E-AC3 to AC3 conversion using ffmpeg

[Nico Darko]

Hello.
I'm currently using ffmpeg to convert my mkv files with e-ac3 audio to ac3, with this command line:

ffmpeg  -hwaccel auto -y -i "input.mkv" -map 0 -c:s copy -c:v copy -c:a ac3 -b:a 640k "output.mkv"

It works great, but it takes a long time when you have more than 1 file. So do you if there is a way to batch convert several files, instead of opening a different command line each time?

Thank you.

[sneaker]

for %a in (*.mkv) do ffmpeg -y -i "%a" -map 0 -c:v copy -c:a ac3 -b:a 640k -c:s copy "output_%~na.mkv"

("%%" instead of "%" if in a batch file)

[Nico Darko]

Sorry, can you explain in more details? I don't get what to do (I'm still a beginner). Thanks.

[pandy]

Sorry, can you explain in more details? I don't get what to do (I'm still a beginner). Thanks.

Just create new script with provided example.
btw '-hwaccel auto' will not increase any speed...

for %%a in (*.mkv) do ffmpeg -y -i "%%a" -map 0 -c:v copy -c:a ac3 -b:a 640k -c:s copy "output_%%~na.mkv"

[Nico Darko]

I'm sorry, I know nothing about coding, I was simply given the instructions to do that one conversion, and it worked. But where do I enter the files names in that code? I have 12 in the same folder.

Sorry if I'm a pain.

[sneaker]

You don't enter file names at all. The "for" command will automatically pick up and enter the file names for you in a loop.

[Nico Darko]

Ok, that's what I thought, but I entered your command line, but it's not working, it says %%a was unexpected.

[sneaker]

If you are entering in command line use single %
In batch file %% (double)

[Nico Darko]

OK! Now it's working! Thank you!!

[Eibol]

You can use this tool in the future for batch converting and saving your ffmpeg long presets:
FFmpeg Batch

[pumpysworld]

I also used the freeware Xmedia Recode to convert the audio tracks of MKVs. I set it to copy (not convert) the video and converted the audio to AC3.

[benvantende]

Just wanted to share this. I am running Ubuntu Linux and none of the above solutions worked for me. I combined stuff and now works like a charm. It just takes a few seconds to convert large files. Hope This Helps for others

#!/bin/bash
for f in *.mkv; do ffmpeg -y -i "$f" -map 0 -c:v copy -c:a ac3 -b:a 640k -c:s copy "${f%.*}-ac3.mkv"; done

[Nico Darko]

Just create new script with provided example.
btw '-hwaccel auto' will not increase any speed...

for %%a in (*.mkv) do ffmpeg -y -i "%%a" -map 0 -c:v copy -c:a ac3 -b:a 640k -c:s copy "output_%%~na.mkv"

Hi,
I'm still using this script and it works great. But now I need to do the same thing only I just need the output file to be the converted ac3 audio, not the whole mkv file. Is there a way to change the script to do that?
Thanks.

[sekininsha]

Try ..

for %%a in (*.mkv) do ffmpeg -i "%%a"  -c:a ac3 -b:a 640k "output_%%~na.ac3"
pause

[Nico Darko]

That's perfect, it works. Thank you!

[Nico Darko]

I have another request (maybe I should open a new thread). Can I use the same command line to convert the audio to ac3 and convert it from 25 fps to 23.976 fps at the same time?
If not, is there at least a script to convert the audio to a different frame rate?

Thanks.

[sekininsha]

try

for %%a in (*.ac3) do ffmpeg -y -i "%%a" -map 0:0 -af "atempo=0.959040" -vn -c:a ac3 -b:a 640k -ar 48000 "%%~na.new.ac3"

[Nico Darko]

It works! thank you.

[Nico Darko]

Actually it didn't work properly, I need to convert the audio to eliminate the PAL speed-up, it is originally NTSC, but your command line seems to have slowed down the files to 23.976 fps but kept the same pitch as it was at 25 fps, it sounds the same! What is the way to just restore the NTSC tempo and pitch?

[sneaker]

Try something like:

-af asetrate=48000*(24000/(1001*25)),aresample=48000

(48000 Hz being the sample rate of the input and output.)

[Nico Darko]

That one does the job, thank you!
I might as well use this to batch convert the videos to 23.976 fps as well, do you know what the full command line for that would be?

[Nico Darko]

Just create new script with provided example.
btw '-hwaccel auto' will not increase any speed...

for %%a in (*.mkv) do ffmpeg -y -i "%%a" -map 0 -c:v copy -c:a ac3 -b:a 640k -c:s copy "output_%%~na.mkv"

Hi,
Does someone know if I can add a command line to that one, within the same script, to remove one of the two audio tracks of the mkv (and only convert the second one to AC3)?

Thank you.

[sneaker]

for %%a in (*.mkv) do ffmpeg -y -i "%%a" -map 0:v -map 0:a:1 -map 0:s? -c:v copy -c:a ac3 -b:a 640k -c:s copy "output_%%~na.mkv"

(Map video from first input file. Map second audio from first input file. Map subtitles from first input file if they exist.)
https://trac.ffmpeg.org/wiki/Map

[Nico Darko]

Perfect, thank you!

[Nico Darko]

Try something like:

-af asetrate=48000*(24000/(1001*25)),aresample=48000

(48000 Hz being the sample rate of the input and output.)

What would it be to go from 23.976 to 25fps? and with aac audio?

Edit: I've just tried:

for %%a in (*.aac) do ffmpeg -y -i "%%a" -map 0:0 -af asetrate=48000*(25000/(1001*24)),aresample=48000 "%%~na.new.aac"

It seems to have worked, but it reduced the bitrate from 192kbs to 130kbs

[sneaker]

-af asetrate=48000*((25*1001)/24000)),aresample=48000

Audio codec does not matter for this part. (Set -c:a aac if you want to encode output to AAC).

But maybe for PAL-Speedup keeping pitch using -atempo as suggested by sekininsha is a better solution?

[Nico Darko]

-af asetrate=48000*((25*1001)/24000)),aresample=48000

Audio codec does not matter for this part. (Set -c:a aac if you want to encode output to AAC).

But maybe for PAL-Speedup keeping pitch using -atempo as suggested by sekininsha is a better solution?

This one is actually to correct a PAL original show slowed down to NTSC, so I need to fix the pitch as well.

I added "-c:a aac" but the bitrate is still reduced.

[Nico Darko]

Ok, I added "-b:a 192k", that did the trick.

Thank you.

[jericho38]

Using:

for %%a in (*.mkv) do ffmpeg -y -i "%%a" -map 0 -c:v copy -c:a ac3 -b:a 640k -c copy "output_%%~na.mkv"

What should I add so it ads the new ac3 audio track as a new track instead of replacing the old track?

[sneaker]

for %%a in (*.mkv) do ffmpeg -y -i "%%a" -map 0:v -map 0:a -map 0:a -map 0:s? -c:v copy -c:a:0 copy -c:a:1 ac3 -b:a:1 640k -c:s copy "output_%%~na.mkv

https://ffmpeg.org/ffmpeg.html#Stream-specifiers
https://trac.ffmpeg.org/wiki/Map