[SOLVED] ffmpeg Encoding audio files

GPGAgent · 03-28-2020, 12:15 PM

I'm re-encoding mp3 files to a bit rate of 48k - it's only radio plays so no music as such.

Code:

ffmpeg -i 02241429.MP2 -acodec libmp3lame -b:a 48k 02241429.mp3

Works fine, but it can get a bit warberly (squeaky) sounding, are there any other parameters I can use to remove this affect?

I could just keep them as they are - dab radio seems to use two bit rate, 80k and 128k, so I'm only saving up to 2/3rds of disk space.

BW-userx · 03-29-2020, 10:03 AM

grep'ing all of my scripts. i got a few different ways I've done it before.

Code:

ffmpeg -b 128k -xerror -i "$f" ""${ARTIST}-${TITLE}-${ALBUM}-192k-"${f%.mp3}.mp3"

I use LAME

Code:

  
    # if MP3 is out of limits then re-sample it if not then send it through
 if [[ "${ext1}" == 'mp3' ]] ; then
     # start bitrate       128        start bitrate       160
	if [[ "${rateis}" -gt "${LameCheckRate}" ]] ; then
		lame -V2 -b"${LameLowEnd}" -B "${LameHighEnd}" -F --vbr-new -m j -q2 "$FILENAME" "$newFile"
		else
			# if MP3 is within limits then skip resmapling then just make 
			# a copy to move it 
			# to new directory/folder
			## WORKING SCRIPT DIRECTORY !
			exiftool "${script_dir}"/"${newFile}"
			
			cp "$FILENAME" "$script_dir"/"$newFile"
	fi
 
 fi # end first if
	fi #END of if off of find working dir

http://wiki.hydrogenaud.io/index.php?title=LAME

GPGAgent · 03-30-2020, 12:38 PM

So my script now uses -q:a 8 as the most obvios option. I use this script to re-encode and change the name of the file to be more readable:

Code:

#!/bin/bash
#
# DAB file name format is MMDDHHMM.MP2 03301414.MP" > 03-Mar-30-1414.mp3
#
MONTHS=(ZZZ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);
for FF in *.MP2; 
do
echo Processing  $FF to ${FF:0:2}-${MONTHS[10#${FF:0:2}]}-${FF:2:2}-${FF:4:2}${FF:6:2}.mp3;
  
  /usr/bin/ffmpeg -y -i "$FF" -acodec libmp3lame  -q:a 8  ${FF:0:2}-${MONTHS[10#${FF:0:2}]}-${FF:2:2}-${FF:4:2}${FF:6:2}.mp3; 

done;
exit

And you can find more here: https://trac.ffmpeg.org/wiki/Encode/MP3

BW-userx · 03-30-2020, 01:39 PM

I use LAME

GPGAgent · 03-31-2020, 04:19 AM

Quote:

Originally Posted by BW-userx

I use LAME

Isn't ffmpeg using LAME when I include?

Code:

-acodec libmp3lame

Anyway I'll take your script and process a few with LAME directly, thanks for the tip.

GPGAgent · 03-31-2020, 05:57 AM

Just tried lame - seems a far better quality of re-encoding, so the files are from DAB radio, and the bit rates are ither 128kbps or 80kbps, no music just voice, plays and so on.

Lame has a number of presets and I've tried them all:

Code:

A few aliases are also available for ABR mode:
phone => 16kbps/mono        phon+/lw/mw-eu/sw => 24kbps/mono
mw-us => 40kbps/mono        voice => 56kbps/mono
fm/radio/tape => 112kbps    hifi => 160kbps
cd => 192kbps               studio => 256kbps

The original file is an MP2 wrapper size of 45MB 128kbps
I re-encoded using all options up to voice and this is what I found:
phone - acceptable, small file 6.2MB
sw - acceptable, file size 9.3MB
mw-us - okay, file size 15.2MB
voice - fine, file size 20.5MB

So I'm going to use sw or mw-us in future, great tip from BW-userx, cheers

BW-userx · 03-31-2020, 09:54 AM

Happy to have been of some help.

GPGAgent · 03-31-2020, 12:08 PM

I forgot to add the modified script

Code:

#!/bin/bash
#
# DAB file name format is MMDDHHMM.MP2 03301414.MP" converted to 03-Mar-30-1414.mp3
# This makes it a bit more legible and using the month number make sure it sorts correctly
#
# Usage: lame --preset mw-us --tt "Episode 4" --ta "Inspector West" 03310600.MP2 Ep04.mp3
#
# lame --preset help
#
## A few aliases are also available for ABR mode:
## phone => 16kbps/mono        phon+/lw/mw-eu/sw => 24kbps/mono
## mw-us => 40kbps/mono        voice => 56kbps/mono
## fm/radio/tape => 112kbps    hifi => 160kbps
## cd => 192kbps               studio => 256kbps
#
MONTHS=(ZZZ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);
##PRESET=sw;
PRESET=mw-us;
TT="Afternoon Play";
TA="BBC R4";
for FF in *.MP2; 
do
echo Processing  $FF to ${FF:0:2}-${MONTHS[10#${FF:0:2}]}-${FF:2:2}-${FF:4:2}${FF:6:2}.mp3;
  
lame --preset $PRESET --tt "$TT" --ta "$TA" $FF ${FF:0:2}-${MONTHS[10#${FF:0:2}]}-${FF:2:2}-${FF:4:2}${FF:6:2}.mp3;
done;
exit