How do I get audio files of a specific file size?

Is there any way to use ffmpeg to accurately break audio files into smaller files of a specific file size, or pull a specific number of samples from a file?

I'm working with a speech-to-text API that needs audio chunks in exactly 160,000 bytes, or 80,000 16-bit samples.

I have a video stream, and I have an ffmpeg command to extract audio from it:

ffmpeg -i "rtmp://MyFMSWorkspace/ingest/test/mp4:test_1000 live=1" -ar 16000 -f segment -segment_time 10 out%04d.wav

So now I have ~10 second audio chunks with a sample rate of 16 kHz. Is there any way to break this into exactly 160kb, 5 second files using ffmpeg?

I tried this:

ffmpeg -t 00:00:05.00 -i out0000.wav outCropped.wav

But the output was this:

Input #0, wav, from 'out0000.wav':
  Metadata:
    encoder         : Lavf56.40.101
  Duration: 00:00:10.00, bitrate: 256 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, 1 channels, s16, 256 kb/s
Output #0, wav, to 'outCropped.wav':
  Metadata:
    ISFT            : Lavf56.40.101
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, mono, s16, 256 kb/s
    Metadata:
      encoder         : Lavc56.60.100 pcm_s16le
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
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size=     156kB time=00:00:05.00 bitrate= 256.1kbits/s

but now the size is 156kb

EDIT:

My finished command is:

ffmpeg -i "url" -map 0:1 -af aresample=16000,asetnsamples=16000 -f segment -segment_time 5 -segment_format sw out%04d.sw

Solution

That output looks perfectly right. That ffmpeg size is expressed in KiB although it says kB. 160000 bytes = 156.25 kB + some header data. ffmpeg shows size with fractional part hidden. If you want a raw file, with no headers, output to .raw instead of .wav.