[FFmpeg-user] hearing higher frequencies than expected from generated audio using aevalsrc

[signalsender103 at gmail.com]

Hello,

When I perform this command to generate what I expect should be a sine wave sweeping from 262 hZ
to the next octave higher over a duration of 10 seconds, using this command:

ffmpeg -f lavfi -i aevalsrc=sin(262*2^^(t/10)*2*PI*t):d=10 test.ogg

I get the following output:

ffmpeg version N-82759-g1f5630a Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 41.101 / 55. 41.101
  libavcodec     57. 66.109 / 57. 66.109
  libavformat    57. 58.101 / 57. 58.101
  libavdevice    57.  2.100 / 57.  2.100
  libavfilter     6. 68.100 /  6. 68.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
Input #0, lavfi, from 'aevalsrc=sin(262*2^(t/10)*2*PI*t):d=10':
  Duration: N/A, start: 0.000000, bitrate: 2822 kb/s
    Stream #0:0: Audio: pcm_f64le, 44100 Hz, mono, dbl, 2822 kb/s
Output #0, ogg, to 'test.ogg':
  Metadata:
    encoder         : Lavf57.58.101
    Stream #0:0: Audio: vorbis (libvorbis), 44100 Hz, mono, fltp
    Metadata:
      encoder         : Lavc57.66.109 libvorbis
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_f64le (native) -> vorbis (libvorbis))
Press [q] to stop, [?] for help
size=      21kB time=00:00:09.99 bitrate=  17.1kbits/s speed=47.7x    
video:0kB audio:17kB subtitle:0kB other streams:0kB global headers:3kB muxing overhead: 23.471869%

resulting in the attached Ogg file. The resulting frequency sweep ends up almost an
octave higher than I expected. What am I doing wrong? How can I fix this?

Thanks,

Adam
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