Build 5145 not using external audio file

[ysbinns]

I used a MKV H264 video only file and an external audio LC-AAC file from AudioCoder to make MP4 file. I used Copy Video and Copy Audio with selected external audio file. The result was a video only file and no audio.

[stanley]

Do not use copy audio if you want to encode audio with external file.

[stanley]

If you just want to mux a video file and an audio file, use a muxer front-end (like yamb).