pcm→wavはこんな感じでやってる
ffmpeg -f s24be -ar 48000 -ac 2 -i hoge.pcm hoge.wav

[s24be @ 00000270bd168dc0] Estimating duration from bitrate, this may be inaccurate
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, s24be, from 'hoge.pcm':
Duration: 00:25:28.53, bitrate: 2304 kb/s
Stream #0:0: Audio: pcm_s24be, 48000 Hz, stereo, s32 (24 bit), 2304 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s24be (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, wav, to 'hoge.wav':
Metadata:
ISFT : Lavf58.28.101
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, stereo, s16, 1536 kb/s
Metadata:
encoder : Lavc58.53.101 pcm_s16le
size= 286599kB time=00:25:28.53 bitrate=1536.0kbits/s speed=2.12e+03x
video:0kB audio:286599kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000027%