Friday, May 2, 2014

How to: Enable Harman & Kardon sound effect of the HTC One M8

Just few days ago HTC announced the new HTC One (M8) Harman & Kardon Edition. The HTC One (M8) Harman & Kardon edition has been designed for consumers who appreciate high-quality audio and want the best smartphone on the market without compromise. It’s a special edition of the critically acclaimed HTC One (M8) that builds upon the iconic all-metal design in a new brushed black finish with champagne accents, and is another example of HTC’s commitment to offer the best audio experience on a smartphone.

Today we present you how to enjoy this revolutionary audio experience on your “regular” HTC One (M8).

First of all it seems that the changes between the regular M8 and the M8 H&K Edition are only or mainly software related. We believe that the sound processor is the same in both units, however the firmware of that sound processor is probably different. To such conclusion led us the particular part of the M8 Sprint firmware.zip package called adsp.img (Advanced Digital Sound Processor) which is usually the same between each device variants and stays the same since the first device software release date, but in this case it was different. We found out that the adsp.img from the Sprint HTC One M8 was different to the others One M8 variants so it's probably needed for a proper H&K sound mod function.

The rest of the changes are located on /system partition:
  • system/customize/ACC/default.xml
<item type="boolean" name="support_harman">false</item> has to be changed to
<item type="boolean" name="support_harman">true</item> to make the OS "think" that you're actually using the H&K M8 Edition. This boolean item wasn't present in the early HTC One M8 1.24.401.4 software version.
  • system/etc/tfa/playbackHM.* / playbackHM_l.* files which are mostly related to the equalizer settings
  • system/etc/audio_policy.conf tuned for higher sampling_rate values (up to 192000)
  • system/lib and system/lib/hw libraries, mostly related to the part of the SoC responsible for the audio
This all might sound a little bit complicated, but in fact it was just an explanation about the changes that are required software-wise to enable the H&K support on the regular HTC One M8.

The tricky part is that to flash adsp.img on international version of the HTC One M8 you'll need to have Security OFF (S-OFF) device. Without S-OFF you can only update files located on the system partition on your device. Below you can find proper ZIP packages that are suppose to be flashed using custom recovery. First one (for S-OFF devices) together with system partition will also update the adsp.img. The other one (for S-ON devices) will update only system files, however you might not notice any sound improvements without the adsp.img.

Download links:

Harman & Kardon sound mod for the HTC One M8 S-OFF
Harman & Kardon sound mod for the HTC One M8 S-ON

Thanks to baadnewz for brining the initial version of the modification.

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