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• Change the default audio and video codec loaded by avformat_alloc_output_context2

  8 juin 2021, par mythili3093

  I'm using ffmpeg library for live streaming via RTMP. I want to know how to give my choice of audio and video codec for the particular format in avformat_alloc_output_context2.

  


  In Detail :

  


  The following command works perfectly for me.

  


  ffmpeg -re -stream_loop -1 -i ~/Downloads/Microsoft_Surface.mp4 -vcodec copy -c:a aac -b:a 160k -ar 44100 -strict -2 -f flv -flvflags no_duration_filesize rtmp://192.168.1.7/live/surface


  


  In the output, I have set my audio codec to be aac and copied the video codec from input, which is H264.
I want to emulate this in the library, but don't know how to.

  


  avformat_alloc_output_context2(&_ctx, NULL, "flv", NULL);


  


  Above code sets oformat audio codec to ADPCM_SWF and video codec to FLV1. How to change that to AAC and H264 ?

  


  So far, used av_guess_format to construct AVOutputFormat. It accepts only format as input. And I don't know where to mention audio and video codec.

  


  AVOutputFormat* output_format = av_guess_format("flv", NULL, NULL);


  


  Also tried giving filename to avformat_alloc_output_context2 with the rest of the parameters NULL.

  


  AVOutputFormat* output_format = av_guess_format(NULL, "flv_acc_sample.flv", NULL);


  


  This file has AAC audio and H264 video. But still ffmpeg loads oformat with ADPCM_SWF audio and FLV1 video codecs.

  


  Searched stackoverflow for similar questions, but could not find the solution I was looking for.
Any hint/guidance is hugely appreciated. Thank you.

  


• ffmpeg built on mac 10.13 fails when ran on other computer (dyld : Library not loaded libmp3lame.0.dylib)

  15 mars 2023, par Martin

  I have a shell script called buildffmpeg.sh which I call with the command $ sh buildffmpeg.sh on my mac os high sierra 10.13 machine :

  


  #!/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=${WORKSPACE} \
    --pkg-config-flags="--static" \
    --extra-cflags="-I$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



  


  When it finishes, I have a folder ffmpeg-mac/ which contains two built executables ffmpeg and ffprobe.

  


  but if I try to move the ffmpeg-mac folder onto my other macbook, running 11.2.3 big sur, and if i try to call my built ffmpeg file with ./ffmpeg-mac/ffmpeg, it fails with this error :

  


  $ ./ffmpeg-mac/ffmpeg 
dyld: Library not loaded: /usr/local/opt/lame/lib/libmp3lame.0.dylib
  Referenced from: /Users/martinbarker/Documents/projects/rendertunev1.1.2/./ffmpeg-mac/ffmpeg
  Reason: image not found
Abort trap: 6



  


  So I think when I run the script to build ffmpeg on my mac 10.13 high sierra machine, it for some reason is not including the file libmp3lame.0.dylib. I've tried using brew to uninstall, install, unlink, and link lame, but no luck. I've tried manually editing my shell script to include the file but no luck.

  


  Can anyone help me fix my build script so that when I build ffmpeg on high sierra, I can use the finished built file on other mac computers ?

  


• ffmpeg produces quality poor gif animation from gnuplot pictures

  6 juillet 2020, par Tobi

  I am using FFmpeg a while, but I never found this strange behavior that I cannot resolve right now. I do have a few plots generated via Gnuplot, and I do want to combine them into an animated gif file.

  


  The code I am using is the following :

  


  cat $(find singleGraphs -maxdepth 1 -name  "*.png" | sort -V) | \               
ffmpeg \                                                                        
    -framerate 2 \                                                              
    -i - \                                                                      
    -pattern_type glob \                                                        
    -q:v 1 \                                                                    
    -y \                                                                        
    Analysis.gif \                                                              
; 


  


  The resulting gif picture is poor in color, as you can see in the animation below. I probably do use any argument wrong, or something is missing. However, if I do create an mp4 video, everything works well here.

  


  

  


  The single PNG files can be found here The single Gnuplot Pictures