Re: [mpg123-users] how to use control interface with streaming input

[Thomas O. <tho...@or...>]

Am Tue, 15 Jun 2010 00:32:24 +0100
schrieb zonyi besk <zo...@gm...>: 

> cat foo.mp3 | pv -L 176400 - | mpg123 -s -R -E like.eq --fifo "cmd.txt" -  |
> lame -x - outp.mp3
> 
> Is there a way using the control interface with that stream input.

Yes;-) I'm trying that now (using 32 bit signed integers to minimize quality loss a bit).


shell$ cat foo.mp3 | mpg123 -R --fifo /dev/shm/mpg123 --remote-err -s -e s32 | lame -r -s 44.1  --bitwidth 32 --signed -m j  - outp.mp3

Another terminal...

shell$ echo silence > /dev/shm/mpg123
shell$ echo load /dev/stdin > /dev/shm/mpg123
shell$ echo quit > /dev/shm/mpg123

That's how the initial terminal output should look:

@R MPG123 (ThOr) v6
@silence
@I stdin
@P 2
@S 1.0 3 44100 Joint-Stereo 2 104 2 0 0 0 32 0 1
Assuming raw pcm input file
LAME 3.98.2 64bits (http://www.mp3dev.org/)
Using polyphase lowpass filter, transition band: 16538 Hz - 17071 Hz
Encoding <stdin> to outp.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III (11x) 128 kbps qval=3

We got a valid output file:

shell$ mpg123 outp.mp3 
High Performance MPEG 1.0/2.0/2.5 Audio Player for Layers 1, 2 and 3
	version 1.12.1; written and copyright by Michael Hipp and others
	free software (LGPL/GPL) without any warranty but with best wishes

Playing MPEG stream 1 of 1: outp.mp3 ...
MPEG 1.0 layer III, 128 kbit/s, 44100 Hz joint-stereo
^C
[0:07] Decoding of outp.mp3 finished.


I'm not sure what your problem is... I see that file name "cmd.txt"... are you trying to feed a prepared script into mpg123? You'd need to do that via

shell1$ mpg123 -R --fifo mpg123-command
shell2$ cat cmd.txt > mpg123-command

Also, when feeding mpg123's standard output via -s, don't forget --remote-err.


Alrighty then,

Thomas.

PS: It should be possible to skip the RAW format settings in the lame command by making mpg123 write WAV to stdout: mpg123 -w /dev/stdout   that adds a header that makes lame see the correct bit width and sampling rate ... but: I see a strange effect there.
I can do mpg123 -w /dev/stdout file.mp3 | lame - test.mp3  just fine, the resulting test.mp3 is good. But doing mpg123 -e s32 -w /dev/stdout file.mp3 | lame - test.mp3 is not funny, static noise.
It gets really funny when observing that this replacement process works again:

shell$ mpg123 -e s32 -w /dev/stdout > testpipe.wav
shell$ cat testpipe.wav | lame - test.mp3

I fail to see how that should do anything different. I suspect a funny bug, not sure where.