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Topic: How to keep transparency after several processing? (Read 1475 times) previous topic - next topic
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How to keep transparency after several processing?

I've extracted the 5.1/ac3/448kbps audio of an entire DVD. I need to make several transformations on the extracted audio, getting, in the end, two sets of mp3 tracks: one with track ReplayGain and another with album ReplayGain, both "hard-coded", i.e. not in tags but in the audio signal itself. Besides, I need to keep transparency as much as possible throughout the entire process, except, of course, relatively to loudness (due to RG) and to some voice removing (see below).

I've imagined these steps to achieve my goal:

1. Convert ac3 to wav
1.a. Output bit depth: 32 bit
1.b. Dither: never
1.c. Processing
1.c.I. ReplayGain: None
1.c.II. Active DSPs: Convert 5.1 to stereo; Advanced limiter
2. Edit tracks with Audacity: cut, merge, append, voice removing, etc.
3. Export Audacity-edited tracks back to wav/32-bit files (no dither)
4. Scan Audacity-edited/exported wav audio for track/album ReplayGain
5. Convert (with foobar2000) Audacity-edited/exported wav audio to mp3 (V2) with album ReplayGain
6. Convert (with foobar2000) Audacity-edited/exported wav audio to mp3 (V2) with track ReplayGain

Are these steps a good pathway to my goal? Is something overkill (e.g. 32 bit wav)? Does it lack something (e.g. dithering)?

Some alternative paths:
- Is there any tool able to edit ac3 files directly? Despite Audacity ability to import ac3 files directly, it indeed first convert them to 48kHz/16-bit PCM.
- Is there any reason to use WaveGain (http://www.hydrogenaudio.org/forums/index.php?showtopic=10637) instead of f2k to get the mp3 files hard-coded ReplayGained?

I'd appreciate any help you guys can give to me.

Thanks in advance.
 

How to keep transparency after several processing?

Reply #2 –
A process similar to WaveGain may be available for AC3 streams, since the stream data does contain gain values. Of course, these gain values are usually pre-calculated by the producer to support dynamic range compression.