[FFmpeg-devel] [RFC] AAC Encoder, now more optimal

Måns Rullgård mans
Fri Sep 5 15:54:57 CEST 2008

Robert Swain wrote:
> 2008/9/5 Kostya <kostya.shishkov at gmail.com>:
>> After some time (I'd like to have more free time to spend on it though),
>> I want to expose my new AAC encoder.
>> It is slower than realtime since it uses search for optimal quantizers
>> for given quality.
>> Known weak points:
>> * no bitrate management (it uses fixed quality for now)
>> * no M/S detection
>> * quantization is not optimal yet
>> I haven't implemented those because it will slow encoder even more, so
>> debug session will include an hour rest (and in case of M/S detection
>> I don't know how to implement it) - 16sec sample coding takes 42 secs
>> on my PPC G4-1.42GHz and 39 secs on Core2 1.8MHz.
>> Any comments, suggestions, speedup tricks are extremely welcomed
>> (especially the latter).
> Obviously this is in the process of being improved. I'm not sure what
> a reasonable target for encoding speed is for AAC but I'm fairly sure
> something around 10-20x realtime is achievable with Nero's encoder.

The PS3 AAC encoder is much faster than realtime, and the quality seems
OK too.

> Less than realtime audio encoding is... unusual. :) Still, if it was
> the best quality AAC encoder around, that would bring it some
> redemption.

There's certainly no harm in having the option of a slow, high-quality
mode.  However, a reasonably fast, decent-quality mode is essential.

A constant (or restricted) bitrate mode is probably desirable too.

M?ns Rullg?rd
mans at mansr.com

More information about the ffmpeg-devel mailing list