Specified sample format s16 is invalid or not supported - ios

Question

I am encoding PCM data to AAC format using ffmpeg:
Following is my code to setup the context object:
-(id)encode:(short*)data{
AVCodecContext *audioCodec;
AVCodec *codec;
avcodec_register_all();
//Set up audio encoder
codec = avcodec_find_encoder(AV_CODEC_ID_AAC);
if (codec == NULL){
NSLog(#"no codec");
}
audioCodec = avcodec_alloc_context3(codec);
audioCodec->strict_std_compliance = -2;
audioCodec->bit_rate = 64000;
audioCodec->sample_fmt = AV_SAMPLE_FMT_S16;
audioCodec->sample_rate = 8000;
audioCodec->channels = 2;
audioCodec->profile = FF_PROFILE_AAC_MAIN;
audioCodec->time_base = (AVRational){1, 8000};
audioCodec->codec_type = 1;
if (avcodec_open2(audioCodec, codec, NULL)) {
NSLog(#"could not open codec");
}
return #"NO";
}
I always get an error log as :
aac # 0x151cda00] Specified sample format s16 is invalid or not supported
If I don't provide any sample format, I get the same log:
aac # 0x151cda00] Specified sample format -1 is invalid or not supported
and that's why avcodec_open2() gives log of could not open codec ;
Can some 1 tell me what is the issue?
ffmpeg compilation script is as follows:
#!/bin/sh
# directories
SOURCE="ffmpeg"
FAT="fat"
VERSION="2.0.2"
SCRATCH="scratch"
# must be an absolute path
THIN=`pwd`/"thin"
# absolute path to x264 library
#X264=`pwd`/fat_x264
CONFIGURE_FLAGS="--enable-cross-compile \
--disable-network \
--disable-encoders \
--disable-decoders \
--disable-muxers \
--disable-demuxers \
--disable-protocols \
--disable-devices \
--disable-ffmpeg \
--disable-ffplay \
--disable-ffprobe \
--disable-ffserver \
--disable-avdevice \
--disable-avfilter \
--disable-iconv \
--disable-bzlib \
--disable-mmx \
--disable-mmxext \
--disable-amd3dnow \
--disable-amd3dnowext \
--disable-sse \
--disable-sse2 \
--disable-sse3 \
--disable-sse4 \
--disable-avx \
--disable-fma4 \
--disable-swresample \
--disable-postproc \
--disable-bsfs \
--disable-filters \
--disable-asm \
--disable-yasm \
--disable-debug \
--disable-doc \
--disable-armv5te \
--disable-armv6 \
--disable-armv6t2 \
--enable-protocol=file \
--enable-avformat \
--enable-avcodec \
--enable-swscale \
--enable-demuxer=mp3 \
--enable-demuxer=aac \
--enable-demuxer=image2 \
--enable-demuxer=mov \
--enable-decoder=rawvideo \
--enable-demuxer=h263 \
--enable-demuxer=h264 \
--enable-decoder=mp3 \
--enable-decoder=aac \
--enable-decoder=mjpeg \
--enable-decoder=h263 \
--enable-decoder=h264 \
--enable-decoder=mpeg4 \
--enable-encoder=mp3 \
--enable-encoder=aac \
--enable-encoder=mjpeg \
--enable-encoder=h263 \
--enable-encoder=h264 \
--enable-encoder=mpeg4 \
--enable-parser=mp3 \
--enable-parser=aac \
--enable-parser=h264 \
--enable-pic"
if [ "$X264" ]
then
CONFIGURE_FLAGS="$CONFIGURE_FLAGS --enable-gpl --enable-libx264"
fi
# avresample
#CONFIGURE_FLAGS="$CONFIGURE_FLAGS --enable-avresample"
ARCHS="arm64 armv7s armv7 x86_64 i386"
COMPILE="y"
LIPO="y"
DEPLOYMENT_TARGET="6.0"
if [ "$*" ]
then
if [ "$*" = "lipo" ]
then
# skip compile
COMPILE=
else
ARCHS="$*"
if [ $# -eq 1 ]
then
# skip lipo
LIPO=
fi
fi
fi
if [ "$COMPILE" ]
then
CWD=`pwd`
for ARCH in $ARCHS
do
echo "building $ARCH..."
mkdir -p "$SCRATCH/$ARCH"
cd "$SCRATCH/$ARCH"
CFLAGS="-arch $ARCH"
if [ "$ARCH" = "i386" -o "$ARCH" = "x86_64" ]
then
PLATFORM="iPhoneSimulator"
CFLAGS="$CFLAGS -mios-simulator-version-min=$DEPLOYMENT_TARGET"
else
PLATFORM="iPhoneOS"
CFLAGS="$CFLAGS -mios-version-min=$DEPLOYMENT_TARGET"
if [ "$ARCH" = "arm64" ]
then
EXPORT="GASPP_FIX_XCODE5=1"
fi
fi
XCRUN_SDK=`echo $PLATFORM | tr '[:upper:]' '[:lower:]'`
CC="xcrun -sdk $XCRUN_SDK clang"
CXXFLAGS="$CFLAGS"
LDFLAGS="$CFLAGS"
if [ "$X264" ]
then
CFLAGS="$CFLAGS -I$X264/include"
LDFLAGS="$LDFLAGS -L$X264/lib"
fi
$CWD/$SOURCE/configure \
--target-os=darwin \
--arch=$ARCH \
--cc="$CC" \
$CONFIGURE_FLAGS \
--extra-cflags="$CFLAGS" \
--extra-cxxflags="$CXXFLAGS" \
--extra-ldflags="$LDFLAGS" \
--prefix="$THIN/$ARCH"
make -j3 install $EXPORT
cd $CWD
done
fi
if [ "$LIPO" ]
then
echo "building fat binaries..."
mkdir -p $FAT/lib
set - $ARCHS
CWD=`pwd`
cd $THIN/$1/lib
for LIB in *.a
do
cd $CWD
lipo -create `find $THIN -name $LIB` -output $FAT/lib/$LIB
done
cd $CWD
cp -rf $THIN/$1/include $FAT
fi

Answer 1

I was having a similar issue as I did not know what format my Windows Phone supported. (turns out it was AV_SAMPLE_FMT_FLTP )
I ended up looking at the avcodec_open2 source code (https://www.ffmpeg.org/doxygen/2.1/libavcodec_2utils_8c_source.html)
And discovered it was referencing the codec to see which samples were supported.
With that in mind you can do something like this:
audioCodec->sample_fmt = audioCodec->codec->sample_fmts[0];

Answer 2

Maybe the error is misleading.
Try removing the line:
audioCodec->profile = FF_PROFILE_AAC_MAIN or changing it to audioCodec->profile = FF_PROFILE_UNKNOWN
Try compiling in the fdk-aac encoder: https://github.com/mstorsjo/fdk-aac The output quality is much better and it supports a wide range of sample rates and bitrates. To my knowledge, the native ffmpeg encoder is not very good in comparison. But maybe you can't use fdk-aac because of the license (you will need to pay patent royalties to Fraunhofer):
http://www.vialicensing.com/licensing/aac-faq.aspx
http://www.vialicensing.com/licensing/aac-fees.aspx