[FFmpeg-trac] #5910(undetermined:new): AAC to PCM conversion inserts extra silence in the beginning

[FFmpeg]

#5910: AAC to PCM conversion inserts extra silence in the beginning
-------------------------------------+-------------------------------------
             Reporter:               |                    Owner:
  jwilhelmsson                       |                   Status:  new
                 Type:  defect       |                Component:
             Priority:  normal       |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:  aac pcm      |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by jwilhelmsson):

 It seems so, yes. I asked our server guy to install the latest, and all
 files convert exactly the same way. Here's the output for the seven second
 movie clip:

 {{{
 ffmpeg -i g_7s.aac -c:a pcm_s24le -ar 48k g_7s_ffmpeg.wav
 ffmpeg version N-82143-gbf14393 Copyright (c) 2000-2016 the FFmpeg
 developers
   built with gcc 4.7.3 (Gentoo 4.7.3-r1 p1.4, pie-0.5.5)
   configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64
 --docdir=/usr/share/doc/ffmpeg-9999/html --mandir=/usr/share/man --enable-
 shared --cc=x86_64-pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-g++
 --ar=x86_64-pc-linux-gnu-ar --optflags='-march=core2 -mtune=generic -O2
 -pipe' --disable-static --enable-avfilter --enable-avresample --disable-
 stripping --disable-indev=v4l2 --disable-outdev=v4l2 --disable-indev=alsa
 --disable-indev=oss --disable-indev=jack --disable-outdev=alsa --disable-
 outdev=oss --disable-outdev=sdl --enable-version3 --enable-nonfree
 --enable-bzlib --disable-runtime-cpudetect --disable-debug --disable-
 gcrypt --disable-gnutls --disable-gmp --enable-gpl --enable-hardcoded-
 tables --enable-iconv --disable-lzma --enable-network --disable-openssl
 --enable-postproc --disable-libsmbclient --disable-ffplay --disable-sdl2
 --disable-vaapi --disable-vdpau --disable-xlib --disable-libxcb --disable-
 libxcb-shm --disable-libxcb-xfixes --enable-zlib --disable-libcdio
 --disable-libiec61883 --disable-libdc1394 --disable-libcaca --disable-
 openal --disable-opengl --disable-libv4l2 --disable-libpulse --enable-
 libopencore-amrwb --enable-libopencore-amrnb --enable-libfdk-aac --enable-
 libopenjpeg --disable-libbluray --disable-libcelt --disable-libgme
 --enable-libgsm --disable-mmal --disable-libmodplug --disable-libopus
 --disable-libilbc --disable-librtmp --disable-libssh --enable-
 libschroedinger --enable-libspeex --enable-libvorbis --disable-libvpx
 --disable-libzvbi --disable-libbs2b --disable-chromaprint --disable-
 libebur128 --disable-libflite --disable-frei0r --disable-libfribidi
 --disable-fontconfig --disable-ladspa --enable-libass --enable-libfreetype
 --disable-librubberband --disable-libzimg --disable-libsoxr --enable-
 pthreads --disable-libvo-amrwbenc --enable-libmp3lame --disable-libkvazaar
 --disable-nvenc --disable-libopenh264 --disable-libsnappy --enable-
 libtheora --disable-libtwolame --disable-libwavpack --disable-libwebp
 --enable-libx264 --disable-libx265 --enable-libxvid --disable-x11grab
 --disable-amd3dnow --disable-amd3dnowext --disable-aesni --disable-avx
 --disable-avx2 --disable-fma3 --disable-fma4 --disable-sse3 --disable-
 ssse3 --disable-sse4 --disable-sse42 --disable-xop --cpu=core2 --disable-
 doc --disable-htmlpages --enable-manpages
   libavutil      55. 35.100 / 55. 35.100
   libavcodec     57. 65.100 / 57. 65.100
   libavformat    57. 57.100 / 57. 57.100
   libavdevice    57.  2.100 / 57.  2.100
   libavfilter     6. 66.100 /  6. 66.100
   libavresample   3.  2.  0 /  3.  2.  0
   libswscale      4.  3.100 /  4.  3.100
   libswresample   2.  4.100 /  2.  4.100
   libpostproc    54.  2.100 / 54.  2.100
 [aac @ 0x88b2b0] Estimating duration from bitrate, this may be inaccurate
 Input #0, aac, from 'g_7s.aac':
   Duration: 00:00:07.01, bitrate: 320 kb/s
     Stream #0:0: Audio: aac (LC), 48000 Hz, stereo, fltp, 320 kb/s
 Output #0, wav, to 'g_7s_ffmpeg.wav':
   Metadata:
     ISFT            : Lavf57.57.100
     Stream #0:0: Audio: pcm_s24le ([1][0][0][0] / 0x0001), 48000 Hz,
 stereo, s32, 2304 kb/s
     Metadata:
       encoder         : Lavc57.65.100 pcm_s24le
 Stream mapping:
   Stream #0:0 -> #0:0 (aac (native) -> pcm_s24le (native))
 Press [q] to stop, [?] for help
 size=    1974kB time=00:00:07.01 bitrate=2304.1kbits/s speed= 297x
 video:0kB audio:1974kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.005046%
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/5910#comment:7>
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