[FFmpeg-user] Is FLAC 8 Bit supported?

[Takashi]

I'm trying to create an 8 Bit FLAC audio file using ffmpeg, but without
success. (It's working with -sample_fmt s16 but not with -sample_fmt
u8). What am I doing wrong? Is this a bug or feature request or not
possible? (8 Bit is at least in the specs:
https://xiph.org/flac/format.html)

/usr/local/bin/ffmpeg -y -i test.mp3 -sample_fmt u8 test.flac
ffmpeg version N-62299-g60ef0c6 Copyright (c) 2000-2014 the FFmpeg
developers
  built on Apr  9 2014 14:43:15 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --enable-version3 --enable-libopenjpeg
--enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame
--enable-libopus --enable-libopencore-amrnb --enable-libopencore-amrwb
--enable-libvorbis --enable-libtheora --enable-libvpx --enable-libspeex
--enable-libxvid --enable-libx264 --disable-network --disable-stripping
--enable-libschroedinger --enable-libgsm --enable-avfilter
--enable-pthreads --disable-ffserver --extra-cflags=-I/usr/local/include
--extra-ldflags=-L/usr/local/lib --disable-protocol=httpproxy
--enable-bzlib --enable-libvpx --enable-zlib
  libavutil      52. 75.100 / 52. 75.100
  libavcodec     55. 58.103 / 55. 58.103
  libavformat    55. 36.102 / 55. 36.102
  libavdevice    55. 11.100 / 55. 11.100
  libavfilter     4.  3.100 /  4.  3.100
  libswscale      2.  6.100 /  2.  6.100
  libswresample   0. 18.100 /  0. 18.100
  libpostproc    52.  3.100 / 52.  3.100
Input #0, mp3, from 'test.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf54.33.100
  Duration: 00:00:55.25, start: 0.025057, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
[flac @ 0x2ac3300] Specified sample format u8 is invalid or not supported
Output #0, flac, to 'test.flac':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf54.33.100
    Stream #0:0: Audio: flac, 44100 Hz, stereo, u8, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 -> flac)
Error while opening encoder for output stream #0:0 - maybe incorrect
parameters such as bit_rate, rate, width or height