If you own the Blu-ray or a digital copy, extracting the audio yourself is the safest and highest-quality method. You will need software like MakeMKV or HandBrake.
If you purchased the film on Amazon Prime, Google TV, or iTunes, standard DRM prevents direct extraction. However, you are legally allowed to screen record (though quality degrades). Better yet, use the offline download feature within the app—though this won't give you a standalone MP3 file, it solves the "I need English audio" problem for mobile viewing. The Dark Knight Rises English Audio Track Download
This is the safest, highest-quality method. If you own the Blu-ray or a digital
What you need:
Steps:
File size example: The 5.1 DTS-HD track alone is ~2.8 GB. The Dolby Digital 5.1 track is ~450 MB. Steps: