Using ffmpeg to mix Cab IRs

[bobthedog]

Hi Guys,

 

Here is a little tip for you that use two (or more) IRs in the Helix.

 

IRs can be mixed together, so for example you might have one with a SM57 on the cone edge and another with a R121 on the cap. Instead of using two IR blocks on the Helix you can mix the IRs and then just use one IR block.

 

You can use FFMPEG for this: https://ffmpeg.org

 

An example command line is this:

 

 

ffmpeg -i IR1.wav -i IR2.wav -filter_complex amix=inputs=2 -ac 1 MixedCab.wav

 

 

Where IR1.wav and IR2. wav are your cab IRs you want to use. If you want to use more than 2 then keep using -i and changed the inputs= 

 

Why Line 6 haven't got this functionality in the helix I don't know!

 

 

[HonestOpinion]

Hi Guys,

 

Here is a little tip for you that use two (or more) IRs in the Helix.

 

IRs can be mixed together, so for example you might have one with a SM57 on the cone edge and another with a R121 on the cap. Instead of using two IR blocks on the Helix you can mix the IRs and then just use one IR block.

 

You can use FFMPEG for this: https://ffmpeg.org

 

An example command line is this:

 

 

ffmpeg -i IR1.wav -i IR2.wav -filter_complex amix=inputs=2 -ac 1 MixedCab.wav

 

 

Where IR1.wav and IR2. wav are your cab IRs you want to use. If you want to use more than 2 then keep using -i and changed the inputs= 

 

Why Line 6 haven't got this functionality in the helix I don't know!

 

Awesome tip! Wonder what kind of algorithm is used for the merge? What is the size of the merged .wav file, is it twice as large?

[spikey]

 Fractal Audio uses a 3rd party app called "Cab-Lab",  that allows you to add 2, 4 , 6 or more Cab IR's in a GUI setting mix down and match with sliders (to mix and match as you see fit) and listen to the results in realtime. Im hoping to see the same for Helix at some point.

[bobthedog]

Awesome tip! Wonder what kind of algorithm is used for the merge? What is the size of the merged .wav file, is it twice as large?

 

It is the same size as the largest input.

 

My guess is that the Helix app truncates the audio to 2048 samples when it sends it to the Helix.

 

 

 Fractal Audio uses a 3rd party app called "Cab-Lab",  that allows you to add 2, 4 , 6 or more Cab IR's in a GUI setting mix down and match with sliders (to mix and match as you see fit) and listen to the results in realtime. Im hoping to see the same for Helix at some point.

 

The helix should be able to do it in the box rather than with an external app. If they added a dual IR block it would only need to "Mix" the two IR's (whenever the user changes the IRs or levels) and then use that data.

 

 

With FFMPEG you can also set the levels that you want, but it's a bit of a pain!

 

ffmpeg -i IR1.wav -i IR2.wav -filter_complex "[0:a]volume=1.0[a0]; [1:a]volume=0.5[a1]; [a0][a1] amix=inputs=2[out]" -map "[out]" -ac 1 TestCab1.wav

 

That would use full volume for IR1 and half volume for IR2

[Ka5par]

You can do it with any DAW I guess. With Reaper for an example.
Test it with an amp + cab VST. Then import and mix the two files with appropriate balance. Or why just too, use a whole lot of them :)

[spikey]

It is the same size as the largest input.

 

My guess is that the Helix app truncates the audio to 2048 samples when it sends it to the Helix.

 

 

 

The helix should be able to do it in the box rather than with an external app. If they added a dual IR block it would only need to "Mix" the two IR's (whenever the user changes the IRs or levels) and then use that data.

 

 

With FFMPEG you can also set the levels that you want, but it's a bit of a pain!

 

ffmpeg -i IR1.wav -i IR2.wav -filter_complex "[0:a]volume=1.0[a0]; [1:a]volume=0.5[a1]; [a0][a1] amix=inputs=2[out]" -map "[out]" -ac 1 TestCab1.wav

 

That would use full volume for IR1 and half volume for IR2

Yea I can see the pain you are talking about, and doubt that many would want to use this way over a slick looking slider built into the icon IR within the Helix routing screen. So at this point, when you save that patch, are the 2 IR settings also saved with it? Also, can you vary the amount of each IR per patch, say 33% of one IR and 66% of the other with Helix yet? You can do this partial % amount setting with Cab-Lab not just with 2 IR's but with many more, and using a slick GUI in the process- that was my point. :) Hope Helix and Line 6 guys can come up with a compatible way to do this too!

[bobthedog]

If Line 6 built this in it would act like the dual cab, so they need to save the two indexes into the cab IRs (1-128) and the mix volume of each.

 

When the DUAL IR loads up it mixes the two IRs into one IR in its ram, rather than at the moment just loading a single IR into ram.

 

As you say they would be an advantage of having it as an external process as you could mess around with many IRs.

 

Unfortunately there is also a major disadvantage as it is not real time as it could be done in the helix. We loose the ability to load up an amp, load up a dual IR and mess around with different IR's to see how it sounds in the box just like the dual cab.

[spikey]

If Line 6 built this in it would act like the dual cab, so they need to save the two indexes into the cab IRs (1-128) and the mix volume of each.

 

When the DUAL IR loads up it mixes the two IRs into one IR in its ram, rather than at the moment just loading a single IR into ram.

 

As you say they would be an advantage of having it as an external process as you could mess around with many IRs.

 

Unfortunately there is also a major disadvantage as it is not real time as it could be done in the helix. We loose the ability to load up an amp, load up a dual IR and mess around with different IR's to see how it sounds in the box just like the dual cab.

Yea the "real-time listen to and adjust" is a must have. Period ! So Im hoping it can be at some point integrated into the editor.