failed request:  4 (X_ShmGetImage)
  
    Serial number of failed request:  11
  
    Current serial number in output stream:  11
  
  Warning: call to srand(1352225865)
  
  Warning: call to rand()
  
  Blocked: call to unsetenv("DBUS_ACTIVATION_ADDRESS")
  
  Blocked: call to unsetenv("DBUS_ACTIVATION_BUS_TYPE")
  
  [0x9782aec] dummy interface: using the dummy interface module...
  
  [0x987258c] main access out: creating httpd
  
  [0x98d0764] main stream error: cannot pre fill buffer

  Please help me to achieve this. Thanks in advance.

• Can't connect to ffserver when running on android device

  11 décembre 2016, par Antonio C G

  I am working on an android app. This will run a ffserver (on the device, not another computer). The server is running and I can access the status page, everything seems ok. But when I try to send the video using ffmpeg I always get connection refused.

  This is my ffserver.conf file :

  HTTPPort 8090
  
  HTTPBindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandwidth 1000
  
  CustomLog /data/user/0/com.antonio.droidcast/files/log.txt
  
  NoDefaults
  
  
  
  <feed>
  
      File /data/user/0/com.antonio.droidcast/cache/feed1.ffm
  
      FileMaxSize 200M
  
      ACL allow 127.0.0.1
  
  </feed>
  
  
  
  <stream>
  
      Format mp4
  
      Feed feed1.ffm
  
  
  
      VideoCodec libx264
  
      VideoFrameRate 30
  
      VideoBitRate 512
  
      VideoSize 320x240
  
      AVOptionVideo crf 23
  
      AVOptionVideo preset medium
  
      AVOptionVideo flags +global_header
  
  
  
      AudioCodec aac
  
      Strict -2
  
      AudioBitRate 128
  
      AudioChannels 2
  
      AudioSampleRate 44100
  
      AVOptionAudio flags +global_header
  
  </stream>

  I connect to server using this command :

  ffmpeg -i VIDEO_PATH2 http://localhost:8090/feed1.ffm

  And this is the ouput I get :

  Splitting the commandline.
  
  Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
  
  Reading option '-i' ... matched as input file with argument '/storage/emulated/0/Download/video1.mp4'.
  
  Reading option 'http://localhost:8090/feed1.ffm' ... matched as output file.
  
  Finished splitting the commandline.
  
  Parsing a group of options: global .
  
  Applying option loglevel (set logging level) with argument debug.
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input file /storage/emulated/0/Download/video1.mp4.
  
  Successfully parsed a group of options.
  
  Opening an input file: /storage/emulated/0/Download/video1.mp4.
  
  [file @ 0xf5f5e060] Setting default whitelist 'file,crypto'
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0xf5f58000] Format mov,mp4,m4a,3gp,3g2,mj2 probed with size=2048 and score=100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0xf5f58000] ISO: File Type Major Brand: isom
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0xf5f58000] Unknown dref type 0x08206c7275 size 12
  
      Last message repeated 1 times
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0xf5f58000] Before avformat_find_stream_info() pos: 5446 bytes read:32768 seeks:0
  
  [h264 @ 0xf5f49000] user data:"x264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=1 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00"
  
  [h264 @ 0xf5f49000] no picture 
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0xf5f58000] All info found
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0xf5f58000] After avformat_find_stream_info() pos: 6081 bytes read:98304 seeks:2 frames:3
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/Download/video1.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
    Duration: 00:02:45.59, start: 0.128000, bitrate: 24 kb/s
  
      Stream #0:0(eng), 2, 1/450000: Video: h264 (High), 4 reference frames (avc1 / 0x31637661), yuv420p(left), 1920x1080 (1920x1088) [SAR 1:1 DAR 16:9], 7451717/900000, 0 kb/s, 0.06 fps, 0.06 tbr, 450k tbn, 0.12 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(eng), 1, 1/8000: Audio: aac (LC) (mp4a / 0x6134706D), 8000 Hz, mono, fltp, 29 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  Successfully opened the file.
  
  Parsing a group of options: output file http://localhost:8090/feed1.ffm.
  
  Successfully parsed a group of options.
  
  Opening an output file: http://localhost:8090/feed1.ffm.
  
  [http @ 0xf5f5e1e0] Setting default whitelist 'http,https,tls,rtp,tcp,udp,crypto,httpproxy'
  
  [tcp @ 0xf5f5e3c0] Connection to tcp://localhost:8090 failed: Connection refused
  
  http://localhost:8090/feed1.ffm: Connection refused

  Does anybody know what could be wrong ?
  Just to be clear, I recompiled ffserver and ffmpeg for android. They both seem to be ok as I can execute commands. Both binaries are part of the app, so everything runs inside the phone.

  Thanks.