I have a mp4-H264 file. I was just testing some effects to see the length of time a render would take. I got the video off the internet because my cameras are done, unfortunately.

The original is about 2400kbp/s. I applied about 10 or 15 effects for the video and changed the settings by 10% or slightly more. I did not change the audio settings.

Export was MOV as mp4 or H264, the bitrate was about 10000kbp/s. And MPEG2, the bitrate was 6000 kbp/s - 10,000 kbp/s. The source video as 24.97 fps. The final export was 25 fps or 24.97 fps.

There was no audio with any exports. But on the AVID timeline there is audio.

I then applied basic channel mixing to the audio and did not change anything or I changed very little. But with the exports there is not audio.

Why does this happen? Is there anything I should do to maintain audio?

Is this potentially why the video industry always has the audio separate from the video or has a duplicate track? Do certain video or audio effects cancel anything?

 Thanks.