v2.0.2 decoder is slower than v0.1.6

[Simon Zolin]

Problem

v2.0.2's AAC-LC decoding is ~15% slower than v0.1.6 on AMD64

Is there anybody who also experiences this issue?

How to reproduce:

1. Prepare a 5 minute int16/44.1kHz/stereo .wav file filled with silence.

2. Encode it to .m4a with ffmpeg:

    ffmpeg -i sil.wav sil.m4a
   

3. Decode sil.m4a with fdk-aac v0.1.6.

4. Now decode sil.m4a with fdk-aac v2.0.2.

5. Compare the time and see that v2.0.2 is ~15% slower.

In my case on i5-8xxx the result is:

Version  Decoding Time
v0.1.6   0.900s
v2.0.0   0.952s (+6%)
v2.0.2   1.045s (+16%)

What's happening, fdk-aac decoding is getting slower with each version?

Notes:

• It doesn't matter if the input file is real music or just pure silence - v2.0.2 decoding is always slower.
• My decoding code is the same for both cases, of course.
• The result doesn't change much after many retries.
• FYI, at the same time, v2.0.2 AAC-LC encoder performs much faster than v0.1.6 encoder.
• ffmpeg decodes the same file in just 0.4s!!

So, it looks like there's a regression in AAC-LC decoding code in v2.0.2?