Problems converting high efficiency aac to mp3

[Caelestis Malus]

[COLOR=Indigo]I've got about 25 .aac files that I need converted to mp3. I've tried with 6 of them so far, and only 3 will convert. I get the "codec cannot be opened error" that everyone seems to be having problems with.

As well, the .mp3 is larger, longer and distorted when it plays. It comes out in slow-motion.

BEFORE

Type: aac File
Extension: .aac
Length: 24:16
Size: 15677KB
Original size: 752456KB
Compression: 47 to 1 (2%)
Frequency: 44100
Channels: 6
Bitrate: 88 kbps
AAC type: High Efficiency [SBR] (Header: ADTS)

AFTER

Type: MPEG Layer 3 Audio
Extension: .mp3
Length: 72:50
Size: 51218KB
Original size: 752800KB
Compression: 14 to 1 (6%)
Bitrate: 96 kbps
Frequency: 44100
Channels: 2
Channel mode: Joint-Stereo
Level: MPEG 1 Layer 3
Encoded by: Lame 3.96

Is the distortion a result of the compression? How can I get a comparably-sized .mp3 file that is the same length as the original?

The length is important, since these are audio tracks extracted from an .mkv anime file which I will be muxing into .avi with the extracted video track.[/COLOR]

[xoas]

Re: Problems converting high efficiency aac to mp3

I am not at all sure whether Lame is able to support 6 channels. I know it could not in the recent past. I do note that the mp3 file is 3 times as long (2 channels by 3 is 6 channels) but this could be a coincidence.

First thing to try is to see if you can do successful test conversions of these files. Open them in dMC and where you would designate format (mp3) for the conversion select Test Convert (no write). This should tell you whether dMC has a problem with reading any of the files. Let us know your results.

If they open and if you can utilize 2 channel mp3 rather than 6, I seem to recall a possible 2-step conversion that might work, I'll have to look it up if you're interested.

Best wishes,
Bill

[LtData]

Re: Problems converting high efficiency aac to mp3

The problem is probably related to the AAC having 6 channels. Try converting to a 6-channel WAV, then to a 2-channel WAV, then to your mp3.

[Spoon]

Re: Problems converting high efficiency aac to mp3

The latest beta version of dMC should accept 6 channels for mp3 (note mp3 is 2 channels maximum only).

[Caelestis Malus]

Re: Problems converting high efficiency aac to mp3

[COLOR=Indigo]Thank you all very much. You had some very helpful suggestions. I didn't need to try the beta version to get the conversion to work, though I'm sure if I'd downloaded it in the first place that would have saved me a lot of grief to begin with.

I did a test conversion which worked perfectly. From there I converted to wave. Though the file sizes were again larger (I assume to decompression) the lengths were perfect and things sounded fine. I then went from wave to .mp3 and everything came out wonderfully.

Thank you for your help and the wonderful program![/COLOR]

[xoas]

Re: Problems converting high efficiency aac to mp3

You're very welcome.

Best wishes and good luck on your project.
Bill