Currently audio streams need to be enclosed in a video file, please encode audio with a black video frame.
Settings for TMPGEnc 5. These settings are general and can be used in other encoding packages.
Format
Mpeg-4 (AVC)
Audio
-MPEG-4 AAC Low Complexity (LC)
-sample rate 44.1khz
-stereo
-bitrate 128kbs
Video
-stream format mpeg-4 avc
-video encoder x264
-profile and level high @automatic level 3
-size (640x480)
-aspect 1:1
-framerate 30fps
-constant bit rate (CBR)
-VBV buffer size 0 (auto)
-Entropy CABAC
-Display mode progressive
-performance normal