two questions about AC3 editing

Sujao · 26th January 2005, 10:27

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:

Code:

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 · 27th January 2005, 13:48

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.

Code:

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 · 30th January 2005, 06:53

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!

26th January 2005, 10:27	#1 \| Link
Sujao Registered User Join Date: Jan 2005 Location: Germany Posts: 32	two questions about AC3 editing 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: Code: 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. __________________ There are no passengers on earth, we are all the crew

27th January 2005, 13:48	#2 \| Link
Sujao Registered User Join Date: Jan 2005 Location: Germany Posts: 32	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. Code: 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. __________________ There are no passengers on earth, we are all the crew Last edited by Sujao; 27th January 2005 at 13:51.

30th January 2005, 06:53	#3 \| Link
six6 "HTML is not allowed" Join Date: Jan 2003 Location: In Adamantine Chains and penal Fire Posts: 67	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!