AudioConverter
Integrates with LAME library to support converting audio to MP3 format in addition to the formats supported by iOS.
How to Build
First create the static libary for LAME using LAME iOS Build. Get the latest
LAME download and place the source in a folder named lame under the build folder.
Then run build-lame.sh which will create various static libraries for each of the
supported architectures as well as FAT binaries which can be used for development.
Then copy the files LAME into this folder with the following paths below the AudioConverter directory.
lame/include/lame/lame.hlame/lib/libmp3lame.a
With these files in place it will be possible to compile the project which includes the
class ExtAudioFileConverter which is used to convert audio files. An example is shown
in ViewController.m which converts source.m4a to output.mp3 which is placed in the
Caches directory. When conversion is completed an AVPlayerViewController is displayed
and the new file is played immediately.
Release Builds
Running the script for LAME iOS Build creates a FAT binary which includes architectures for devices as well as the iOS Simulator. When a release build is submitted to the App Store it will be rejected if architectures for the iOS Simulator are included source they must be excluded. Running the build script can be run again to build with the valid architures only. First the previous output folders must be deleted.
rm -rf fat-lame/
rm -rf scratch-lame/
rm -rf thin-lame/
./build-lame.sh arm64 armv7s armv7A tool like CocoaPods includes scripts which strip out these architectures using the
lipo tool. It is also possible to create Debug and Release static libaries with
the required architectures based on the current build configuration.
NOTE: It is possible that current versions of Xcode will strip out the invalid architectures when the archive is created for submitting a build to the App Store, making this work unnecessary.
Source Audio
Creating the source audio for testing is easily done using macOS using the following command.
say -o source.m4a "Start and Stop"Any text can be converted to speech and stored in the output file.