filters

Added commandline options for the DC high-pass filter and the LFE low-pass filter.
The commandline switches are '-dcfilter <0|1>' and '-lfefilter <0|1>'.

CRC split

Moved the CRC code to its own file.
1 down, 5 to go.

short-term plans

Here is a small list of short-term development plans. I hope to get all this done in the next week or so. Once these are done, I will release a new version 0.04.

1. separate the CRC code to its own file
   
2. add optional DC high-pass and LFE low-pass filters
   
3. completely redo the variable bandwidth system
4. add an optional bandwidth low-pass filter
5. overhaul the configuration system
   
6. separate aften frontend, libaften, libfilter, and utils

Filter Library

I created a separate filter library, which will be used for all input audio filters. Currently it is only used for the transient-detection high-pass filter. Also, I changed Aften to use doubles instead of floats for pretty much everything.

The configuration system might be a little unstable on non-Linux systems right now. I am planning on doing some updates soon.

Small xbsi change

Added 2 commandline options, '-xbsi1' and '-xbsi2'. These must be used if the user wants the extended bit stream info to be written to the AC-3 file. Even if options in the extended bit stream info are specified on the commandline, they will not be encoded without explicitly adding the corresponding xbsi option. This was done to make simplifying the option parsing easier.

Header Reorganization

As one step forward in creating a libaften, I have reorganized the stucts to provide more complete separation of aften.h as a public header from the other private headers.

Alternate Bit Stream Syntax

I have added 8 new commandline options to Aften which correspond to the parameters in the Alternate Bit Stream Syntax, which is defined by Annex C of the A/52A spec. These are metadata parameters which affect interpretation by the decoder and/or receiver. Run "aften -h" to view the new options.

channel map changes

In order to support broken/incorrect/non-standard wav files, I have made a couple changes. The first was to detect use of either back-left/back-right or side-left/side-right as the stereo surround channels. The second was to allow the user to specify the audio coding mode and presence of the LFE channel on the commandline (e.g. "-acmod 7 -lfe 1"). Only the number of channels must match the specified settings.

First post

Aftenblog is open. This is a development blog for Aften, an AC3 encoder. I created it so I can have a space to post program updates and general thoughts regarding Aften and the AC3 format.