.mkv to .mp3 conversion
October 10, 2012 6:54 PM   Subscribe

How can I keep these .mkv to .mp3 conversions from getting screwed up?

So I have all 3 seasons of In Treatment in nice 720p .mkv files and I've been using Gizmo's Freeware-recommended iWisoft Free Video Converter to turn them into .mp3 files (128 kbps, if that matters) I can listen to while driving to work.

The Gina and Adele episodes all converted fine. Most of the Frances ones did as well. But some of them - and all of the Mia ones - would start out all right, sounding normal during the "Previously on In Treatment..." part, but then everything from the HBO Original "television picking up static" logo and after would come out croaky and sepulchral like a vinyl record played at 8 RPM.

I assume something in the original ripper's audio encoding is poorly structured or something. But I can't figure out why it only affects some of that ripper's episodes and - even more bafflingly - why the problem only starts partway through the episode. Maddening!

I tried converting to .mp4 instead to see if it made any difference. It didn't. I could try playing the video files, which sound perfectly fine, and capture the output with the Freecorder toolbar. But I'm hoping the hive mind can spare me the hassle.
posted by Egg Shen to Technology (8 answers total) 3 users marked this as a favorite
Are you watching your system resources during the conversions? In my experience that sort of random-ish distortion is a result of the program bumping up against RAM or processor limits during the conversion. You might want to look into limiting the program's resource usage manually.
posted by carsonb at 7:18 PM on October 10, 2012

Have you tried other audio/video conversion software? It's often worth using something else if only to confirm or disprove the idea that there's something wrong with the conversion process.

My personal favorite for audio/video conversion is FFMPEG, though it's rather a pain to setup and use in Windows. (It's a great inside a Linux environment if you have access to one.) Fortunately, there are numerous fancy programs for conversion that use FFMPEG behind the scenes. I haven't used one in years, so I can't make any specific recommendations, but a quick search on Google will give you lots of options. As always, be careful what you download!
posted by circleofconfusion at 8:02 PM on October 10, 2012

Are you watching your system resources during the conversions?

I just tried another conversion with no other program runnings. Task Manager showed CPU usage steady around 25% and Physical Memory usage steady around 35%. I don't think that's it.

It just occurred to me that the Gina episodes that were converting without problems were ones that didn't have the "television picking up static" intro. That - combined with the fact that the problem always starts at that intro - makes me think that the intro is somehow fouling all the audio that comes after it.

I used Avidemux to snip out that intro from the video file and then converted what was left. But the problem persisted.
posted by Egg Shen at 8:19 PM on October 10, 2012

How can I keep these .mkv to .mp3 conversions from getting screwed up?

By using Handbrake.
posted by mhoye at 8:31 PM on October 10, 2012 [2 favorites]

By using Handbrake

I just used Handbrake to convert the mkv file (containing aac audio, apparently) to an mp4 containing mp3 audio. iWisoft then converted the mp4 successfully. So I guess .aac was contributing to the problem.

If there's a way to have Handbrake output just the .mp3 audio, I wasn't able to find it. Is there one?
posted by Egg Shen at 9:09 PM on October 10, 2012

Apparently not.

At any rate, by approaching this from the audio extraction angle, I found Free Video to MP3 Converter - which got the job done with no fuss.
posted by Egg Shen at 9:41 PM on October 10, 2012

You could use VLC.

Media -> Open (advanced), select your source file with the Add button, then select Convert from the menu that pops up if you press the downwards arrow next to the play button.
In the Convert dialog select Audio - MP3 from the Profile drop-down menu. You can customize the birate by adding/editing a profile.
posted by mirage pine at 1:19 AM on October 11, 2012 [3 favorites]

Try MPEG Streamclip. I've found it to be the Swiss Army knife of video conversion apps. Extract the audio to WAV with it, then convert to MP3.
posted by omnidrew at 6:57 AM on October 11, 2012

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