two questions about AC3 editing

[Sujao]

Hi everyone,

the last weeks I have been searching the net for a possibility to reduce the bitrate of AC3 streams in linux. Do you know something? I quite desperate as I will have to face a 1.2GB audiostream for two audiostreams with 5.1 sound in a DVD rip.

Another question I have is: How can I merge several AC3 files together into one big ac3 stream? I tried doing it with:

cat file2.ac3 >> file1.ac3

This works during playback just fine, but when I search while being in the part of the second file I get CRC errors and the playback aborts.

Everything will be put into a matroska container, so if matroska offers an option on merging them together automatically that would be just fine.

Oh and I preferably need a console solution, since I am writing a script for ripping DVDs into matroska.

[Sujao]

I finally found a possibility on how to reduce the bitrate of an ac3 stream. It is pretty easy with ffmpeg...if you know how.

ffmpeg -i input.ac3 -ab 256 output.ac3

256 ist the target bitrate.

The problem is that the volume is lowered significantly. I think its the same problem windows users have with BeSweet and ac3enc.dll.

So a new problem arises: How to raise the volume after reencoding? And I still dont know how to merge different ac3-streams.

[six6]

If you feel it's ok going from ac3 -> wav...

a52dec -o wav file.ac3 > file.wav
then join streams, normalize, etc, then go back to ac3 with ffmpeg.

Good luck on your project!