Utility to check contents of (HE)-AAC files

2009-04-23 11:34:45

Is there a simple utility that can look at an "AAC" file, and tell me:

• what level/profile of AAC it is
• whether it uses SBR and/or PS
• what the base sample rate is
• over what frequency range SBR is used

If there's nothing that does all of this, what is available that does some of it? Thanks!

Cheers,
David.

Utility to check contents of (HE)-AAC files

Reply #1 – 2009-04-23 13:06:48

Have you tried MediaInfo?
http://www.videohelp.com/tools/MediaInfo

Utility to check contents of (HE)-AAC files

Reply #2 – 2009-04-23 14:11:59

Thanks.

I hadn't tried it, and a looked good (it'll be useful for something else) - but the information for AAC is wrong!

It's showing a file as basic AAC 22.05kHz, when it's clearly got SBR and decodes at 44.1kHz!

Cheers,
David.

Utility to check contents of (HE)-AAC files

Reply #3 – 2009-04-23 14:42:49

Hi,
Actually when SBR is present AAC will be running at half the sampling rate....so after AAC is done it upsamples it by 2 and produces double the samples....The profile information will be available in MP4 header...

Utility to check contents of (HE)-AAC files

Reply #4 – 2009-04-23 15:06:24

There are number of weird implicit/explicit signaling rules. If you do need correct information use ISO reference decoder with "-c" "-D n" options.

Utility to check contents of (HE)-AAC files

Reply #5 – 2009-04-23 15:26:11

Hmm - I'll try that!

Strangely, MediaInfo reported things correctly while the AAC streams were wrapped in FLV, but gave the incorrect information once FLVextract had produced aac files. Maybe FLVextract messes something up or hid the HE-AAC part? The extracted AAC files still play correctly in VLC though (SBR included).

Cheers,
David.