Pipe input in to ffmpeg stdin

Question

I am trying to use ffmpeg to decode audio data. While it works to load from a file, I would like to avoid using files because to do so, means I would have to use a temporary. Instead, I'd like to pipe in the data(which I've previously loaded) using stdin.

Is this possible?

e.g.,

Manually load mp3 file
Pipe it in to the ffmpeg spawned process
Get raw output

(it should work with ffprobe and ffplay also)

MrBar · Answer 1 · 2018-07-19T11:36:49.037

35

ffmpeg has a special pipe flag that instructs the program to consume stdin. note that almost always the input format needs to be defined explicitly.

example (output is in PCM signed 16-bit little-endian format):

cat file.mp3 | ffmpeg -f mp3 -i pipe: -c:a pcm_s16le -f s16le pipe:

pipe docs are here
supported audio types are here

edited Jul 19 '18 at 11:36

answered Aug 27 '17 at 07:35

MrBar

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@AbstractDissonance updated the answer to explain better a raw format – MrBar Dec 29 '17 at 22:57
Can the output of an ffmpeg command be piped as input to a subsequent ffmpeg command? I'm having trouble figuring out if it can be. – Sridhar Sarnobat Jun 10 '19 at 20:01
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yes you can! `ffmpeg -i file.mp3 -c:a pcm_s16le -f s16le pipe: | ffmpeg -f mp3 -i pipe: -c:a pcm_s16le -f s16le encoded.mp3` – MrBar Jun 11 '19 at 09:51
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Thank you very much. I'm surprised almost nobody mentions this. Unix pipelines are the best thing since since sliced bread (though I don't know what's so great about sliced bread) – Sridhar Sarnobat Jun 11 '19 at 15:42
```Unable to find a suitable output format for 'cat'``` – Oliver Dixon Apr 29 '20 at 15:31
What is the exact command you are using and on which platform? – MrBar Apr 30 '20 at 13:42
On Windows, `-i pipe:0` seems to work for input piped in – rakslice Feb 20 '22 at 09:25

Ciro Santilli OurBigBook.com · Answer 2 · 2020-12-08T21:58:35.790

- is the same as pipe:

I couldn't find where it's documented, and I don't have the patience to check the source, but - appears to be the exact same as pipe: according to my tests with ffmpeg 4.2.4, where pipe: does what you usually expect from - in other Linux utilities as mentioned in the documentation of the pipe protocol:

If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading.

So for example you could rewrite the command from https://stackoverflow.com/a/45902691/895245

ffmpeg -f mp3 -i pipe: -c:a pcm_s16le -f s16le pipe: < file.mp3

a bit more simply as:

ffmpeg -f mp3 -i - -c:a pcm_s16le -f s16le - < file.mp3

Related: What does "dash" - mean as ffmpeg output filename

otacky_taka · Answer 3 · 2020-07-08T01:06:40.253

6

I don't have enough reputation to add a comment, so...

MrBar's example

ffmpeg -i file.mp3  -c:a pcm_s16le -f s16le pipe: | ffmpeg -f mp3 -i pipe: -c:a pcm_s16le -f s16le encoded.mp3

should read,

ffmpeg -i file.mp3  -c:a pcm_s16le -f s16le pipe: | ffmpeg -f s16le -i pipe: -f mp3 encoded.mp3

edited Jul 08 '20 at 01:06

answered Jul 05 '20 at 04:50

otacky_taka

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score 0 · Answer 4 · answered Jun 03 '21 at 17:28

Since you have to set the incoming stream's properties - and you may not feel like it - here's an alternative that I've used: use a fifo or a pipe (not the one mentioned above).

Here is an example using wget as a stream source, but cou can use anything, cat, nc, you name it:

$ mkfifo tmp.mp4 # or any other format
$ wget -O tmp.mp4 https://link.mp4 &
$ ffmpeg -i tmp.mp4 YourFileHere.mp4

Finally you may want to delete the pipe - you remove it like a normal file:

$ rm tmp.mp4

Voila!

Pipe input in to ffmpeg stdin

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