encoding question

[bruce lang]

When encoding a 5.1 mix to AC3, what size would the typical file be? I've been playing some with a version of Apack, 6 20MB files were compressed to a 10MB AC3, just wondering if that's about right.

[tom_lowe]

Originally Posted by bruce lang

When encoding a 5.1 mix to AC3, what size would the typical file be? I've been playing some with a version of Apack, 6 20MB files were compressed to a 10MB AC3, just wondering if that's about right.

Depends on the bit rate, but for a 6 channel AC-3 file, the data rate should either be 384kbit/sec or 448 kbit/sec. Once you know that, the calculation is easy.

Remember a 2 channel uncompressed PCM at 24/48 is around 2.4Mbit/sec.

[bruce lang]

Thanks for the reply, I just wanted to make sure the AC3 process was supposed to compress the wav files, even though the apack compression options were turned off. I've read in previous posts this was the thing to do. I'm just looking to make an DVD-video with some surround mixes I've made in PT to see how they sound on my home entertainment setup.

[Postman]

Yes,

AC3 compression reduces the amount of data by quite a bit, its whole reason to exist. I haven't done the math but what you've posted sounds totally reasonable.

Don't confuse audio dynamic range reduction (compression) with data reduction (compression). They are unrelated operations.

[bruce lang]

Thanks much.