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October 21st, 2008 Posted in Uncategorized


for some time I was unable to find a decent free AC-3 encoder DirectShow filter so I’ve decided to make one. I’ve extracted the AC-3 encoder source from libavcodec (ffmpeg project) and wrapped it into a simple filter. The filter is released under the GNU LGPL license. It also takes advantage of a CBaseAudioEncoder base class which I intend to describe soon in a nice tutorial :)


  • Support for 32 KHz, 44.1 KHz, 48 KHz sample rates
  • Support for 1 - 6 (5.1) channels
  • Customizable bit rate

Source : (41 KB)

Binary : (118 KB)



  1. 26 Responses to “MONOGRAM AC3 Encoder”

  2. By Sina™ on Oct 22, 2008

    It’s great…
    So, what about LAME filter?

  3. By Igor Janos on Oct 22, 2008

    I’we downloaded the lame library. And written a simple DirectShow filter to find out how it works (I hope to upload it later today) - so the next step is the audition filter (possibly tomorrow or the next day).

  4. By Sina™ on Oct 24, 2008

    Thank you…
    Great work.
    There is a best-end LAME Front-End here:
    But there is no source.
    Could you please copy/past all features of this front-end?

  5. By Sina™ on Oct 24, 2008

    Sorry for fast writing.
    Correct it if you want.

  6. By Igor Janos on Oct 25, 2008

    I think that might be possible - it’s basically all that the LAME API offers. But I would definitely use different style of user interface :)

  7. By Sina™ on Oct 25, 2008

    That front-end has 2 mode: basic & advance.
    Please, you have to add those.
    The important thing is: command line console.
    You should add this too.
    Command Line input is very important.
    Thank you for your great support.
    R♂ck ♂n Igor…

  8. By Igor Janos on Oct 26, 2008

    btw. Why do you want a command line? My idea was to link the lame library statically so there would be no need for lame.exe.

  9. By Sina™ on Oct 26, 2008

    Why CL?
    The answer is here:

  10. By Igor Janos on Oct 26, 2008

    Sorry but I really don’t get it. Could you put it in words? Why do you need a command line?

  11. By Sina™ on Oct 26, 2008

    When you want to encode using command line, & also using Recommended LAME settings using command line like: -b 320, you need CL feature.

    -b 320 means 320KBPS, CBR, Joint Stereo, q=2 &…

  12. By Igor Janos on Oct 26, 2008

    All these features can be configured using the LAME API with the library linked as static as well. Everything works the same way but there’s no need for the external lame.exe file and it’s easier for me to feed the encoder data. So why shouldn’t I be doing that ?

  13. By Sina™ on Oct 26, 2008

    Please read this page:

  14. By Sina™ on Nov 1, 2008


  15. By Igor Janos on Nov 3, 2008

    A few things got screwed up causing me extremely busy times :-\. And also the new Fallout 3 is out :)

  16. By Sina™ on Nov 5, 2008

    Did you play Fallout 3?

  17. By Sina™ on Nov 9, 2008

    how u doing?

  18. By winnydows on Mar 15, 2009

    Tested AC3 encoding. Found bug: channels map changed after encoding. Will try find right positions later.

  19. By winnydows on Mar 15, 2009

    Also problems with direct muxing to TS with Elecard MPEG Muxer, if - ffdshow decoding > monogram ac3 > elecard mpeg muxer. AC3 muxed as MP2. I reported to Elecard, but they say bug in AC3 encoder (”if ask prefered connection - AC3, if try connect - connect as MP2 (wrong)”). All bug can be easy reproduce in Winnydows Commander DAILY (link in MP4 muxer blog.

  20. By winnydows on Mar 15, 2009

    Wrong mapping result:
    1 > 1 - ok
    2 > 5 - wrong
    3 > 4 - wrong
    4 > 6 - wrong
    5 > 2 - wrong
    6 > 3 - wrong

    Decoder don`t change map, bug in coder. I can fix it be force remaping in decoder, but it a wrong.

  21. By Igor Janos on Mar 16, 2009

    Thanks for the info. I’ve been already informed about this. I hope to do some fixes soon.

  22. By andy vt on May 13, 2009

    any chance you can add 24-bit support as well?

  23. By Igor Janos on May 13, 2009

    Yes sure. It is already in the todo list but at the moment I have a few more important issues to solve.

  24. By winnydows on May 13, 2009

    Hope this issues is mapping and connection with elecard ts :).

  25. By andy vt on May 13, 2009


  26. By andy vt on Aug 23, 2009

    I tried to build, but libMonoDShow.h is missing. Thanks

  27. By Keny on Dec 5, 2009

    Does this codec also support DTS decoding? Because in Win 7, we now have a native AC3 decoder, but unfortunately it doesn’t support DTS. And I don’t wanna install the whole ffshow package just for the DTS codec.

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