I'am new about ac3, hope someone can give more information about of the lfe channel.
I also don't know how to play the lfe channel sample, becasue the sample's number is only 48(7*6) in lfe channel(is that right?),but 1536(256*6) in other channels.Are their palying frequecies same?

waiting for your reply

The Low Frequency Effect channel is sampled at a lower frequency than the others. That's why it's also known as a ".1" channel.

Thanks for your reply.
However I still don't know how to determing the lfe channel's sample frequency?

Oops, I was wrong. I was going to guess 1/32 the rate of the other channels, or 1.5 kHz if the main frequency is 48 kHz. But the LFE channel has lower bandwidth but not necessarily lower sampling rate.
I just scanned my copy of the ATSC A/52 (AC-3) specification and I now believe that the LFE is sampled at the same rate as the other channels. Since everything is in the frequency domain, they just don't store anything beyond the first few frequency coefficients of the LFE channel.

It's hard to find the details, but 'lfeexps' says the DC coefficient is a 4-bit absolute value, and there are two elements which are 7-bit groups of 3 exponents. That's 7 total exponents. 'lfemant' holds 7 mantissa values of 0 to 16 bits. I don't expect this to make much sense, as I just looked at it for the first time, and I am not familiar with how all the data is organized.

Another interesting find:

It is limited bandwidth, as you found out with 7 mantissas out of 256. If 256 mantissas equal 24 kHz (well, roughly), so 7 would mean ~650 Hz...
And yes, it needs the inverse transform too, it is treated as a normal channel, just with less mantissas
to unpack and then the rest probably filled up with zeroes.