[FFmpeg-user] Large Sized output files recieved while encoding the audio

[Shubham Tiwari]

Hi,

When I run ffmpeg command on a wav file, the received output file is of
large size as compared to the original file. The command and the output are
below,

*FFMPEG command*

 % ~/Downloads/audio/ffmpeg -i call-redacted.wav output.wav

ffmpeg version 4.4.1-tessus  https://evermeet.cx/ffmpeg/  Copyright (c)
2000-2021 the FFmpeg developers

  built with Apple clang version 11.0.0 (clang-1100.0.33.17)

  configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg
--extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl
--enable-libaom --enable-libass --enable-libbluray --enable-libdav1d
--enable-libfreetype --enable-libgsm --enable-libmodplug
--enable-libmp3lame --enable-libmysofa --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg
--enable-libopus --enable-librubberband --enable-libshine
--enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora
--enable-libtwolame --enable-libvidstab --enable-libvmaf
--enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwebp
--enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid
--enable-libzimg --enable-libzmq --enable-libzvbi --enable-version3
--pkg-config-flags=--static --disable-ffplay

  libavutil      56. 70.100 / 56. 70.100

  libavcodec     58.134.100 / 58.134.100

  libavformat    58. 76.100 / 58. 76.100

  libavdevice    58. 13.100 / 58. 13.100

  libavfilter     7.110.100 /  7.110.100

  libswscale      5.  9.100 /  5.  9.100

  libswresample   3.  9.100 /  3.  9.100

  libpostproc    55.  9.100 / 55.  9.100

Input #0, mp3, from 'call-redacted.wav':

  Metadata:

    encoder         : Lavf58.45.100

  Duration: 00:13:06.38, start: 0.138125, bitrate: 64 kb/s

  Stream #0:0: Audio: mp3, 8000 Hz, stereo, fltp, 64 kb/s

Stream mapping:

  Stream #0:0 -> #0:0 (mp3 (mp3float) -> pcm_s16le (native))

Press [q] to stop, [?] for help

Output #0, wav, to 'output.wav':

  Metadata:

    ISFT            : Lavf58.76.100

  Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 8000 Hz, stereo,
s16, 256 kb/s

    Metadata:

      encoder         : Lavc58.134.100 pcm_s16le

size=   24569kB time=00:13:06.17 bitrate= 256.0kbits/s speed=2.97e+03x

video:0kB audio:24569kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.000310


*Input and output file sizes*

du -sh call-redacted.wav

6.5M call-redacted.wav

du -sh output.wav

 24M output.wav


Alternatively, when I run the same command but change the output
file's extension to mp3, the correct sized file is returned. But the time
taken (6 seconds) in this case is quite higher than the previous case(less
than 1 second). The command and output is below,



~/Downloads/audio/ffmpeg -i call-redacted.wav output.mp3

ffmpeg version 4.4.1-tessus  https://evermeet.cx/ffmpeg/  Copyright (c)
2000-2021 the FFmpeg developers

  built with Apple clang version 11.0.0 (clang-1100.0.33.17)

  configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg
--extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl
--enable-libaom --enable-libass --enable-libbluray --enable-libdav1d
--enable-libfreetype --enable-libgsm --enable-libmodplug
--enable-libmp3lame --enable-libmysofa --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg
--enable-libopus --enable-librubberband --enable-libshine
--enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora
--enable-libtwolame --enable-libvidstab --enable-libvmaf
--enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwebp
--enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid
--enable-libzimg --enable-libzmq --enable-libzvbi --enable-version3
--pkg-config-flags=--static --disable-ffplay

  libavutil      56. 70.100 / 56. 70.100

  libavcodec     58.134.100 / 58.134.100

  libavformat    58. 76.100 / 58. 76.100

  libavdevice    58. 13.100 / 58. 13.100

  libavfilter     7.110.100 /  7.110.100

  libswscale      5.  9.100 /  5.  9.100

  libswresample   3.  9.100 /  3.  9.100

  libpostproc    55.  9.100 / 55.  9.100

Input #0, mp3, from 'call-redacted.wav':

  Metadata:

    encoder         : Lavf58.45.100

  Duration: 00:13:06.38, start: 0.138125, bitrate: 64 kb/s

  Stream #0:0: Audio: mp3, 8000 Hz, stereo, fltp, 64 kb/s

Stream mapping:

  Stream #0:0 -> #0:0 (mp3 (mp3float) -> mp3 (libmp3lame))

Press [q] to stop, [?] for help

Output #0, mp3, to 'output.mp3':

  Metadata:

    TSSE            : Lavf58.76.100

  Stream #0:0: Audio: mp3, 8000 Hz, stereo, fltp

    Metadata:

      encoder         : Lavc58.134.100 libmp3lame

size=    2304kB time=00:13:06.17 bitrate=  24.0kbits/s speed= 130x

video:0kB audio:2304kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.011063

du -sh output.mp3

3.3M output.mp3


Please help me out in identifying the right command options for optimum
time and filesize.


Regards,

Shubham