Help automating demux, transcode, & remux of eac3 audio stream

[Pando]

Goal: Trying to avoid unnecessary transcoding due to eac3 audio streams on some mkv files in my library by adding a second (converted/transcoded) ac3 audio stream to mkv files. (While still preserving original mkv/eac3 streams)

Disclaimer: I’m new to this sort of thing and the only method I’ve found that works is to manually use these GUI apps with the following steps...

Current Working Method:
1. Using UsEac3To:
a. Demux mkv video & eac3 audio streams
b. Use libAften to encode a new ac3 stream from the demuxed eac3 stream
2. Using MKVToolNix GUI:
a. Use "multiplexing" task to remux mkv video stream and eac3/ac3 audio streams (ac3 set to default audio track)

Result: Mkv file with 2 audio streams (default set to ac3) able to direct stream without the need for transcoding.

Problem: This is far too many steps if I'm trying to convert an entire season. I have hundreds of files that could benefit from the addition of a default ac3 audio track.

Failed attempts using existing AIO tools...
1. Attempts using PopCorn MKV AudioConverter failed (Received "VideoTrack Not Found!" error, using latest version w/all necessary tools downloaded)
2. Attempts using MKV2AC3 failed (Fails to convert audio stream to ac3)

Questions:
1. Are there any other tools with which I can accomplish this?
2. How difficult would it be to create something like a batch file that I could drop video files onto in order to create the desired result? (Something that could do batch processing within a folder would be amazing)

Any direction here would be greatly appreciated. Apologies in advance if I used any incorrect terminology. Please let me know of any errors and I'll clarify/fix them.

[jagabo]

Given that Aften is based on ffmpeg's A52 encoder, can't you just use ffmpeg? You could perform the entire process with a single ffmpeg command line.

[Pando]

Given that Aften is based on ffmpeg's A52 encoder, can't you just use ffmpeg? You could perform the entire process with a single ffmpeg command line.

You're absolutely correct. After giving it another look, I was able to replicate the same results utilizing ffmpeg.

I also found that myFFmpeg makes for easy batch editing as well.

Thank you!

[cletusb]

You had the exact same problem i do!! And your initial solution mine too - however I was not so intrepid as you with your final solution
Would you please share the command line you used for ffmpeg - i am not so familiar with that
Thanks in advance