ac3 @ low bitrates

[Malcolm]

hi there,
i'd like to use 2-channel ac3 with bitrates at 64 or 80 kbits/s. can anyone tell me how good ac3 performs at such bitrates? i'd like to encode simple dialog-based film material (no music / hifi, etc.)
are there any quality-comparisions at these bitrates?

thank you,
Malcolm

[KpeX]

Hi,

Unfortunately, most good audio comparisons don't compare speech tracks, and don't feature AC3. AC3 is definitely not optimized for these bitrates, but for a speech-only track from an uncompressed source the quality will likely be acceptable, I'd recommend encoding a short portion and testing yourself. I'd also recommend using the Dolby libraries for encoding (virtually all commercial encoders do).