How to record AC3Filter's output.

You may want to save the result of AC3Filter processing to a file for different purposes. For example some audio editors do not support AC3/DTS files and you may need to decode it to uncompressed WAV file. Or you may want to re-encode AC3 audio to MP3 to save some space. This article describes how to record output of AC3Filter to a file.

In this guide we will use following programs:
1. Graphedit
2. WAVDest filter (if you need WAV output)
3. Lame MP3 encoder filter (if you want MP3 output)
4. Dump filter (if you want MP3 or AC3 output)

You may download all this programs in a single Graphedit pack (or you may find all this programs in Google).

Graphedit

Graphedit is very powerful instrument. Here I will describe some simple could be done, but power of this program is much greater. You may experiment yourself, it's very easy and interesting. But, let's go...

Run Graphedit, choose menu File->Render Media File and find the file you want to convert (you may need AC3File filter to open raw AC3/DTS file). You will see something like this (click to enlarge):

Graphedit displays all filters used for file playback. All this is called 'filter graph', or simply 'graph'. Now it's time to run the graph to ensure that everything works well. Press green 'Play' button (you should see the movie and/or hear the sound).

Now we should setup the graph and filters. We do not need video, so just remove the video decoder and renderer (select and press 'delete'):

Well, it's time to adjust the sound. For example, you may wish to adjust the gain if movie is not loud enough, enable DRC, etc... Right-click on AC3Filter and choose 'Properties'. You'll see AC3Filter settings. You may change everything as you wish. Run the graph and you'll hear the result. You may change settings during playback, but note that it may require about 2 seconds for the sound to change.

At last, you're satisfied with the result... Now we need to write it to the file.

WAV file

Delete Default DirectSound Device filter and insert 2 filters: File Writer and WAVDest. To do this choose menu Filters->Insert Filters->DirectShow Filters. You'll see a list of filters installed:

Double click on File writer and WAVDest (File writer will ask you for a file name to write). Connect AC3Filter output pin to the input pin of WAVDest (just by dragging) and WAVDest to File writer:

Oughhh. Run the graph and wait for hard drive to stop chirring... Congratulations, we've done!

Note that some programs cannot work with multi-channel WAV files!

MP3 file

Producing of MP3 file is very similar to producing of WAV file. But now we need Lame and Dump filters. Insert these filters (Dump will ask for an output file) and build following graph:

Obviously, you must set AC3Filter to stereo (Lame filter would not agree to connect to AC3Filter otherwise). By calling Lame filter properties you may change encoding parameters:

Run the graph and enjoy the result! This method produces mp3 without need to decode AC3 to huge uncompressed WAV file!

AC3 file

AC3Filter has a built-in AC3 encoder. So you can make AC3 file out of AC3filter. But note, that AC3Filter produces AC3 in SPDIF format and some programs can not understand it. Also, it's about twice larger than normal AC3 file due to zero padding required by SPDIF (I will describe different file formats in a separate article). But... Maybe someone need it.

Again, producing of AC3 file is very similar to producing of WAV file. Now we need only Dump filter. Here I will convert a DTS file to AC3 format, so to read DTS file AC3File filter will be used. Render the source file and build following graph:

Here I do not want to keep original number of channels, therefore I set output format to 'AS IS'. To make the filter to produce AC3 output we must enable 'Use SPDIF' (Main page) and 'Use AC3 encoder' (System page) options. Also I don't want to do DTS passthrough (I want DTS to be encoded to AC3), therefore we must disable 'DTS' mark in 'SPDIF passthrough' (System page). My source DTS has 44100 sample rate, therefore I must permit it:

If you want stereo AC3 file, disable 'Do not encode stereo PCM' option (System page), or set multi-channel output otherwise.

Run the graph and it will create the file required. Do not forget to change all settings back! Otherwise you may have problems with SPDIF playback.

Note that resulting file is not an usual AC3 file. You may need AC3File filter to playback it.