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Need to transcoding AC3/MP3 to AAC (unfortunately...)

hi. Im experimenting at work on a Harmonic Flexa RT transcoder where i need to transcode any audiosource to a specific AAC format.
My sources are typically AC3 @ 448, 384 kbps or Mpeg1-l2 at 256 or 384kbps.
The transcoder has the option of : LC-AAC, HE-AACv1, HE-AACv2 as output

Im trying to achieve as close to audio transparency as possible, and ive landed on 96kbps on HE-AACv1.. Is this a sane rationale?
In the situation i have both a 2channel AC3(448kbps) and a 2channel mp2 track (256kbps), which one would u use as source?

PS! Im fully aware that lossy to lossy will have impact on the quality, but in this context, passthrough aint an option..

/TE

Re: Need to transcoding AC3/MP3 to AAC (unfortunately...)

Reply #1
He-aac is for very low bitrates, which will never be transparent. At 96kpbs lc-aac should be nearer to transparancy.

Any idea which aac encoder is used? This can make a huge difference.

Not sure about the ac3 vs mp2. They are both not very efficent.
I'd say listen very carefully (downmixed to stereo) and choose the better one.

Re: Need to transcoding AC3/MP3 to AAC (unfortunately...)

Reply #2
In the situation i have both a 2channel AC3(448kbps) and a 2channel mp2 track (256kbps), which one would u use as source?

AC3 at such an extreme bit rate will be transparent.  You should use that. 

 
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