audio channel positions

[chazz spacey]

why Adobe Premiere Pro maps channels different than source?

adobe:




this is how it must be:



and what should i choose on 5.1 mixdown type?:

[Cornucopia]

They're not mapped differently, they're just visually listed/arranged differently. All of those look to be the same: industry-standard 5.1 arrangement for AC3 coding.

The nomenclature might be slightly different, though. Some apps explicitly mention the LFE's ".1" channel, some assume it. Some consider the surrounds to be side-firing, some consider them to be rear-firing. Only in this modern era where there is the possibility of side AND rear speakers (7.1 or greater) does that actually begin to need clarification.

Your mixdown type ought to be determined by what system you physically have available at your disposal.

Scott

[hello_hello]

Different formats use different channel mappings. Most programs (probably all) remap imported audio using the wav channel mapping. See the list of channel mappings at the bottom of this page. http://avisynth.nl/index.php/GetChannel

Why Adobe Premiere Pro isn't displaying the channels in that order, I have no idea. I've never used it. As long as it's labelling them correctly though, the order in which they're displayed shouldn't matter.

When you export audio, it should be remapped as required according to the output format. It's not something the user should normally need to think about.

I don't understand the 5.1ch mixdown options.

MediaInfo displays the same channel positions regardless of the format (AC3, DTS, AAC etc). I don't know why, but it doesn't display the real channel mapping.

[Cornucopia]

All surround channel "mappings" are going to be out of SOME order if they're listed in a sequential order that doesn't visually represent their spatial positioning. But, it doesn't matter so long as they are actually MAPPED correctly. IOW, if the channel labelled LF is in the file where it is expected to be, and that signal shows up in LF's waveform slot and then gets rendered to the channel you expected LF to get assigned to, all is good.

We've already had the discussion about channel ordering in file formats, hello_hello. I don't think we want to dredge that up again do we? I though we informally agreed to disagree.
Again, MI is giving a casual listing, not a definitive ordering. It doesn't need to, because for any given format, that format is supposed to define how the ordering should be. You don't see MI getting literal with RGB or YUV color channel bitstream ordering either (for probably the same reason).

Scott

[hello_hello]

We've already had the discussion about channel ordering in file formats, hello_hello. I don't think we want to dredge that up again do we? I though we informally agreed to disagree.

I'd thought we'd agreed I was correct.

The "industry-standard 5.1 arrangement for AC3 coding" in the original post isn't the same industry standard channel mapping you mentioned here.
I thought I'd proven Aften uses the same channel mapping for AC3 as shown in the original post even though you claimed it must be doing it wrong (see -chmap).
I thought I'd offered definitive proof QAAC uses the AAC channel mapping, which differs from the channel mapping you mentioned.
It seems pretty clear DTS Parser sees the DTS channel mapping as being the same as the channel mapping at the bottom of this page and the same order shown here.
And I thought it was beyond denial Wikipedia agrees with me when it comes to the various channel mappings.

But no, there's no need to dredge all that up again.

[Cornucopia]

OK, you use reverse-engineered Aften and amateur (non-pro expert) publicly-written Wikipedia* as your sources, and cite AAC which uses flexible named mapping.
I'll continue to use industry-standard specs from the people who designed the specs, as well as named-mapped formats.
We'll see who has less problems or confusion overall.
So, no there is no need to dredge this all up again.

Scott

*What wikipedia gets wrong could fill a book, I'm sorry to have to say (because I cherish the idea behind it). Don't get me started on how mangled and/or incomplete their stated understanding of Stereo3D is...

[hello_hello]

I linked to a description of the channel mapping from the "DTS Audio in MPEG-2" pdf which shows the channel order for DTS being as I described. It would have been nice to understand why that's wrong.

What you seem to be missing is the fact I don't choose to continue doing anything. If I convert a 5.1ch AC3 file to AAC it gets remapped in the process or it doesn't. Nothing I can do about it. If I change the channel mappings on the way through I'll end up with the channels in the wrong places on playback.
If I import a 5.1ch AC3 file into Audacity it's remapped and imported as 5.1ch wave. When it's exported to another format it's remapped by the encoder as required or it isn't. Nothing I can do about it. If I change the channel mappings on the way through I'll end up with the channels in the wrong places on playback.

I think we've seen maybe it's possible to change the channel mapping when using some encoders (ie Dolby AC3 encoder) and still have the channels labelled correctly, and probably still have them decoded to the correct channels on playback, but for the average person encoding with QAAC or NeroAAC or AFTEN or FLAC or Ogg etc it's pretty much out of their control. The channels are decoded using 5.1ch wav mapping and remapped by the encoder as required or they're not. Nothing they can do about it. If the user changes the channel mappings on the way through they'll end up with the channels in the wrong places on playback.

I've proven AFTEN uses the AC3 channel mapping I referred to, and QAAC uses the AAC channel mapping. Vague generalisations about industry standards don't change the fact they use different channel mappings as I've said they do, and it doesn't change the fact I've been using those encoders for a long time without any issues in relation to channel mapping on playback.

Which encoders do you use? Which ones allow you to feed them an industry standard 5.1ch wav file and choose how the channels will be mapped when they're encoded, or in reality is that out of your control too?

I'll continue to use industry-standard specs from the people who designed the specs, as well as named-mapped formats.

What does that mean? You'll continue to use industry-standard specs but when you're not you'll use something else?

[chazz spacey]

as they are correctly mapped then no problem.

but i want to understand what is this. what does 5.1 mixdown type actually mean? what you mean with front only?



and i want it for internet. i mean stereo.

[poisondeathray]

It indicates when PP mixes down to stereo, what channels are used in the mix. If you pick Front only, then L + R are used only , the others are discarded