FFMpeg cannot write length for piped WAV files

[Artem S. Tashkinov]

How to reproduce:

$ ffmpeg -ss 00:00:30 -i 1.flac -vn -acodec pcm_s16le -ar 44100 -f wav -loglevel warning - > 1.wav

$ ffmpeg -i 1.wav -f null - 
ffmpeg version 4.1 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 8 (GCC)
  configuration: --disable-static --enable-nonfree --enable-avfilter --enable-shared --enable-gpl --enable-postproc --enable-pthreads --enable-libspeex --enable-libmp3lame --enable-libx264 --enable-libxvid --enable-libopus --enable-libopenjpeg --disable-debug --disable-doc --enable-libpulse --extra-cflags='-mtune=generic' --enable-version3 --enable-libvorbis --enable-libfdk-aac --enable-gnutls --enable-libfreetype --enable-libx265 --libdir=/usr/local/lib64 --enable-lto
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
[wav @ 0x12f4140] Ignoring maximum wav data size, file may be invalid
[wav @ 0x12f4140] Estimating duration from bitrate, this may be inaccurate
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, wav, from '1.wav':
  Duration: 00:03:15.19, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
    Metadata:
      encoder         : Lavc58.35.100 pcm_s16le
1.wav: corrupt input packet in stream 0
size=N/A time=00:03:15.19 bitrate=N/A speed=2.94e+03x    
video:0kB audio:33625kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

[Hendrik]

Don't use redirection to write your file. FFmpeg can't write a proper size tag if it cannot seek in the file.

right:
ffmpeg -ss 00:00:30 -i 1.flac -vn -acodec pcm_s16le -ar 44100 -f wav -loglevel warning 1.wav

wrong:
ffmpeg -ss 00:00:30 -i 1.flac -vn -acodec pcm_s16le -ar 44100 -f wav -loglevel warning - > 1.wav

[Artem S. Tashkinov]

I need to pipe the resulting file to sox. I can't see any other way to do that and previous FFMpeg versions worked fine, e.g. FFMpeg 3.2.2.

[Artem S. Tashkinov]

Nevermind, I managed to pipe it without using WAV:

ffmpeg -i source.flac -vn -acodec pcm_s16le -ar 44100 -f s16le \
-loglevel warning - | sox -t raw -r 44100 -e signed -b 16 -c 2 - out.wav reverse

Though it's still a loss since I perfectly remember that it worked in the past.

I'll leave it as WONTFIX since this feature used to work in the past and now you're refusing to change it back.

[James]

Replying to birdie:

I need to pipe the resulting file to sox. I can't see any other way to do that and previous FFMpeg versions worked fine, e.g. FFMpeg 3.2.2.

Applications that accept pipping of wav files should ignore the size field. See for example --ignorelength in opusenc.

ffmpeg can't write a size field if the output is not seekable.

[Artem S. Tashkinov]

Replying to jamrial:

Applications that accept pipping of wav files should ignore the size field. See for example --ignorelength in opusenc.

ffmpeg can't write a size field if the output is not seekable.

This is perhaps the best comment in this bug report: you're right, sox manual says such an option exists:

−−ignore−length

Override an (incorrect) audio length given in an audio file’s header. If this option is given then SoX will keep reading audio until it reaches the end of the input file.

Thank you!