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• Managing Music Playback Channels

  30 juin 2013, par Multimedia Mike — General

  My Game Music Appreciation site allows users to interact with old video game music by toggling various channels, as long as the underlying synthesizer engine supports it.

  
  
  

  Users often find their way to the Nintendo DS section pretty quickly. This is when they notice an obnoxious quirk with the channel toggling feature : specifically, one channel doesn’t seem to map to a particular instrument or track.

  When it comes to computer music playback methodologies, I have long observed that there are 2 general strategies : Fixed channel and dynamic channel allocation.

  Fixed Channel Approach
  One of my primary sources of computer-based entertainment used to be watching music. Sure I listened to it as well. But for things like Amiga MOD files and related tracker formats, there was a rich ecosystem of fun music playback programs that visualized the music. There exist music visualization modes in various music players these days (such as iTunes and Windows Media Player), but those largely just show you a single wave form. These files were real time syntheses based on multiple audio channels and usually showed some form of analysis for each channel. My personal favorite was Cubic Player :

  
  
  

  Most of these players supported the concept of masking individual channels. In doing so, the user could isolate, study, and enjoy different components of the song. For many 4-channel Amiga MOD files, I observed that the common arrangement was to use the 4 channels for beat (percussion track), bass line, chords, and melody. Thus, it was easy to just listen to, e.g., the bass line in isolation.

  MODs and similar formats specified precisely which digital audio sample to play at what time and on which specific audio channel. To view the internals of one of these formats, one gets the impression that they contain an extremely computer-centric view of music.

  Dynamic Channel Allocation Algorithm
  MODs et al. enjoyed a lot of popularity, but the standard for computer music is MIDI. While MOD and friends took a computer-centric view of music, MIDI takes, well, a music-centric view of music.

  There are MIDI visualization programs as well. The one that came with my Gravis Ultrasound was called PLAYMIDI.EXE. It looked like this…

  
  
  

  … and it confused me. There are 16 distinct channels being visualized but some channels are shown playing multiple notes. When I dug into the technical details, I learned that MIDI just specifies what notes need to be played, at what times and frequencies and using which instrument samples, and it was the MIDI playback program’s job to make it happen.

  Thus, if a MIDI file specifies that track 1 should play a C major chord consisting of notes C, E, and G, it would transmit events “key-on C ; delta time 0 ; key-on E ; delta time 0 ; key-on G ; delta time … ; [other commands]“. If the playback program has access to multiple channels (say, up to 32, in the case of the GUS), the intuitive approach would be to maintain a pool of all available channels. Then, when it’s time to process the “key-on C” event, fetch the first available channel from the pool, mark it as in-use, play C on the channel, and return that channel to the pool when either the sample runs its course or the corresponding “key-off C” event is encountered in the MIDI command stream.

  About That Game Music
  Circling back around to my game music website, numerous supported systems use the fixed channel approach for playback while others use dynamic channel allocation approach, including evey Nintendo DS game I have so far analyzed.

  Which approach is better ? As in many technical matters, there are trade-offs either way. For many systems, the fixed channel approach is necessary because for many older audio synthesis systems, different channels had very specific purposes. The 8-bit NES had 5 channels : 2 square wave generators (used musically for melody/treble), 1 triangle wave generator (usually used for bass line), a noise generator (subverted for all manner of percussive sounds), and a limited digital channel (was sometimes assigned richer percussive sounds). Dynamic channel allocation wouldn’t work here.

  But the dynamic approach works great on hardware with 16 digital channels available like, for example, the Nintendo DS. Digital channels are very general-purpose. What about the SNES, with its 8 digital channels ? Either approach could work. In practice, most games used a fixed channel approach : Games might use 4-6 channels for music while reserving the remainder for various in-game sound effects. Some notable exceptions to this pattern were David Wise’s compositions for Rare’s SNES games (think Battletoads and the various Donkey Kong Country titles). These clearly use some dynamic channel approach since masking all but one channel will give you a variety of instrument sounds.

  Epilogue
  There ! That took a long time to explain but I find it fascinating for some reason. I need to distill it down to far fewer words because I want to make it a FAQ on my website for “Why can’t I isolate specific tracks for Nintendo DS games ?”

  Actually, perhaps I should remove the ability to toggle Nintendo DS channels in the first place. Here’s a funny tale of needless work : I found the Vio2sf engine for synthesizing Nintendo DS music and incorporated it into the program. It didn’t support toggling of individual channels so I figured out a way to add that feature to the engine. And then I noticed that most Nintendo DS games render that feature moot. After I released the webapp, I learned that I was out of date on the Vio2sf engine. The final insult was that the latest version already supports channel toggling. So I did the work for nothing. But then again, since I want to remove that feature from the UI, doubly so.

• ffmpeg build fails with gcc error even with gcc installed (C compiler test failed)

  15 mars 2023, par Martin

  I am on macos 11.2.3, trying to build ffmpeg in my terminal. When I run my script sh buildffmpeg.sh which is below :

  


  #!/bin/bash

# If you get error `c compiler failed` run `sudo apt install libglfw3-dev libglew-dev`
# apt-get install build-essential
# apt-get build-dep ffmpeg
# when running this on mac, you need to install some libraries such as 'brew install opus'

set -e

CWD=$(pwd)
PACKAGES="$CWD/packages"
WORKSPACE="$CWD/workspace"
ADDITIONAL_CONFIGURE_OPTIONS=""


mkdir -p "$PACKAGES"
mkdir -p "$WORKSPACE"

FFMPEG_TAG="$1"
FFMPEG_URL="http://git.ffmpeg.org/gitweb/ffmpeg.git/snapshot/74c4c539538e36d8df02de2484b045010d292f2c.tar.gz"

FFMPEG_ARCHIVE="$PACKAGES/ffmpeg.tar.gz"

if [ ! -f "$FFMPEG_ARCHIVE" ]; then
    echo "Downloading tag ${FFMPEG_TAG}..."
    curl -L -o "$FFMPEG_ARCHIVE" "$FFMPEG_URL"
fi

EXTRACTED_DIR="$PACKAGES/extracted"

mkdir -p "$EXTRACTED_DIR"

echo "Extracting..."
tar -xf "$FFMPEG_ARCHIVE" --strip-components=1 -C "$EXTRACTED_DIR"

cd "$EXTRACTED_DIR"

echo "Building..."

# Min electron supported version
MACOS_MIN="10.10"

./configure $ADDITIONAL_CONFIGURE_OPTIONS \
    --pkgconfigdir="$WORKSPACE/lib/pkgconfig" \
    --prefix=${WORKSPACE} \
    --pkg-config-flags="--static" \
    --extra-libs=-static \
    --extra-cflags=--static \
    --enable-cross-compile \
    --extra-cflags="-I$WORKSPACE/include -mmacosx-version-min=${MACOS_MIN}" \
    --extra-ldflags="-L$WORKSPACE/lib -mmacosx-version-min=${MACOS_MIN} -L/usr/local/opt/lame/lib -Wl,-rpath,/usr/local/opt/lame/lib" \
    --extra-libs="-lpthread -lm" \
    --enable-static \
    --disable-securetransport \
    --disable-debug \
    --disable-shared \
    --disable-ffplay \
    --disable-lzma \
    --disable-doc \
    --enable-version3 \
    --enable-pthreads \
    --enable-runtime-cpudetect \
    --enable-avfilter \
    --enable-filters \
    --disable-libxcb \
    --enable-gpl \
    --disable-libass \
    --enable-libmp3lame \
    --enable-libx264 \
    --enable-libopus

make -j 4
make install

otool -L "$WORKSPACE/bin/ffmpeg"
otool -L "$WORKSPACE/bin/ffprobe"

echo "Building done. The binaries can be found here: $WORKSPACE/bin/ffmpeg $WORKSPACE/bin/ffprobe"

mkdir ffmpeg-mac/ 
cp -r "$WORKSPACE/bin/" "$CWD/ffmpeg-mac/"

rm -rf "$PACKAGES"
rm -rf "$WORKSPACE"

exit 0



  


  It fails with this error :

  


  > sh buildffmpeg.sh

Extracting...
Building...
gcc is unable to create an executable file.
C compiler test failed.

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.


  


  I have been trying to solve this error, and have installed gcc with brew, if i run gcc -v I can see my installed gcc version :

  


  $ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/12.2.0/bin/../libexec/gcc/x86_64-apple-darwin20/12/lto-wrapper
Target: x86_64-apple-darwin20
Configured with: ../configure --prefix=/usr/local/opt/gcc --libdir=/usr/local/opt/gcc/lib/gcc/current --disable-nls --enable-checking=release --with-gcc-major-version-only --enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-12 --with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr --with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl --with-zstd=/usr/local/opt/zstd --with-pkgversion='Homebrew GCC 12.2.0' --with-bugurl=https://github.com/Homebrew/homebrew-core/issues --with-system-zlib --build=x86_64-apple-darwin20 --with-sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.2.0 (Homebrew GCC 12.2.0) 


  


  So if gcc is installed correctly (i think) why is it failing with a gcc error when I build ffmpeg ?

  


  ffbuild/config.log :

  


  ...
mktemp -u XXXXXX
9v9a2o
test_ld cc
test_cc
BEGIN /var/folders/p7/w8ysrm_x76v_z4n3nk70yd6m0000gn/T//ffconf.rUw6aGKJ/test.c
    1   int main(void){ return 0; }
END /var/folders/p7/w8ysrm_x76v_z4n3nk70yd6m0000gn/T//ffconf.rUw6aGKJ/test.c
gcc --static -I/Users/martinbarker/Documents/projects/rendertunev1.1.2/workspace/include -mmacosx-version-min=10.10 -c -o /var/folders/p7/w8ysrm_x76v_z4n3nk70yd6m0000gn/T//ffconf.rUw6aGKJ/test.o /var/folders/p7/w8ysrm_x76v_z4n3nk70yd6m0000gn/T//ffconf.rUw6aGKJ/test.c
gcc -L/Users/martinbarker/Documents/projects/rendertunev1.1.2/workspace/lib -mmacosx-version-min=10.10 -L/usr/local/opt/lame/lib -Wl,-rpath,/usr/local/opt/lame/lib -o /var/folders/p7/w8ysrm_x76v_z4n3nk70yd6m0000gn/T//ffconf.rUw6aGKJ/test /var/folders/p7/w8ysrm_x76v_z4n3nk70yd6m0000gn/T//ffconf.rUw6aGKJ/test.o -lpthread -lm -static
ld: warning: directory not found for option '-L/Users/martinbarker/Documents/projects/rendertunev1.1.2/workspace/lib'
ld: library not found for -lcrt0.o
collect2: error: ld returned 1 exit status
C compiler test failed.



  


  gcc test :

  


  apples-MacBook:gcctest apple$ export CC=$(which gcc)
apples-MacBook:gcctest apple$ export CXX=$(which g++)
apples-MacBook:gcctest apple$ ls
minimal.c
apples-MacBook:gcctest apple$ gcc -static -Wall -o minimal minimal.c -v
Apple LLVM version 10.0.0 (clang-1000.10.44.4)
Target: x86_64-apple-darwin17.0.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
 "/Library/Developer/CommandLineTools/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.13.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name minimal.c -static-define -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fno-strict-return -masm-verbose -munwind-tables -target-cpu penryn -dwarf-column-info -debugger-tuning=lldb -target-linker-version 409.12 -v -resource-dir /Library/Developer/CommandLineTools/usr/lib/clang/10.0.0 -Wall -fdebug-compilation-dir /Users/apple/Documents/projects/gcctest -ferror-limit 19 -fmessage-length 157 -stack-protector 1 -fblocks -fencode-extended-block-signature -fobjc-runtime=macosx-10.13.0 -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/7t/d2z0gq194s92vn5xz923gq5h0000gn/T/minimal-8cfbfc.o -x c minimal.c
clang -cc1 version 10.0.0 (clang-1000.10.44.4) default target x86_64-apple-darwin17.0.0
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /Library/Developer/CommandLineTools/usr/lib/clang/10.0.0/include
 /Library/Developer/CommandLineTools/usr/include
 /usr/include
 /System/Library/Frameworks (framework directory)
 /Library/Frameworks (framework directory)
End of search list.
 "/Library/Developer/CommandLineTools/usr/bin/ld" -demangle -lto_library /Library/Developer/CommandLineTools/usr/lib/libLTO.dylib -no_deduplicate -static -arch x86_64 -macosx_version_min 10.13.0 -o minimal -lcrt0.o /var/folders/7t/d2z0gq194s92vn5xz923gq5h0000gn/T/minimal-8cfbfc.o
ld: library not found for -lcrt0.o
clang: error: linker command failed with exit code 1 (use -v to see invocation)


  


• Adding ffmpeg OMX codec to Genymotion Android 4.4.2 emulator

  22 avril 2016, par photon

  Basic Question :

  Is there a way to add a new audio codec to the Genymotion Android emulator, short of downloading the entire Android source, learning how to build it, and creating my own version of Android ?

  ---

  Context :

  I have written a java Android app that acts as an audio renderer, as well as being a DLNA/OpenHome server and client. Think "BubbleUpnp" without video. My primary development platform is Win8.1. The program started as an ActiveState "pure-perl" DLNA MediaServer on Windows, which I then ported to Ubuntu, which I got working under Android a few years ago. It was pretty funky ... all UI being presented thru an HTTP server/jquery/jquery-ui, served from an Ubuntu shell running under Android (a trick in itself), serving up HTML pages to Chrome running on the same (Android) device. Besides being "funky" it had a major drawback that it required a valid IP address to work ... as I could not figure out how to get ubuntu to have a local loopback device for a 127.0.0.01 localhost I use the app as a "car stereo" on my boat (which is my home), which is often not hooked up to the internet.

  I had a hard time getting started in Android app development because the speed of the Android emulators in Eclipse was horrid, and the ADB drivers did not work from Win8 for the longest time.

  Then one day, about a year ago, I ran into Genymotion (kudos to the authors), and all of a sudden I had a workable Android development environment, so I added a Java implementation of the DLNA server, which then grew into a renderer also, using Android’s MediaPlayer class, and, adding the ability to act as a DLNA control point, and more recently also added OpenHome servers and renderers to it.

  In a separate effort, I created a build environment for this program called fpCalc, based on ffMpeg, on a variety of platforms, including Win, Linux, and Android x86, arm, and arm7 devices (bitbucket.org/phorton1/) and did an extensive series of tests to determine the validity, and longevity of fpcalc fingerprints, discovering that the fpCalc fingerprint changed based on the version of ffmpeg it was built against, a separate topic to be sure, but in the process, learned at least a bit about how to build ffmpeg as well as Android shared libraries, JNI interfaces, etc.

  So now the Android-Java version of the program has advanced past the old perl version, and I am debating whether I want to continue to try to build the perl version (and or add an wxPerl UI) to it.

  One issue that has arisen, for me, is that the Genymotion emulator does not support WMA decoding ... as Android dropped support for WMA due to licensing issues, etc, a ways back in time ... yet my music library has significant numbers of tunes in WMA files, and I don’t want to "convert" them, my carefully thought-out philosophy is that my program does not modify the contents, or tags, or anything in the original media files that I have accumulated, or will receive in the future, rather treating them as "artifacts" worth preserving "as is". No conversion is going to make a file "better" than it was, and I wish to preserve ALL of the original sources for ALL of my music going forward.

  So, I’m thinking, gee, I can build FFMPEG on 7 different platforms, and I see all these references to "OMX FFMPEG Codec Support for Android" on the net, so I’m thinking, "All I need to do is create the OMX Component and somehow get it into Genymotion".

  I have studied up OMX, OpenMaxIL, seen Michael Chen’s posts, seen the stack overflow questions

  How to make ffmpeg codec componet as OMX component

  and

  Android : How to integrate a decoder to multimedia framework

  and Cedric Fung’s page https://vec.io/posts/use-android-hardware-decoder-with-omxcodec-in-ndk, and Michael Chen’s repository at https://github.com/omxcodec , as well as virtually every other page on the net that mentions any combination of libstagefright, OMX, Genymotion, and FFMPEG.

  (this page would not let me put more than 2 links as i don’t have a "10" reputation, or I would have listed some of the sources I have seen) ..

  My Linux development environment is a Ubuntu12.04 vbox running on my win machine. I have downloaded and run the Android-x86 iso as a vbox, and IT contains the ffmpeg codecs, but unfortunately, it neither supports a wifi interface, nor the vbox "guest additions", so it has a really funky mouse. I tried for about 3 days to address those two issues, but in the end do not feel it is usable for my puproses, and I really like the way genymotion "feels", particularly the moust support, so I’d like to keep genymotion as my "windows android" virtual device under which I may run my program, deprecate and stop using my old perl source,

  except genymotion does not support WMA files ...

  ---

  Several side notes :

  (a) There is no good way to write a single sourced application in Java that runs natively in Windows, AND as an Android app.

  (b) I don’t want to reboot my Windows machine to a "real" Android device just to play my music files. The machine has to stay in Windows as I use it for other things as well.

  (c) I am writing this as my machine is in the 36th hour of downloading the entire ASOP source code base to a partition in my Ubuntu vbox while I am sitting in a hotel room on a not-so-good internet connection in Panama City, Panama, before I return to my boat in remote Bocas Del Toro Panama, where the internet connection is even worse.

  (d) I did get WMA decoding to work in my app by calling my FFMPEG executable from Java (converting it to either WAV/PCM or AAC), but, because of limitations in Android’s MediaPlayer, it does not work well, particularly for remotely hosted WMA files ... MediaPlayer insists on having the whole file present before it starts to play, which can take several seconds or longer, and I am hoping that by getting a ’real’ WMA codec underneath MediaPlayer, that problem will just disappear ....

  ---

  So, I’m trying to figure this whole mess out. There are a lot of tantalizing clues, and suggestions, but what I have found, or at least what I am starting to believe, is that if I want to add a simple WMA audio decoding codec to Android (Genymotion), not only do I have to download, basically, the ENTIRE ASOP Android source tree, and learn a new set of tools (repo, etc), but I have to (be able to) rebuild, from scratch, the entire Android system, esp. libstagefright.so in such a way as to be COMPLETELY compatible with the existing one in GenyMotion, while at the same time adding ffmpeg codecs ala Michael Chen’s page.

  And I’m just asking, is it, could it really be that difficult ?

  ---

  Anyways, this makes me crazy. Is there no way to just build a new component, or at worst a new OMX core, and add it to Genymotion, WITHOUT building all of Android, and preferably, based only on the OMX h files ? Or do I REALLY have to replace the existing libstagefright.so, which means, basically, rebuilding all of Android ...

  p.s. I thought it would be nice to get this figured out, build it, and then post the installable new FFMPEG codecs someplace for other people to use, so that they don’t also grow warts on their ears and have steam shooting out of their eyeballs, while they get old trying to figure it out ....