FLAC to mono mp3/vorbis

[Yellow Pasque]

I have a situation where I can only listen through one earbud of my mp3 player (Sansa Clip). Obviously, stereo files don't work well for that.

So I have .flac files that I want to re-encode in mono lossy format (preferably vorbis, but mp3 works). I tried ffmpeg (2.2.1) to encode to vorbis mono, but the Clip played them with horrible static sound even though they played fine on my home stereo.

This is the script I'm using (not worried about tags right now).

#!/bin/sh

for f in *.flac; do
  # give output correct extension
  #OUTF="${a[@]/%flac/mp3}"

  # get the tags
  #ARTIST=$(metaflac "$f" --show-tag=ARTIST | sed s/.*=//g)
  #TITLE=$(metaflac "$f" --show-tag=TITLE | sed s/.*=//g)
  #ALBUM=$(metaflac "$f" --show-tag=ALBUM | sed s/.*=//g)
  flac -c -d "$f" | lame -m m --preset extreme --noreplaygain - "$f"mono.mp3
done

I'll update this more when I have time tonight. I just wanted to see if anyone has done something similar.

[FakeOutdoorsman]

Please show your ffmpeg command and the complete ffmpeg console output.
Does oggenc also produce static in the Sansa Clip?
Is your script using lame working as expected?

[shantiq]

or Temüjin you can use this

for mp3

for f in *.flac; do sox "$f" -C 192 -c 1 "${f%.flac}.mp3" ;done

-c for channel number -C for bitrate

for ogg [-C here goes 1-10]

for f in *.flac; do sox "$f" -C 8 -c 1 "${f%.flac}.ogg" ;done

if not yet installed sox

sudo apt-get install sox libsox-fmt-all

[Yellow Pasque]

@Outdoorsman: thanks for the idea about oggenc. It was much simpler than ffmpeg because it preserves tags and automatically renames the file.

oggenc --downmix -q 5 file.flac

I'm going to test the files on my mp3 player tonight. I'll let you know...

@shantiq: I'll keep sox in mind for easier mp3 processing if the oggenc files play static too.

[Yellow Pasque]

Oh, and Outdoorsman, I was using a fairly simple ffmpeg command, something like:

ffmpeg -i file -c 2 -ac libvorbis file.ogg

I don't have the exact error it kept spitting out, but for almost every file, it said something like: "stream 0:0 has 100 buffers waiting. Something may be wrong."

[Yellow Pasque]

Okay, so I just gave it a quick test and the oggenc files also play with static. I guess my Clip doesn't like mono vorbis files for some reason.. (stereo vorbis plays well).

[FakeOutdoorsman]

@Outdoorsman: thanks for the idea about oggenc. It was much simpler than ffmpeg because it preserves tags and automatically renames the file.

ffmpeg should preserve metadata (I'm not sure about the fake "ffmpeg" or avconv in the repository).

Okay, so I just gave it a quick test and the oggenc files also play with static. I guess my Clip doesn't like mono vorbis files for some reason.. (stereo vorbis plays well).

What version of Ubuntu are you using, or more specifically, what version of libvorbis are you using?

Okay, so I just gave it a quick test and the oggenc files also play with static. I guess my Clip doesn't like mono vorbis files for some reason.. (stereo vorbis plays well).

Another option would be to create a stereo file but with both channels in uhh... both channels. If that makes sense.

ffmpeg -i input -af "pan=stereo:c0<c0+c1:c1<c0+c1" -acodec libvorbis -qscale:a 4 -vcodec copy output.ogg

Libav does not support the pan audio filter, so you'll have to use a real ffmpeg from FFmpeg (isn't it great that Ubuntu switched?). You can follow a step-by-step guide to compile ffmpeg or simply download a Linux build of ffmpeg. For the lazy/efficient:

wget http://ffmpeg.gusari.org/static/32bit/ffmpeg.static.32bit.$(date +"%F").tar.gz
tar xzvf ffmpeg.static.32bit.$(date +"%F").tar.gz
./ffmpeg -i input ...

[Yellow Pasque]

I'm actually using Debian sid(uction)
ffmpeg (not libav) 2.1.2 (from debmultimedia repo)
libvorbis 1.3.2-1.3
vorbis-tools 1.4.0

ffmpeg should preserve metadata

Actually, I guess it did for the .oggs.
It didn't autocomplete tags for mp3's, but I'll worry about tagging spcriptfu later. I just have the player shuffle through the whole library anyway (it's all upbeat working music and I don't have time to select specific artists/albums while I'm working).

[FakeOutdoorsman]

Attached are a mono and a mixed stereo sample (from a friend's band) from ffmpeg using libvorbis 1.3.3. If the mono works maybe a bug was fixed in libvorbis (but I doubt libvorbis is at fault), but if not then I think it is safe to blame the Sansa Clip.

[Yellow Pasque]

Thanks for the samples! The clip played your mono file just fine. There have only been a few commits to libvorbis for 1.3.3 and I don't see anything that looks even remotely related to my issue.

I'm thinking it may have something to do with my libflac? Investigation continues...