2 Channel AC3 25fps to 24fps eac3to problem

[Pegbeard]

When I attempt the -slowdown command, it completes, but with an undesirable end result. The audio file is twice as large as the original and it is slowed down way too much. Its length is doubled and there is an annoying high pitch ringing. It is atrocious!
Here is the log:
command line: eac3to star.track_2.ac3 star.track_2a.ac3 -slowdown
------------------------------------------------------------------------------
AC3 Surround, 2.0 channels, 0:21:36, 384kbps, 48khz, dialnorm: -27dB
The Nero decoder doesn't seem to work, will use libav instead.
Removing AC3 dialog normalization...
Decoding with libav/ffmpeg...
Changing FPS from 25.000 to 23.976...
Encoding AC3 <448kbps> with libAften...
Creating file "star.track_2a.ac3"...
eac3to processing took 2 minutes, 9 seconds.
Done.

Any help would be appreciated as I have 11 audio sources from the same encoder I wish to convert. Thanks.

[jagabo]

If you're making an NTSC DVD you could avoid the audio conversion by encoding at 25 fps and applying 3:2:3:2:2 pulldown flags with DgPulldown.

[Pegbeard]

I'm encoding mkv files. I use mkvmerge to get the video at 24fps. I use Tsmuxer to extract the AC3. I then run it through eac3to to slow down the audio then put it back together with mkvtoolnix mkvmerge. It normally works fine with 5.1 ac3's, but this 2 channel ac3 doesn't convert right at all. It's all wonky and slow. Horrible.

[AlanHK]

command line: eac3to star.track_2.ac3 star.track_2a.ac3 -slowdown
------------------------------------------------------------------------------
AC3 Surround, 2.0 channels, 0:21:36, 384kbps, 48khz, dialnorm: -27dB
The Nero decoder doesn't seem to work, will use libav instead.
Removing AC3 dialog normalization...
Decoding with libav/ffmpeg...
Changing FPS from 25.000 to 23.976...
Encoding AC3 <448kbps> with libAften...

Well, it's bigger because you're going from 384kbps to 448kbps -- though that shouldn't be "twice as big".
Are you specifying the output rate?
Are you specifying how many channels-- maybe it's making 5.1 from stereo?


I'd be inclined to use Audacity, the recent 1.3 version use ffmpeg to input and oputput AC3, and you can use "Change tempo" to speed/slow a track without changing the tone.

[Pegbeard]

I figure it had something to do with the increase of kbps. I am not specifying the output rate. I do not know how. I was simply plugging input output files into the command prompt. As for changing the tempo without changing the tone in Audacity, my original problem is with the 25fps audio sounds too high pitched. Would the Audacity method lower the pitch to normal levels? Thanks for the replies!

[jagabo]

my original problem is with the 25fps audio sounds too high pitched. Would the Audacity method lower the pitch to normal levels?

Yes.

[Pegbeard]

What should I set it to so that i will be in sync with the now 24fps video? I know the difference is something like 4%. How would I calculate that and plug it into Audacity?

Thanks!

[jagabo]

To go from 25.000 to 24000/1001 it's -4.095904 in Audacity's Change Speed filter.

[Pegbeard]

Wow, even audacity 1.3 won't recognize the .ac3. Man alive!

[jagabo]

Did you import the ffmpeg lib?

http://manual.audacityteam.org/index.php?title=FAQ:Installation_and_Plug-Ins#installffmpeg

[Pegbeard]

I believe my version of Audacity referenced that, but still said that it could not read it. I'll try importing it and see. Thanks.

[jagabo]

If you have AC3ACM installed you can open the file with VirtualDub and save as a WAV file that you can import into Audacity.

[El Heggunte]

Just a side note: even the latest version of eac3to (3.18) is not "bug-free"

--- it cannot decode (convert to .WAV) correctly stereo DTS below 768kbps,
for example.

[manono]

I use BeSweet and its PAL to NTSC preset (25.000->23.976). It also gets rid of the higher pitched audio. I make a WAV file and then use something else to reencode to AC3.

[Pegbeard]

I tried using besweet but I couldn't find any good documentation on what command lines would do what i needed. Would it be any help if I were to post a link to the file and see what you all could do with it? Thanks again everyone.

[manono]

Sure, post it if you like. It's not like this is rocket science, though. Probably 90% of the people here could do it with no trouble at all, assuming the source AC3 file isn't corrupt in some way. Command line? It comes included with a GUI.

[Pegbeard]

Wow. The gui really takes a lot of the work out of it. Nice. Here's a download link for the 90th percentile who can do this easily. Any tips would be appreciated. Thanks. http://www.2shared.com/file/12568580/dee497dd/Startrack_2.html

[manono]

Any tips would be appreciated.

You want a tip? Upload to some place from which it's easy to download. I have no interest in popups, ringtones, toolbars, or any of the other garbage it's foisting on me.

[jagabo]

LOL, yeah that site is really annoying if you don't block popups, java script, etc.

[Pegbeard]

Sorry. I had to catch the bus to work and uploaded to the first place google gave me. Don't hate me. Hate the internet. Thanks, again for all the help.

[manono]

For future reference, try Sendspace or MediaFire.

[Pegbeard]

Will do! Were any of you able to obtain the .ac3 file?

[jagabo]

I got it and was able to open it in Audacity with no problems. Got six channels.

[poisondeathray]

^I can confirm audacity works fine.

The problem is some programs "see" your file as 2 channel (including eac3to), so you end up getting garbled results

IIRC, in order to get audacity to work with ac3 files properly for 6-ch export, you have to set it up in the options with ffmpeg . There was a guide somewhere with pictures showing what to do...

EDIT: go to edit=>preferences=>Libraries=> setup ffmpeg library
also, under import/export , highlight "use custom mix" for 5.1 audio (otherwise audacity will downmix to stereo)