Mp3 Advanced Channels

[Haplo]

Hi Peeps,

I have dbpoweramp 1.3 but when i covert a .flac or a 320kb mp3 file
to mp3 vbr then i get a joint stereo mp3.

I have chosing Stereo in Advanced Channels but get joint stereo ?

help me Plz ...

[Spoon]

Re: Mp3 Advanced Channels

Joint Stereo is a better form of Stereo for Lame (it uses more bits for encoding data rather then stereo).

If you need 2 channels select the Dual Channel Mono.

[Haplo]

Re: Mp3 Advanced Channels

Tnx Spoon, but it is a bug in the program , or not ?

[Spoon]

Re: Mp3 Advanced Channels

It is not a bug, Lame was designed to be joint stereo for stereo, if you are not using that then you are not using lame as designed (and have sub-optimal mp3 files).

[Jellings]

Re: Mp3 Advanced Channels

Dear Spoon,

You say that Lame was designed to use joint stereo for stereo, so why was stereo an option in dbpoweramp versions proior to 13?

Also I read that "as Joint stereo is more efficient it leaves more room for encoding quality, so Joint Stereo should give higher quality files.".

While this is true for CBR files, if you one chooses 'Stereo' over 'Joint Stereo' in VBR, the bitrate is higher to compensate for the fact that Stereo is less efficient.

Not only do I prefer to use Stereo on anything over 192kbps (most specifically on VBR as it doesn't matter if I use Stereo because the quality is the same and the slightly higher bitrate and size that results doesn't matter to me), but I find it strange, confusing and misleading to have both a Stereo and Joint Stereo option in dbpoweramp even though they both result in a Joint-Stereo file.

I am aware that Joint-Stereo is superior in most situations, but removing Stereo entirely from dbpoweramp as an option seems unnecessary.

(ps. Please don't post links to websites with articles on why Joint Stereo is better, I've read them. You could say that my preference for Stereo files is not necessary, but then the same could be said for people who encode at 320kbps or people who use Dual Channel Stereo - It's really a matter of personal preference)

[bhoar]

Re: Mp3 Advanced Channels

Unfortunately, while I won't post links to elsewhere, I still have to correct some incorrect assertions above.

In general, the problem is one of terminology. The Joint Stereo flag does not force non-independent coding, per se.

With joint stereo enabled, each frame is assessed to see if the best quality at the target bitrate will be given with separate encoding of each channel or with a separate encoding of the Mid/Side transform of each channel. For most music, most of the time, the Mid/Side transforms give a substantially higher audio quality at a particular bitrate for most frames. However, if the current frame contains substantially different audio on both channels, the encoder will encode each channel independently.

With the joint stereo flag disabled, each frame always uses separate encoding of each channel. This forces the encoder to waste a substantial amount of bits most of the time. That is, at the target bitrate for that frame, the audio quality is poorer.

The default approach for LAME is to have joint stereo enabled at high bitrates. Each frame is looked at both ways and the winning approach is kept.

Not only do I prefer to use Stereo on anything over 192kbps (most specifically on VBR as it doesn't matter if I use Stereo because the quality is the same and the slightly higher bitrate and size that results doesn't matter to me), but I find it strange, confusing and misleading to have both a Stereo and Joint Stereo option in dbpoweramp even though they both result in a Joint-Stereo file.

A file that is flagged as a "Joint-Stereo" file means that the decoder should be prepared to decode both independent as well as Mid/Side transforms of the channels. Note that this does not mean that both types of frames exist in the file, just that the decoder should be prepared for it. A Joint-Stereo file may contain only independently encoded frames.

So, you cannot rely on the header to verify that the Stereo flag is being ignored. You have to use a tool to analyze all frames to verify that at least one is Mid/Side encoded.

-brendan

[Jellings]

Re: Mp3 Advanced Channels

I just find it strange that there is even a possibility of Joint-Stereo when specifically selecting Stereo, whatever the LAME default.

Anything else I've used that uses LAME gives me real stereo when I use a stereo setting, and joint stereo when I use the joint stereo setting.

[Spoon]

Re: Mp3 Advanced Channels

To get stereo select the 'dual channels' option.

[LtData]

Re: Mp3 Advanced Channels

I think Jellings point is that selecting "Stereo" still gives you Joint Stereo, especially when the LAME help file says this:

Stereo - forces separate encoding of left and right channels, only recommended when high bitrates are used.

[Jellings]

Re: Mp3 Advanced Channels

I think Jellings point is that selecting "Stereo" still gives you Joint Stereo, especially when the LAME help file says this:

Stereo - forces separate encoding of left and right channels, only recommended when high bitrates are used.

Thank you LtData, that is exactly what I meant. The stereo option in dbpoweramp does not match the definition of as defined by LAME itself.

Using Dual Channel Stereo as a replacement for Stereo would be rather a strange thing to do, especially after reading the definition in the lame documentation:

Dual Channels.
In this mode, the 2 channels will be totally independently encoded. Each channel will have exactly half of the bitrate. This mode is designed for applications like dual languages encoding...

Please spoon, in the next minor release of dbpoweramp, could you put stereo back how it was? If I wanted joint-stereo I would have selected it.

[bhoar]

Re: Mp3 Advanced Channels

Using Dual Channel Stereo as a replacement for Stereo would be rather a strange thing to do, especially after reading the definition in the lame documentation:

Please spoon, in the next minor release of dbpoweramp, could you put stereo back how it was? If I wanted joint-stereo I would have selected it.

Jellings, your lack of knowledge of how contemporary LAME works is showing...but that's fine...I don't blame you...it's a problem with the docs. There's been heavy discussion on HA, which included the authors of LAME, on the unintended consequences of the poor/inexact terminology used in the LAME documentation. I say this as someone who recently learned himself.

Each frame in high-bitrate files can either be mid-side encoded or independently encoded. Normally LAME chooses on a frame-by-frame basis. If you want to force all frames to be independently encoded, select Dual Channel. That's it.

Yes, it's a waste of resources (in terms of quality/bitrate ratio), but do it you want to. No one is stopping you.

The fact that the LAME header says the file in joint-stereo is beside the point - it always says that now. If you set dual channel, all the frames will be independently encoded. What you call "stereo".

-brendan

[Jellings]

Re: Mp3 Advanced Channels

Yes, my knowledge on the different types of stereo is far from superior.

But here's how I see it, if I import the same track from CD using iTunes-Lame with LAME 3.98 using the 3 different types of stereo, I get 3 different files: one Stereo, one Joint Stereo, and one Dual Channel. This was the same with dbpoweramp r11.

With dbpoweramp r13 the 'Stereo' and 'Joint Stereo' options produce output .mp3s with exactly the same bitrate and exactly the same filesize as each other. Even using r13.1 beta, which uses the same version of LAME as the version of iTunes-Lame I'm using. You say that LAME always puts joint-stereo in the header whatever the settings used, but that just isn't true for any other software that uses LAME for MP3.

To me, the only explaination as to why the Stereo and Joint-Stereo options give the same output file, the same bitrate, the same filesize is that both settings in dbpoweramp send the same command line to the LAME encoder (which would be '-m j'), if the Stereo option sent (-m s) then the file would be the same as if i used (-m s) in itunes-lame or any other software that uses the lame 3.98, and different from the output resulting from Joint Stereo (-m j).


Edit:
Also as far as I am aware, both dbpoweramp r12, and dbpoweramp r13 both use lame 3.97, but r12 can do normal/legacy stereo, and r13 will do joint-stereo despite what the user selects. As they both use the same version of Lame I find it hard to believe that it is a change in Lame that has caused this change - the only thing that can possibly have caused this is a change in dbpoweramp!

(also, completely off-topic, but I registered on hydrogenaudio earlier today because I had a question about a different subject, and apparently I have to wait 5 days because I'm using a free email address. I've already proven I'm human by completing a CAPTCHA and verified my email address, so I don't quite understand why there's a need for a 5 day suspension)

[Jellings]

Re: Mp3 Advanced Channels

Ok, I'll try to simplify my question.

When I use any other software that uses LAME for MP3 encoding I am given the option of Stereo/Joint Stereo/Dual Channel. In dbpoweramp the Stereo option simply does not do what it does in other applications. Why?

I have never, for exammple, used '-v V0 -m s' and imported the output file into iTunes to find that it is Joint Stereo (or that it has joint stereo headers for that matter). So why is it that when I select V0 & Stereo, then click convert dbpoweramp I get a Joint Stereo file?