BUG: stereo -> mono not working

[mhavo]

Hi!

I'm trying to transcode audio from soundcard to mono mp3. Not working... "channel=1" setup is not recognized. Audio is always joint-stereo. Version is 0.8.6.b

[DJ]

If I may be so bold to ask the stupid question? How are you determining this?

[mhavo]

Code: Select all

vlc.exe --intf rc dshow:// :dshow-vdev="" :dshow-adev="" :dshow-size="" :sout="#duplicate{dst='transcode{acodec=mp3,ab=192,channels=2}:duplicate{dst=std{access=file,mux=raw,dst="C:\test192.mp3"}}',dst='transcode{acodec=mp3,ab=128,channels=1}:duplicate{dst=std{access=file,mux=raw,dst="C:\test128.mp3"}}'}"

Both files are joint-stereo. Am I missing something?

[mhavo]

Well I'm not the only one with this problem. viewtopic.php?t=35687&sid=f11de573814cd ... c2024b525a
So it would be nice if developers say at least something about this.

[DJ]

I'm doing this from memory as I seldom do mono MP3 files. There are 2 options in the format (rather confusing as I recall) Joint stereo was designed for stereo files where as stereo was designed for by lingual files (Mono). Left channel is the default language and Right channel is optional. I know this works in VLC because occasionally I get files that default to the left channel and were encoded in the wrong way. Also VLC plays mono through both speakers. Personally I believe this is incorrect. While most people do like and want this.

[mhavo]

Ok?

But how do I encode stereo input to mono mp3? And how do I tell to encoder to produce real stereo? (Not joint-stereo) Am I still missing something? (Yes I do )

[DJ]

I know that the default for the decoder is Stereo and NOT Joint-stereo. But a flag in the file will change this to what it needs to be.

As far as the encoding goes, I don't know what the default is. I assume it is Joint-stereo or the stereo would default to the left channel and not do a real stereo. There are no options to change this that I am aware of, other than the 1 channel option in the Stream output menu. I have tried to go the other direction and do multi-channel when the source is multi-channel, but that doesn't work either. I suspect that this option was never finished.

[mhavo]

So.

Are there going to be fix for this mono-problem? Or is it so 'minor' that this BUG will remain as it is?



Is there any workaround to produce mono file????

[DJ]

https://trac.videolan.org/vlc/ticket/1198

[mhavo]

Thank you so much!

[mhavo]

04.06.2007: The status of Ticket #1198 is still in 'Not started' state... too sad.
21.08.2007: Still not started. Still waiting.

[mhavo]

It would be great if we can hear at least something about this from the coders. I can guess that this issue is not so big to fix in the code...

[funman]

unfortunately nobody in the team has time/knowledge to work on this item

try aenc=twolame in the transcode chain

[funman]

by the way mono encoding works fine for me (using nightly build)

Code: Select all

file in.mp3 in.mp3: MPEG ADTS, layer III, v1, 128 kBits, 44.1 kHz, JntStereo

this looks like stereo

Code: Select all

./vlc/bin/vlc -I dummy -vvv --color in.mp3 --sout "#transcode{acodec=mp3,channels=1}:standard{access=file,mux=raw,dst=out.mp3}" vlc:quit

and then this looks like mono:

Code: Select all

file out.mp3 out.mp3: MPEG ADTS, layer III, v1, 64 kBits, 44.1 kHz, Monaural

listening is fine

can you please try a nightly build ? you can get one at http://nightlies.videolan.org

the bug may have resolved itself, so let us know !

[fouj@x]

Actually, it works when converting a stereo file to mono, but not when trying to get a dshow input and save it as a mono file.