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fido083
12-18-2006, 11:28 AM
I am new to the aac/mp4/m4a world.
I have learned from this forum that m4a with LC encoding is the way to go for music. (I will tackle filetag issues later)

I test converted a song 3:31 to m4a.

I found if I convert the song selecting quality .5, I get a file at 167 kbps and LC as read by winamp. (size 4411 KB)

If I do the same conversion and check the "Force LC AAC" box, I get a file of 208 kbps. Still LC by winamp. (size 5466 KB)

I tested winamp by using a low bitrate (64) and allowed HE encoding and winamp recognizes the HE in the file info. So it seems winamp is able to correctly read the file format. (unlike db, another thread)

Why am I getting two different bitrates at the same quality of .5, while both are LC encoded?

Does "Force LC AAC" use an entire different compression algorithm?

Thanks.

xoas
12-18-2006, 04:11 PM
I cannot answer many of the specifics about the various aspects of different .m4a settings.

I can tell you that the way in which quality settings work in different codecs (such as .mp3, .ogg, and .m4a) will result in different bitrates for different audio files as the bitrate will be adjusted depending on the amount of audio information in each part of the file. This is nothing to be alarmed about as long as the differences are within a general range (as they appear to be in your example).

Hope this helps.
Best wishes,
Bill

Deano
12-19-2006, 05:28 AM
When using the Force LC box, you are forcing the Nero Encoder to run through a different algorithm. This has the tendency to produce a higher bitrate file. Without forcing, you are still likely to get a high quality file. It is only pertinent to use HE-AAC at lower bitrates (around 64kbps and below).

I would go with using .5 without forcing LC. You'll still get an LC file, just without the inflated (and possibly unnecessary) bitrate.