Is there a way to override Handbrake excluding the subwoofer track?

[mp4_guy]

I have been using Handbrake for all my conversions (and for ripping) but recently found that it excludes the subwoofer/LFE channel when creating videos with the most compatible audio format: stereo AAC with Dolby Pro Logic II encoding. The result is 5.0 surround sound instead of 5.1. Is there a way to override this?? If not, which program should I switch to? (I need my subwoofer channel preserved).

Here is more info at Handbrake's website concerning the above: https://trac.handbrake.fr/wiki/SurroundSoundGuide

Thanks in advance (& sorry if this has been asked before).

[Bernix]

Cant you just passtru the audio ? Or you want to reconvert it ? Try instead of Dolby pro logic choose 5.1 channels.
You can use Vidcoder, that is on handbrake engine and bit similiar.
Here is Tutorial how to make 5.1 audio in vidcoder.

Bernix

[mp4_guy]

Thanks Bernix. I'll look at Vidcoder. I found that all 4 of my playback devices won't play videos with AC3 audio (using passthru), and all of my Dolby receivers won't decode AAC 5.1, only AAC-stereo with Pro Logic II (and I think Youtube requires AAC-stereo but I could be wrong).

[hello_hello]

Dolby Prologic II doesn't support an LFE channel.

The LFE channel isn't a subwoofer channel as such. It's a "low frequency effects" channel. I think it's misleading of the Handbrake guide to refer to it as a subwoofer channel. The normal stereo/surround channels contain all the necessary sub frequencies with the LFE channel optionally being used to "enhance" them. Originally in a movie theatre, the 5ch sound system would reproduce the full range of frequencies (no doubt including sub speakers) and the LFE channel could be used to drive additional sub speakers for a low frequency boost without the main sound system being worked any harder or the surround channels being saturated by excessive low frequencies.

In a home theatre setup.... stereo speakers with a separate sub speaker, for example.... the audio is downmixed to stereo and the decoder/amp splits off the low frequencies and sends them to the sub speaker. The LFE channel can be included when downmixing 5.1ch to stereo but it isn't required. In fact the Dolby recommended method for downmixing 5.1ch to stereo doesn't include the LFE channel.
Even if you have a "5.1ch sound system" (five surround speakers with a sub) the low frequencies in the stereo/surround channels are split off by the decoder/amp and sent to the sub speaker. If the LFE channel is included it'd be mixed with the sub frequencies from the surround channels, not sent directly to the sub speaker.

Handbrake is no doubt doing it correctly.
https://en.wikipedia.org/wiki/Low-frequency_effects
http://www.dolby.com/uploadedFiles/Assets/US/Doc/Professional/38_LFE.pdf

The Handbrake guide says:
Be aware that, due to technical concerns, Dolby Pro Logic II is currently created as 5.0 sound. This means there is no separate subwoofer channel. Adding the sub channel can cause serious distortion, depending on how the DVD's audio was mastered.

I suspect that simply means the LFE channel is not included when downmixing to Prologic II, even though the wording isn't very clear.
Which is what Dolby recommends.

Mixing Information for Dolby Pro Logic II, Page 7 (PDF):
In a typical 5.1 downmix the LFE signal is not used. This is true for every Dolby Digital decoder ever built into a consumer product. When the DP563 was designed, the option of including some of the LFE signal was included. However, it needs to be restated that there is no LFE channel provision in the Dolby Pro Logic II matrix. Once the information from the LFE channel is added in, the decoder processes it as Center channel information, or information common to Left and Right channels. In order for the LFE information to get to a subwoofer on playback, the consumer decoder needs to be using bass management and redirecting bass information to a subwoofer.
There are other concerns when adding an LFE signal to the mix. If the LFE is simply redistributed within the other channels of the mix, they will usually be subject to some low-frequency bandpass filtering. This filtering causes phase shifts of the LFE signal. When they are acoustically added within a room, these phase shifts are fairly subtle and often go unnoticed. However, when they are electronically added together with the five main channels in the encoder, they may produce less than desirable results at certain frequencies. For this reason, it is recommended that the LFE signal not be used in a Dolby Pro Logic II downmix unless it contains unique information that is not repeated in any of the five main channels.

[pandy]

I have been using Handbrake for all my conversions (and for ripping) but recently found that it excludes the subwoofer/LFE channel when creating videos with the most compatible audio format: stereo AAC with Dolby Pro Logic II encoding. The result is 5.0 surround sound instead of 5.1. Is there a way to override this?? If not, which program should I switch to? (I need my subwoofer channel preserved).

I use ffmpeg with custom downmixing coefficients to create auxiliary 2 channel version of 5.1 (i keep 5.1 original and adding second track with 2 channel).

pan=stereo|FL < FL + 1.414FC + .5BL + .5SL + .25LFE + .125BR|FR < FR + 1.414FC + .5BR + .5SR + .25LFE + .125BL,dynaudnorm=p=1/sqrt(2):m=100,firequalizer=gain='if(gte(f,20),0,-INF)+if(lte(f,15749),0,-INF)':accuracy=1:fixed=on

Side to this i believe that AAC-LC is somehow less popular than mp3 (at least not popular as mp3)

To address some concerns - yes i know what i'm doing - checked few audio tracks and on most of them LFE was unique and not present in other channels.

[mp4_guy]

Thanks Pandy for sharing those ffmpeg command options, wow...

And, thanks Hello_hello for all the invaluable info & insight on DPLII and Dolby's recommendation! I can now rest assured that my conversions are fine ...and am spared the long task of re-converting!