Ogg vorbis why mono?

[blub47474]

Hi there,
I am using audacity to convert and edit audio tracks from mp4 or vob's as sources.
To open to these video files i use the standard ffmpeg plugin from audacity.
When exporting these tracks in into vorbis files a lot of the time audacity wants to save them as mono ones?
This happens primarely when trying to export multitracks.
Can someone please tell if this is a bug or if i need to change any setting (the current setting for exporting is the default one '5')
eg is there a set limit of how many tracks which ogg vorbis can handle?
Cheers for any help

[Irish]

Whether the Export command exports as mono or stereo depends on whether the tracks to be exported are mono or stereo.

As far as I am aware, if all the source tracks are mono, they will be mixed down to a mono track for export.
If they are all stereo, or a mix of stereo and mono, they will be mixed down to a stereo track for export.

PO'L

[blub47474]

Hi there,
I just tried to convert a vob file into a ogg one.
On a different machine. just to be on save side about my installation.
To be on the save that the source is not mono.
Iam posting a copy of the stream info file.

0x80 - Audio - AC3 / 6ch / 48kHz / DRC / LBA: 100198 / PTS: 00:00:00.280 / Delay: -100ms
0xE0 - Video - MPEG-2 / 720x480 (NTSC) / 4:3 / LBA: 100179 / PTS: 00:00:00.380 / Delay: 0ms

still [img]

[/img]

Ogg vorbis error

ogg vorbis WTF.JPG (180.02 KiB) Viewed 3052 times

sorry about the extra 'edge' of the screen shoot
still does anybody have idea of why audacity or the ogg codec goes wrong?

cheers for any help

[Irish]

The source may be 6-channel audio, but it is being brought into Audacity as 6 mono tracks, (on the track panel to the left of each track it says "Mono 48000Hz, 16-bit PCM), and because of that, the Export command mixes them to a mono file by default.

What you can do is to select "Use custom mix" in the Import / Export preferences. This will give you an "Advanced Mixing Options" dialog box when you go to export, and will allow you to choose which channels in your ogg file correspond with which Audacity tracks. You can have up to 32 channels in an ogg file. However, Audacity will not do multi-channel playback. You will need to play the file in another application to hear the result properly.

See this page from the manual:
http://manual.audacityteam.org/index.ph ... ng_Options


PO'L

[blub47474]

Hi there,
sorry about my late reply.
thx alot for the help.
That pointer really did help.
Except that the result where too good for my mp3 player
How can I please downmix them five channels to 'standard stereo'?
Without having all data squashed down into just one channel?
Cheers for any help

[Irish]

How can I please downmix them five channels to 'standard stereo'?

This method is a little convoluted, but I can't think of any other way to do it.

1. Open your Audacity project with your five mono tracks.
2. Create five new blank (mono) audio tracks (Tracks > Add New > Audio Track)
2. By clicking and dragging with the mouse on the track panel to the left of each new track, move the five new tracks up so that, from the top down, you have Original track, New track, Original Track, New track, etc.
3. Copy the audio from each original track to the new track immediately below it, (click on the track panel of the original track, then CTRL-C, click on the track panel of the new track, then CTRL-V) so that you have ten mono tracks which are Original track 1, copy of track 1, original track 2, copy of track 2, original track 3, etc.
4. In the dropdown menu of each original track (the little arrow to the right of the track name), select Make Stereo Track. You now have five stereo tracks where the left and right are identical.
5. Use the Pan (L-R) slider on each track to position it where you want it in the stereo image.
6. Export the project. This will give you a stereo audio file from the five stereo tracks.

PO'L

[steve]

I think that the normal channel mapping for AC3 is:
1) FL
2) FC
3) FR
4) SL
5) SR
6) LFE

or
1) C
2) FL
3) FR
4) SL
5) SR
6) LFE

You will need to check because not all 5.1 encoders use the same order.

The simplest way would be to just use Front Left and Front Right and discard the rest of the tracks. The FL and FR can then be combined by clicking on the name of the upper track (should be FL) and from the drop down menu select "Make Stereo Track".

If you want to do a full stereo mix of all 6 channels, yo need to map:
FL -> Left
SL -> Left
C -> Left
LFE -> Left
FR -> Right
SR -> Right
C -> Right
LFE -> Right

The channel map will look something like this:

5-1-to-l-r.png (29.94 KiB) Viewed 2865 times